PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. DATE DUE DATE DUE DATE DUE L_ ELA- | IE“ I LJ-LJ —1 _ |____|| [ 1m! 1 MSU Is An Afirmdive ActlorVEquel Opportunity lnetltutton cmma-ot FLOODING TOLERANCE OF SOUR CHERRIES By Thomas George Beckman A.DISSERTATION Submitted to Michigan State university in partial fulfillment of the requirements for the degree of DOCFOR OF'PHIDOSOPHY Department of Horticulture 1988 ‘ABI‘RACI' FILDDII‘B mm 01" SCXJR CHERRIES by 'lhomas George Beckman The effect of soil flooding on growth. leaf gas exchange characteristics and survival of sour cherries (P1141113; ger_a_sue; L. 'Montmorency' on I; mahaleb L.) was studied utilizing 1 year-old containerized trees. In one experiment. actively growing sour cherry trees were subjected to soil flooding for 2. 4, 8. 16 or 32 days under greenhouse conditions (total treatment/recovery period of 48 days). In all flooding treatments longer than 2 days, net (202 assimilation (A). stomatal conductance to 002 (g1) and shoot extension rates fell to ca. zero within 8 and 12 days. respectively, after initiation of flooding treatment. Gas exchange rates and shoot extension eventually returned to control levels only for the 2 and 4 day flooding treatments. doing so by day 24 and 40 respectively. Chlorophyll content declined for trees flooded longer than 8 days; falling to zero by day 40. Flooding for longer than 2 days resulted in significant defoliation of trees by the end of the 48 day treatment and recovery period. Survival of trees through a second growth period following chilling was inversely related to flooding duration. with an estimated L050 of 6 days. In a second experiment conducted within a growth chamber. 032 and light response curves of sour cherry trees were determined during a five day flooding regime. Soil flooding significantly reduced A within 24 hr after am of flooding. Net 002 assimilation of flooded trees declined to 32% that of controls after 5 days of flooding. Residual conductance to 002 (9;) responded in a similar manner. Intercellular 002 (Ci) and stomatal conductance to 002 (91) were initially depressed by soil flooding. However. as flooding continued. g1 became markedly depressed while Ci eventually rose above that of control trees. Apparent quantum efficiency was reduced after 24 hrs of flooding and continued to decline throughout the flooding period" Bark respiration increased within 24 hrs after flooding. Results were interpreted within the framework of recent models of leaf gas exchange and indicate that the various stomatal and nonstomatal factors limiting A in sour cherries change in their relative importance as flooding persists. The relative flooding tolerance of various cherry rootstocks was studied in a separate greenhouse experiment in which trees were flooded for 5 days and then allowed to recover for 10 days. Rootstocks tested included Mahaleb. Mazzard. Montmorency. Colt. MxM clones 2. 39 and 60. and Giessen clones (GC) 148/1. 148/9. 195/1. 195/2 and 196/4 (all grafted with Mentmorency). Nonflooded control trees displayed significant rootstock effects on A. 91 and shoot extension rate when averaged over one 15 day experimental period. However. there was no apparent correlation of A. g1 or shoot extension with relative dwarfing ability of the various rootstocks. When compared on the basis of net carbon assimilation rate at end of recovery period and net shoot extension during treatment/recovery period several rootstocks stood out. Montmorency on MxH 2 was the most tolerant to flooding while Montmorency on MxM 39 was the least tolerant. As a group. tested rootstocks displayed a smaller range of tolerance and a more rapid onset of injury than has been reported for rootstocks of other temperate deciduous tree fruit species. e.g. apples and pear. To all those who don’t know enough to quit while they're ahead.- ii AW I am grateful to my major professors. ups. J.A. Flore and R.L. Perry for their direction. support and helpful criticism during the course of my graduate studies. I would also like to thank Drs. B. Branham. A.E. Erickson. J.F. Hancock. A.L. Putnam and A.J.M. snooker for serving on my guidance committee and Ms. LLB. Teichman for her assistance in the lab and field“ Special thanks to Roch Gaussoin for his assistance with the preparation of figures. And to the “cast of thousands" who helped in ways both large and small... I hope you all got even somehow because its too late now! iii Guidance Comittee: - The journal paper format was chosen for this dissertation in accordance with departmental and university regulations. The dissertation is divided into 3 sections and an appendix. All sectiors were prepared for publication in The Journal of the American Society for Horticultural Science. iv TAHEOFODNI'ENI‘S Section I Effects of flooding of varying duration on growth. gas exchange characteristics and survival of containerized sour cherry trees (Montmorency/Mahaleb) ...................... Abstract .......................... Section II Relative tolerance of various cherry rootstocks to waterlogging and rootstock effects on net carbon assimilation. stomatal conductance arri shoot extension rates of Montmorency 30 ions Introduction ...................... _ . . Materials and. Methods .................... 12 20 49 56 59 63 72 Section III Short-term flooding effects on gas exchange characteristics of sour cherry trees (Prunus cerasus L.. cv. Montmorency/E‘ mahaleb L.) . 89 Abstract ........... . . . . . . ..... . . . . 90 Introduction ....... . . . . . . . . . . . . . . . . . 91 Materials and Methods . . . . . . . . . . ..... . . . . . 92 Results and Discussion . . . . . . . . . . . . . . . . . . . 99 Literature Cited ....... . . ............. 128 SUMMARY AND CONCLUSIONS ..... . . . . ........ . . . . 131 Appendix A Effect of xylem sap from flooded and check trees on gas exchange characteristics of sour cherry leaf explants ........... 136 Appendix.B Ethanol and acetaldehyde concentration in root exudate from flooded and control sour cherry'trees (Montmorency/Mahaleb) . . . 141 Appendix C Effects of ethanol. acetaldehyde and sodium bicarbonate on gas exchange characteristics of sour cherry leaf explants (Montmorency) .......................... 144 LISI'OFREFHENCES.. .................. 149 vi LISTOFTAELES Table Page Section I 1. Effects of 1—4 days of flooding on net (I); assimilation (A). stomatal conductance to CD2 (g1). intercellular (1)2 (Ci). stem water potential (SWP) and leaf chlorophyll content (Chlor) of sour cherry trees (Montmorency/Mahaleb) ........... 21 2. Effects of flooding for 2-32 days during active shoot growth of sour cherry trees (Montmorency/Mahaleb) on defoliation (DEF) at end of 48 day treatment/recovery period arr! on survival (S). net COZ assimilation (A). stomatal conductance to CD2 (91). total new shoot length (soar) and total leaf chlorophyll (CI-ma?) at the end of 60 day regrowth period , fol lowing dormancy ...................... 32 3. Effects of flooding for 4—32 days during dormancy of I; mahaleb on survival (3). net CD2 assimilation (A). stomatal conductance to 002 (gl) and total new shoot length (S-KDT) at end of 60 day regrowth period ................ 35 4. Effects of repeated short term flooding on relative change (25 of control) of net CD2 assimilation (A). stomatal conductance to (1)2 (91) and shoot extension rate of sour cherry trees (Mont/Mahaleb) ........................ 38 5. Effects of repeated short term flooding on total leaf chlorophyll of sour cherry trees (Montmorency/Mahaleb). . . . 40 6. Effects of repeated short term flooding on final component dry weights (gm). shoot/root ratio (S/R). percent defoliation (DEF) and percent root rot (ROI) of sour cherry trees (Montmorency/Mahaleb) .................... 41 Section II 1. Sour cherry rootstocks utilized in study ........ . . . 61 2. Rootstock effects on mean net (1)2 assimilation (A). stomatal conductance to C02 (91) and shoot extension rate of Montmorency scions (nonflooded trees) during treatment/recovery period .................. 64 vii Table 3. 10. Flooding effects on total new shoot and leaf dry weight (at end of treatment/recovery period) of Montmorency on various rootstocks .......................... Flooding effects on root. trunk and total dry weight of sour cherry trees (Montmorency grafted onto various rootstocks) . . Flooding effects on shoot extersion rate of Montmorency scions on various rootstocks . . . . ............ Flooding effects on leaf expansion rate of Montmorency scions on various rootstocks .................... Reduction of stomatal conductance (gl) in leaves of Montmorency sciors on various rootstocks during five days of flooding and 10 days after relief .............. Reduction of net CD2 assimilation (A) in leaves cf Montmorency on various rootstock during five days of flooding and 10 days after relief ................... Rootstock effects on net (1)2 assimilation 10 days after relief of flooding and net shoot extension during 15 day flooding/recovery period. . Relative flooding tolerance of various containerized sour cherry rootstocks under greenhouse conditions . . Section III Effects of flooding duration on quantum efficiency. dark respiration (Rd) and light compensation point (LC) of sour cherry (Montmorency/Mahaleb) ................. Appendix A Effects of xylem emdate from flooded and check sour cherry trees (Montmorency/Mahaleb) on net C02 assimilation (A). residual mesophyll conductance to (132 (gr). and stomatal conductance to 002 (g1) of Montmorency leaf explants. . . . leaf water potential (LWP) and stem hydraulic conductivity (K) of leaf explants (Mont) receiving xylem exudate from either flooded or check sour cherry trees (Mont/Mahaleb) ...... viii Page 66 67 69 70 71 82 113 139 140 Table Appendix B 1. Cbncentration of ethanol and acetaldehyde in xylem exudate from flooded and control sour cherry trees (Montmorency/Mahaleb) .................... Appendix C 1. Effects of various concentrations of ethanol on net assimilation (A). residual mesophyll conductance to 002 (g;). and stomatal conductance to 002 (g1) of Montmorency leaf explants. . . . . ................... 2. Effects of various concentrations of acetaldehyde on net 002 assimilation (A). residual mesophyll conductance to 002 (g}). and stomatal conductance to 002 (91) of Montmorency leaf explants. . ........................ 3. Effects of various concentrations of sodium bicarbonate on net 002 assimilation (A). residual mesophyll conductance to 002 (gr). and stomatal conductance to C02 (Q1) of Montmorency leaf explants ................ ix Page 142 146 147 148 LIST OF FIGURES Figure Page Section I 1. Effects of 2—32 days of flooding on net (1)2 assimilation (A) of containerized sour cherry trees (Montmorency/Mahaleb) . Arrows indicate day flooding relieved for various treatments. Bars represent 150.05 at each sampling date ......... 23 2. Effects of 2-32 days of flooding on stomatal conductance to (D2 (gl) of containerized sour cherry trees (Montmorency/Mahaleb). Arrows indicate day flooding relieved for various treatments. Bars represent 130.05 at each sampling date . ....................... 26 3. Effects of 2-32 days of flooding on shoot extension rate of containerized sow cherry trees (Montmorency/Mahaleb) . Arrows indicate day flooding relieved for various treatments. Bars represent 1313.05 at each sampling date ............ 28 4. Effects of 2—32 days of flooding on total leaf chlorophyll content of containerized sour cherry trees (Montmorency/Mahaleb). Arrows indicate day flooding relieved for various treatments. Bars represent 150.05 at each sampling date ........................ 30 '5. Percent survival vs. number of days flooding for containerized sour cherry trees (Montmorency/Mahaleb) ........... 34 6. Relationship of total shoot growth (during 60 day regrowth period) and previous flooding treatment for unbudded Mahaleb rootstocks. Each point represents mean of 5 trees per treatment (2 shoot per tree) 1: ed (except 4 and 32 flooding treatments. meanof4trees each). rZ- 0.88 (P< 0.02) . .. 37 7. Effect of 1 or 10 days of flooding on oxygen diffusion rate (0112) of containerized sour cherry trees (Mont/Mahaleb). Flooding relieved at times indicated by filled triangles. Each point represents mean of 3 trees per sampling time (5 determinations per tree) ................... 43 Figure . Page Section II > 1. Relationship between A and g1 of flooded and nonflooded sour cherry trees (Montmorency on 12 different rootstocks). Each point represents mean of 4 replications of each rootstock for each flooding treatment and date of sampling ......... 74 2. Relationship between A and shoot extersion rate of flooded and nonflooded sour cherry trees (Montmorency on 12 different rootstocks). Each point represents mean of 4 replications of each rootstock for each flooding treatment and date of sampling. . ......................... 76 Section III 1. Typical relationship of net (1)2 assimilation (A) and intercellular 002 (Ci). Curve represents "demand function" in a leaf. Solid line represents "supply function". Dotted vertical line represents the "supply function" if resistance to (I); diffusion were zero. Point AC) on figure represents assimilation rate that would occw if there were no stomatal limitation to 002 diffusion. while point A represents actual assimilation rate. Stomatal limitation to net (I); assimilation is calmlated by the formla indicated (after Farquhar and Siarkey. 1982) ................. 97 2. Effects of 1-5 days of flooding on net (132 assimilation (A) of sour cherry trees (Montmorency/Mahaleb). Data points are mears of 2 plants/time :1: ed. Significance of difference between 2 treatments at each time indicated at the 10% (+) or 5% (*) level. otherwise ns. t test ............ 101 3. Effects of 1-5 days of flooding on stomatal conductance to 002 (91) of sour cherry trees (Montmorency/Mahaleb) . Data points are means of 2 plants/time :1: ed. Significance of difference between 2 treatments at each time indicated at the 10% (+) or 5% (*) level. otherwise ns. t test .............. 104 4. Effects of 1-5 days of flooding on residual conductance to (I); (gr) of sour cherry trees (Montmorency/Mahaleb). Data points are means of 2 plants/time :t ed. Significance of difference between 2 treatments at each time indicated at the 10% (+) or 5% (*) level. otherwise ns. t test .............. 106 5. Effects of 1—5 days of flooding on intercellular (D2 (Ci) -of sour cherry trees (Montmorency/Mahaleb). Data points are mears of 2 plants/time :t: ed. Significance of difference between 2 treatments at each time irrlicated at the 10% (+) or 58 (*) level. otherwise ns. t test .............. 108 xi Figure > Page 10. 11. Net 002 assimilation as a function of incident PPF in sour cherry trees (Montmorency/Mahaleb) before and after 1—5 days of flooding ......................... 111 Stomatal conductance to 002 (91) as a function of ambient 002 (Ca) in sour cherry trees (Montmorency/Mahaleb) after 2 and 5 days of flooding ....................... 115 Net 002 assimilation (A) as a function of ambient 002 (Ca) in sour cherry trees (Montmorency/Mahaleb) after 2 and 5 days of flooding. .Dashed and solid.curves. control and flooded treatments. respectively ................... 117 Net 002 assimilation rate (A) as a function of intercellular C02 (Ci) in sour cherry trees (Montmorency/Mahaleb) after 2 and 5 days of flooding. Dashed and solid curves. control and flooded treatments. respectively. Dotted vertical lines represent supply curves for infinite g1 ........... 120 Effect of vapor pressure deficit (VPD) on net 002 assimilation (A) of sour cherry trees (Montmorency/Mbhaleb) after 2 and 5 , days of soil flooding .................... 125 Effect of vapor pressure deficit (VPD) on.stomatal conductance to 00; (gl) of sour cherry trees (Montmorency/Mahaleb) after 2 and 5 days of soil flooding ................. 127 xii A/Ci Rubisco S/R LIST OF’AEEREVIATIONS net 002 assimilation 002 assimilation response curve to internal 002 002 assimilation response curve to ambient 002 ambient 002 concentration intercellular 002 concentration transpiration stomatal conductance to 002 residual mesophyll conductance to 002 hydraulic conductiv1ty stomatal limitation to’photosynthesis lethal dose for 50% of population oxygen diffusion rate leaf water potential photOsynthetic photon flux inorganic phosphate leaf vapor pressure dark respiration relative humidity ribulose bisphosphate ribulose bisphosphate carboxylase/oxygenase stem water potential shoot to root ratio vapor pressure deficit xiii IN’I'ROUJCI‘ION Soil flooding has negative effects on most growth ard physiological [recesses of woody plants. (howers. aware of the potential for damage. will rarely deliberately plant trees on sites likely to flood (hiring the growing season. Nevertheless. locally restrictive soils that are prone to rootzone flooding when subjected to heavy rainfall and/or irrigation are not uncomon in glacial soils typically utilized for agricultural purposes in the Great Lakes region. Many sour cherry growers have experienced reduced lorgevity of orchards and trees in Michigan in recent years. Researchers at 16) have addressed this issue in attempting to identify the causal factor(s) . mile a number of biotic (root rots. irsects. diseases. nematodes) and abiotic (soil drainage. winter damage. mechanical harvesting damage) factors apparently involved. researchers have generally observed affected trees in conjunction with locally restrictive soils. i.e. heavy subsoils. plow pans. etc.. that are conducive to rootzone flooding when subjected to heavy rainfall and/or irrigation. Temperate tree fruit species vary widely in their tolerance to soil waterlogging. Within a given species a considerable range of tolerance can often be found among available rootstocks. The two most comon cherry rootstocks. seedlings of Pn_n'n_1§ ma_haLe_b L. and E._ m L. (Mazzard). have consistently been found to be extremely sensitive to waterlogging. miservations of field performance over the years have generally noted 2; cerasus cv. Stockton Morello to be considerably more tolerant to soil flooding than Mazzard. and Mazzard to be only slightly more tolerant to excess soil moisture than Mahaleb. Recently. a number of prospective cherry rootstocks have been subjected to limited comercial trials. i.e. MxM clones (presumed natm'al hybrids of I; mahaleb and E; w). L cerasus cv. Montmorency and Colt. Neither these nor new advanced releases from breeding programs have been extersively evaluated for tolerance to waterlogging. Detailed information concerning the effects of waterlogging on fruit trees is limited. especially for cherries. Herbaceous and woody plants subjected to soil flooding generally display reduced stomatal conductance (gs) . often in conjunction with reduced CD2 assimilation (A). Decline in gs is not usually accompanied by a drop in leaf water potential. however. there are some reports of an opposite effect. Recent investigations have shown that soil flooding may cause a reduction in A of various fruit species through a combination of stomatal and nonstomatal limitations. Models of leaf gas exchange have been developed which allow critical evaluation of the presence and relative contribution of some of these proposed mechanisms to limitation of A in stressed plants. The primary objectives of this series of experiments were: 1. Greene and determine differences in symptom development of sour cherry scions during both long and short term soil flooding. 2. Determine ID50. i.e. lethal "dme". of flooding. 3. My available cherry rootstocks and determine their relative sensitivity to soil flooding. 4. Determine physiological causes of plant injury during soil flooding. Section I MWMIMOFVARYIPGIXEATIONONM. GAS momma CHARACI'ERISI'IS AND SJRVIVAL OF CONTAINERIZI'D 311R CHERRY TREES (WW). AEI‘RACI' Soil flooding of containerized one year-old sour cherry trees (WWW. Montmorencyonggwb) producedamarked reduction in net (1)2 assimilation (A). stomatal conductance to 002 (91) and stem water potential (SVIP) within 24 hours fol lowing imposition of treatment. Over a 4 day flooding period A and g1 declined to 6% and 12% p‘ of controls. respectively. Stem water potential was significantly more negative in flooded trees the morning after floodirg and continued to be ._ more negative for the duration of the treatment period. In a second experiment. actively growing containerized sour cherry trees (Montmorency/Mahaleb) were subjected to soil flooding for 2. 4. 8. 16 or 32 days under greenhouse conditiors (total treatment/recovery period of 48 days). In all flooding treatments longer than 2 days. gas exchange characteristics and shoot extension rates fell to ca. zero within 8 and 12 days. respectively. after flooding. Leaf gas exchange characteristics eventually returned to control levels only for the 2 and 4 day floodirg treatments. doing so by ca. day 20 and 32 respectively. Chlorophyll content declined in leaves of trees flooded longer than 8 days; falling to zero by day 40. Flooding for longer than 2 days resulted in significant defoliation of trees by the end of the 48 day treatment and recovery period. Survival of trees through a second growth period fol lowing chilling was inversely related to flooding duration. with an ID50 (mmber of days of flooding required to kill 5025 of material) of 6 days. In a third experiment in which containerized. dormant tart cherry rootstocks (Mahaleb on its own roots) were flooded for 4. 8. 16 or 32 days while in storage at 2 0C. no effects were noted'on gas exchange characteristics during a follow—up growth cycle in the greenhouse. although net shoot growth during this period was inversely related to duration of previous flooding treatment. In a fourth experiment. a fourteen day treatment regime consisting of 2 days flooding followed by a 12 day recovery period was repeated 4 times over an 8 week period during active growth. Net 002 assimilation and stomatal conductance of containerized.tart cherry trees (Montmorency/Mahaleb) declined significantly only during the second and third cycles but eventually returned to control levels in all cycles. Shoot growth declined significantly below controls during the second cycle; eventually falling to zero by the end of the fourth cycle. At conclusion of experiment. Phytophthora could not be isolated from any plots. Imnowcnon Soil flooding has negative effects on most growth and physiological processes of woody plants (Kozlowski. 1984; Kozlowski and Pallardy. 1984: Pereira and Kozlowski. 1977). Most growers. aware of the potential for damage will not deliberately plant trees on sites likely to flood during the growing season. Nevertheless. locally restrictive soils. i.e. clay subsoils. plowpans. etc.. that are prone to rootzone flooding when subjected to heavy rainfall and/or irrigation are not uncomon in glacial soils typically utilized for agricultural purposes in the Great lakes region (Whiteside et a1. 1963) . Soil flooding results in low soil oxygen levels due to the displacement of soil air and subsequent deplietion of the remaining oxygen by root tissues and aerobic soil microorganim. Additionally. the low solubility and diffusion rate of oxygen in water compared to air slows the movement of oxygen to plant roots. Investigators have reported the depletion of oxygen in waterlogged soils within one day (Patrick and Mahapatra. 1968.- Turner and Patrick. 1968) or even a few hours (Van't Woudt and Hagen. 1957). ‘ Shoot growth and root initiation. growth and survival of apples have been shown to reduced by low oxygen levels (Boyton. 1940: Dayton and Reuther. 1938; Boyton and Compton. 1943). In general. however. oxygen concentration alone has been weakly correlated with plant response (Letey and Stolzy. 1964) . .In contrast. oxygen diffusion rate (013R) has proven to be a reliable indicator of oxygen availability (Glirski and Stepniewski. 1985; Stolzy and Letey. 1964) presumably because this measurement technique mimics oxygen use by roots; responding to not only the oxygen concentration gradient between the soil and root but also the diffusion 7 path resistance (matey and Stolzy.'1964). Generally. ours below 0.3- 0.4 micrograms 02 cm‘2 min‘3l impair root function and 0112's below 0.2 result in root death (Stolzy and letey. 1964) . Levels below 0.2 have been correlated with reduced root hydraulic conductivity and/or growth in pear and peach (Arriersen et al.. 1984a). blueberry (Crane and Davies. 1988) and apple (Olien. 1987). Stomatal conductance decreases significantly within 4-5 days after onset of flooding in sour orange (Syver'tsen et al. 1983). rabbiteye and highbmh blueberries (Davies and Flore. 1986a). and peach (Andersen et al. 1984a). Smith and Agar (1988) observed a significant reduction after only 1 day of flooding in pecan. However. some species of Em and selections of 9131933 appear to be tolerant for 20 or more days (Andersen et al. 1984a) . Net carbon assimilation generally follows a similar pattern. decreasing rapidly after imposition of flooding in citrus (Phung and Knipling. 1976) . rabbiteye and highbush blueberries (Davies and Flore. 1986a). pecan (Snith and Ager. 1988) and apple (Childers and White. 1942) . . Reductions in A and g1 have been accompanied by reductions in leaf water potential (more negative) in bears (Madman-van Schravendijk and van Andel. 1986) and tobacco (Kramer and Jackson. 1954) suggesting that stomatal closure in response to leaf water stress limits A. However. stomatal closure during soil flooding has been observed without concurrent reductions in leaf water potential in m (Andersen et al. 1984b). peas (Jackson and Hall. 1987) and hardwood species (Pereira and Kozlowski. 1977; Tang and Kozlowski. 1982) indicating that stomatal clomlre is not necessarily due to water stress. Additionally. reductions in A during soil flooding have been observed without stomatal closure in sunflowers (Wample and Thornton. 1984) and m; (Sivakumaran and Hall. 1977) indicating a limitation of A at a more fundamental level. Stomatal and nonstomatal limitation of A during soil flooding has been observed in blueberries (Davies and Flore. 1986a and 1986b). tomato (Bradford. 1983a). beans (Moldau. 1973) and pecan (Smith and Ager. 1988). Sloot growth is typically reduced durirg soil flooding of pears and peaches (Andersen et al. 1984a) and apples (Olien. 1987) and many hardwood species (Kozlowski. 1984). In contrast. Dickson. et al (1965) observed that height growth of the flooding tolerant Ema @9343; increased during soil flooding. Significant reductions in shoot growth of peach were observed after flooding treatments as short as 3 days during active shoot growth (Rom and Brown. 1979) . However. effect was dependent on time of application: flooding just as buds troke in early spring actually improved growth of trees. if treatment was less than 5 days in duration. otherwise a reduction in subsequent growth was omerved. Flooding during dormancy has generally not reduced subsequent shoot growth in apple (Heinicke. 1932: Ron and flown. 1979) and hoadfoot (1967) oberved that dormant season flooding actually improved albsequent growth of some hardwood species. Tree survival is dependent upon duration and season of flooding. Fruit species are more likely to survive prolonged periods of waterlogging if it occurs when trees are not actively growing (Crane and Davies. 1988; Hein'icke. 1932: Kongsgrud. 1969: Olien. 1987: Real and flown. 1979). A mmber of hypotheses have been postulated to explain this increased sensitivity during active growth. Flooding typically reduces the hydraulic conductivity of the root system. i.e. reduces capacity of the root system to supply water to the canopy (Andersen et al. 1984b; Syvertsen et al. 1983). Clearly. this will be more of a problem during the growing season when the tree carries maximum leaf area. Alternatively. soil temperatures will be lower during the dormant season thus reducing root system respiration and hence demand for oxygen. Interestingly. some materials. i.e. some Eggs; and ngonia species. are able to survive prolonged flooding even when imposed during active growth (Andersen et al. 1984a). A number of plant growth regulators have been implicated in plant responses to soil flooding. Redford and Yang (1980) daonstrated in tomato that flooding promoted the synthesis of ACC. an ethylene precursor. in the root system. Subsequent transport to shoots in the ' transpiration stream and conversion to ethylene resulted in petiole epinasty. However. Bradford (1983b) demonstrated that ethylene had no effect on stomatal conductance or photosynthesis of nonflooded tomato plants although exposure to ethylene resulted in typical petiole epinasty. Nevertheless. stomatal (Pallas and Kaye. 1982) and norstomatal (Govindarajan and Poovaiah. 1982) irhibition of photosynthesis has been reported in the literature. Abscisic acid (ABA) has been shown to accumulate in the leaves of flooded plants (Hiron and Wright. 1973: Jackson and Hall. 1987: Siaybany arri Martin. 1977). Bradford (1983b) demorstrated that although applications of ABA to nonflooded tomato plants caused stomatal closure similar to that of flooded plants. it did not produce a similar reduction in photosynthetic capacity. Raschke (1982). however. has reported norstomatal inhibition of photosynthesis by ABA in a variety of species. 10 Blrrows and Carr (1969) have reported a marked reduction in cytokinin content of xylem sap of flooded sunflowers. Cytokinirs are known to delay senescence of detached leaves (Richmond and Lang. 1957) . maintain photosynthetic rates in senescencing leaves (Adedipe. et al. 1971). promote synthesis of photosynthetic emymes and components of the electron transport chain (Feierabend and de Boer. 1978) and maintain stomatal aperature in stmed plants (Bengston. et al. 1979; Kirkham. et al. 1974) . This suggests that cytokinins may be involved in the altered leaf gas exchange characteristics typically observed in flooded plants. Bradford (1983b) reported that applications of benzyladenine maintained both stomatal aperature and photosynthetic capacity in flooded tomato plants. Reid. et al (1969) and Reid and Crozier (1971) have reported that gibberellin levels drop markedly in tissues and xylem sap in flooded plants. They have also shown that applications of GA3 produced a relatively greater improvement in shoot growth of flooded tomato plants than in nonflooded tomato plants. Increased auxin has been implicated . in causing leaf epinasty. Phillips (1964a). observed that waterlogging induced leaf epinasty in sunflower was relieved by shoot decapitation. Application of IAA to the cut surface restored the epinasty. Phillips (1964b) later reported markedly greater amounts of auxin in shoots of flooded sunflowers than in controls. Soil flooding and the concurrent reduction in redooc potential. oxygen concentration and diffusion rate (0m) lead to complex charges in both soil chemistry and root metabolism. Under anaerobic conditions a number of potentially toxic compounds are synthesized. several of which have been the subject of research efforts. Hydrogen sulphide evolution 11 in anaerobic soils has been studied extensively in relation to M response to soil flooding. Gilbert and Ford (1972) demonstrated that oxygen deficiency was not damaging in itself during short term flooding but if accompanied by 2—3 ppm of hydrogen sulphide severe root damage occurred. Additionally. they demonstrated that rough lemon. a flooding tolerant citrus rootstock (Hayashi and Wakiska. 1956). was less sensitive to hydrogen sulphide than other flooding sensitive citrus rootstocks. Under waterlogged conditions root tissue metabolim shifts from aerobic to anaerobic pathways resulting in the formation of ethanol and acetaldehyde. with ethanol formation being favored the more limited the oxygen supply (Rowe. 1966) . Although ethanol has been detected in xylem exudate of flooded tomato plants (Fulton and Erickson. 1964) and its production correlated with flooding sensitivity in Senecio (McMamon and Crawford. 1971). conclusive proof that observed amounts are indeed toxic to plant tissues is lacking. Additionally. Phung and Knipling (1976) was unable to detect any difference in ethanol concentratiors in tissues of flooded vs non flooded citrus rootstocks. Cyanogenic glycosides are common in tissues of Prunus §Qp_._ (Seigler. 1975). Rowe (1966) observed that under anaerobic stress detached roots of these species evolved phytotoxic amounts of hydrogen cyanide. Additionally. Rowe and Catlin (1971) have demonstrated that the differential sensitivity of peach. apricot and plum to soil flooding was correlated with the cyanogenic glycoside content of their root tissue. Detailed information concerning the effects of waterlogging on fruit trees is limited. especially for cherries. Sour cherries (Pru__ms_ 12 cerasus. cv. Montmorency) are typically propagated on P_. mahaleb (Perry. 1987). a rootstock. characterized as very sensitive to soil flooding (Saunier. 1966) . The purpose of this series of experiments was to characterize the response of this particular scion/rootstock combination to flooding stress under a ranged of controlled conditions and regimes. MATERIALS AND MED-DIE iment _1_: Ecl_1r gay diurnal m Ch May 29. 1986. 8 maiden trees of P_. cerasus cv. Montmorency grafted on E; mahaleb were pruned to a single. unbranched stem ca. 80 cm tall and planted in 7 liter plastic containers filled with a steam sterilized mineral soil mix (ca. 50% sandy loam. 30%spaghnumpeat and ZOSsandv/v). Trees were ca. 1.3cm caliper (measured ca. 2.5 cm above graft union) ‘at time of planting. T‘reesweremovedtoashadedgreenhouse (ca. 50%full sun) atthe Pesticide Research Center. 16} and set in wooden racks (ca. 60 cm off the floor). Racks were then covered with aluminum foil to prevent direct solar heating of the containers. Plants were fertilized at planting and again 3 weeks later with a soluble fertilizer (20—20—20 NPK) diluted to 200 ppm N. otherwise trees were watered to saturation as needed with tap water. Three unbranched shoots were allowed to develop on each plant: all others were removed as they appeared. Pests and diseases were controlled as needed according to comercial recomendatiors (Mich. Ebct. Bil. E154. Fruit Pesticide Handbook). Mean minimum/maximum air temperatures during pretreatment period were 18:): 3/3315 0C. At 1100 hr. July 9th. flooding treatments were imposed on one half of the trees by placing each tree container in an 11 liter container 13 lined with a plastic bag and filled with tap water adequate to cover the soil surface. The experiment was concluded 4 days later after afternoon data was collected. Bring the treatment period A and g1 were determined in the morning (1000-1100 hr) and afternoon (1800—1900 hr) with a portable system consisting of an Analytical Development Co. (Hoddeston. England) Infrared (I); Gas Analyzer (LCA-2). Regulated Air Supply Unit (ASU) and Parkinson leaf Chamber (PIC-B). A single measurement was made on a randomly selected fully expanied mid-shoot leaf on each shoot (3 per tree). Readings typically equilibrated within 1 minute after sealing chamber on leaf. Measurements were made at ambient daytime temperatures and 002 concentrations (typically 340—360 ppm). Supplemental light was provided with a 400 W high pressure sodium vapor lamp whenever ambient light levels fell below saturation for photosynthesis. i.e. 1000 micromols m-2 s-1 PPF (Sams and Flore.1982). Gas exchange parameters were calculated as previously described (Moon and Flore. 1986) with the exception that leaf vapor pressure was estimated in the manner by Richards (1971) and that sample and ambient vapor pressures were calculated as: p- (RH/100) *ps. where p equals sample or ambient vapor pressure (with or without leaf within cuvette. respectively) at cuvette temperature. p3 equals leaf vapor pressure at cuvette temperature (presumed to equal the saturation vapor pressure of water) and RH is the appropriate percent relative humidity measured within the cuvette. 1 Stem water potential (SWP) was measured each morning (800 hr) with the use'of a portable pressure bomb (PIB Irstrument Co.. Corvallis. Oregon). Samples were processed inmannerdescribedbyTurner andlong 14 (1%0) whereby the leaf was enclwed the evenirg before by slippirg a plastic bag over a single basal leaf and sealing with a wire tie wrapped around the petiole. This allows leaf to equilibrate more rapidly and completely with stem water and gave a better estimate of plant water status. Chlorophyll content was determined throughout the treatment period by collecting 5 leaf disks (0.32 an each) from a single randomly selected basal fully expanded leaf on each plant. This leaf was reused for amequent chlorophyll samplings only. Samples were collected after gas exchange measurements in the afternoon of each day. Chlorophyll was extracted in 5 mls of N.N—Dimethylformamide and the content determined in the manner described by Moran (1980 and 1982). Controls were watered whenever soil moisture tension exceeded -20 KPa. as measured with a Soil Moisture Equipment Corp. "mick—mew“ soil moisture probe (Model 2900F) . inserted ca. 10 cm into the soil midway between center of pot and rim. Mean minimm/maximum air temperatures during flooding treatments were 191:1/3417 °C. A randomized complete block (blocked on the basis of Meline net (1)2 assimilation rates) with 4 replications of two treatments (flooded vs check) was used. W 2: Floodim gurigg 29.21.29. ML. cm February 6. 1987. 20 bladed cherry rootstocks of E mahaleb grafted with 13_._ m cv. Montmorency (prunedca. 1cmabovechipbudandmeanfwof 699m) were planted in 7 liter plastic containers filled with the steam sterilized mineral soil mix described in Experiment 1. Before filling. a single 2.5 cm diameter aquarium aerator (Krislin. Lansing. MI. Model 062380) connected to ca. 20 cm of plastic tubing was placed in the bottom center 15 of each pot: with the free end of the tubing exiting through a drainage hole. Trees were placed in a greenhouse at the Pesticide Research Center. EU and watered regularly with a soluble fertilizer (Peter's 20- 20—20 NPK) diluted to 200 ppm N. Trees were trained to a single untranched stem. Mean minim/maximum air temperatures dmring the pretreatment period were 2011/3114 °C. In order to complete experimental design. 4 additional trees were brought from a neighboring greerhouse 4 weeks before start of treatments. trees had been planted in identical soil mix. grown under similar regime and were similar in appearance and size to other trees utilized in this experiment. However. the eleven liter containers these trees had been planted in could not be accomodated by the methodology used to impose flooding treatments. therefore. these trees were used as controls. (m the evening of day zero (April 23). flooding was imposed as described in Ebcperiment 1. Flooding was relieved in the evening 2. 4. 8. 16 or 32 days later. Pots were first allowed to gravity drain for 30 minutes after which a vacuum pump was attached via rubber hose and a collection flask to the buried aquarium aerator. Pumping for 10 minutes (typically generating a vacuum of 25-30 KPa in collection flask) allowed the removal of an additional 300—500 mls of water from each pot and the imposition of a soil moisture tension of ca. -3 KPa. DJring treatment/recovery period trees were watered to saturation whenever soil moisture tension exceeded -40 KPa and mean minimm/maximum air temperatures were 19:2/2914 °C. Data collections were made on day 0. 2. 4. 8. 12. 16. 20. 24. 28. 32. 40 and 48 of treatment/recovey period. Shoot length was measured from graft union to middle of shoot apex. Leaf gas exchange 16 characteristics (A and 9;) were determined on 2 randomly selected. recently fully exparded. mid-shoot leaves on each tree as described in Ebcperiment 1. Chlorophyll content was determined as described in Dcperiment 1. Forty-eight days after initiation of the flooding treatments all trees were pruned ca. 10 cm above graft union. defoliated and placed in a refrigerated storage at ca. 2 °C. Trees were watered to saturation once with tap water during storage. Seven weeks later all plants were returned to the greenhouse for a regrowth period (all trees trained to a single unlranched stem). Mean minimum/maximum air temperatures during regrowth period were 2011/2914 °C. Trees were watered as needed with tap water. After 60 days. percent survival was noted for each treatment and experiment concluded. Pests and diseases were controlled as needed according to commercial recomendations (Mich. Ext. Ell. E154. Fruit Pesticide Handbook). A modified Spearman—Karber Method (Bittenbender and Howell. 1974) was used to calculate an L050. i.e. number of days of flooding required to kill 50% of trees: 1950 " [(13144 - Pi) * (xiii 4- xi) / 2]. where Pi - bi / ni (mortality index of 1th treatment) and xi-time value of ith treatment. A randomized complete block (blocked on baseline (DZ assimilation rates.) with 4 replications of 6 treatments (0. 2. 4. 8. 16. or 32 days of flooding) was used. iment g; Floodim d__ul;_im gm On June 11. 1987. twenty- five rootstocks of E_._ mahaleb (primed ca. 10 cm. above mrsery grouni level. mean fw of 64 gm) were planted in 7 liter plastic containers as 17 Mined in Bcperiment 1. Trees were watered and placed in total darlmem in a refrigerated storage (2 °C). In the evening of June 20th. flooding was imposed as described in Experiment 1. Flooding was relieved in the evening 4. 8. 16 or 32 days later as described in Experiment 2. Eighteen days after relief of last flooding treatment (32 day). all plants were moved from the cooler to a shaded greemome (ca 50% full sun) at the Pesticide Research Center. l3}. airing this growth period all trees were trained with two unbranched stems (Mahaleb shoots arising from latent buds) and watered as needed with a soluble fertilizer (Peter's 20—20—20 NPK) diluted to 200 ppm N. Mean minimm/maxim air temperatures were 2011/2814 °C. After 60 days. shoot length ani leaf gas exchange characteristics were determined as described in Ebcperiment 1. Percent survival for each treatment was noted and experiment concluded. Pests and diseases were control led as needed according to comercial recomendations (Mich. Ebct. Bil. E154. Fruit Pesticide Handbook). A randomized complete block (blocked on initial fresh weight) with 5 replications of 5 treatments (0. 4. 8. 16. or 32 days of flooding) was used. W; 3 Reflted gm term floodigg. On April 12. 1987. 10 L mahaleb rootstocks budded with I; cerasus cv. Montmorency (pruned ca. 1 cm above chip bud and ca. 65 gm fw) were planted in 7 liter plastic containers as described in Experiment 2. Trees were placed in an unshaded greenhouse at the Pesticide Research Center. MSU and watered once per week with a soluble fertilizer (Peter's 20—20—20 NPK) diluted to 200 ppm N. otherwise with tap water as needed. Trees were trained to a single unbranched stem. Mean minimm/maximum air temperatures during 18 the 50 day pretreatment period were 19t2/30t5 °C. Siading (ca. 508 full sun) was applied to the greerhcuse glass 22 days post-planting. 0n the evening of day zero (June 2). flooding treatments were imposed on half of the plots as described in Ebcperiment 1. Flooding was relieved in the evening 2 days later as described in Dcperiment 2. After a twelve day recovery period. flooding was reimposed on the same trees as described above. ‘lhis 2 week treatment regime was repeated 3 more times for a total of 4 cycles. after which the experiment was terminated. Mean mininm/maxilmnn air temperatures during the 8 week treatment period were 211:1/32:l:4 °C and trees were watered with tap water whenever soil moisture tension exceeded -20 KPa. Pests and diseases were controlled as needed according to comercial recomendations (Mich. Ext. 311. E154. Fruit Pesticide Handbook). Brery 2 days during experiment. shoot length was measured from graft union to middle of shoot apex. Ch days 0. 2. 6. 10. and 14 of each 2 week cycle. leaf gas exchange characteristics (A. 91) were determined. Data was collected from 2 randomly selected. recently fully expanded. mid-shoot leaves of each tree as described in Ebcperiment 1. Leaf chlorophyll content of a fully expanded leaf in the lower third of each shoot was determined at start of flooding treatment as described in Deperiment 2. Whenever possible. this leaf was reused for subsequent chlorophyll determinations only which were made every 7 days through the end of the experiment. At the conclusion of experiment. percent defoliation was estimated as lergth of shoot defoliated divided by total lergth of shoot (x100). Treeswereremovedfrompotsarrltheirrootsystemswashedcleanofsoil 19 by gentle agitation in water filled bucket. Root system were visually rated for S of tissue rotted and samples collected for isolation of W spp. (performed in the manner described by Harris. 1986) . Trees were then partitioned into root system. stem (separated at graft union) and leaves. All samples were oven dried for 2 weeks at 90 0C before weighing. A randomized complete block (blocked on baseline C02 assimilation rates) with 5 replicatiors of 2 treatments (check vs flooded) was used. Miment 5_:_ Measurement g 913. Soil oxygen diffusion rates were measure in a separate experiment. Nine actively growing sour cherry trees (Montmorency/Mahaleb). ca. 75 cm tall. planted in same manner as described in EXperiment 2 were utilized. Six plants were flooded on day 0. Flooding was relieved after 1 day on three plants and after 10 days on the remaining three. Flooding was imposed and relieved in the manner described in Dcperiment 2. Mean minimum/maxim air temperature during the 16 day flooding/recovery period was 2011/26t4 °C. Soil oxygen diffusion rates were measured periodically during this experiment with an oxygen diffusion ratemeter (manufacturer unknown) equipped with a Ag"’/AgCl reference electrode. Five 25 gauge platinum electrodes were irserted ca. 10 cm into the soil midway between the pot rim and its center on each sampling date. our measurements were taken after a 3 mimte equilibration period at an applied voltage of 0.65 V (lemon and Erickson. 1952: Stolzy and Letey. 1964) . Statistical analyses were performed with PBI'AT Microcomputer Statistical Program (Michigan State University. E. Lansing. MI). Regression analyses and figures were prepared with Plotit Interactive Graphics and Statistics Package (Scientific Programing Enterprises. Haslett. MI). 20 RESIL‘I‘S mrimntl: FO_U_1_’_' gay diurnal M Effects of flooding over a 4 day period on net 002 assimilation (A). stomatal conductance to 002 (91) intercellular 002 (Ci). stem water potential (SWP) and leaf chlorophyll content are shown in Table 1. Flooding produced a significant reduction in net 002 assimilation the morning after imposition (21 hours later). Net photosynthesis of flooded plants dropped to near zero in 3 days. carbon assimilation rates were generally lower in the afternoon than morning for both treatments. declining an average of 27% and 37% for control and flooded trees. respectively. .Effects on stomatal conductance displayed a similar pattern in.that a significant depression was evident in the flooded.trees the morning after imposition of treatment. Afternoon measurements were uniformly lower than those collected in the morning of each day. declining an average of 38% and 41% through the day for control and flooded trees respectively. Intercellular 002 in flooded plants did not differ Significantly from controls throughout experimental period. Stem water potential was significantly more negative the morning following imposition of flooding (21 hours) and.was invariably more negative for flooded trees throughout the treatment period. Leaf chlorophyll content did not differ significantly from controls throughout experimental period. Miment 2_:_ Floodigy (AM 2613—122 m Flooding exhibited marked effects on net 002 assimilation (Figure 1). Within 4 days after imposition of flooding treatments all trees displayed a significant reduction in A compared to controls. Flooding treatments of 4—32 days all dropped to ca. 0 net assimilation within 8 days after initiation of 21 .mcowuo>homno e no some on» ma osdo> zoom snob e . B>2 rm ecu no aconouumo x~u:00wmwcmwm heaped accumumwo.sn oesoHHOH houosohoo coco ecu cssgoo meow cw mo:~o>.x .38 m xfigoofloxu dzm no“ cofiuoofiaoo oboe mcwcnos £33888." .3 82188 ace .3 82:88 x2833 5 ace < sou EoBoozoo Sac c893:v Be 8.58: x .o x8 so is 83 838:8 38 82.8.: not... opposes 888E N vN.m I mm.m I nm.m I mn.m I om.m I ooooodm Amlso may mm.m I mo.v I on.n I wo.m I uh.m I ~onucoo Lo~£u I H.nHI I on.NHI I N.hI I nv.mHI I N.©I souoodm.. Aodzv I m.mI I oo.ml I o.mI I om.ol I o.oI donucoo dxm Hmm 0mm mom New Haw moa Hod NNH mod mom soooofih Aalaos “OSOMUHEV sod oHN NNN on oom aha 00H aha mma mod donucou so nma and own AN¢ ANN one nNm nNm he saw oesoofim AHIm NIB Hoses ohm comm omom comm one puma one coma hm mma Honucou mm no.0 no.a nm.o no.0 om.v n©.m om.m nv.¢ a.m o.ma oesooam AdIm mls ~050h0wsm on.m om.va oh.oH om.mH oo.oH cm.ma om.h om.m 0.0 .xo.mH fioxucou < Ilsa so mdl me. am .mw so .mo so. .«mo ugh nouoscucm v son m >pa N wed H >mo 0 son .Aoofiozo:\xocososucozv moon» sneeze .38 no 226. ocoscoo #18982... use“ c5 8.6. 33:38 hose: soon .38 N8 8320835 .23 m8 3 eofioosfloe saucepan .2: 832889 N8 so: so mango: no Rae Tn so Boots .H ofinoh 22 Figure 1. Effects of 2-32 days of flooding on net (1)2 assimilation (A) of containerized sour cherry trees (Montmorency/Mahaleb). Arrows indicate day flooding relieved for various treatments. Bars represent 1.50.05 at each sampling date. 02500.: Era mic mw.c_s..mm_e_m:mr m o tat... ..l. e 4: 1m >3 8. I e 20 m: ale \w... :3 m oo >3 1. aze e m :3 N as ”n nomszoo 0.. 24 flooding. In contrast. the 2 day flooding treatment was still fixing 002 at 44B of control levels at that point and slowly recovered to control levels by day 16. The 4 day flooding treatment was the only other treatment to eventually recover. returning to control levels by day 28. Effects on stomatal conductance to 002 (91) were equally marked and similar in pattern (Figure 2). Within 4 days after imposition of flooding treatments all trees displayed a significant reduction in g1 compared to controls. Flooding treatments of 4 to 32 days declined rapidly to near zero within 8 days of orset of flooding while the 2 day treatment still retained 3358 of control levels at that point and eventually recovered to control levels by day 20. The 4 day flooding' treatment also recovered to control levels by day 40. All other treatments showed no apparent recovery even by day 48 . Within 6 days after imposition of flooding all trees displayed a significant reduction in shoot extension rate compared to controls (Figure 3). Flooding treatments of 4 to 32 days all dropped to near zero levels by day 12 while the 2 day flooding treatment dropped more slowly. falling to near zero levels only by day 28. Sioot extension of control treatment dropped gradually near the end of the experiment. as a result. by day 28 differences between control and any flooded treatments were not significant. Chlorophyll content of the 16 and 32' day flooding treatments declined significantly below that of control trees by day 24. eventually falling to near zero levels by day 40 and 32. respectively (Figure 4). Chlorosis and abscission of the most basal leaves of flooded treatments was first observed on ca. day 6 and day 12. respectively. and proceeded Figure 2. Effects of 2—32 days of flooding on stomatal conductance to Q32 (91) of containerized sour cherry trees (Montmorency/Mahaleb). Arrows indicate day flooding relieved for various treatments. Bars represent 15005 at each sampling date. 26 FIGURE 2 m> aaae 025004“; mmE< m> case 4, a 9 +3 m .r. j] o (Lip UJUJ) °l><3 100HS 29 Figure 4. Effects of 2—32 days of flooding on total leaf chlorophyll content of containerized sour cherry trees (Montmorency/Mahaleb). Arrows indicate day flooding relieved for various treatments. Bars represent 1.5005 at each sampling date. 30 FIGURE4 >45 Nm >46 N JOmHZOO 117 QUoog\ucosboohu so we so oca ea Ewe Nconezouoc co 30385088585 news Sago 8.8 no 56.6 s88 2,38 8E6 exec mmIm no“ 8:8: so 385.5 .m ounce Figure 5. Percent survival vs. number of days flooding for containerized sour cherry trees (Montmorency/Mahaleb) . FIGURES OZ_QOO.E do m>§3+oslu> Sums Home <20 >3. o .3 .00 ‘I‘V’NAH HS % Table 3. Effects of flooding for 4-32 days during dormancy of L mahaleb on survival (S). net C02 assimilation (A). stomatal conductance to 002 (9}) and total new shoot length (3031‘) at end of 60 day regrowth period. DAYS S A 91 m noon-:0 In my III-2 s-lz (mol III-2 23-11 (cm) 0 100 11.5 *- 2.8 133.0 1 38.5 79.7 i’ 5.6 4 80 12.6 t 1.4 143.5 *- 6.8 80.2 t 4.7 8 100 11.7 t 3.5 121.5 ’1 39.2 71.1 t 5.0 16 100 11.2 *- 0.6 135.3 t 11.3 67.5 *- 11.1 32 80 11.6 t 1.6 138.3 t 22.3 61.8 t 17.2 Figure 6. Relationship of total shoot growth (during 60 day regrowth period) and previous flooding treatment for unbudded Mahaleb rootstocks. Each point represents mean of 5 trees per treatment (2 shoot per tree) i: sd (except 4 and 32 flooding treatments. mean of 4 trees each). r2 - 0.88 (P < 0.02) . Heme BOOGIE mar/B Nm.mm.¢_N.o_N.m_P.N_F. m. remnant ”0mm <20 .x*.\Imm.ol Town} to o O (Luv) H10N3‘I ioOI-IS Table 4. Effects of repeated short term flooding on relative charge (8 of control) of net 002 assimilation (A). stomatal conductance to (D2 (91) and shoot extension rate of sour cherry trees (Mont/Mahaleb) . 1291! Parameterz gcley 0 2L 6 10 14 Mean Control Rate A 1 88 104 85 88 93 10.4 1 1.1 (micromol III-2 s-1) 2 - 67*X 82 83 109 10.8 e 1.9 3 - 80* 78 96 89 9.8 a: 2.1 4 - 98 80 79 93 10.5 1 2.8 gl 1 82 112 83 118 89 111.5 a 23.8 (mmol n-Z s-1) 2 — 63* 72“ 74* 100 121.5 a: 37.3 3 - 79* 72 82 80 115.0 1 32.8 4 - 99 86 82 95 120.8 1 25.5 Sioot Ectension 1 104 89 96 76 83 12.0 t 1.6 (m d-l) 2 — 52" 43“ 42* 42 9.0 1: 2.5 3 — 23* 15* 12* 2* 9.9 1 2.3 4 - 2* 4* 0* 0* 8.4 a 2.0 z Ebcpreseed as percent of control mean. 7 14 day cycle consisted of 2 day flooding treatment fol lowed by 12 day recovery period. X Significance of difference between control and flooded treatments within each cycle at each date indicated at 5% (*) or 1% (**) level. otherwise nonsignificant. 1“ Test. 39 002 assimilation of flooded trees fell significantly below controls only on day 2 of the second and third cycles. Effects on stomatal conductance were similar: flooded trees dropped significantly below controls durirg cycle 2 from day 2 to 10 and again during cycle 3 on day 2. Invariably. both parameters returned to ca. control levels by the end of each 14 day cycle. During cycle 1. shoot extension of flooded trees initially declined but returned near to control levels by the end of the 12 recovery period. Daring cycles 2 and 3. however. shoot extension declined steadily and eventually dropped to zero by the end of cycle 4. Chlorophyll content of flooded trees generally declined throughout the experiment. becoming significantly different from control trees midway through cycle 3 and again from the midpoint of cycle 4 to the end of the experiment (Table 5) . Flooding effects on final component dry weights. percent defoliation and percent root system rotted are shown in Table 6. Flooding treatments produced a significant reduction in total leaf dry weight (dw) and non-significant reductions in stem dw ard total dw. Root dw was greater for flooded trees than controls. though not significantly. Swot/root ratio for controls was more than twice that for flooded trees. though difference was not significant. At end of the experiment flooded trees had suffered slightly more leaf abscission and root rot than controls. though neither difference was significant. All Phfigmthorg cultures were negative (data not shown). Mriment 5:_ % Measurements. Oxygen diffusion rates during 1- 10 days of soi flooding are shown in Figure 7. ODR falls below 0.3 micrograms 02 cm‘2 min“1 within minutes of floodirg. eventually falling Table 5. Effects of repeated short term flooding on total leaf chlorophyllz of sour cherry trees (Montmorency/Mahaleb). Mean Control cycler Day 0 Day 7 Day 14 Content ggggdmzl 1 109.0 103.1 99.6 6.60 :I: 0.82 2 - 101.4 90.6+X 6.47 :l: 1.79 3 - 81.7'" 85.1*‘ 8.25 :I: 0.98 4 - 74.0 66.4 8.19 :I: 1.60 z mpressed as 25 of control. Y 14 day cycle consisted of 2 day flooding treatment fol lowed by 12 day recovery period. ' X Significance of difference between control and flooded treatment within each cycle at each date indicated at 10% (+) level. otherwise not significantly different from control. F Test. 41 Table 6. Effects of repeated short term floodirg on final component dry weights (gm). shoot/root ratio (S/R). percent defoliation (DEF) and percent root rot (ROI) of sour cherry trees (Montmorency/Mahaleb). Treatment Leaf Stem Root Total SLR 8 f 8 t Control 15.7az 16.1 33.5 65.4 1.00 3.9 3.4 Flooded 9.3b 10.2 42.0 61.5 0.46 5.5 5.4 2 Values in same column fol lowed by different letter significantly different at 5% level. otherwise nonsignificant. F Test. Figure 7. Effect of 1 or 10 days of flooding on oxygen diffusion rate (ODR) of containerized sour cherry trees (Mont/Mahaleb). Flooding relieved at times indicated by filled triangles. Each point represents man of 3 trees per sampling time (5 determinations per tree). FIGURE7 m_. ‘0 0.? 4 F @2500: mm: .2 was < I 9- It.‘ 0 _ 3 < o .‘B u .. 000.: had or 4. .4 QOOJL > pear > apple > plum > cherry > apricot - peach - almond. Within a given species a considerable range of tolerance can often be found among available rootstocks. In a survey of apple rootstocks. Remy and Bidabe (1962) found Northern Spy to be extremely sensitive to waterlogging: M2. and M104 very sensitive: M9. and M26 moderately sensitive and M7 fairly resistant. The two most cannon cherry rootstocks. seedlings of Pm__n;l§ mahaleb L. and & m L. (Mazzard). were found by Saunier (1966) to be extremely sensitive to waterlogging. Gruppe (1982) reported that Giessen clones (GC) 172/9 (E_._ fruticosa x M) and GC 173/9 (E._ fruticosa x cerasus) to be more tolerant than Colt (L m x- geudocerasus) or Mazzard F12/1 which in turn were more tolerant than Mahaleb .SL64. Observatiors of field performance over the years have generally noted L cerasus cv. Stockton Morello to be comiderably more 59 tolerant to soil flooding than Mazzard. and Mazzard.to be only slightly more tolerant to excess soil moisture than Mahaleb (Coe. 1945; Day 1951; Hutchinson. 1969) . Recently. a number of relatively new rootstocks have been subjected to limited commercial trials. i.e. MxM clones (presumed natural hybrids of E; mahaleb and 2; gngm). 2; cerasus cv. Montmorency and Colt. Neither these nor new advanced.releases from breeding programs have been evaluated for tolerance to waterlogging. The purpose of this research was to evaluate the relative flooding tolerance of a number of rootstocks (Table 1.) under controlled conditions. MATERIALS AND METHODS On July 24. 1985. 96 maiden. tart cherry trees. (8 each of Montmorency on 12 different rootstocks) were cut back to a single unbranched stem ca. 50 cm tall and planted in 7 liter plastic containers filled with a steam sterilized soil mix (ca. 50% sandy loam. 30% sphagnum peat and 20% sand v/v). Trees were ca. 1.3 cm caliper (measured ca. 2.5 cm above graft union) and a mean fresh weight of 156 gm (after pruning). Plants were set in wooden racks (ca. 60 cm off floor) in an unshaded greenhouse at the Pesticide Research Center. MSU. Racks were then covered with aluminum foil to prevent direct solar heating of the containers. Three or four unbranched shoots were allowed to grow on each plant (all other growing points were removed as they appeared). Plants were watered regularly with a soluble fertilizer (Peters. 20—20-20 NPK) diluted to 200 ppm N until the start of flooding treatments. Pests and diseases were controlled as needed according to commercial recommendations (Mich. Ext. Bul. E154. Fruit Pesticide Handbook). 60 On August 12th. half the trees of each rootstock combination were flooded by placing each tree container in an 11 liter container lined with a plastic bag and filled with tap water adequate to cover the soil surface. Flooding was relieved 5 days later by allowing pots to first gravity drain for ca. 1 hour. then a vacuum pump was attached via rubber hose and a collection flask to a 2.4 cm diameter aquarium aerator that had been buried in the bottom center of each pot at planting. The pump was activated for ca. 10 minutes (typically generating a vacuum of 25-30 KPa in collection flask) which allowed.the collection of an additional 300—500 ml of water and imposed a soil moisture tension of ca. 2 KPa (as measured with a Soil Moisture Equipment Corp. "Quick Draw" soil moisture probe. Model 2900?). During 5 day flooding treatment. all controls were watered to saturation as needed with tap water (ca. 1 liter) as were all treatments during 10 day recovery period which followed. Mean minimum/maximum air temperature during the treatment and recovery period was 15.6:2.3/28.0¢3.7 °C. Leaf gas exchange data was collected periodically from a randomly selected. fully expanded midrshoot leaf on the uppermost shoot of each tree. Measurements were made with Analytical Development Co. (Hoddeston. England) portable photosynthesis equipment consisting of an Infrared 002 Gas Analyzer (LCA-2). Regulated Air supply (ASU) and a Parkinson Leaf Chamber (PLC-B). Measurements were made between 1200 and 1400 hours: cuvette temperature range of ca. 25-30 0C and 002 concentration (ca. 350 micromol mol‘l). Supplemental light was provided as needed with a 400 W high pressure sodium vapor lamp to bring light levels above 1000 micromols m"2 5‘1 PP? during measurements. This level of light has been shown to be above light saturation for sour cherry 61 Table 1. Sour cherry rootstocksz utilized in study. Seedling Stocks: Virus Free Status Prunus mahaleb (Mahaleb) presumed P. avium (Mazzard) presumed Clonal Stocks: P. cerasus (Montmorency) certified P. avitun x pseudocerasus (Colt) certified P. avium x mahaleb (MxM2, 39 and 60)? presumed P. cerasus x canescens (148/1 and 148/9)X certified P. canescers x cerasus (195/1 and 195/2)X certified P. canescers x avium (195/4)x certified z Supplied by Hilltop Corp. . Hartford. MI. All grafted with P_. cerasus cv . Montmorency except own—rooted Montmorency. Y Presumed natural hybrids X Advanced selections from Giessen. W. Germany Breeding Program 62 (Sams and Flore. 1982) . Carbon assimilation and stomatal conductance values were calculated as previously described (Moon and Flore. 1986) with the exception that leaf vapor pressure was estimated in the manner described by Richards (1971) and that sample and ambient vapor pressures were calculated as: P " (RH/100) * p3. where p equals sample or ambient vapor pressure (with or without leaf within cuvette. respectively) at cuvette temperature. p5 equals leaf vapor pressure at cuvette temperature (presumed to equal saturatirg vapor pressure of water) and RH is the appropriate relative humidity measured within the cuvette. Sioot length was measured on the uppermost shoot of each tree from point of origin on trunk to midsapex. Leaf area was estimated in the manner described by Kappes (1985): Area - length * width * 0.65. where length is measured along midrib of expanding leaf from base of blade to tip. width is measured at the widest part of the blade and 0.65 is a correction factor for sour cherry derived by Kappes (r2-0.998"). A single leaf (between 20 and 60 mm length) was measured per plant. On August 29th. 10 days after relief of flooding treatments. the experiment was concluded. Trees were then separated at the graft union and partitioned into root system. trurk. new shoots and leaves. Materials were oven dried for at least 1 week at 90 °C. A randomized complete block design was used (blocked on basis of initial fresh weight) with 4 replications of each treatment. Rootstock effects on growth and leaf gas exchange characteristics were determined by performing an analysis of variance (ANOVA) on data collected from non 63 flooded trees (data combined for each tree over all sampling dates during treatment/recovery period). An ANOMA was also performed for flooding treatment effects within each rootstock. 'In order to facilitate the comparison of the various rootstocks. in spite of obvious inherent differences in growth rates. data was standardized by expressing each flooded rootstock's performance as a percentage of it's control within each block. i.e. all controls were set to 100%. An ANOVA was then performed for rootstock effect. Statistical analysis was performed with MSTAT Microcomputer Statistical Program (Michigan State University. East Lansing. MI). Regression analyses and'figures were prepared with Plotit Interactive Graphics and Statistics Package (Scientific Programming Enterprises. Haslett. MI). we Rootstock effects 9g non flooded trees. Rootstock had a marked effect on mean net 002 assimilation (A). stomatal conductance to 002 (gl) and shoot extension rate of Montmorency scions during this experiment (Table 2). Trees on cc 195/2 and Colt displayed the highest A. while trees on GC 148/9 and 148/1 displayed the lowest A. Pattern was similar for g1 and shoot extension. There was no apparent correlation between A. 91 or shoot extension with relative dwarfing ability of the various rootstocks; all r2<.002. ns. (data not shown). Floodigg effects. Nilting occurred on recently emerged leaves of flooded trees within 2—3 days after imposition of flooding. Symptoms often disappeared overnight and recurred whenever conditions likely to promote high vapor pressure deficits prevailed. New leaves on flooded trees were typically smaller and cupped with a dull finish compared to .umou m5 493 man we £8,333 xqucooflwcuwm no: .332 each .3 603023 5300 each 5 mogg k .29: Sad soé 8:28 a as due one 98 one 9; 8 an 2x: on #3 Be 98 one 8.3 8 accuse: 3 ed on use as 8d 8 ass on dd 3 #8 on 86 8 6:98.58: one v.2 one «.8 one 86 me 8 2x: a 93 a 98 no 8.: ma :8 o as u ”an a and 2: <9: 3 9a 3 9% and was 02 m xx: at odd one has. one 8.2 o8 Hanna: so was at 9.3. a 8.: o: ~82 on v.0 B 98 one mod on HRS at 92 use has has a; o2 e32 sue ms :t... as Sena. film «also? and 38m gamma: co 8 soosmsSm c2203 s86 3 s Nona cicadas .823 5608355093 323 Ammo: 380355 803m 6:985:02 no 33 83:0be pooch Be :9 N_8 B 023388 sBasBm .2: 832388 N8 so: :8... co Beebe xSsBSm .m 033. 65 nonflooded controls. At end of 10'day recovery period. visible chlorosis was evident in basal leaves of flooded trees. although very little leaf abscission had occurred by that time. Flooded trees of Montmorency on MxM 2. MxM 39 and Giessen clone (GC) 195/2 and 196/4 produced significantly less total new stem and leaf dw when compared to their respective controls (Table 3). Total. root and trunk dw was generally higher for control trees compared with their flooded counterparts although differences were not significant for any of the rootstocks tested (Table 4). Shoot extension of flooded treatments slowed markedly within a few days after imposition of flooding (Table 5). At end of 5 day flooding treatment. shoot extension rates of most rootstocks had fallen significantly below that of their respective controls. Ten days later (after relief of flooding treatments). only those trees on MxM 2. SC 148/1. Mazzard and MxM 60 were growing at rates not significantly different from their respective controls. Leaf expansion rates of flooded treatments slowed gradually after imposition of flooding (Table 6). By the end of the 5 day flooding treatment. only trees on Mahaleb and MxM 60 had fallen significantly below that of their respective controls. However. ten days later (after relief of flooding treatments). only those trees on GC 148/9. MxM 2. Mahaleb. MxM 60 and GC 195/1 displayed leaf expansion rates not significantly different from their respective controls. Stomatal conductance to 002 and net 002 assimilation of flooded trees generally declined slowly over the first 2-3 days of flooding and then dropped rapidly on most rootstocks (Tables 7 and 8. respectively). At end of 10 day recovery period. flooding had significantly reduced g1 66 Table 3. Flooding effects on total new shoot and leaf dry weight (at end of treatment/recovery period) of Montmorency on various rootstocks. Shoot dw (g) Leaf dw (g) as of 5!; of Rootstock Control Flooded Control Control Flooded Control Mahaleb 1.73 1.68 97 5.75 5.31 92 Mazzard 2.50 1.38 55 6.34 4.30 68 Montmorency 1.39 1.22 88 4.49 3.96 88 Colt 3.06 1.68 55 8.46 6.24 74 MxM 2 1.32 0.74 56*2 3.94 2.67 68* MxM 39 1.67 0.83 50* 4.82 2.72 56* MxM 60 2.76 1.29 47 6.87 3.91 57 148/1 1.20 0.86 72 4.18 3.51 84 148/9 1 .41 1. 10 78 4 .43 3. 96 89 195/1 1.42 1.10 70 4.43 3.96 73 195/2 2.10 1.02 49“ 5.65 3.66 65* 196/4 1.71 0.86 50“ 5.67 3.42 60** 2 Significance of difference between control and flooded treatments within each rootstock and component dw indicated at the 5% (*) or 1% (**) levels. otherwise nonsignificant. F test. 67 Table 4. Flooding effects on root. trunk and totalz dry weight of sour cherry trees (Montmorency grafted onto various rootstocks). Root dw (g) m dw (a) Total dw (g) Rootstock Control Flooded Control Flooded Control Flooded Mahaleb 65.7 62.8 19.3 17.8 92.5 87.5 Mazzard 51.4 48.3 22.5 22.8 82.7 76.8 Montmorency 50.8 51.4 21.2 22.1 77.8 78.7 Colt 62.5 61.7 28.3 18.0 102.4 87.6 MxM 2 35.1 51.2 14.2 20.3 54.6 74.9 MxM 39 36.7 34.5 19.9 15.4 63.1 53.5 MxM 60 91.6 83.4 38.9 49.6 140.2 138.3 148/1 50.1 52.7 41.1 35.8 96.5 92.8 148/9 30.5 27.2 15.1 17.4 52.1 49.6 .195/1 33.5 29.7 14.3 15.4 54.1 49.6 195/2 41.5 43.9 19.5 18.1 68.8 66.7 196/4 54.6 50.7 16.8 22.8 78.7 77.7 2 Calculated as total-root+trunk+shoot+leaf .0000 60 5503390000: 00030050 .293 3;; x0 0:0 TL an 00 00000065 0000000090 :000 :05; 00:05005 000003 0:00 093:8 :0053 00:00:00 no 00:03:55 2 #:0500900 00 9 0:0 00.0.m.0.m.m.0.o x00 :0 :000 000.0 0 "00:30:00.0. 00 no :00: x .00 x00 :0 0000:0506. 0:03000098 an .000 no 05:05 :0 00620.0 .0 .000 “0 0:30.00 :0 0600000: 050600060 .6 .0000 :000 :0 0000 0900:00 :00... no 06 00 0.00: 00000.03 N 00.0 a 00.0 ..60 .60 .00 60 00 06 0\060 00.6 0 00.0 ..0 ..00 60 66 00 06 0\060 00.6 a 00.6 .0 60 .00 60 000 00 0\060 00.6 0 06.6 .00 00 00 00 00 000 6\000 60.6 0 66.6 06 00 60 600 600 000 0\000 00.6 0 00.0 00 ..00 .00 00 60 60 60 2x: 00.6 a 00.0 ..6 .00 ..00 .60 .00 660 60 xx: 00.6 0 66.6 60 60 00 00 60 660 0 2x: 00.6 0 60.0 .60 .00 ..00 60 00.. 00 0066 00.6 0 06.6 ..00 ..00 .00 00 060 000 xocotosseoz 60.6 0 60.0 60 ..00 ..60 60 00 000 606006: 00.6 0 06.0 ..00 00 .00 .6.06 000 600 060626: 0600 >66\s6. 00 0 0 0 0 0 066606660 .x0660666 06 000m :00: 43500070 u0o 0.0000 (000.00 0.03 06000000090 0:00.000, :0 9.0000 5:305:02 no 00000 80900600 000:0 :0 000030 9800C .m 030.0. 69 .0000.0 .0666000660066: 600306606 .000>60 A..6 00 0:0 0.. 00 06 060060060 x66000660 0660 :0200: 00:0:00000 0000000 0:0 0000:00 :003000 00:0000000 no 00:00505:owm.0 .0:0a0000x0 00 9 0:0 m.v.m.m.0.o :00 :0 :000 000.0 0 "00:0:000000: mm .000 :00: x .00 x00 :0 0000:03000 0:050000X0 “m .000 00 05:30 :0 00520.0 .0 :00 00 05000.00 :0 000005 05000060 x .0000 :000 :0 0000 0000:00 :00: 00 w 00 0.00: 0000006x0 .00060 .006600 ...066..006 00.6.00002.c06600u000< 00 0006066000_0 mm. mm. om. 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HHHQ—IOOHOHOOO fl-fl « u «‘0 fl!“ 0 a «'0 ONHO‘IDBOIDMOID‘O 0000000%9090 0505630505050a0104040a0a 0000 600\~a66 .x0000cou 00 000: :00: .00 00 .60 00 00 000 .00 00 00 66 00 66 00 06 00 00 60 00 66 00 00 660 660 000 ..6 00 00 00 00 000 60 ..60 .00 00 60 06 ..0 60 . 00 60 00 00 00 00 00 66 00 00 .00 60 00 00 60. 60 .60 60 ..00 .60 60 060 ..00 00 00 00 00 .00 00 .00 _..00 06 06 66 00 0 0 0 0 0 ¢\oma m\moH 0\mma o\wva 0\©¢0 cm :x: on :x: m :x: 0000 >0:00050:0: .000NN0: £00020: x00000oom .0x00000000 000000> :0 0:500 6:000:08: no h0000.0 000590900 00000 :0 00000.00 05000060 .0 030.0. 70 .0000 . .m .0:00000:000:0: 005300c00 .000>00 A000 *0 0:0 :00 km 00 0000000cw x00000oo0 2000 :0c00: 00:0:00000 0000000 0:0 0000:00 :00300: 00:0000000 mo 00:00000:mwm.= .0:0:000QX0 00 m0 0:0 00.0.m.v.m.m.0.o :00 :0 :000 0000 v u00:0:003000: on 00 :00:.x .m0 .000. :0 000055000 0:05.898 0m :00 00 0:0:0>0 :0 00>00000 .0 >00 00 0:0:0>0 :0 00000:0 0:00000m.a .0000 :000 :0 000.0 0000:00 :00: 00 00 00 000: 00000096: N o.m0 « 0.00 .00 N0 0m 00 no on V\000 m.mm a 0.00 .m0 m0 oo .05 mm 00 m\mma 0.60 0 0.60 ..00 00 .00 60 66 60 0\060 m.om H 0.mo .mm .00 00 mm mm mod m\000 n.00 « 0.mm mo .00 mn 00 mu no 0\mVH m.om a m.ao .0m .0m om ma 000 am om :x: o.mm « o.m0 .00 mm oo 0.00 on N0 mm :x: n.0N H m.mo m0 0.00 000 «on mm 000 m :x: 0.00 0 0.00 «on 00m .00 no: mm 000 0000 de ”0 0.0.0 90 00 mm mm cm. 000 0000000050000: m.om « n.mh «.00 mm 00 0N0 000 000 000000: m.mm « 0.00 .00 .zaom 00 om am 0:0 000020: 0000 010 ml: 00::. m0 n v m m 0 x00000oom .x0m 0000:00 :00: .Aucw0oo0u no 00000 00000 0>0D .000000 00000 0:00 on 0:0 0:000000 00 0:00 0>00 0:0030 0x00000000 030000> :o 0:0000 :0:000:0:o: no 00>000 :0 .0mv_000:000:0:00 0000:000 no :0000000m .0 00:09 71 .0000 0 .0:00000:000:0: 000300000 .0_0>00 A..0 *0 0:0 0.. *0 00 0000000:0 x00000000 0000 c0200: 00:0:00000 0000000 0:0 0000:00 :00300: 00:0000000 00 00:00000:00m_; .0:0a0000X0 00 00 0:0 00.0.0.0.m.m.0.o 000 :o :000 0000 0 "00:000030003 0m 00 :00:Lx .00 000 co 0000:0500 0:000000X0 00 000 00 0:0:0>0 :0 00>00000 .o 000 00 0:0:0>0 :0 0000000 0:000000.a .0000 :000 :0 0000 0000:00 :00: 00 w 00 000: 0000000xm.N 000 H H t§<§r§cvcvcncficfit0cvcutu H «40 H-fl‘fl‘fi “'0 fl 0‘“ 0 00300000708 V‘NOQDOCDQ‘CDID DOV o§c§a§~30§oso§aaaioxe«o§ kONNOs [\ Nl\[\ 000% 010 ml: 003000050 .x< 0000:00 :00: ..00 ..00 .00 00 00 00 .00 .0m .00 cm 00 00 ..00 ..0m ..00 00 00 00 .00 .00 00 000 00 000 .00 .00 .00 00 N0 00 ..mm ..00 00 00 000 00 .00 ..00 ..00 00 00 00 00 av av .00 00 00 00 ..o~ ..00 00 ..mm ooH .00 ..0v 00 00 000 000 ..00 .mm 00 000 000 000 00 .00 .:.00 00 00 00 00 0 v 0 m 0 .0uc0uo000.0o 00000 00000 0000 v\000 «\000 0\000 0\0¢0 0\0¢0 00 :x: 0m :x: m :x: 0000 00:000:0:0: 000NN0: 000000: xoo000oom .000000 00000 0000 00 0:0 0:00oo00 0o 0000 0>00 000020 xuo000oo0 050000> :o 00:00oauco: no 00>000 :0 A¢Q.N:000000a0000 N00 00: no :o0uoa0om .m.00:00 72 of Montmorency on all rootstocks except MxM 2. GC 148/1 and Montmorency: while A was significantly depressed on all rootstocks except MxM 2. Mahaleb and Colt. Net C02 assimilation was correlated with g1 throughout experiment for flooded and control trees (Figure 1), r2-o.862** and 0.515". respectively (slopes significantly different at 1% level. t test). Net 002 assimilation was also correlated with shoot extension rate (Figure 2). r2-0.59o** and 0.131" for flooded and control trees. respectively (slopes significantly different at 1% level. t test). When A and net shoot extension data was analyzed as percent of control response several rootstocks stood out (Table 9). IFlooded trees of Montmorency on MxM 2 fixed 002 significantly more like their control counterparts than did trees on MXM 39. GC 195/1 or GC 196/4. Net shoot extension (during the treatment/recovery period) of flooded trees on HRH 2 and.GC 148/1 was significantly more like that of their control counterparts than it was for flooded trees on MxM 39. Discussion very few reports of rootstock effects on photosynthetic rates of scion leaves have appeared in the literature. Ferree and Harden.(1971) observed.higher A in 'Delicious' strains grafted to seedling apple rootstocks vs dwarfing. HOwever. Marro and Cerghini (1976) observed higher A of 'Richared Delicious' scions grafted on M9 vs seedling. and Titova and Shiskanu (1976) reported higher rates in leaves of dwarfing apple rootstocks vs those of seedlings. In contrast. Harden and Ferree (1979) reported no difference in A of 'Delicious' trees on seedling and dwarfing rootstocks. In this study we observed significant differences 73 Figure 1. Relationship between A and g1 of flooded and nonflooded sour cherry trees (Montmorency on 12 different rootstocks) . Each point represents mean of 4 replications of each rootstock for each flooding treatment and date of sampling. 74 FIGURE 1 :Im NIE BEEV :w ONF OOF Om Om 9V ON. 0 mesa... a: +_.... . a. .0 m5. ns. 2.5 o o yeah... . V + \ . \./ ++ 12? Ifl o . w . .01 1m w _ s Z fiNF 8_ s2 . (u. . .m: Figure 2. Relationship between A and shoot extension rate of flooded and nonf looded sour cherry trees (Montmorency on 12 different rootstocks). Each point represents mean of 4 replications of each rootstock for each flooding treatment and date of sampling. 76 Flow-3 2 31s .25 cm. 50% pm my mu m .w o 0%.”... 5.: T. H e .o .n u . + ++ i z: a. v.10 o o + f. Thins... . 0 it» 1.? w+ +Ho + *+ 1 0 mm. o . .. . m 9 %oo does 2.. . m 00 0 +08 .7... +0 Tm oo oeaoow...+.o+& . 88 .+. o&% .. ns....so... % . o . . .. o a: o soodms . O O %0u0++rfi.++ 1NF 0 .0 .s .. 0 e. i + T. . nmw (L-S Z_UJ low’n’) v Table 9. Rootstock effectsz'on net assimilation 10 days after relief of flooding and net shoot extension during 15 day flooding/recovery period. Net 002 Net Shoot Assimilation Extension Rootstock (% of Control) (8 of Control) MxM 2 75 a7" 60 a Mahaleb 68 ab 55 ab Colt 62 abc 41 abc 148/1 52 abod 60 a Mazzard 49 abcd 49 ab Montmorency 33 abcd 36 abc MxM 60 27 bed 34 abc 148/9 23 od 35 abc 195/2 21 ad 31 abc 195/1 17 d 33 abc 196/4 15 d 31 abc MxM 39 15 d 21 bc 2 ANOVA performed on flooded treatment response expressed as x of respective control within each block. y'values in same column followed by same letter not significantly different at the 5% level. DMR test. 78 in A of 'Montmorency' scions grafted onto a number of cherry rootstocks differing substantially in dwarfing ability. However. there was no apparent correlation between A and.reported relative dwarfing ability of these rootstocks. Lack of any correlation between shoot extension rates and relative tree size at maturity is not surprising in light of reports by Hutchinson and Upshall (1964) and Westwood (1978) that young cherry trees on Mahaleb often grow more vigorously than on Mazzard even though final tree size is usually larger on.Mazzard. Additionally. in rootstock tests in Washington (Webster. 1980) and Michigan (Perry. unpublished) trees on Colt have grown as vigorously as trees on other rootstocks generally regarded as more vigorous than Cblt. ENddently growth rate of each scion/rootstock combination adjusts differentially as trees mature and crOpping begins. Overall visual impressions of tree response to flooding were similar to those reported.by other researchers working with temperate fruit species (Andersen et al. 1984a; Childers and White. 1942 and 1950: crane and Davies. 1988; Heinicke. 1932. Rom and Brown. 1979). Wilting symptoms suggest an increased internal water deficit which could be caused by a reduction in water conduction by the root system. One possible explanation is loss of root surface due to attack by soil pathogens encouraged by soil flooding. i.e. Phytophthora root rot. We did.not test for presence of Phytophthora spp; in this experiment. however. in a similar study in which sour cherry trees (Montmorency/Mahaleb) were subjected to repeated short term flooding we were unable to isolate Phytophthora from any plot (Beckman. in preparation). 79 Alternatively. the inability of the root system to supply water to the shoot might be due to a decrease in root hydraulic conductivity after imposition of anaerobic conditions. Although not measured in this experiment. we have verified that oxygen diffusion rates (OUR) typically fall below 0.2 within a few hours after imposition of soil flooding in the soil mix used in this experiment. ODR rises to nearly 0.4 immediately following drainage and pumping: ultimately returning to control levels (ca. 0.6) within 2-3 days (Beckman. in preparation). Levels below 0.2 have been correlated with reduced.hydraulic conductivity and/or growth in pear and peach (Andersen et al. 1984a); blueberry (Crane and Davies, 1988); and apple (Olien. 1987). Although treatment/recovery period represented ca. 80% of total time period for shoot growth. reductions in total new Shoot and leaf dw due to flooding were small on most rootstocks. including Mahaleb. a rootstock generally regarded as very sensitive to flooding. Flooded trees on Mahaleb.displayed a significant reduction in shoot extension rate throughout most of the experimental period and one would expect a reduction in shoot and leaf dw as a consequence. Lack of a correlative reduction in shoot and leaf dw might be a result of variability in shoot growth rate within a tree. i.e. shoot extension rate was measured on only the uppermost shoot in each tree. and suggests the necessity of either training experimental trees to a single shoot or measuring shoot extension on all shoots. Shoot extension and leaf expansion data displayed essentially the same trends in response to flooding. However, significant differences detected in shoot extension did not always coincide with those detected in leaf expansion perhaps because leaf expansion was measured on a 80 lateral shoot rather than the uppermost shoot utilized for shoot extension and. thus. may reflect differential growth rates of the variohs plant parts. Higher correlation coefficient and steeper slope of the A vs g1 regression line for flooded vs control trees during this experiment suggests the possibility that stomatal closure limits photosynthesis during soil flooding. However. in other experiments we have estimated stomatal limitations from C02 response curve and found very similar limitations in.both control and flooded trees of Montmorency/Mahaleb throughout a five day flooding treatment (Beckman. in preparation). Perhaps this correlation indicates not so much a stomatal limitation to photosynthesis as a photosynthetic regulation of stomatal aperture. A number of possible mechanisms for this have been discussed by Parquhar and Sharkey (1982) and Smith and Ager (1987). We might speculate that the higher correlation and steeper slope of the A vs shoot extension regression line for flooded trees may be the result of different source-sink relationships in the two treatments. Although not measured in this experiment. we would expect distinctly root growth rates in the two treatments. Stolzy and Letey (1964) have demonstrated that root function ceases at 02 diffusion rates (ODR) below 0.3 micrograms 02 cm."2 min‘1 and that root death occurs at ODR's below 0.2; levels which we presume to have attained in this experiment (Beckman. in preparation) . Thus. if virtually all root growth has ceased in the flooded treatments then shoot growth becomes the primary sink for photosynthates. Conversely. in control trees. it seems reasonable to assume that both shoots and roots serve as important sinks for photosynthates. Therefore. one would expect a better correlation 81 between A and shoot growth in flooded trees where shoot growth represents a relatively better estimate of total sink strength than in control trees where we have not taken into account the possibly strong sink strength of the roots. Flooding tolerant woody species generally maintain growth and stomatal aperture during flooding better than intolerant species. This has been observed in Pimp; and Monia species (Andersen et al. 1984a); am; and Bicalyptus species (Pereira and Kozlowski. 1977): 915mg species (Phung and Knipling. 1976) and Pomlus deltoides (Regehr et al. 1975) . MxM 2 and GC 148/1 were the only rootstocks for which shoot extension rates did not fall significantly below their respective controls throughout the course of this experiment . No rootstock included in this study maintained both stomatal conductance ard net 002 assimilation near control levels at all sample dates. However. differences were statistically significant on fewer occasions for trees on MxM 2. GC 148/1 and Montmorency. During the growing season. flooding is likely to be of relatively short duration in most orchards since growers will typically avoid extremely poorly drained sites for cherries. Therefore. ability to recover from temporary waterlogging should be a more useful criteria for selecting superior rootstocks than ability to survive long periods of floodirg. With this consideration in mind and the data Stmarized in Table 9 we have tentatively ranked the twelve rootstocks included in this study for relative flooding tolerance (Table 10). We have some limited field experience with MxM 2 indicating that it may provide superior performance compared to Mahaleb or Mazzard on sites with heavy soils prone to transient soil flooding (Perry. unpublished). 82 Table 10. Relative flooding tolerance of various containerized.sour cherry rootstocks under greenhouse conditions. fi Moderately Tblerant Sensitive very Sensitive MxM 2 Mahaleb 196/4 148/1 MxM 39 Colt Mazzmni Mbntmorency MxM 60 148/9 195/1 195/2 83 we must caution. however. that in this ranking considerable overlap occurs from one class to the next. Moreover. the range of tolerance exhibited in these rootstocks does not appear to be nearly as wide as that observed in other temperate fruit species. most notably pears in which some rootstock species can maintain shoot growth and stomatal conductance near control levels for up to 30 days of flooding (Andersen et al. 1984a and 1984b). Additionally. our rankings fail to differentiate between Mahaleb and Mazzard in flooding tolerance which is contrary to observations of field performance through the years (C06. 1945: Day. 1951: Hutchinson. 1969). This might be due to the age of the trees utilized in this study. Older trees generally tolerant flooding much better than young trees of the same species (KOzlowski. 1984) suggesting that differences between these species may be too small at one year of age to be detected in our experiment. Alternatively. field grown trees may have available to them mechanisms for tolerating or "escaping" flooding that cannot be expressed when the entire root system is flooded as in this experiment. Mazzard's root system is typically more horizontal and spreading than Mahaleb's (Coe. 1945; Day. 1951). Therefore. a perched water would typically inundate a relatively smaller portion of a Mazzard root system than a deep rooted Mahaleb root system. Work by Roth and Gruppe (1985) and ourselves (Beckman. unpublished) in which the entire rootzone was never completelyflooded (or flooded for only a part of each day). has demonstrated that cherry rootstocks are considerably more tolerant in terms of both growth and survival than when subjected to treatments like those used in this experiment. This response may be due to some escape mechanism. i.e. compensatory root growth. or perhaps increased water 84 conduction. growth regulator production or detoxification of anaerobic products by the nonflooded portion of the plant's root system. Some support for compensatory root growth as an escape mechanism can be found in the literature. In an experiment in which half of a cherry tree's root system was continuously flooded and the other half flooded only 12 hours each day Roth and Gruppe (1985) observed a marked increase in root growth in the intermittently flooded portion of the root system compared to nonflooded controls. At the same time. root growth dropped to near zero in the continuously flooded portion of the root system. Following relief of the flooding regime. root growth of the entire root system increased markedly compared to controls. This response was more pronounced in Mazzard F12/1 and Colt than Mahaleb SL64. especially when flooding regime was imposed late in the season. Mendoga (1987) observed a differential response in root and shoot growth of Montmorency on seedling Mazzard.and Mahaleb rootstocks subjected to an interposed high bulk density soil layer in a containerized study. Both rootstocks produced similar shoot dw and displayed a similar rooting pattern when the interposed layer was the same bulk density as the remaining soil volume (ca. 1.0 gm/cc). However. when a high bulk density layer (ca. 1.7 gm/cc) was interposed. the response of the two rootstocks was markedly different. Shoot dw was significantly reduced on both rootstocks. but markedly more so on.Mahaleb than Mazzard. The total number of roots was reduced by more than 50% on Mahaleb and by only 10% on.Mazzard. FUrthermore. ca. 10% of Mazzard's roots successfully penetrated the barrier layer while all of Mahaleb's were confined to the upper layer. In another study. Beckman (1984) demonstrated Mazzard's superiority over Mahaleb in regenerating roots 85 lost through root pruning. This effect was evident only during active shoot growth and disappeared at other times of the year. These observations indicate Mazzardfs advantages over Mahaleb in exploiting the available soil volume favorable for root growth when confronted with a soil stress and correlate well with observed field performance of these two rootstocks in heavy soils (Coe. 1945; Day. 1951; Hutchinson. 1969). This area is clearly deserving of more researdh. There appears to be no consistent relationship between flooding tolerance and parentage exhibited by the rootstocks examined in this survey. -For example. rootstocks with E; ggigm parentage. i.e. Mazzard. Colt. MxM clones and GC 196/4. are present in each of the four classifications even though 2; 92139 (Mazzard) is generally regarded as moderately tolerant of flooding. An analogous point can be made for those rootstocks with E; mahaleb or E; cerasus parentage. However. with the exception of GC 148/1. those rootstocks with E; canescens parentage. i.e. GC 148/8. 195/1. 195/2 and 196/4. generally fell into the bottom two rankings. which is in agreement with the observation by Gruppe (personal communication. cited in Perry. 1987) that hybrid rootstocks with E‘ canescens parentage are generally very sensitive to flooding. In summary. all rootstocks were affected negatively by the short flooding treatment utilized in this experiment. however. MxM 2 was generally the least sensitive and clearly superior to MxM 39 in most parameters. Due to its simplicity and the short time required to generate significant flooding effects. the methodology employed in this experiment may prove useful as an initial screen for flooding tolerance. 86 LITERATURE CITED Andersen. P.C.. P.B. Lombard and M.N. Westwood. 1984a. Leaf conductance. growth and survival of willow and deciduous fruit tree species under flooded soil conditions. J. Amer. Soc. Hort. Sci. 109:132-138. Andersen. P.C.. P.B. Lombard and M.N. Westwood. 1984b. Effect of root anaerobiosis on the water relations of several Eggs; species. Physiol. Plant. 62:245-252. Barden. J.A. and D.C. Ferree. 1979. Rootstock does not effect net photosynthesis. dark respiration. specific leaf weight. and transpiration of apple leaves. J. Amer. Soc. Hort. Sci. 104:526- 528. Beckman. T.G. 1984. Seasonal patterns of root growth potential of two containerized cherry rootstocks. L mahaleb L. and E_._ avium L. . cv. Mazzard. MS Thesis. Michigan State Univ.. E. Laming. MI. Childers. N.F. and D.G. White. 1950. Some physiological effects of excess soil moisture on Stayman Winesap apple trees. (hi0 Agric. E>3 405.200 0.0 auoood 0.0 3. 0 ><0 405.200 0.0 3000.: 0.0 (L-‘S Z_LU [oww) 76 105 Figure 4. Effects of 1—5 days of flooding on residual conductance to CD2 (gr) of sour cherry trees (Montmorency/Mahaleb). Data points are mans of 2 plants/time 1: ed. Significance of difference between 2 treatments at each time indicated at the 10% (+) or 5% (*) level. otherwise ns. t test. 106 FIGURE4 05 m2: m w— o I. N— 0" m b o .b I? b h b! b - TL (PL b L h o s s To“ .3 .3 .3 100 .00 r v .00 N >3 .8 . >3 .8 l-.. ...--o ....-J. .-...-l-o .8 . .8 e . .3 .3 I v e .00 .00 SE28 9.. 6528 9. .8 n >3 338.: e .e .8 o >3. 838.: e .. (L-S Z_UJ lowLu);'6 107 Figure 5. Effects of 1-5 days of flooding on intercellular (1)2 (Ci) of sour cherry trees (Montmorency/Mahaleb). Data points are means of 2 plants/time i sd. Significance of difference between 2 treatments at each time indicated at the 10% (+) or 5% (*) level. otherwise ns. t test. 108 mm 5 as as: . 0 ¢ 53 - 330.5 To. .5528 one ‘ n >o~ *a on» no UOHoUwocH mucoauoOMH .0000000 use dosucoo commune mucoseumwo no ooccowuficmfim .omfl acosucohu sea noes» N no one: N 50 00.0 w 00.0 0000.0 cocoorm nu ma no.0 « 0v.0 m0H0.0 0000000 00H 0 an 00.0 w 00.0 5000.0 0000000 0H m: 0H.0 « 00.0 NOH0.o Monacoo 00 v hm no.0 A 00.0 00H0.0 0000000 NH m: 00.0 A No.0 mmm0.0 mosucoo 50 0 mm 00.0 a 00.0 0HH0.0 oeuoofim 0H m: 00.0 A 0v.0 0nHo.o dosecoo me N 00 No.0 0 00.0 50H0.0 oouoofim 0H ea v0.0 A 00.0 00m0.0 aosucou ma H am and a. one 385. 888$ 50 um: no.0 w v¢.0 emm0.0 Hosucou n: 0 Read film was 005000030 1m mls moo 005000060 Ammm alsosmoo 0030 acosueots. ooogm x00 bosom cowucmceaspu om socofiofiuumnasuccso 00004. 033 2232 mad: . 322£§ocoto§8£ moot» xkueno soon 00 mucwoa cosponcoqsoo 0:000 oouaafiuno use A000 comuosfiames xuao .xUCOwaumo asucoso someones oeuosflume co mcflooodu mxoo mid no mucouum .H ofinoh 114 Figure 7. Stomatal conductance to 002 (gl) as a function of ambient 002 (Ca) in sour cherry trees (Montmorency/Mahaleb) after 2 and 5 days of flooding. Fitted Lines: Day 2, Control: g1 - 104.9 — (0.0565 x Ca). r2 - 0.52 Flooded: g1 - 99.4 - (0.0852 x Ca). r?- - 0.45 Day 5. Control: g1- 100.5 — (0.0832 x Ca). r2 - 0.54 Flooded: g1 = 57.3 - (0.0490 x Ca). r2 - 0.83 120‘ . . , 0 DAY 2 100- - 80- 60- 47‘ 40-. I . e U) (\l 20‘ O-o CONTROL |E O. .;. IFLOVODED 1 T ' l t 1 i I "' 120- 0 DAY 5 E O 0 O \§’100- 0. o _ d . O U3 80": O O o 0' 60- 404 20: O-o CONTROL 0 e-e FLOODED O ' 100' 200' 300' 400' 500' 600 CO (11mm moi—1) Figure 8. 116 Net 002 assimilation (A) as a function of ambient 002 (Ca) in sour cherry trees (Montmorency/Mahaleb) after 2 and 5 days of flooding. Dashed and solid curves. control and flooded treatments. respectively. Fitted curves: Day 2. Control: A - 35.9 — 38.0 x e(-0-0014 X Ca). r2 - 0.93 Flooded: A - 19.3 — 21.2 x e(-0-0024 X Ca). r2 - 0.87 Day 5. Control: A - 26.6 — 28 1 x e(-0-0015 X Ca). r2 - 0.97 Flooded: A - 0.0728 x Cam-07745) — 0.9164. r2 - 0.92 117 am 8 24.. e FLOODED DAY 20 l O CONTROL ‘T‘ E ‘0 244 e FLOODED DAY 5 E l O CONTROL :3 < O ' 1001200' 300' 400'500' 600 CO (umOl mOl—1) 118 of control plants was roughly linear throughout the range tested. while A of flooded plants was linear only up to ca. 250 micromol (1)2 mol‘l. On day 5 the situation was reversed. with control plants responding in a linear fashion only up to ca. 300 micromol 002 mol‘1 and flooded plants responding in a roughly linear fashion throughout the range tested. Sans and Flore (1982) observed a linear respome of A in sour cherry trees to increasing ambient C02 up to ca. 300 micromol 002 mol‘l. After 2 days. carbon assimilation of flooded plants was lower than controls at all ambient C02 concentrations greater than ca. 300 micromol mol‘l. After 5 days. carbon assimilation of flooded plants was lower than controls at all C02 concentrations greater than ca. 100 micromol mol‘l. Additionally. differences between controls and flooded trees were larger after 5 days compared to differences observed between the two treatments after 2 days of flooding. Estimated C02 compensation points (calculated from A/Ca regression curves) were lower for flooded plants on both dates (40.5 and 38.1 micromol not1 002 for control and flooded trees. respectively. on day 2 and 35.4 and 26.3 micromol mol -1 002 for controls and flooded trees. respectively. on day 5). probably as a reflection of increased dark respiration in flooded plants. Figure 9 shows the relationship between A and intercellular (D2 concentration (Ci) for flooded and control trees after 2 and 5 days flooding. Pattern is similar to that of A vs ambient (D2 concentration. Carbon assimilation of flooded plants was lower than controls at virtually all Ci on both days. However. differences were very small at low Ci on day 2. Differences between control and flooded trees were larger after 5 days of flooding than they were after only 2 days of flooding. Figure 9. 119 Net C02 assimilation rate (A) as a function of intercellular C02 (Ci) in sour cherry trees (Montmorency/Mahaleb) after 2 and 5 days of flooding. Dashed and solid curves. control and flooded treatments. respectively. Dotted vertical lines represent supply curves for infinite g1. Demand Curves: my 2' conch]: Flooded: Day 5. Control: Flooded: Supply CUrves: Boy 2. Control: Flooded: Day 5. Control: Flooded: - 19.8 - 34.4 x e(-0.0088 x Ci) ' 20.1 - 27.8 x e(-0.0057 x Ci) 28.7 x e(-0.0101 x Ci) 15,5 x e(-0.0077 x Ci) 3’3, 3’), II P*P* OUI thin ll 0.084 x (363 - Ci) 0.069 x (363 - Ci) 0. 0 072 x (348 - Ci) .040 x (348 - Ci) 393’ >35 II .r2-0.84 .r2-0.87 .r2-0.86 . r2 - 0.87 120 FIGURE9 O FLOODED CONTROL FLOODED 'DAY 5 CONTROL 0 (‘1! O4 2 lqldldiqllldi- . O 2 l—JJlIl-lflld 6 1 31m NIE 6239 < 2 1 8 4 Ci (limo! moi-1) 121 Estimates of stomatal limitations to A on day 2 were 24.8% and 32.52 for control and flooded trees. respectively. am on day 5 were 22.8% and 29.9%. respectively. The relative importance of stomatal limitations to A in flooded plants can be estimated by assuming that the flooded plants had stomatal limitations similar to controls and recalculating net assimilation rates at ambient 00; concentrations from the equations in Figure 9. Such an analysis shows that increased stomatal limitations in flooded plants account for 48% and 14% of the observed reductions in A at ambient 002 concentrations on days 2 and 5. respectively. Clearly increased stomatal limitations are a significant factor initially in reducing net 002 assimilation.rates in flooded plants but their importance declines as flooding continues. Recent contributions to models of leaf gas exchange (Farquhar and von Caemerer. 1982: Farquhar et al.. 1980: von Caemerer and Farquhar. 1981) have identified the low Ci portion of the A vs Ci curve (i.e. initial slope) as reflecting the relative activity/amount of ribulose bisphosphate carboxylase/oxygenase (Rubisco) in the leaf. and the high Ci region reflecting the relative ribulose bisphosphate (RuEP) regeneration capacity. Based on this model. it appears that flooding initially impairs the RuBP regeneration capacity of sour cherries and not its activity or amount. However. as flooding continues both the activity of Rubisco and the RuEP regeneration capacity are diminished. Initial resporse in flooded trees is similar to that observed by Bradford.(1983a) in tomato plants flooded for 1 day. According to the model (Farquhar and von Caemmerer. 1982: von Caemmerer and Farquhar. 1981) reductions in RuEP regeneration capacity may be due to limitations in photosynthetic electron transport. NADPH 5; 122 and ATP synthesis and the reductive pentose phosphate cycle. The decline in quantlml efficiency of flooded cherry trees. observed in Experiment 1. indicates some limitation in the light harvesting component of the leaf. This is probably not due to loss of chlorophyll. however. since we have previously observed no charge in chlorophyll content of cherry trees durirg short term flooding under greemouse conditions (Beckman et al.. in preparation). Bradford (1983a) suggested that reduced RuHD regeneration in flooded tomato plants might be due to depletion of Pi needed for Run-7 regeneration. possibly because of a buildup in sucrose and/or starch due to reduced sink activity. Reduced activity of Rubisco after prolorged floodirg might be related to alteratiors of plant growth regulators normally supplied by the root system. Burrows and Carr (1969) demonstrated that floodirg recbiced cytokinin export from the roots of flooded sunflowers. Cytokinins have been shown to retard leaf senescence and loss of protein. and maintain photosynthetic capacity (Adedipe et al. . 1971; Richmond and Lang. 1957). This suggests that reduced cytokinin export from the root system of sour cherry durirg soil floodirg could be the cause of a number of the symptoms typically observed in the canopy of sour cherries durirg soil floodirg. Bradford (1983b) demonstrated that cytokinin applications not only prevented stomatal closure in flooded tomato plants. but it also prevented much of the decline in photosynthetic capacity normally observed after imposition of floodirg. ABA and ethylene (or its precursor AOC) have often been shown to increase in plants subjected to soil floodirg and in some experiments they appear to be directly related to the symptoms observed (Bradford and Yang. 1980 and 1981: Hiron and Wright. 1973; Wadman—van Schravendijk 123 and van Andel. 1985 and 1986). Applications of ABA to unstressed plants can depress A. although effects are generally exercised through reductions in stomatal conductance (Bradford. 1983b: Dubbe et al.. 1978; Hiron and Wright. 1973). In contrast. Raschke (1982) reported non— stomatal limitation of A by ABA in a number of species. Ethylene. once thought to have no effect on either gs or A. has recently been shown to have both stomatal and non—stomatal effects on A (Govindarajan and Poovaiah. 1982: Pallas and Kays. 1982). Nevertheless. ability of ABA and ethylene to cause non—stomatal reductions in A appears to be species—specific (Pallas and Kaye. 1982: Raschke. 1982). Therefore. further research will be necessary to determine the role. if any. of these plant growth regulators in flooding stress of sour cherries. Response of A and g1 to varying VPD's in EXperiment 3 is similar for both control and flooded plants after 2 days. except at VPD's less than 1 kPa. where A of flooded plants was higher than that of controls (Figures 10 and 11. respectively) . After 5 days of flooding. both A and g] were lower in flooded trees than in controls at all VPD's tested. Davies and Flore (1986c) observed a similar drop in stomatal responsiveness to VPD in blueberries subjected to flooding. In summary. data indicates that flooding affects carbon assimilation of sour cherries in a number of ways. whose relative importance change as flooding persists. Loss of assimilative capacity and increased stomatal limitations seem to be of primary importance: initially the effeCt on assimilative capacity appears to be confined to RuBP regeneration capacity. As flooding continues. reductions in A due to stomatal limitations decline while reductions in A due to reduced Rubisco activity/amount appear. Figure 10 . 124 Effect of vapor pressure deficit (VPD) on net C02 assimilation (A) of sour cherry trees (Montmorency/Mahaleb) after 2 and 5 days of soil floodirg. 12- . O-O CONTROL e-e FLOODED A (,umol m"2 3‘1) 1 DAY 5 0 O 00 O O 800 O .' OO O 0' C . O O '0 C . O .'.Oe 1:5 ' 2:5 VPD (kPa) 3.5 126 Figm'e 11. Effect of vapor pressure deficit (VPD) on stomatal conductance to CD2 (g1) of sour cherry trees (Montmorency/Mahaleb) after 2 and 5 days of soil floodirg. ‘ O-o CONTROL DAY 2 - e-e FLOODED VPD (kPa) 3J5 128 LITERATURE CITED Adedipe. N.O.. L.A. Hunt and R.A. Fletcher. 1971. Effect of benzyladenine on photosynthesis. growth and senescence of the bean plant. Physiol. Plant. 25:151—153. Blackman. F.F. 1905. Optima and limitirg factors. Ann. bot. 19:281— 295. Radford. K.J. 1983a. Effects of soil floodirg on leaf gas excharge of tomato plants. Plant Physiol. 73:475—479. Redford. K.J. 1983b. Involvement of plant growth substances in the alteration of leaf gas exchange of flooded tomato plants. Plant Physiol. 73:480-483. Bradford. K.J. and T.C. Hsiao. 1982. Stomatal behavior and water relations of waterlogged tomato plants. Plant. Physiol. 70:1508— 1513. Redford. K.J. and S.F. Yang. 1981. Physiological responses of plants to waterlogging. HortScience 16:25—30. Redford. K.J. and S.F. Yarg. 1980. Xylem transport of 1- aminocyclopropane—l—carboxylic acid. an ethylene precursor. in waterlogged plants. Plant Physiol. 65:322—326. Burrows. W.J. and D.J. Carr. 1969. Effects of floodirg the root system of sunflower plants on cytokinin content in the xylem sap. Physiol. Plant. 22:1105-1112. Davies. F.S. and J.A. Flore. 1986a. Slort—term floodirg effects on gas exchange and quantum yield of rabbiteye blueberry (Vaccinium ashei Reade). Plant Physiol. 81:289—292. Davies. F.S. and J.A. Flore. 1986b. Floodirg. gas excharge and hydraulic root conductivity of highbush blueberry. Physiol. Plant. 67:545—551. Davies. F.S. and J.A. Flore. 1986c. Gas exchange and flooding stress of highbush and rabbiteye blueberries. J. Amer. Soc. Hort. Sci. 111:565—571. . Dubbe. D. R. G. D. Farquhar and K. Raschke. 1978. Effect of abscisic acid on the gain of the feedback loop involvirg carbon dioxide and stomata. Plant Physiol. 62. 413—417. Farquhar. G.D. and T.D. alarkey. 1982. Stomatal conductance and photosynthesis. Ann. Rev. Plant Physiol. 33:317-345. Farquhar. G.D. and S. von Caemmerer. 1982. Modelirg of photosynthetic response to environmental conditions. In: O.L. Large. P.S. Nobel. C.B. Osmond and H. Ziegler (eds). Physiological Ecology II. Encyclopedia of plant physiology. (NS). Vol 12B. Springer—Verlag. Berlin. pp 549-587. 129 Farquhar. G.D.. 8. von Caemmerer and J.A. Berry. 1980. A biochemical model of photosynthetic C02 assimilation in leaves of C3 species. Planta 149:78-90. Gaastra. P. 1959. Photosynthesis of crop plants as influenced by light. carbon dioxide. temperature and stomatal diffusion resistance. Meded. Landb. Hogesch. Wagenirgen 59:1—68. Goff. J.A. and s. Gratch. 1946. Trans. Amer. Soc. Heat and Vent. Erg. 52:95. Govindarajan. A.G. and B.W. Poovaiah. 1982. Effect of root zone carbon dioxide enrichment on ethylene inhibition of carbon assimilation in potato plants. Physiol. Plant. 55:465-469. Guy. R.D. and R.L. Wample. 1984. Stable carbon isotope ratios of flooded and unflooded sunflowers (Helianthus annuus). Can. J. bot. 62:1770-1774. Hiron. R.W. and S.T.C. Wright. 1973. The role of endogenous abscisic acid in the response of plants to stress. J. Exp. Bot. 24:769—781. Jackson. M.B.. K. Gales and D.J. Campbell. 1978. Effect of waterlogged soil conditiors on the production of ethylene and on water relationships in tomato plants. J. Exp. Bot. 29:183-193. Jones. H.G. 1973. Limiting factors in photosynthesis. New Phyto. 72:1089—1094. Kramer. P.J. and W.T. Jackson. 1954. Causes of injury to flooded tobacco plants. Plant Physiol. 29:241-245. Moldau. H. 1973. Effects of various water regimes on stomatal and mesophyll conductance of bean leaves . Photosynthetica 7: 1-7. Moon. J.W.. Jr. and J.A. Flore. 1986. A BASIC computer program for calculation of photosynthesis. stomatal conductance and related parameters in an open gas excharge system. Photo. Res. 7:269—279. Pallas. Jr.. J.E. and S.J. Kays. 1982. Inhibition of photosynthesis by ethylene—a stomatal effect. Plant Physiol. 70:598-601. Pereira. J.S. and T.T. Kozlowski. 1977. Variations among woody argiosperns in response to floodirg. Physiol. Plant. 41:184—192. Phung. H.T. and E.B. Kniplirg. 1976. Photosynthesis and trarspiration of citrus seedlings under flooded conditions. HortScience 11:131- 133. Raschke. K. 1982. Involvement of abscisic acid in the regulation of gas excharge: evidence and inconsistencies. In: P.F. Wareing (ed). Plant growth substances. Academic. London. pp 581-590. 130 Richmond. A. ard A. Larg. 1957. Effects of kinetin on protein content ard survival of detached Xanthium leaves. Science 125:650—651. Sams. C.B. and J.A. Flore. 1982. The influence of age. position and environmental variables on net photosynthetic rate of sour cherry leaves. J. Amer. Soc. Hort. Sci. 107:339—344. Smith. N.W. and P.L. Ager. 1988. Effects of soil flooding on leaf gas excharge of seedling pecan trees. HortScience 23:370—372. Targ. Z.C. and T.T. Kozlowski. 1982. Some physiological and morpholgical responses of Mcus W seedlings to floodirg. Can. J. For. Res. 12:196-202. von Caemmerer. S.. G.D. Farquhar. 1981. Some relationships between the biochemistry of photosynthesis and gas excharge of leaves. Planta 153:376-387. Wadmmvm Schravendijk. H. and O.M. van Andel. 1986.. The role of ethylene durirg flooding of Phaseolus vulgaris. Physiol. Plant. 66:257—264. Wadman—van Schravendi jk. H. and O.M. van Andel . 1985 . Interdependence of growth. water relations and abscisic acid level in Phaseolus vulgaris durirg waterlogging. Physiol Plant. 63:215—220. SUMRYANDCONCLUSIONS 131 132 Although cherry trees are rarely planted on uniformly poorly drained sites. significant numbers of trees within an orchard block may be subjected to the effects of soil floodirg due to the presence of locally restrictive soils commonly found in midwestern glacial soils. Researchers at MSU have observed that prematurely declining cherry trees in Michigan are typically situated in such soils. Research with a number of temperate fruit species has invariably found even short term floodirg to have significant deleterious effects on both long and short term productivity of an orchard. Moreover. both of the commonly utilized cherry rootstocks. Mahaleb and Mazzard seedl ings. have been consistently found to be extremely sensitive to soil floodirg in controlled tests: conclusions which are supported by many years of field observations. This study was undertaken to determine the effects of short and lorg term effects of soil floodirg on cherry trees. which. if any. of the available cherry rootstocks differed in their sensitivity to flooding and what were the physiological causes of plant injury durirg floodirg. Our observations on symptom dvelopment of Montmorency/Mahaleb durirg soil f loodirg were similar to those made by other researchers workirg with various flooding intolerant plant species. All gas exchange characteristics and growth parameters dropped rapidly fol lowirg imposition of floodirg. Wilting was observed during floodirg only when environmental conditiors were conducive. i.e. high temperature and low relative humidity. Stem water potential was observed to drop transiently in flooded plants durirg one experiment. Significant leaf chlorosis developed only durirg prolorged floodirg. i.e. lorger than 8 133 days. and then was slow to develop. However. significant leaf abscission was subsequently observed if trees were flooded for more than 2 days. Recovery of gas exchange rates was possible only if flooding stress was brief. i.e. 2-4 days. but required a recovery period 7-8 times the length of the flooding stress. Gas exchange rates appeared.normal during a subsequent growth cycle following dormancy. However. flooding stress as brief as 2 days brought shoot extension and leaf expansion to a permanent halt for that growth cycle and tended to reduce shoot growth during the subsequent growth cycle following dormancy. It was estimated that fifty percent of trees subjected to flooding for 6 days during active growth would subsequently die. as would all trees subjected to flooding for 16 or more days. Our results indicate that short term.flooding stress. i.e. 2-4 days. was survivable. albeit with profound reductions in current season's growth. On the other hand. long term flooding stress. i.e. 8 or more days. was usually fatal. These observations have profound implications for cherry growers since their profitability is a function of both consistent annual productivity and longevity of their orchard .blocks. In a survey of both standard and experimental rootstocks we found remarkably little variability in sensitivity to flooding. we were able to statistically separate very few rootstocks on the basis of parameters measured in the survey study. Nevertheless. MxM 2 appeared to be the most tolerant stock tested. while GC 196/4 and.MxH 39 were the most sensitive. Clearly there is much work to be done by breeders and horticulturists in the production and identification of more flooding 134 tolerant materials for use as cherry rootstocks. Dirirg some preliminary experiments with Montmorency/Mahaleb. we occasionally observed trees survive and recover from 10—14 days of floodirg. Following dormancy fulfillment. several of these individuals produced suckers from the Mahaleb rootstock and. thus. could be clonally propagated and retested agaitst an unselected population of Mahaleb seedlirgs. If these selections proved to be more floodirg tolerant than the unselected population then this method would lend itself to the selection of superior individuals in seedlirg lines which could in turn be utilized as superior clonal rootstocks or as parents in breedirg W- _ The major limitation of these studies was that they were performed exclusively on containerized plants and involved flooding of the entire root system. In field plots and containerized systems where the entire root system was not flooded we have observed that plant injury was somewhat ameliorated and presumably more survivable. Therefore. one research area deservirg of attention is to determine the importance of root system architecture. i.e. horizontal vs. vertical rootirg patterns. as a floodirg avoidance strategy. alould this prove to be a viable strategy then presumably this trait could be a selection criteria in a needing program. A related area also deserving attention is the role of compersatory root growth in reducing plant injury and mortality during soil floodirg. This might come into play either in those parts of the root system situated in a portion of the soil profile not subjected to floodirg or in roots damaged by floodirg. In the first case. elaboration of those portions of the root system not subjected to floodirg might allow the 135 plant to compensate for the loss of function in other roots damaged or lost during flooding. In the latter case rapid replacement of damaged roots might allow the plant to continue to grow and function optimally following flooding. In either case maintenance of photosynthetic rates during flooding or rapid recovery of photosynthetic capacity following flooding would.play a major role in providing the necessary photosynthates to support root growth. Many questions remain as to how flooding causes plant injury. While we were able to demonstrate that a translocatable factor from the roots may reduce photosynthetic rates in the canopy during flooding. its identity remains unknown. A number of possibilities exist: a toxin produced by the roots or imported into them.during flooding. a reduced quantity of some essential metabolite or hormone from the rootsystem. or perhaps a 002 source which releases 002 in the leaves thus appearing to reduce net photosynthesis. The use of fluorescence to measure gas exchange would allow one to determine whether the electron transport pathway is inhibited durirg soil floodirg. Determinations of leaf hormone and starch levels during flooding or exogenous applications of hormones may also help elucidate the mechanism of apparent photosynthetic inhibition. Indeed. such experiments may point the way to treatments that would reduce the negative effects of flooding in trees grafted onto flooding sensitive rootstocks. APPENDIX A APPENDIX A EFFECT OF XYLEM SAP FRG4 HOODED AND cm TREES ONGASHG-IANGEQiARACIERISTICSOFSOURQ-IERRYIEAFEDGDIANTS. The purpose of this experiment was to determine if the xylem sap from flooded plants had an effect on photosynthesis of sour cherry leaf explants. Exudate was collected from flooded and check trees (2 of 4 reps) at conclusion of Experiment 1 described in Section 1. Trees were gently removed from pots and roots washed clean in tap water (ca. 22 °C) . T‘rurks were severed ca. 25 cm above the graft union. A moprene stopper with an appropriate diameter hole was slipped down the trunk to within a few cm of the graft union. Assembly was then sealed into a large custom made pressure bomb filled with enough tap water to completely cover root system. System was pressurized to ca. 8 bars and ca. 1 ml of expressed sap collected in a short length of plastic tubing attached to the cut end of the tree stem protruding from the top of the pressure bomb. Sap was transferred with a pipette to a small vial (ca. 20 ml). Vial was immediately sealed. placed on ice and stored at 2 0C until commencement of experiment the next day . Dcplant system consisted of a sirgle fully expanded sour cherry leaf (Montmorency) with ca. 4 cm of attached stem. Well exposed shoots (ca. 20 cm long) were collected from field grown trees the morning of the experiment and cut ends immediately recut while surmerged in tap water. Dcplants were prepared by cuttirg stem ca. 0.5 cm above and ca. 3.5 cm below point of petiole attachment. taking care that all cuts were performed under water to maintain continuity of water column to leaf. 136 137 Stem were placed in 5 ml vials filled with deionized water and held in place with a small lump of modelilg clay. Leaves were then sealed in environmentally controlled plexiglass chambers (Sam and Flore. 1982) with petioles. stems and vials protrudirg. Gas excharge measurements were made every 15 minutes (900 hr —1700 hr). usirg an open gas-excharge system described previously (Sam and Flore. 1982). Gas excharge measurements were made within optimum enviromental conditions for sour cherries (Sam and Flore. 1982). photosynthetic photon flux (PPF) of 1000 micromols m-Z s-l. leaf temperature of 25 °C. ambient carbon dioxide concentration of 350 micromol mol"1 and leaf to air vapor pressure deficit (VPD) of 0.5-1.0 KPa. Flow rate through individual chambers was ca. 1.65 1 min-1. Carbon assimilation and conductance values were calculated as described previously (Moon and Flore. 1986). Leaves were allowed to equilibrate ca. 3 hr at which time deionized water was suctioned from explant vials and immediately replaced with a 5025 solution (v/v) of deionized water and sap collected from eith control or flooded trees (sap from 2 reps of each treatment combined before dilution). Vials were replenished periodically durirg experiment with deionized water to maintain ca. 2 ml of fluid in each vial. At conclusion of experiment leaves were released from chambers. petioles severed at point of attachment to stem and leaf water potential measured with a portable pressure bomb (PPS Instrument Co.. Corvallis. OR). Measurements were made in the manner of Boyer (1967). Hydraulic conductivity of explant stem was measured by first trimirg ca. 1 of tissue from the apical portion of stem. A short piece of water filled tubirg was attached to the basal portion and the stem inserted tightly 138 into the collar of the portable pressure bomb. The free end of the water filled.tubing was placed in a small water filled.beaker in the bottom of the chamber to maintain continuity of water column and the system sealed. A pressure of ca. 3.5 bar was applied and flow through stem section collected in a short length of tubing attached to the protruding stem end. Hydraulic conductivity was estimated as: K:.§Ig where. PA K equals hydraulic conductivity (cm 3'1).‘Q equals flow (mg 371). L equals length of stem (cm). P equals pressure (mg cm‘z) and A equals mean cross sectional area of stem (cmz). Net carbon assimilation of explants receiving exudate from flooded plants dropped more rapidly than explants receiving exudate from check plants. differences becoming significant 2 hours after introduction of exudate as shown in Table 1. Residual mesophyll conductance to 002 of explants receiving exudate from flooded plants also dropped significantly below that of explants receiving exudate from control plants. differences becoming significant 2.75 hours after introduction of exudate. No significant differences in transpiration or stomatal conductance to 002 was observed between the 2 treatments. No significant differences were detected in LWP or hydraulic conductivity of stem sections of the two treatments at conclusion of the experiment as shown in Table 2. Results indicate that some factor contained (or missing) in exudate from flooded plants causes net carbon assimilation to fall in explant leaves. Effect is probably not via plugging of the xylem since no differences in hydraulic conductivity of stems or in LWP of the two treatments was detected at conclusion of experiment. if. A‘m 139 .000... .0 #3230000» ~00. 3 .so *0 05 so 0:000qu 50038808 L300— 008 has: .so .032 30.838 .3 0032 ~00 5.300 280 5 002g £30833 2000 :80 x .938 v 888: Baez n 00A 0: «Na 00 0: 00d 00... 00 0: 00 0: 0: 000. can 00m 000 00— L :1 0 N1... 3.5.: Non 00 N00 «0 0mm 00 0d a 0m. 00" 00a 00H 00 00a 0m. .0“ 00 Y: 0 _ 0 ._...0 0N.~. 0.0 0N.0 00.0." Rudd 0. 0H 0.8 04m 0.3 000 v.3» N. «0 0.00 0.00 0.00 0.00 h :1 m min. 33.5 fivm 000 0.0 0.0 0.0 0.0a v.0." 0.0“ 0.: 0.: 0 < 00.—w 00.0 00.0 00.0 00.0 000 00.N 0N.N 00.0 004 00... 0m..." 00.« 05.0 00.0 0N0 00.0 0.0. (80060.30 000038 00 8303093.: .0000 0:30: 03398 0000 46:05.58: 00 20. «8 3 03303500 3003000 use .10. Na 0... 00:30:38 2.30000... 32:00.. .2: 0032. 2:000 N8 00: so 30_cfi=\>u:0mosaco§ 000.3 E000 (Son x0020 0:0 £00000: so: 000038 501x 00 0000000 .a 0300. 140 Table 2. Leaf water potential (LWP) and stem hydraulic corductivity (K) of leaf explants (Mont) receiving xylem exudate from either floodedz or check sour cherry treaa (Mont/Mam1eb). Exudate pr (MPa) K (cm 3'1) Check —0.58 0.000377 Flood —o.43 0.000247 2 Trees flooded 4 days. APPENDIX B APPENDIX B Ell-1AM. AND ACEI'ALDB-IYDE (DNCENI‘RATION IN RCDT EXUDATE FROMFKDDEDANDCONI‘ROLSCMRG-ERRYIREES (WW/W). The purpose of this experiment was to determine the concentration of ethanol and acetaldehyde in root exudate from flooded and control sour cherry trees. Containerized two year old sour cherry trees (Montmorency/Mahaleb) were flooded for 12 days in manner described in Section 1. E>