MSU LIBRARIES .—:—. RETURNING MATERIALS: "I Place in book drop to remove this checkout from your record. FINES will be charged if book is refbrned after the"date stamped below. GAS EXCHANGE CHARACTERISTICS OF VACCINIUM CORYMBOSUM L. AND VACCINIUM DARROWII CAMP. By John W. Moon Jr. A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Horticulture 1985 ACKNOWLEDGMENTS I wish to express my appreciation to Dr. J. A. Flore and Dr.tL F. Hancock for support and encouragement during my graduate studies. I also wish to thank my wife Karen Marie for her love and encouragement and for helping me to keep life in perspective. ii Guidance Committee: The journal paper format was chosen for this thesis in accordance with departmental and university regulations. The thesis is divided into four sections. Section one is intended for publication in Photosynthesis Reasearch and the remaining sections are intended for publication in The Journal of the American Society for Horticultural Science. iii ABSTRACT GAS EXCHANGE CHARACTERISTICS (H? VACCINIUM CORYMBOSUM L. AND VACCINIUM DARROWII CAMP. BY John W. Moon Jr. Comparisons were made between two highbush blueberry cultivars ('Jersey' and 'Bluecrop') and between 'Bluecrop' and Florida 48, a selection of Vaccinium darrowi, with respect to influences of light, C02 concentration, temperature and vapor pressure deficit on net C02 assimilation, transpiration (E), leaf conductance to water vapor (g1), and water use efficiency (WUE). The effect of temperature on the gas exchange characteristics of the interspecific hybrid (U875) between 'Bluecrop' and X. darrowii (Fla.éB) and two backcrosses to 'Bluecrop' (U8239 and USZAS) were also determined When measured under optimum conditions, non-signifi- cant. differences were observed between 'Jersey' and 'Bluecrop' for net C02 assimilation, mesophyll conductance, C02 compensation point, E, g1, and WUE. C02 assimilation, mesophyll. conductance, E, anui g1 were significantly fianS) lower for X. darrowii compared to 'Bluecrop'. C02 assimilation of leaves approached light 1 saturation between 500-800 pmols s- In"2 for VBluecrop', 'Jersey' and X, darrowii. C02 assimilation increased and g1 decreased with increasing C02 up to 300—350 pl liter-1 and leveled off with further increases in C02 up to 800 pl liter‘l. There was a 55-65% reduction in g1 for LJersey'and 'Bluecrop' when vapor pressure deficit (VPD) was increased from 1tx>3 KPa but only a 20-25% reduction was observed in C02 assimilation. Significant reductions (p=.OS) in C02 assimilation, g1} and WUE, enui significant increases in E were observed in _Y_. darrowii in response to a VPD increase from 1 to 3 KPa. C02 assimilation for 'Bluecrop' was significantly higher than rates for X, darrowii at 1 KPa but not at 3KPa, while E and g1 were significantly lower for X. darrowii at both 1 and 3 KPa. WUE was significantly higher for 1. darrowii at 1 KPa but not at 3 KPa. The temperature optimums for C02 assimilation ranged between 181x326 degrees C for'Jersey'euHibetween 14 to 22 degrees C for 'Bluecrop'. The temperature optimums for 1. darrowii and U875 were approximately 8 to 10 degrees higher than the optimum for Wlluecropfl The two backcrosses had contrasting temperature optimums with U3239 having a optimum at 20 degrees C similar to 'Bluecrop' and USZAS having a optimum at 30 degrees C similar to X, darrowii. !. darrowii had higher WUE's than 'Bluecrop'at both 202nu130 degrees C, while USZ39 and U8245 had significantly higher WUE's at 30 degrees C compared to 'BluecropC TABLE OF CONTENTS Page LIST OF TABLES O C O C C O O O O O 0 Vi LIST OF FIGURES . . . . . . . . . . . ix INTRODUCTION 0 O O O O O O C O C O 1 SECTION ONE: A BASIC COMPUTER PROGRAM FOR THE CALCULATION OF PHOTOSYNTHESIS, STOMATAL CONDUCTANCE, AND RELATED PARAMETERS IN AN OPEN GAS EXCHANGE SYSTEM . . . . . . . . . . 3 Abstract . . . . . . . . . . . 4 Introduction . . . . . . . . . . 4 Calculations . . . . . . . . . . 6 Summary . . . . . . . . . . . 18 Literature Cited . . . . . . . . . 21 SECTION TWO: THE EFFECTS OF LIGHT, TEMPERATURE, C02, AND VAPOR PRESSURE DEFICIT ON PHOTOSYNTHETIC CO ASSIMILATION, STOMATAL CONDUCTANCE, TR NSPIRATION, AND WATER USE EFFICIENCY IN 'BLUECROP' AND 'JERSEY' HIGHBUSH BLUEBERRY (VACCINIUM CORYMBOSUM L.) . . . . . . . . 23 Abstract . . . . . . . . . . . 24 Introduction . . . . . . . . . . 25 Materials and Methods . . . . . . . 26 Results . . . . . . . . . . . 29 Discussion . . . . . . . . . . . 33 Literature Cited . . . . . . . . . 43 iv Page SECTION III: A COMPARISON OF A LOWBUSH BLUEBERRY (VACCINIUM DARROWII CAMP.) VERSUS HIGHBUSH BLUE- BERRY (VACCINIUM CORYMBOSUM L.): EFFECTS OF LIGHT, TEMPERATURE, CO , AND VAPOR PRESSURE DEFICIT ON PHOTOSYNTHETIC O ASSIMILATION, STOMATAL CONDUC— TANCE, TRANSPIRAT ON, AND WATER USE EFFICIENCY. . . . 47 Abstract . . . . . . . . . . . . 48 Introduction . . . . . . . . . . 49 Materials and Methods . . . . . . . 50 Results . . . . . . . . . . . 50 Discussion . . . . . . . . . . . 59 Literature Cited . . . . . . . . . 62 SECTION FOUR: GENOTYPIC DIFFERENCES IN THE EFFECT OF TEMPERATURE ON CO ASSIMILATION AND WATER USE EFFICIENCY IN BLUEBER Y . . . . . . . . 65 Abstract . . . . . . . . . . . 66 Introduction . . . . . . . . . . 67 Materials and Methods . . . . . . . 67 Results . . . . . . . . . . . 69 Discussion . . . . . . . . . . . 75 Literature Cited . . . . . . . . . 77 Table LIST OF TABLES Page Section One Variables that must be entered interactively or through the use of READ statements to make calculations of plant gas exchange . . . . . 8 Sample output of a BASIC program to analyze plant gas exchange . . . . . . . . . . . . 20 Section Two Summary (Hf gas exchange characteristics for 'Bluecrop' and 'Jersey'. C02 assimilation (A), transpiration (E), and water use efficiency (WUE) were measured at 21.2 degrees C (+/-1.5) a leaf to air vapor pressure deficit of 1.06 (+/—.26), satTrating light intensitys (1020.6 +/- 37.4 pmols s' m‘ PPFD) and at ambient C0 levels (328.5 +/- 5.1 p1 liter-1). CarboxyIation efficiency (g ) and C02 compensation points were estimated from the linear portion of the response of A to increasing intercellular C02. 30 Comparison of the effect of vapor pressure deficit on the gas exchange characteristics of 'Bluecrop' and 'Jersey'. C02 assimilation (A) leaf conductance to water vapor (g1), and water use efficiency (WUE) were measured at 28.6 degrees C (+/- 2.0), satarating light intensities (985 pmols s"1 m" PPFD), and a ambient C02 concentrations (322.8 p1 liter- +/— 4.9) . . . . . . . . . . . . . 38 vi Table Page Section Three Summary of gas exchange characteristics for X. darrowii. C0 assimilation (A), leaf conductance to water vapor (g1), transpiration (E), and water use efficiency (WUE) were measured at 30.7 degrees C (+/- 0.5), a leaf to air vapor pressure deficit (VPD) of 1.08 KPa (+/— 0137)2 saturating light intensities 1017 pmol s' m- (+/- 24.4) PPFD, and ambient C02 concentration (337.7 p1 liter-1 +/— 24.4). Carboxylation efficiency (gm) and C02 compensation point were estimated from the linear portion of the response of A to increasing intercellular C02. . . . 52 Summary of the effect of leaf to air vapor pressure deficit in kilopascals (KPa) on the gas exchange characteristics of V. darrowii. C02 assimilation (A), leaf conductance to water vapor (g ), transpiration (E) and water use efficiency (WUE) were measured at 30.6 degrees C (+/— 1.3), saturating light intensities (1033 pmol s"1 m7 +/- 34), and at ambient C02 concentrations (334.7 +/— 3.1). . . . . . 57 Comparison of the effects of leaf temperature on the gas exchange characteristics of highbush blueberry 'Bluecrop' and V. darrowii. Mean values for C0 assimilation (A), transpiration (E), leaf confiuctance to water vapor (g1), residual conductance to C02 (g ), and water use efficiency (WUE) were obtalned from temperature response curves measured at vapor pressure deficits less than 1.0 RPa, saturating light intensities (1000 pmols s- m'z) and ambient C02 levels (330 p1 liter-l). . . . 58 Comparison of the effects of leaf to air vapor pressure deficit on the gas exchange charac- teristics of highbush blueberry 'Bluecrop' and 1. darrowii. Mean values for C0 assimilation (A), transpiration (E), leaf conductance to water vapor (g1), residual conductance to C02 (gr) and water use efficiency (WUE) were obtained from vapor pressure deficit response curves measured at 28-31 degrees C, ambient C02 concentrations 320—335 pl liter“ and at saturating light intensities 985-1035 pmols s' m- PPFD. . . . . . . . . . 60 vii Table Page Section Four 1. Summary of the effect of two levels of leaf temperature on the gas exchange characteristics of different blueberry genotypes. C02 assimila— tion (A), transpiration (E) and water use efficiency (WUE) were measured at leaf to air vapor pressure deficits less than 1 KPa, at safiurating light intensities (1006 pmols s-1 m— +/-14.7) and at ambient C02 concentrations (341.7 +/-7.3 pl liter“ ). . . . . . . . 72 2. Summary of the effect of two levels of leaf temperature on gas exchange characteristics of different blueberry genotypes. Leaf conduc— tance to water vapor (g1) and residual conduc- tance to C02 (g ) were measured at leaf to air vapor pressure deficits less than 1.0 KPa, at saEurating light intensities (1006 pmols s- m- +/-14.7) and at ambient C02 concentrations (341.7 +/—7.3 pl liter” ). . . . . . . . 73 3. Significance levels of F-tests of the analysis of variance of the effects of two levels of leaf temperature (20 and 30 degrees C) on C02 assimilation (A), transpiration (E), water use efficiency (WUE), leaf conductance to water vapor (g1) and residual conductance to C02 (gr). . o o o o o o o o o o o 74 viii LIST OF FIGURES Figure Page Section Two Effects of photosynthetic photon flux density PPFD (A and B) and leaf temperature (C and D) on C0 assimilation (A) in 'Jersey' (A,C) and ' luecrop' (B,D). Measurements were made at ambient C02 levels (320-345 pl liter” ) Response to PPFD was measured at 20 C and response tozleaf temperature was made at 1000 pmol s' m- PPFD. Each value is the mean of 20 determinations and different symbols represent different plants. . . . . . . . 31 Effects of C02 on C02 assimilation (A) (A and B) and on leaf conductance (g1) (C and D) in 'Jersey' (A,C) and 'Bluecrop' (B,D). Measurements were made a5 20'C and at saturating PPFD (1000 pmol s- m' ). Each value is the mean of 20 determinations and different symbols represent different plants. . . . . . . . . . . 34 Effects of vapor pressure deficit (VPD) on C02 assimilation (A) (A and B) and on leaf conduc tance (g1) (C and D) in 'Jersey' (A,C) and 'Bluecrop' (B,D). Measurements were made a5 28'C, at saturating PPFD (1000 pmol s' m- ) and at ambient C0 concentrations (314—328 pl liter-1). Each va ue is the mean of 20 deter— minations and different symbols represent different plants. . . . . . . . . . . 36 ix Figure Page Section Three Effect of photosynthetic photon flux density (PPFD) (A), leaf temperature (B), CO (C), and leaf to air vapor pressure defic1t (VPD) (D) on net C02 assimilation in 1. darrowii. Measurements were made at 30 degrees C (A,C, and D), saturating PPFD (B,C, and D), and at ambient C02 levels (330-345 pl liter“1) (A,B, and D). Each value is the mean of 20 deter- minations and different symbols represent different plants. . . . . . . . . . . 53 Effect of ambient C02 concentration (A) and leaf to air vapor pressure deficit (VPD) (B) on leaf conductance (g1) for V. darrowii. MeasureTentS were made at saturating PPFD (1000 pmol s“ m“ , and at 30 degrees C. Response to VPD (B) was measured at ambient C0 levels (330-335 pl liter“ ). Each value is t e mean of 20 determinations and different symbols represent different plants. . . . . . . . 55 Section Four Effect of leaf temperature on net C0 assimi- lation (A) for 'Bluecrop', X. darrowii (Fla 4B), and U875 (A), and U8239 and US245 (B). Measurement? were made at saturating PPFD (1000 pmol s“ m“ , at ambient C02 levels (340 pl liter“ ) and at leaf to air vapor pressure deficits less than 1 KPa. Each symbol represents the mean of 20 determinations and each curve is representative of a typical response for its respective genotype. . . . . . . . . . 70 INTRODUCTION Genotypes which are native to differing environmental habitats may contain differences in C02 assimilation, transpiration (E), or water use efficiency (WUE) which contribute to their success le their respective environments. If useful adaptive mechanisms could be identified they might be incorporated into a plant breeding program or manipulated by cultural practices. The tetraploid highbush blueberry (Vaccinium corymbosum L.) is native to swamps, bogs and stream margins from Michigantx>Nova Scotia.It is well adapted to organic sandy soils of low pH and is poorly adapted to drought conditions and high temperature. In contrast, Vaccinium darrowii Camp.it;a diploid lowbush blueberry species native to the Southeastern United States from Louisiana to Florida. Florida 4B, a selection of I; darrowii, is native to the sandy scrublands of the Ocala National Forest in central Florida, and survives under the high temperatures and the frequent drought conditions of its native habitat. However, there isru>information on the mechanisms contributing to the survival of Fla. 4B under hot euui dry conditions. Additionallyy C02 assimilation, E, and leaf conductance to water vapor (g1) of V;_darrowii and the highbush blueberry V;_corymbosum have not been evaluated. Fla. 4B frequently produces fertile hybrids when crossed with tetraploid Vaccinium species, presumably through the production of unreduced gametes. Fla. 4B was initially used in rabbiteye blueberry (V; aghgi) breeding programs with major goals of developing cultivars requiring low chilling and possessing heat and drought resistance. Recently Fla. 4B has been used as a parent in an effort to accomplish these same goals in a highbush blueberry breeding program developed by A.D. Draper of the U.SJLA. Fruit Lab at Beltsville, Md. Thus the tolerance of highbush blueberry to heat and drought might be improved through incorporation of genes from Fla. 4B. The two major objectives of this study were to (1) compare the effects of light, C02, vapor pressure deficit, and temperature on C02 assimilation, E, g1 and WUE of two highbush blueberry cultivars ('Bluecrop' and 'Jersey') and Florida 4B and (2) to test the hypothesis that the tolerance of Fla. 4B to heat and drought results from WUE. SECTION I A BASIC COMPUTER PROGRAM FOR CALCULATION OF PHOTOSYNTHESIS, STOMATAL CONDUCTANCE AND RELATED PARAMETERS IN AN OPEN GAS EXCHANGE SYSTEM Abstract Computer programs written in BASICA (IMB'S VERSION OF BASIC) language were developed for the calculation of the gas exchange parameters of C02 assimilation, leaf conduc- tance, stomatal conductance, residual conductance, inter- cellular C02 concentration, transpiration, water use effi- ciency and transpiration ratio in an open system. Formulas are discussed in both an algebraic and in a BASIC computer program form. Calculations based on mole fractions of C02 and water vapor are explained and both molar and mass fluxes are included in the program output to facilitate comparisons with data from the literature. Corrections are made in the program to accout for underestimation of C02 assimilation due to the increase in flow rates out of sample chambers caused by simultaneous transpiration. A sample output is included to illustrate the formatting capability of the program. Introduction Closed, semi-closed, and open systems have been used for the study of plant gas exchange (10,11).Of the three systems the open system provides the greatest flexibility for studying environmental effects on photosynthesis, transpiration, and stomatal conductance. The open system offers several convenient features useful in gas exchange studies, such as: 1) the ability to switch between server— al sample chambers to provide for replication; 2) manipu- 5 lation of C02,(%p and water vapor concentration; and 3) simultaneous measurement of C02 and water vapor fluxes (8). Additionally, since the open system is a positive pressure system the technical difficulty of maintaining a totally leak—free system is avoided. Frequent measurements are required to establish the effects that environmental variables such a C02 or vapor pressure concentration have on processes related to plant gas exchange. Measurements of plant gas exchange are often quite variable due to differences in plant material being measured, and interactions between complicated physiologi- cal processes, such as control of stomatal aperture, and the environment of the sample chamber. Thus when trying to characterize plant gas exchange, it is desirable to col- lect large quantities of data. For this reason computer programs were developed to facilitate the rapid calcula— tion and analysis of net C02 assimilation, transpiration, leaf conductance, stomatal conductance, residual conduc- tance, intercellular C02 concentration, transpiration ratio and water use efficiency in an open system. The programs were written in BASICA which can be used with IBM and IBM-compatible systems. BASIC is a simple and easily learned language which allows for easy manipulation of these programs to meet special needs. The programs were written to calculate resistance in molar fluxes (m2 s mol“1), which are now preferred by many students of stomatal activity (3,4,6L.The mass of water 6 vapor and C02 are affected by changes in temperature and pressure. Thus corrections for pressure and temperature are required when calculating mass flux. The use of mole fractions to calculate leaf and stomatal resistances re- moves the pressure and temperature dependence from the calculations (4). Additionally, molar fluxes (m2 5 mol“1 2 or mol m“ s“1 for conductance) are more meaningful to the biologist than are the curious units arising form the 1 calculation of mass fluxes (s cm“ or cm s“1). Since the use of molar flux is relatively new in the literature, conversion factors are included which simulta- neously calculate units in mass flux. The format of the program outputs both molar flux and mass flux of each parameter to facilitate comparison. Calculations The data that must be collected from the gas exchange system to use these programs is listed in Table 1. The fundamental body of calculations used in the programs is sixty—one lines in length as shown below. SAMPDEWPT=SAMPDPREADING * SAMPDPCORR AMBDEWPT=AMBDPREADING * AMBDPCORR SAMPDPCENT=(SAMPDEWPT-32)*5/9 AMBDPCENT=(AMBDEWPT-32)*5/9 T3=LEAFTEMP + 273 T2=SAMPDPCENT + 273 T1=AMBDPCENT + 273 T8=373.16 R1=TS/T1 10 R2=TS/T2 11 R3=TS/T3 12 PART1=-7.90298*(R1—1)+5.02808 * FNLGT(R1,10) 13 PART2=-1.3816*(10“(-7))*(10“(11.344*(1-T1/TS)—1)) 14 PART3=8.1328*10“(-8)*(10“(-3.19149*(T8/(T1-—1)))-1) +FNLGT(1013.246,10) ©mVC‘UlJ-‘wNH 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 61 7 AMBIENTVAPORPRESSURE=10“(PART1+PART2+PART3) AMBIENTVAPORPRESSURE(KPA)=AMBIENTVAPORPRESSURE/10 PART4=-7.90298*(R2-1)+5.02808*FNLGT(R2,10) PART5=-1.3816*(10‘(—7))*(10“(11.344*(1-T2/TS)—1)) PART6=8.1328*10“(-8)*(10‘(-3.19149*(TS/T2-1)))-1) +FNLGT(1013.246,10) SAMPLEVAPORPRESSURE=10‘(PART4+PART5+PART6) SAMPLEVAPORPRESSURE(KPA)=SAMPLEVAPORPRESSURE/10 PART7=-7.90298*(R3-1)+5.02808*FNLGT(R3,10) PART8=-1.3816*(10‘(~7))*(10“(11.344*(1-T3/TS)-1)) PART9=8.1328*10“(-8)*(10“(-3.19149*(TS/(T3—1)))-l) +FNLGT(1013.246,10) LEAFVAPORPRESSURE=10‘(PART7+PART8+PART9) LEAFVAPORPRESSURE(KPA)=LEAFVAPORPRESSURE/10 VPD=LEAFVAPORPRESSURE(KPA)— SAMPLEVAPORPRESSURE(KPA) WIN=AMBIENTVAPORPRESSURE*.001 WOUT=SAMPLEVAPORPRESSURE*.001 WLEAF=LEAFVAPORPRESSURE*.001 DELTACOZREADING=IRGACF*DELTAIRGA CALIRGA=.00148*C02+.5498 COZMICROMOLPERMOL=CALIRGA*DELTAC02READING D=((P*29)/(.0821*T3))/29*1000 LEAFAREAM2=LEAFAREA*.01 FLOWMBPERS=FLOW*1.667E—05 FLOWIN=D*FLOWM3PERS FLOWOUT=FLOWIN*(1—WIN)/(1-WOUT) EMOLAR=FLOWOUT*(WOUT-WIN)/(l—WOUT)/LEAFAREAM2 E=EMOLAR*1000 WAVG=(WLEAF+WOUT)/2 TRANS=EMOLAR*1.8 RLMOLAR=(WLEAF-WOUT)/(EMOLAR*(1-WAVG)) RLMASS=RLMOLAR/2.5 RSMOLAR=RLMOLAR*1.6 RSMASS=RLMASS*1.6 GLMOLAR=l/RLMOLAR GLMASS=1/RLMASS GL=GLMOLAR * 1000 GSMOLAR=1/RSMOLAR GSMASS=1/RSMASS GS=GSMOLAR * 1000 A=FLOWOUT*COZMICROMOLPERMOL*(1-WIN)/(1-w0UT) /LEAFAREAM2 COZINTERCELLULAR=((C02*(GSMOLAR-(EMOLAR/2)))—A/ (GSMOLAR+(EMOLAR/2)) RM=COZINTERCELLULAR/A GM=1/RM * 1000 PNET=A*1.584 WUE=(A*.OOOOOl)/EMOLAR TRATIO=1/WUE RMMASS=RM/2.5 GMMASS=1/RMMASS 8 Table L.Varibles that mustlneentered interactively or through the use of READ statements to make calculations of plant gas exchange. Input Variable Description- PLANTID$ Plant material identification LEAFAREA Leaf area in dm2 SAMPLEDEWPT Sample dew pointw AMBDEWPT Ambient dew pointw LEAFTEMP Leaf temperature in degrees C C02 Ambient C02 concentration DELTAIRGA Delta C02 reading from IRGAx FLOW Flow rate (liters min“1)y LIGHT PPFD (pmol s“1 m“2)z wThe program will interactively ask for a correction factor to convert these variables to dew point. This allows for the use of a voltage reading from dew point hygrometers. xThe program will ask for a conversion factor to convert this reading to pmol mol“ yFlow rate is entered interactively into the program. 2This variable is entered interactively except in programs designed to analyze response to changing PPFD. 9 An algebraic description of the calculations used is listed below and referenced to the pertinent lines where these functions are performed in the program. (1) Calculation of readings. vapor pressure in KPa from dew point (a) Water vapor calculations form dew point readings (see references 1,7) Logloew = Where: EN = TS GWS = In the program this the air dew point, -7.90298 (TS/T-1)+5.02808 loglO(T8/T) -1.3816x10‘7(1011~344(1‘T/TS)—1) +8.1328x10-8(10-3-19149| .aouoosam. Hfl3ouumc .> o moumwow cm 0 moouwoc ON youoempma owcmnuxo mmu moo OCOHQEO use .A E Hoam> um wounwmme mm m HOE: ooofiv Qmmm wcwumusumm .mmx o.H cmzu >p=o omcoamou ouaumpoqsmu scum cocwmuno who; Amazv mocowOmeo mm: A Iaaaae Ha ommv afieeea mmoa muwuwmou whammoum “mum: cam .Auwv Nov ou oucmuoswcoo Hmsvwwou .Aawv oucmuusvcou mama .Amv cowumpwawcmuu .A cmoz .szouumu . > use .aouomsam. muuonosan cmsnnwwn mo mowumfluouompmno owcmnuxo mow ozu co ousumuoasou mmoa mo muoommo onu mo :omapmaaoo .m magma 59 while calculated residual conductance to C02 (gr) decreased in 'Bluecrop' but increased in X; darrowii (Table 3). Transpiration and g1 were significantly lower (p=005) in L darrowii at VPD's of both 1 and 3 KPa (Table 4). C02 assimilation was significantly higher for 'Bluecrop' at 1 KPa but not at 3 KPa (Table 4). WUE of V_.darrowii was 35— 40% higher than 'Bluecrop' at 1 KPa but no significant difference in WUE was observed at 3 KPa (Table 4). Discussion Maximum C02 assimilation rates under optimum conditions for V; darrowii were 12-20% higher than rates reported for rabbiteye blueberries (19) and 25-35% lower than those re- ported for highbush blueberry (14). The light response curve for V;_darrowii was similar to those reported for rabbiteye (19) and highbush blueberry (14), as well as for other fruit crops (5, 6, 7, 9, 20) in that light saturation was approached between 500 and 800 pmols s“1m“2 PPFD. 002 assimilation increased and g1 de- creased with increasing 002 in a manner similar to that reported for highbush blueberry (14). Mesophyll conductance (gm) which was estimated from the C02 response curve, was lower than in highbush blueberry (14). This lower capacity for C02 assimilation may reflect the lower range of g1 observed, which restricts intercellular C02 concentration. A similar restriction in gm due to stomatal aperture has been reported for apricot, some cultivars of which are adapted to desert conditions (7). 60 .HO>OH Nm ozu um ucmowMflcme uoc .m.c .Ho>oa Nm onu um unmowMchflm * .a.e wR.N oe.~ * ma.e wa.e Acme Hoee\Noo Hoaav m2: .a.e 8.03 3.8m .a.e e.em N.am AHIa NIa Noo Hoaav am * a.mm a.oms * H.waa m.omm AHIm Nua Hoeav am * ma.~ aa.m * mm.H mN.N AHIm NIe on Hoaev m .a.a ma.e om.w * em.m ma.oH AHIm NIe moo Hoeav a szouumv .M caouooaam. Hflzouumc .N .aouoonam. umuoemuma max m may H owcmnoxm mmu . IE H1m HOE: mmoHImwo Qmmm wcwumusumm um use Iuouwa H1 mMMIon mcowumuucoocoo moo ucomnem .U moouwoc Hm ou mm um wousmmos mo>u=o omcoamou ueuamov whammouq uoam> scum uocfimuno mum: Amazv >OCOHOHMMO om: umumz cam Aumv moo ou mocmuonccoo Hmswflmwu .AHwV mocmuosccoo mama .Amv cowumufiamcmuu .A coo: .ww3ouumv .> cam .aouoosam. >uuonosan nmanzwwn mo mowumwuouomumco owcmnuxo mow onu co uwowmov ousmmoua Hoqm> yam Ou «OOH mo muuommo onu wo comfiumaeoo .q manme 61 VPD had a greater effect on g1 than on C02 assimila- tion, as reported for highbush blueberry (14). C02 assimilation was optimum between 25 and 30 degrees C, as reported for peach (5), apple (11), and cherry (18); this is several degrees higher than the temperature optimum reported for highbush blueberry (14). Transpiration and g1 at 20 and 30 degrees C, were much lower for X; darrowii than for 'Bluecrop' highbush blueberry. Therefore one factor that determines the survival of I; darrowii under high tempera— tures and drought conditions may be an ability to restrict water loss by decreasing stomatal aperture. Such a response has also been suggested in rabbiteye blueberry which is reported to be drought resistant (10, 16, 19), and exhibits even lower ranges of g1 than 1; darrowii (19). The restric- tion of water loss under conditions of high evaporative demand may more than compensate for the slightly lower rates of 002 assimilation in these drought resistant blueberries. X; darrowii may possess a heritable component favoring survival at higher temperatures. Similar types Of ecologi— cal differentiation have been reported in other species (2). Because crosses are possible between highbush blueberry and .1; darrowii (16), the possibility that heat tolerance and drought resistance can be improved in highbush blueberry through the incorporation of genes from V; darrowii should be evaluated. 62 Literature cited Arnon, D.I. 1949. Copper enzymes in isolated chloroplasts. Plant physiol. 24:1—15. Berry, J.A. and O. Bjorkman 1980. Photosynthetic response and adaptation to temperature in higher plants. Ann. Rev. Plant Physiol. 31:491-543. Camp WJL 1945. The North American blueberries with notes on other groups of Vacciniaceae. Brittonia 5:203—275. Cowan, I.R. 1977. Stomatal behavior and environment. Advances in Botanical Research. 4:117-228. Crews, CJL, SJ“ Williams and HAL.Vines 1975. Characteristics of photosynthesis in peach leaves. Planta 126:97-104. Crews, CJL, RJL Worley, JJK Syvertsen and M.G. Bausher 1980. Carboxylase activity and seasonal changes in CO2 assimilation rates in three cultivars of pecan.;L Amer. Soc.}knflu Sci. 105:798-801. DeJong, T.M. 1983. C02 assimilation characteristics of five Prunus tree fruit species..J.Amera Soc.HOrt. Sci. 108:303—307. Fanjul, L. and H.G. Jones 1982. Rapid stomatal responses to humidity. Planta 154:135—138. 10. 11. 12. 13. 14. 15. 16. 63 Kappel, F.and JJL Flore 1983.The effectcflfshade on photosynthesis, specific leaf weight, leaf chlorophyll content, and morphology on young peach trees. J. Amer. Soc.1kn15 Sci.108:541-544. Kender, W. J. and W. T. Brightwell 1966. Environmental relationships. In:Eck,P. and N.F. Childers (eds.) Blueberry culture.Rutgers University Press,New Brunswick, New Jersey.75-93. Lakso, A.N. and E.J. Seely 1978. Environmentally induced responses of apple tree photosynthesis. HortScience 13:646-649. Little, T.M. and FKJ. Hills 1978. Agricultural Experimentation: Design and Analysis. John Wiley and Sons, New York. pp 195-225. Lyrene, P.M. and W.B. Sherman 1980. Horticultural characteristics of native Vaccinium darrowii, I; elliottii, V; fuscatum, and V; myrsinites in Alachua county, Florida..L Amer.80c.1hnflu Sci.105:393-396. Moon, J.W. 1984. Gas exchange characteristics of Vaccinium corymbosum L. and Vaccinium darrowii Camp. PhD Thesis Michigan State University. Moon, JJL and JJL Flore 1984.A basic computer program for calculation of photosynthesis, stomatal conductance and related parameters in an open gas exchange system. Photosynthesis Research (submitted). Moore, JJL 1965. Improving highbush blueberries by breeding and selection. Euphytica 14:39—48. 17. 18. 19. 20. 64 Moran, R. and D. Porath 1980. Chlorophyll determinations in intact tissues using n,n— dimethylformamide. Plant Physiol. 65:478-479. Sams,(LE.enu1J.A.Flore 1982.The influencecfifage, position, and environmental variables on net photosynthetic rate of sour cherry leaves. J. Amer. Soc. Hort.Sci.107:339-344. Teramura, AJL, EAL Davies and DAL Buchanan 1979. Comparative photosynthesis and transpiration in excised shoots of rabbiteye blueberry. HortScience 14:723-724. Tombesi, A., T.M. DeJong and K. Ryugo 1983. Net C02 assimilation characteristics of walnut leaves under field and laboratory conditions. J. Amer. Soc. Hort. Sci. 108:558—561. SECTION IV GENOTYPIC DIFFERENCES IN THE EFFECT OF TEMPERATURE ON C02 ASSIMILATION AND WATER USE EFFICIENCY IN BLUEBERRY 65 66 Abstract In order to determine the feasibility of improving the net C02 assimilation and water use efficiency of highbush blueberry under high temperature, gas exchange determina— tions were made for a selection of Vaccinium darrowii (Florida 4B), 8 highbush cultivar 'Bluecrop' (X. corymbosum), their F1 hybrid (U875) and two backcrosses to 'Bluecrop' (U8239 and U8245). Maximum 002 assimilation of U875 (15 pmols 002 m“2 s“1) was 30-40% higher than that of either parent. All genotypes responded parabolically to increasing temperature at vapor pressure deficits less than 1 KPa. C02 assimilation of U875 and Fla. 4B was optimum at 30 degrees C, that of 'Bluecrop' at 20 degrees. U8239 had an optimum at 20 degrees C, similar to 'Bluecrop', and U8245 had a higher temperature optimum (30 degrees C) similar to Fla 4B. Fla 4B had higher WUE's than 'Bluecrop' at both 20 (5.64 pmols C02/mmol H20 to 4.01) and 30 degrees C (3.73 to 2.53). The backcrosses U8239 and U8245 had significantly (p=.05) higher WUE's at 30 degrees C than did 'Bluecrop'. Residual conductance to 002 decreased in 'Bluecrop' when temperature was raised from 20 to 30 degrees C but increased in all other genotypes. Due to the favorable gas exchange properties of U875 and U8245 at 30 degrees C, we suggest that high temperature tolerance of l. darrowii may be heri- table and that U8245 may be a useful parent in a breeding program to improve the heat tolerance of highbush blueberry. 67 Vaccinium corymbosum L. grows well under relatively cool moist conditions; 1. darrowii (Fla 4B) in contrast, occurs on hot dry sandy scrublands in central Florida (10). As such, they may possess physiological adaptations that improve their net C02 assimilation and water use efficiency under the temperature conditions of their respective habi— tats. One selection of 1. darrowii (Florida 4B) has a temper- ature optimum for net C02 assimilation approximately eight to ten degrees higher than that of 'Bluecrop', a cultivar of 1. corymbosum (14). Although 1. corymbosum and X. darrowii differ in ploidy, A. Draper (6) has developed a series of hybrids between these species presumably involving unreduced gametes. This study was undertaken to compare the photosyn- thetic performances of the parent genotypes with those of both an F1 hybrid (U875) and backcrosses between U875 and 'Bluecrop' (U8239 and 245). Material and Methods Plant material. Dormant, one-year-old rooted cuttings of 'Bluecrop', Fla. 4B, U875, 08239 and U8245 (BC) blueberry were transplanted into ten liter plastic pots in a mixture of 1 sand:1 peat (v/v) in April of 1983. Plants were grown together for one year in a completely randomized design in a glasshouse under 14 hour photoperiods. Growth and cultural conditions were the same as those previously described (14). To induce dormancy plants were put into a growth cham— ber on January 26, 1984. Temperature in the growth chamber 68 was maintained at 3 degrees C and eight hour photoperiods were supplied with high pressure sodium lamps which provided light intensities between 200-350 pmols s“1 m“2 PPFD. Plants were removed from the growth chamber on April 16, 1984 and were again placed in the greenhouse in a completely randomized design. The maximum day temperature ranged from 22-40 degrees C and the minimum night temperatures from 22- 28 degrees C. Maximum light intensities during the growth and maturation of the vegetative flush used in measurements 1 m“2 PPFD. Gas exchange measure— ranged from 600-950 pmols s“ ments were made during July Of 1984 on 6-10 week old termi- nal shoots of lateral branches. The terminal 1-3 leaves of a mature flush of 'Bluecrop', U875, U8239, and U8245 and the terminal 10-20 leaves of an active vegetative terminal shoot of Fla 43 were enclosed in environmentally controlled leaf chambers. Measurements were made in an open gas exchange system previously described (14). Measurements were made on four different plants per genotype, and twenty determi- nations were made per leaf per treatment level. Data analysis. Gas exchange parameters were calculated as molar fluxes using the mole fractions of water vapor and C02 as suggested by Cowan (5). The calculations were made using computer programs described by Moon and Flore (15). Data were analyzed for a completely randomized design with each plant being a replication. The effect of temperatures (20 and 30 degrees C) was analyzed statistically as a split 69 plot with four replications (plants) with genotype being the main effect. Results All genotypes responded to increasing temperature in a parobolic manner. C02 assimilation was greatest for 'Bluecrop' at about 20 degrees C (Fig. 1), whereas the optimum for Fla 4B was 28-30 degrees C. The interspecific hybrid (U875) had significantly (p=.05) higher rates of C02 assimilation than either parent (Fig l,Table l) and a broad temperature optimum 20 to 30 degrees C, that parallels Fla 4B. The two backcrosses appeared to be segregating for response of C02 assimilation to temperature with U8239 re- sembling the 'Bluecrop' parent and U8245 resembling Fla 4B (Fig. 1). Transpiration (E) increased and WUE decreased in all genotypes as temperature rose from 20 to 30 degrees C (Table 1). Leaf conductance to water vapor (g1) declined by 35% in 'Bluecrop' and 21% in Fla 4B when temperature in— creased from 20 to 30 degrees C but g1 was unaffected in the two backcrosses (Table 2). There was a 91% increase in g1 in U875 as temperature increased (Table 2). High temperature reduced residual conductance to C02 (8r) in 'Bluecrop' and 'U8239', increased it in U8245 and Fla 4B, but had no effect in U875 (Table 2). The effects of genotype and temperature on all gas exchange parameters examined were significant with one ex- ception (Table 3). Lack of significance in this case was probably due to the large differences in maximum rates of 70 Figure 1. Effect of leaf temperature on net C02 assimilation (A) for 'Bluecrop', X. darrowii (Fla 4B), and U875 (A), and U8239 and US245 (B). Measurements were made at saturating PPFD (1000 pmol s“1 m“2), at ambient C02 levels (340 pl liter“1) and at leaf to air vapor pressure deficits less than 1 KPa. Each symbol represents the mean of 20 determinations and each curve is representative of a typical response for its respective genotype. A (pmols m"s") A (pmols m"s") 71 S :d 2.: 2d ‘0- ‘0- '7 lIl BLUECROP O FLA 4B a A U375 N °b BI 12 10 24 30 38 42 4a TEMPERATURE ('0) FIGRUE 1 3 :d g— 2— °.. 0. I [I] U3239 O U5245 N.. o I I I I I I I 0 s 12 10 24 30 as 42 4a TEMPERATURE (°c) 72 .Ho>mH Nm map um ucouommau sauOOOHMchflm won me momumov om um owcmno .m.: .HO>OH Nm onu um moouwov ON um o=Hm> ecu scum ucouommaw xaucmowwwcwfim ma moouwmu om um owcmao * .ummu m.>oxse wawm: HO>OH Nm mnu um ucouowwfic maucmowwflcwfim no: one Houuoa oemm map wcflumnm mcssHOO :HnuH3 mcmozm *NHmI aaoa.~ eeom.e *NRR+ amw.m eaaaH.N .m.aNH~+ eeao.HH 08H.o memms *NmaI ammo.m eaaoe.m 4N8R+ ammo.m eeame.a .m.eNaI eaaN.a eea.oH ammm: *Naal amo.m ace.k *Namfi+ aaw.m euea.a ANSN+ ao.mfi aa.NH mum: *NemI ama.m eeaea.m *Nma+ mom.m ema.H .m.aNo+ aem.m Ua.w ma .aaa ANAmI amm.~ eao.e .a.eNmH+ aaao.m aae.~ *NaNI ae.e eae.ofi .aoaueaam. MMMMN. MHdN MWdM. MMHNN MWdM deM. mmmmm. WHdM wwww. mazuocou Acme Hoae\mou Hoaav AHIa NIa ON: Hoaav AHIm NIe moo Heaav mm; m a N.A Iuouwa H: m.n I\+ m.~qu maowumnucoocoo moo aaeflaea be eea Ae.eH I\+ NIe Ia Hoe; a oHV name meeeaaaeam be .eax H eeea mmmH muwuwmow ousmmoua uoqm> Ham ou MOH um vowsmmoe who: Amszv 50:0fl0flmmm mm: noun: vcm .Amv coaumuflamcmnu .AwH Ozu mo uoowmo onu mo mumsasm .H maan 73 .HO>OH Nm onu um ucouommwu saucmowmwcwwm uoc mH moouwoc om um mmcmno .m.c .HO>OH Mm 050 um moouwow om um osam> map 500% UGOAOMMHO zaucmOflmwcme ma mmouwov om um owcmso * .umou m.»ox=9 wawm: Ho>oa Nm onu um ucouommwv >Hu=OOAMchflm uo: mum nouuoa 08mm ecu wcflnmnm massaoo cwnufiz mcmozN .m.a Na.e+ am.ao~ am.oom .a.e Nm.mm+ 880.84 aam.em mamm: .m.e Na.ml eA.amH eao.oaH .a.e NN.mHI aao.ae aaA.Hm amm m: * N~.Ho+ aN.mHe a~.AHN .m.a Nm.m+ eH.am e~.em me m: .m.a Nw.oNI 8H.ma am.AHA * Nm.ae+ aaa.aa UH.am ma .aae * Nm.em1 ew.mmH am.em~ * Nm.eNI ao.~m eaam.ma .aoeeeaam. MMAMMA m WWdW MWdM mmamm. lwdm. MWdM mamuocoo HI NI aw m HOEEV AHIm NIB ku HOEEV N.A Ipoufla H1 m.n 1\+ n.H¢mv m:OHumuucoucou N00 uaownEm um cam An.qfi I\+ Ia HIm HOE: omofiv ommm weaponsumm um .mmu H :mnu mmoH muflowmmc ounmmmua woam> new cu mama um cousmmoa who: AHwV oocmuosucou mama cam .Auwv moo AX. mocmuosccoo Hmscwmom .mmazuocow znuonosan ucouommwv mo mowuwfiuouomumno owcmcuxo now map so ousumuoaeou mama mo mHO>OH Osu mo uommmm ocu mo sumaasm .N OHan 74 Table 3. Significance levels of F-tests of the analysis of variance of the effects of two levels of leaf temperature (20 and 30 degrees C) on C0 assimilation (A), transpiration (E), water use efficiency (RUE), leaf conductance (g1), and residual conductance to C02 (gr).a Significance level Effect A E WUE 81 gr Genotype * ** ** ** ** Temperature n.s. ** ** * * Genotype x Temperature ** ** ** ** ** ** - significant at the 1% level. * - significant at the 5% level. n.s. - not significant at the 5% level. aMeasurement conditions were those described in Table 1 and Table 2. 75 002 assimilation and in temperature optimums between the genotypes. However, interaction between genotype x tempera- ture was significant in all cases (Table 3). Discussion C02 assimilation decreased 30% in 'Bluecrop' as tem- perature was increased from 20 to 30 degrees C and both g1 and g1. declined. The ratio of 81/8r was constant for 'Bluecrop' at 20 and 30 degrees C, which indicates that the reduction in 002 assimilation was due mainly to a reduction in stomatal aperture, but other non-stomatal aspects of photosynthesis and respiration may also be involved. In other studies, a decline in C02 assimilation at high temper- ature has been associated with an increase in respiration and a reduction in the efficiency of the Carboxylase enzyme with increasing photorespiration (3, 7, 12, 13). Such a response could be the cause of the decline in the calculated gr observed in 'Bluecrop'. Both C02 assimilation and gr were decreased in U8239 at 30 degrees C. In contrast, gr increased with temperature in Fla 4B, the interspecific hybrid (U875) and U8245. We suggest that the heat tolerance of Fla 4B is heritable and that it may be due to non-stomatal factors. Similar levels of heat tolerance due to non-stomatal factors have been reported for other species (2, 8, 9, 13) and heat tolerance has been associated in tomato with a heritable variation in the RuBP carboxylase- oxygenase enzyme (12). 76 The interspecific hybrid U875 had maximum photosyn- thetic rates that were 20 to 50% higher than the highbush parent and 30 to 80% higher than Fla 4B. This enhanced photosynthetic efficiency may be due to heterosis. Blueberry is sensitive to inbreeding depression and enhanced growth rates have been reported from crosses between unrelated Vaccinium genotypes (11). The temperature plasticity and environmental range of highbush blueberry might be expanded through interspecific crosses with V; darrowii. Such crosses are possible due to the fact that X; darrowii frequently produces unreduced (diploid) gametes which form fertile hybrids when crossed with the tetraploid highbush blueberries (l, 6, 16). The backcrosses exhibited 002 assimilation values close to 'Bluecrop' at 20 degrees C, and that of U8245 was 60% higher than 'Bluecrop' at 30 degrees C. In addition, U8245 had only moderately higher rates of transpiration than 'Bluecrop' at 30 degrees C and a higher WUE. If these traits are heritable, as the variation in the temperature optimums of the two backcrosses indicates, the high tempera- ture tolerance of I; darrowii can be transferred to highbush blueberry. 77 Literature cited Ballington, J.R. and G.J. Galletta 1976. Potential fertility levels in four diploid Vaccinium species. J} Amer. Soc.1knnn Sci. 101:507-509. Berry, J.A. and O. Bjorkman 1980. Photosynthetic response and adaptation to temperature in higher plants. Ann. Rev. Plant Physiol. 31:491-543. Berry,.LA.znulJ.K.Raison 1982.Responses of macrophytes to temperature In:Encyclopedia of Plant Physiology 12A, 0J3 Lange, PAL Nobel, CJL Osmond and H. Zeigler (eds.) pp 277-338. Camp, WJL 1945. The North American blueberries with notes on other groups of Vacciniaceae. Brittonia 5:203-275. Cowan, I.R. 1977. Stomatal behavior and environment. Advances in Botanical Research. 4:117-228. Draper, AJL, JJL.Ballington and G“L Galletta 1982. Breeding methods for improving southern tetraploid blueberries..L Amer.Soc.ikn15 Sci.107:106-109. Fock H., K. Klug and D.T. Canvin 1979. Effect of carbon dioxide and temperature on photosynthetic C02 uptake and photorespiratory C02 evolution in sunflower leaves. Planta 145:219-223. Khairi, M.A. and A.E. Hall 1976. Temperature and humidity effects on net photosynthesis and transpiration of citrus. Physiol. Plant. 36:29-34. 10. 11. 12. 13. 14. 15. 78 Khairi, FLA. and AWE. Hall 1976. Comparative studies of net photosynthesis and transpiration of some citrus species and relatives. Physiol. Plant. 36:35-39. Lyrene, P.M. and W.B. Sherman 1980. Horticultural characteristics of native Vaccinium darrowii, V. elliottii, I; fuscatum, and I; myrsinites in Alachua county, Florida..L Amer.Soc. Hort.Sci. 105:393-396. Lyrene, P.M. 1984. Broadening the germplasm base in rabbiteye blueberry breeding. In: Proceedings Of the fifth North American blueberry reasearch workers conference.T.E.Crocker and P.Lyrene (edsfi)pp 72-76. Markus, V., S. Lurie, B. Bravdo, M.A. Stevens and J. Rudich 1981. High temperature effects on RuBP carboxylase and carbonic anhydrase activity in two tomato cultivars. Physiol. Plant. 53:407—412. Monson, R.K., M.A. Stidham, G.J. Williams III, G.E. Edwards and ERG. Uribe 1982. Temperature dependence of photosynthesis in Agropyron smithii Rydv. Plant Physiol. 69:921-928. Moon, .LW. 1984. Gas exchange characteristics of Vaccinium corymbosum L. and Vaccinium darrowii Camp. PhD Thesis Michigan State University. Moon,J}W.and JJL Flore 1984.A basic computer program for calculation of photosynthesis, stomatal conductance and related parameters in an open gas exchange system. Photosynthesis Research (submitted). 79 16. Moore, JJL 1965. Improving highbush blueberries by breeding and selection. Euphytica 14:39-48.