‘8‘ WIN”WIMIWUHIWWillIUHHIIHIINHI”WI 621 _' I (D I' THESit' - u if I: I] 4 ~ II 34-5 Li 1314‘» _"l ‘ Michigan State Univers'ty This is to certify that the thesis entitled SOIL AND PLANT WATER POTENTIALS IN RELATION TO TOMATO FRUIT CRACKING presented by DOROTA HAMAN BURGESS has been accepted towards fulfillment of the requirements for M.S. degree in A9. Eng. 5 MM ajor professor mawo 0-7639 SOIL AND PLANT WATER POTENTIALS IN RELATION TO TGWATO FRUIT CRACKING By Dorota Haman Burgess A THESIS Submitted to Michigan State University In partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Agricultural Engineering 1979 -»' 7‘37 ABSTRACT SOIL AND PLANT WATER POTENTIALS IN RELATION TO TLTMTO FRUIT CRACKING By Dorota Haman Burgess Body of Abstract The objective of this investigation was to examine water potential of the ripe tomato fruit as a function of drastical change in water potential of the soil. A sudden increase of water potential of the soil was reflected in the water potential of the ripe fruit. However, the water potential change in the fruit appeared to be inversely proportional to the water potential change in the root zone. Aspects of tomato fruit cracking were also discussed. Approved Department Ch rperson ACKNOWLEDGMENTS I would like to thank Dr. George E. Merva, Dr. Haruhiko Murase and Dr. Hugh C. Price (Horticulture) for serving onthe guidance committee. Special thanks to all of them for the time spent with me discussing the results of experiments. Special thanks to Dr. George E. Merva for guidance during all the time of the project. I would like to thank Dr. Haruhiko Murase for his technical guidance and Dr. S. Honma for his help with greenhouse facilities. Thanks to my husband, Gary, for help and patience. ii TABLE OF CONTENTS Page ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . ..... ii LIST OF FIGURES . . . . ...... iv Chapter I. INTRODUCTION . . . . . . . . . . . . . . . . . . 1 II. LITERATURE REVIEW . . . . . . . . . . ...... 3 l. Cracking of tomato fruit — irrigation, rain, humidity, temperature and radiation 3 2. Minerals - their influence on tomato cracking 7 3. Tomato fruit cracking - genetic and anatomical factors 9 4. Water potential . ll 5. Plant water potential measurement . 13 III. EXPERIMENTAL PROCEDURE . . . 15 IV. RESULTS . 19 V. DISCUSSION . . 28 1. Discussion of the results of the experiment performed in the environmental chamber . . . 28 2. Discussion of the observation connected with tomato fruit cracking . 31 VI. CONCLUSIONS 35 VII. SUGGESTIONS . 36 APPENDIX . 39 REFERENCES . 44 iii LIST OF FIGURES Figure Page 1. Experiment #1 . . . . . . . . . . . . . . . . . . . . . . . 23 Water potential of the ripe tomato fruit and the leaf in relation to the sudden change of water potential of the soil. 2. Experiment #2 . . . . . . . . . . . . . . . . . . . . . . . 24 The response of the water potential of the ripe tomato fruit to the sudden change of water potential of the soil. 3. Experiment #3 . . . . . . . . . . . . . . . . . . . . . . . 25 Two measurements of the change of water potential of the tomato fruit in relation to the sudden change of soil water potential. 4. Experiment #4 . . . . . . . . . . . . . . . . . . . . . . . 26 The response of the water potential of the ripe tomato fruit to the sudden change of water potential of the soil. 5. Experiment #5 . . . . . . . . . . . . . . . . . . . . . . . 27 water potential of two tomato fruits from the same plant in relation to the sudden change of soil water potential. iv I. INTRODUCTION The tomato plant, Lycopersicon esculentum L.(cv Michigan—Ohio Hybrid) nightshade family, which includes also potato, tobacco and many poisonous plants as well. The fruit of the tomato plant requires from 40 to 60 days to ripen from flowering. It takes about one week from mature green stage to fully ripe. The week from mature green to fully ripe is the time when cracking mostly occurs if conditions are favor— able. Only in the very immature stage is there no cracking of tomato fruits. It is known that the water status of the fruit is a direct cause of tomato fruit cracking. The water status can be modeled by the water potential of the fruit tissue. It is very likely that cracking is related to a rapid change of water potential in the fruit. However, there are many different factors which influence water potential and indirectly cause tomato cracking. For example: 1. Water influence — irrigation, rain, dew, humidity 2. Temperature and radiation 3. Minerals applied to the soil and directly to the plant 4. Genetic and anatomical properties of the plant A proper understanding of these influences can help control the water potential of the fruit, and, possibly prevent it from cracking. The objective of this investigation was to find the relationship between water potential of the soil and water potential of the mature, ripe tomato fruit, especially in the transient phases after saturation of very dry soil. II. LITERATURE REVIEW 1. Cracking of tomato fruit — irrigation, rain, humidity, tempera— ture and radiation. The opinion of many is that rain and overhead irrigation can cause the most damage in tomato fruits (Frazier 1934, 1935, Brown 5 Price 1934, Reynard 1960). Tomato fruit cracking is not supposed to be the major problem when a continuous supply of water is available provided it is not overhead irrigation, but furrow or trickle irrigation (Reynard 1960). Drip irrigation which allows for wetting the soil to the extent that the water potential approaches zero and maintains low water tension for a desired duration of time (Rudich, et. a1. 1977), should decrease tomato cracking. Tomato cracking is also a minor problem in areas with very little or no rain during the picking season such as Hawaii (Frazier 1947). It appears that rain or overhead irrigation causes a significant change in water status of the plant by changing soil moisture, humidity, and temperature, and allowing water to accumulate near the stem end, where it may be absorbed through the stem scar into the fruit. Frazier (1947) found that a "water deficit of sufficient severity to affect the cell occurred as a result of daily fluctuation in the evaporating power of the air, regardless of soil moisture content”. This is understandable if one remembers that cracking is caused by the plant state, not by the soil water state. Plant water stress depends on relative rates of water absorption and water loss, not on the water absorption alone (Brix 1962). This means that it is mainly influenced by transpiration of the plant which occures mostly through the stomata in the leaves. Rain or overhead irrigation likely causes stomatal closure by change of environmental conditions (like temperature, humidity). Stomatal closure must be followed by serious changes in transpiration. Stomata closure is also the main cause for transpiration decline during development of water stress. Since stomata control only part of the total resistance, their closure will vary the magnitude of stomatal resistance relative to that of boundary layer (Hsiao 1973). Since some- times very small amounts of water have to be absorbed by a fruit for cracking to occur (Frazier 1934), the small decrease in transpiration can be sufficient to cause damage. Most authors assume that water cannot be absorbed through the skin of the fruit, since it is known that a tomato fruit does not have stomata. It was found that the fruit apparently does transpire because dew con- densation was found after bagging the fruits (Sing and Young 1970). This could be due to the gases and vapor exchange through the cuticle (Schonherr and Bukovak 1973, Schonherr 1979) in the skin of the fruit. Transpiration of the plant can also be influenced by many other factors. The main ones are atmospheric conditions, e.g., temperature, humidity, wind and radiation. -5- I.V. Inverson (1938) has related tomato fruit cracking to soil moisture. He indicates that with high soil moisture and high relative humidity, practically no tomato cracking occurs. It is known that hydroponic plants which have a continuous supply of water can crack severely (Herrera 1978). Hydroponic plants have a higher rate of transpiration than plants grown in soil. The root zone has a high moisture supply, but very often a deficit of water in a left tissue follows high transpiration (Ledovskii 1980). This means that the water potential inside the plant changes significantly which can result in tomato fruit cracking. The temperature of the fruit, which is due mostly to radiation, appears to have significant effect on the tomato cracking. Fruits which are not protected by the foliage have the greatest daily range of temperatures. Such fruits are from 13 to 25°F (7 to 14°C) higher in temperature at noon than ones which are protected by leaves, and also slightly cooler at night because of radiation losses (MacGillvray 1934). The temperature of the air itself can be critical for tomato fruit cracking. In Florida, fluctuation in temperature along with a drive of cold air (which frequently occurs in the southern part of the state) can cause severe cracking (Reynard 1934). Frazier (1935) also checked the influence of pruning the plant on the cracking of tomato fruits. ”Pruning and stacking increased the occurrence of cracking but further pruning of these plants by leaf removal reduced it, but not to the extent shown by unpruned, unstaked plants”. -6- It was found that shading of whole plants with muslin decreased the severity of cracking (Frazier 1934), but covering the plants with a plastic tent (no movement of the air) enhanced cracking significantly (Sing and Young 1970). However, protection from radiation usually results in decrease in quality of the fruit. Shaded fruits are high in water content and low in total sugars and carbohydrates (Frazier 1934). We know that carbohydrates is transported from the tomato plant leaf in two directions; upwards towards the apex, and downwards towards the root. The suggestion was that carbon flows upward via internal phloem and downward via external phloem (Bonnemain 1965). The translocation of carbohydrates is not a process confined to dark periods. Some authors are of the opinion that translocation is favored by low temperature and that it limits the growth and flowering of fruit at temperatures above 18°C (Kristoffersen 1963). The widely held belief that a plant can fully compensate for a missing truss through yields on other trusses is not necessarily true (Slack, et. a1. 1977). However, cracking was shown to be positively related to the numbers of fruits produced in clusters of six of more (Howlett and Kretchman 1968). Sugars constitute 1.5—4.S% of the fresh weight in a ripe fruit. The sugar content increases through maturation and ripening. Shading or removal of the leaves decreases the level of sugars in ripe fruit. The sugars in a fruit reflect differences in the intensity and duration of light (Hobson and Davies 1970). -7- hbximum starch content can be found in 8 week old tomato fruits, shortly before they start to color. The starch disappeares rapidly during ripening of the fruits. We can assume that the starch content of the fruit is 0.1% (Hobson and Davies 1970), and only half of this breaks down into sugars during ripening. The predominant acid in a ripe tomato is citric acid, with malic acid second in abundance (traces of few others exist). Maximum acidity (pH 4.1) coincides with an appearence of pink color. The level of acidity drops during ripening (pH 4.5) (Charles, et. a1. 1978). 2. Minerals - their influence on tomato cracking. Many experiments were done to check the influence of different chemicals on the tomato plant. The amount of cracking has been shown to increase with added nitrogen. An interesting interaction has been found with nitrogen and potassium; at lower potassium levels, cracking increased with added nitrogen and than decreased after a certain level of nitrogen had been reached. At higher potassium levels, cracking appeared uniformly in large amounts with added nitrogen (Howlett 1973). There was a very close relationship between the potassium level of the fruit and acidity of the fruit. Any increase of potassium level of the fruit produced a corresponding increase in organic acids in order to maintain a constant pH. The acidity of the tomato also increased with increasing levels of nitrogen and decreased with increasing levels of phosphates (Hobson and Davies 1970). Application of potassium permanganate to the soil was found to increase biological activity of the tomato plants and to stimulate production of a more fiberous type of root system. This was largely due to the effect of magnesium, not to the chemical oxidation. The plant size was increased overall and there was a reduction in fruit cracking (Inverson 1938). It was also found that an excess accumulation of Mg induces a physiological deficit of Ca in the tissue of the plants. The calcium deficit leads to an inhibition of nitrate assimilation (Suder et. a1. 1977). It was found that a high calcium level decreased acidity when combined with high amounts of potassium. The influence of Ca on the plant appeares to be the more important factor in tomato fruit cracking. Sodium and calcium ions change the pennability of the outer membranes of the root tissue of the plants (Pridhod'ko 1970). Van Goor (1968) showed that the permability of the fruit tissue in Ca deficient tomato plants is higher then that for plants receiving nonnal Ca applications. However, by spraying only the leaves with radioactive 45Ca, it was shown that Ca does not move from the leaves to the fruit (Bangerth 1973). Patterns of transport change with the development of the plant (Khan, et. a1. 1967). All tested ions which have a strong effect in preventing fruit cracking have also a strong precipitating or cross linking effect on pectins. It appears that Ca in the cell walls and especially in the middle lamella plays an important role in the cracking process (Bangerth 1973). Protopectin is highest in the ovary wall stem end tissue. -9- It would seen that the breakdown of protopectin, which accompanies maturity, may be the reason for cracking of ripe fruit (Frazier 1934). The percentage of cracked fruits is increased drastically by immersing the fruits in a solution, such as pure acids, which dissolves Ca from the cell wall (Bangerth 1973). It was also shown that the addition of Ca to the sprinkler system water reduced cracking and that Ca reduced it more than other divalent ions. Also overhead sprinkler with tap water caused less cracking than rain water. Application of calcium during the rainfall was suggested (Bangerth 1973). 3. Tomato fruit cracking - genetic and anatomical factors. There are many reasons why the tomato has become a favorite subject for genetic studies. One is the plant's high rate of self pollination which leads to early expression of recessive mutation (Charles, et. a1. 1978). Some authors (Frazier 1947, Thompson 1965, Reynard 1960, Armstrong, et. a1. 1967) suggested the breeding of tomato varieties with increased resistance to fruit cracking. The chromosome maps for the tomato are among the best (Charles, et. a1. 1978). Many genes governing crack resistance in tomato fruit are found in a number of different varieties and strains. Gene effects are usually considered to be multiplicative rather then additive (Reynard 1960). Apparently, two separate gene systems govern radial crack resistance and concentric crack resistance. Nhuchi and Honda (1959) induced concentric cracking by water uptake from the outside through -10- the corky spots, and radial cracking by expansion pressure of the fruit. It is known that detenninate Vine habit (sp) and (y) - clear skin genes are associated with radial crack resistance. Concentric crack resistance is associated with (fl) — flashy calyx and the number of fruits per plant. (Mi) - root knot resistance gives susceptibility to concentric cracking. Radial and concentric crack resistance are associated with (u) — uniform ripening and (d) — dwarf genes (reynard 1960). The positive association of crack resistance and flashy calyx indicates that the (£1) gene can be utilized as a morfological marker in the selection of crack resistance tomato varieties (Mel Chinh—Yu Chu, et. al. 1972). Thompson (1967) emphasize that certain types of crack resistance are conditioned by a large number of genetic factors, each having a relatively small individual effect. It was shown that resistance to cracking can be improved through recombination and selection of two unrelated lines (Thompson 1965). Some anatomical differences between tomato fruits susceptible to cracking and tomato fruits resistant to cracking were found. For example, fruits showing resistance to concentric cracking possessed flattened epidermal cells. No consistent anatomical differences were linked to radial crack resistance (Cotner, et. a1. 1969). There are also some differences in the cutinized layer between tomatoes resistant to cracking and tomatoes susceptible to cracking. Cracking resistance depends on skin strength and its ability to stretch; it does not depend on the thickness (Voisey 1970). The elastic modulus -11- of the tomato skin is a function of water potential GWurase and Merva 1977). 4. water potential. The energy status of water is called water potential and is composed of several components (Feddes, et. al. 1978) wTot = wp + ms + wg + wT where (Merva 1975): w — osmotic potential w ~ matrix potential m - gravitational potential w - pressure potential The potentials are defined relative to the potential or pure water at the same temperature and atmospheric pressure. Water potential can be expressed in dimensions of pressure (Pa-Pascal). Under equilibrium conditions, using vapor pressure, the water potential can be expressed in terms of relative humidity: pm = RT ln(e/e°)/VQ _12_ where (Merva 1975): R - ideal gas constant (82.05 cm3 - atm/k°—mole) T - absolute temperature (°K) e - partial pressure of water vapor e°— saturated partial pressure of water vapor Vw- partial molal volume of liquid water (cmS/mole) e/e°- relative humidity The water potential can be measured using a Peltier psychrometer at a constant temperature and pressure. It can be done by measuring the vapor pressure over a freely evaporating surface of the sample (in this case, a piece of tissue). The equilibrium conditions necessary require that the psychrometer either be sealed in a vapor tight chamber with the sample, or that it be placed in intimate contact with the system for in—situ measurements (Van Haveren and Brown 1972). The water potential of the plant cell can be modeled by: m = ms + up (Merva 1975) (D where: ws - solute potential due to the sugars and minerals inside the cell mp — pressure potential due to the turgor pressure inside the cell Water always moves from the points where it has a high energy status to points where it has a lower one (Feddes, et. al. 1978). -13_ This is in agreement with Merva (1975) who pointed out that water movement in the plant occurs as a result of water potential gradient. It has been found that the modulus of elasticity of tomato skin is a function of water potential (Murase and Merva 1977). It was concluded that cracking phenomena is possibly a skin failure of fruits due to stresses produced in fruit skin by changes in tissue water potential. 5. Plant water potential measurement The need for accurate measurement of water potential of green plants was pointed out by Kramer (1963). The water potential is a key property of the plant influencing turgor, growth, transpiration, photosynthesis and respiration. Miniature thermocouple psychrometers necessary for water potential measurement was developed by Spanner (1951) and Richards and Ogata (1958). Thermocouple psychrometers provide a measurement of water potential by sensing the relative humidity of their environ- ment. They function as follows: The junction of the thermocouple is cooled by the passage of a Peltier current to a temperature below the dew point, causing water condensation on the junction. The cooling current is then discontinued and water from the junction is allowed to evaporate back into the surrounding atmosphere. This causes a temperature depression of the junction due to heat of vaporization. The magnitude of the depression depends on the rela- tive humidity of the surrounding atmosphere, since, as indicated, -14- the water potential is a function of the relative humidity and absolute temperature (Merva 1975). Murase and Horinkowa (l977)** developed a method of fruit water potential measurement using a left thermocouple transducer. The measurements technique requires removal of the cuticle. Since the cuticle is extremely thin, it is impossible to avoid excision of epidennal and parenchym cells. This however, does not affect the measurement of water potential since, after removal of cuticle, it is possible to measure the relative humidity in the intercellular spaces. Under equilibrium conditions, this gives the water potential of the fruit cells. ** Murase and Horinkova unpublished paper, Department of Agricultural Engineering, Michigan State University. -15- III. EXPERIMENTAL PROCEDURE Tomato plants of the Michigan—Ohio Hybrid WR-7 were grown under greenhouse conditions in 9 inch clay pots using a greenhouse soil mix. The plants were fumigated Mdth Orethene to control insect infestation. The flowers were pollinated by shaking flower clusters during warm, sunny days around noon. The plants were heavily watered (saturated) once or twice a day depending on the weather until the first fruit matured on each plant. After maturation of the first fruit, 100—200 ml. of water per day was added depending on the weather conditions and leaf water potential. Leaf samples were taken using a paper punch. The discs were placed in the C-52 sample chamber, where the water potential of the sample was measured using the dew point method**. The thermocouples were cleaned before measurements using steam. Samples were taken before adding the water and one hour after adding the water. Sufficient water was added to maintain the water potential of the plant near —8 atmospheres. It was assumed that the water potential did not vary significantly throughout the plant. However, the plant is almost never in an equilibrium state (Herrera 1978). It was also pointed by Kozlowski (1964) that the water is often transported from old to the young tissues under conditions of internal water stress and it may cause a nonequilibrium state throughout the plant (Herrera 1978). When this is taken under consideration it can be **WESCOR INC. - Instruction manual to HR—33 Dew Point Microvoltometer -16- only concluded that the tomato plants had limited supply of water during ripening and that water stress developed in the plant. Consequently, a single measurement of the water potential of any leaf probably does not describe the water status of the entire plant. Following fruit ripening, the plants were transported to the laboratory at different times and placed in the Sherer environmental chamber in preparation for the experiment. Each plant was kept for 3 days at constant temperature, humidity and light before the experi- ment was started. The plants were not watered during this time. A ripe fruit that had no cracks was selected for the experiment. It was placed in a ring stand for support and the spot near the stem end where the thermocouple was to be placed was wiped with distilled water. An L-51 leaf psychrometer was removed from it's metal casing and fastened in a swivel damp. The small circular piece of epidermis was removed with a scalpel and forcepts to expose the intercellular spaces to the thermocouple psychrometer. Distilled water was used to clean the broken epidermal and parenchyma cells. An L-Sl thermocouple psychrometer was placed against the tomato, and exposed to the fleshy parenchyma where the epidermis was removed. A positive contact between tomato and the outside ring of the psy- chrometer was attempted to insure a good vapor seal. Petroleum jelly was placed around the outside edge of the left psychrometer to further prevent any vapor escape. Two L—51 leaf psychrometers were used for leaf water potential measurements, but the date thus obtained were not reliable since it was the end of the summer and the tomato plants were -17- quite old. Continuous exposure to light in the environmental chamber together with the very dry conditions caused the leaves to die rapidly and frequent changes of psychrometers from one left to another were necessary. To be representative, the measurement should have been taken from the same leaf since water moves from one leaf to the other depending on the age and position of the leaves and this may cause the nonequilibrium of the water potential throughout the plant (Kozlowski 1964). In the side of each pot two holes were drilled to allow for inertion of soil psychrometers; the first was 6 cm from the top and the second 13 cm from the top of the pot. The soil psychrometers were placed perpendicular to the wall where they appeared to work satisfactorily. However, after adding the water to the soil to the point of saturation, the water potential reading from the soil psychrometers remained far below zero indicating that they did not function properly. If leaf water potential is a good indication of the soil water potential, it can be assume that the soil water potential was about ~1200 Pascals. The soil was first dried to a powder and then saturated to the point where the water appeared in a pan below the pot. Since drainage occured it can be assumed that after adding water, the soil water potential approached zero. The purpose of the experiment was to observe the reaction of the ripe fruit to the saturation of the soil after a very dry period. The water potential of the fruit was measured by passing a Peltier current through the junction of the thermocouple, an HR—33T Microvoltometer was used. An automatic switching device -18- incorporating the FIR—33T design“ was used for the measurement. The output of each transducer was recorded sequentially on chart paper using a 10 mv VOMS Chart Recorder. Mconstructed by Murase 1977. -19- IV. RESULTS The experiments were performed on 5 different tomato plants. All numerical data for the experiments are included in the appendix. The results of the first experiment are presented graphically in figure 1. For the first 4600 minutes (during the dry period) the average water potential of the ripe fruit dropped down from about -300 kPa to -500 kPa. In the first experiment we have records of water potential for the leaf during the dry period. The average water potential for the leaf, which is an indication of the water status of the whole plant, was about -l800 kPa. Since the soil psychrometers did not equilibrate after adding the water to the soil we can only assume that the water potential of the saturated soil (4600 min) was close to zero. We therefore treat the water potential of the soil as a step function following addition of water. When the water was added (after 4600 min) to the soil, a sudden drop in the water potential of the fruit was observed. In this experiment possibility of the influence of the different temperature of the water added to the soil on equilibrium conditions was not taken under consideration. In all of the following experiments, the water tem— perature was brought up to the temperature of the environmental chamber before adding it to the soil. In the first experiment the drop in the water potential of the ripe tomato fruit down to -2500 kPa was probably due to some kind of nonequilibrium state when the cold water was added to the soil. After achieving an equilibrium state, -20_ (440 min later), the records during the next 936 minutes showed that on the average the water potential of the tomato fruit dropped to —900 kPa. The second experiment is presented graphically in figure 2. The water potential of the fruit during the dry time (first 1380 min) was on the average —450 kPa. After adding the water to the soil we observed a drop in the fruit water potential to -l300 kPa for about 420 minutes; than during the next 1800 minutesnere'recorded an average water potential of -1000 kPa. The last part of the recording shows much bigger fluctuations since a less precise scale was used in an attempt to measure the soil and fruit water potential simultaneously. However, the same problems with the psychrometers occured as in the first experiment so that a step function for the soil water potential had to be assumed. In the third experiment, two psychrometers (L—51) were placed on the same fruit in order to get more frequent recordings immediately after saturation of the soil. Each psychrometer had a twenty minutes equilibration time so the water potential of the fruit was recorded every ten minutes. The average water potential of the fruit during the dry period was -1100 kPa. For the first 180 minutes after satura— tion of the soil, the measurement were taken every ten minutes. How— ever, except for big fluctuations in the observed values (from -400 kPa to —l700 kPa), the average value seemed to stay at about -1100 kPa. There can be a few reasons for this: the plant did not respond during the first three hours because of the physiological reasons, -21- anatomical reasons or the psychrometers were not given enough time to equilibrate (twenty minutes), so that the readings were not very precise. However, later on, when the reading was taken from only one psychrometer, with equilibration time 60 minutes, we can see an analogical drop in the water potential of the fruit as in the first and second experiments. For the last 1020 minutes, the water poten- tial was on the average —l700 kPa. The fourth plant followed a similar pattern; the water potential of the ripe tomato fruit during the dry time was an average of -400 kPa. After adding the water to the soil, it dropped down to -600 kPa (average). In the fifth experiment, two fruit psychrometers on two different fruits and one soil psychrometer were to record the data. From the beginning of the experiment, during the first 5070 minutes the water potential of the soil dropped down from —1850 kPa to —3000 kPa. Then water was added to one of the fruits by spraying the stem area with distilled water twice: the first time after 3330 minutes (from the beginning of the experiment) and later after 4080 minutes. The other fruit was left dry. The water potential of the first fruit dropped down and then came back to about same level as before adding the water. The water potential of the second fruit dropped slightly, especially spetially after adding the water the second time to the first fruit (50 kPa). It was observed that the water potential of both fruits fluctuated more about the average value than in the first 3330 minutes of the experiment. After 5070 minutes the water was added to the soil. a— . 4. ’ , 7 :fruit dropped from ~600 kPa to -900 kPa after soil saturation. The :second fruit dropped from -600 kPa to -700 kPa after adding the water to the first fruit and to -1100 kPa after saturation of the soil. .38 93 mo Hose-Bog won-ms mo won-EU swoon-m 05 ou 20333 E E3 wfi one udflm cum-gov omen ecu mo Heir-Boa .8me .. 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