The Influence of the Concentration of the Hydroponic Nutrient. Culture Solutions on the Cracking of Cherry Tomato with Special Emphasis

Transcription

1 J. Japan. Soc. Hort. Sci. 62(4) : The Influence of the Concentration of the Hydroponic Nutrient Culture Solutions on the Cracking of Cherry Tomato with Special Emphasis on Water Relationship Katsumi Ohta, Norihiro Ito, Takashi Hosoki, Kunio Inaba and Takanori Bessho Faculty of Agriculture, Shimane University, Matsue, Shimane 690 Summary The relationships between the concentration of nutrient culture solutions and cracking in cherry tomato cv. Sun Cherry were studied. 1. From 10 days after planting to the end of harvest, plants were grown in a half, one and double concentrations of the nutrient solution. The frequency of fruit cracking increased as the solution became more concentrated. With increasing concentration, fruit weight and fruit and leaf water potentials (ƒõw) decreased, whereas the soluble solids content of fruit increased. 2. Diurnal differences in ƒõw of fully ripe fruit and of the leaf became larger as the solution concentrations increased; conversely, the fruit osmotic potential (ƒõs) decreased. Therefore, fruit pressure potential (ƒõp) approached a maximam at 2 AM and a minimum at 2 PM. 3. Compared to a bright, sunny day, fruit and leaf ƒõw were greater on a rainy day. Fruit ƒõw increased as the culture solution became more concentrated. Introdution Cracking in cherry tomato is a serious problem (Fukumoto et al., 1990: Ito et al., 1990: Murase et al., 1993). Ohta et al. (1991b) clarified the relationships between relative humidity and occurrence of fruit cracking of cherry tomato grown hydroponically. Ohta et al. (1993) reported that as the nutrient culture solution became more concentrated, the frequency of fruit cracking increased. However, there is little information on the relationships between fruit cracking and water relation in tomato or cherry tomato. In tomato Murase (1981) reported that when fruit cracking occurred, fruit water potential (ƒõ w) was high. There were some reports about the relationships between fruit cracking and pressure potential (ƒõp) in sweet cherry (Andersen and Richardson, 1982: Yamamoto et al., 1990), citrus (Elfving and Kaufmann, 1972) and grape (Considine and Kriedemann, 1972: Yamamura et al., 1986). In these results, the relatioships bewteen fruit ƒõp and fruit crack- Received for publication 1 July ing are not clear. However, Milad and Shackel (1992) reported that increase in fruit ƒõp followed by irrigation after water stress induced fruit cracking in 'French' prune. Ohta et al. (1993) reported that low fruit osmotic potential (ƒõs) induced fruit cracking in cherry tomato. Therefore, we postulate that fruit cracking is related to fruit and leaf water status (ƒõw, ƒõs and ƒõp) which fluctuates diurnally. Diurnal changes in fruit Yr w were noted in citrus (Elfving and Kaufmann, 1972) and sweet cherry (Tvergyak and Richardson, 1979). The objective of this study was to clarify the mechanism of fruit cracking in cherry tomato by growing plants hydroponically at different nutrient solution concentrations and closely observing the plant water status. Material and Methods Seeds of the cherry tomato esun Cherry' were sown on 14 July 1992 and the seedlings transplanted into a culture bed with 12 plants per 3.3m2 on 17 August, The shoot terminal was pinched leaving three leaves above the third flower truss. 811

2 812 K. Oht, N. Ito, T. Hosoki, K. Inaba and T. Bessho The nutrient solution (1.0 unit: the abbreviation is 1.0 u) contained NO3-N, NH4-N, P, K, Ca and Mg at the concentration of 16, 1.3, 4, 8, 8 and 4 me E liter-1, respectively. During raising seedlings, the solution culture was kept at 0.5 u; 10 days after planting to the end of harvest of the third truss crop, it was maintained to 0.5 u, 1.0 u or 2.0 u (the respcetive electrical conductivity, EC, were: 1.2±0.2 ms Ecm-1, 2.4±0.2 ms E cm-1 or 4.0±0.3 ms E cm-1). EC of each solution was adjusted to initial level by adding water twice a week; the solutions were totally renewed biweekly. ph of the solution was adjusted between 5.0 and 7.0 by adding either 4 N sulfuric acid or 4 N potassium hydroxide. During flowering period 15 ppm p-chlorophenoxyacetic acid (PCPA) was sprayed twice a week to promote fruit set and growth. Fruits were harvested from 9 October to 8 December, During harvesting period the percentage of cracked fruits was recorded. The other culture methods were same as in the previous study (Ohta et al., 1993). Fruit and leaf ƒõw were measured with a pressure chamber (Soil Moisture Equipment Corp. Experiment 1. Weekly and biweekly changes of fruit characteristics, and fruit and leaf ƒõw The following fruit parameters were measured: L, a and b values by a color difference meter, fresh weight, soluble solids content with a % by a refractometer, and ƒõw between 11 AM and 2 PM on sunny days at 3, 4, 5, 6, 7 and 8 weeks after anthesis. Leaf ƒõw of three leaflets of the 7th true leaf were measured 2 weeks after planting; leaf w of one leaflet of the 7th and 14th true leaves ƒõ were measured on 4, 6, 8, 10 and 12 weeks after planting. Experiment 2. Diurnal changes of fruit and leaf water status w of fully ƒõripe fruit and that of a leaflet on the 11th or 12th true leaf were measured 8 weeks after anthesis. Measurements were taken at 3-hour intervals from 11 AM on a sunny day. After the fruit ƒõw were measured at 2 PM and 2 AM, the tips of pedicels with fruits still attached were dipped in distilled water for more than 2 hours after which the fruit ƒõs was measured by cryoscopic method. Fruit ƒõp was estimated by subtracting Model 3005) within 20 sec after sampling. The s from ƒõw. ƒõ press speed was at 0.03 MPa Esec-1 according to the previous report (Araki and Gotoo, 1987). The sites where the fruit and leaf were excised for pressure chamber measurements are shown in Fig. 1. The fruit and leafƒõww measured in this study were estimated according to Boyer (1969). Experiment 3. Fruit and leaf ƒõw in different weather w of fully ripe fruit and of a leaflet ƒõ on the 13th true leaf were measured on the same day between 11 AM and 2 PM. Measurements were made on both sunny and rainy days. Results The percentage of cracked fruits in nutrient solutions of 0.5 u, 1.0 u and 2.0 u were 15.2, 24.7 and 30.1, respectively. The values are significantly different when tested by regression analysis (P=0.05). Experiment 1. Weekly and biweekly changes of fruit characteristics, and fruit and leaf ƒõw The differences in fruit coloration were not clearly evident among plants grown in three concentrations (data not shown). Seven weeks after anthesis, fruit reached the pink mature stage; one Fig. 1. Cut position ( ) of fruit (left) and leaf (right) applied to pressure chamber. A: From 4 to 12 weeks after anthesis. B: 2 weeks after anthesis. week later, the fruits were fully ripe. The differences in fruit weight were significant among the treatments 3 weeks after anthesis; fruit weight of plants kept at 2.0 u was smaller than that held at

3 J. Japan. Soc. Hort. Sci. 62(4) : u (data not shown). Soluble solids content of fruits collected from the 2.0 u treatment was higher than those of fruits from the other treatments at 6 weeks after anthesis (Fig. 2). Fruit ƒõw of the ƒõrw was lowest at 11 AM or 2 PM, and highest at 2 AM among all treatments. From 8 AM to 2 PM leaf ƒõw in the 2.0 u plot was lower than those of other treatments. However, during the rest of the 2.0 u treatment was the smallest of the 3 treatments since 3 weeks after anthesis. ƒõtw of the fruit from the 0.5 u treatment was highest during the entire experimental period. The differences in leaf ƒõ w among the treatments at 2 and 4 weeks after anthesis were not evident (Fig. 3). However, beginning 6 weeks after anthesis, the differences in leaf ƒõw among treatments became apparent; that of the 0.5 u treatments was highest, whereas, leaf ƒõw from the 2.0 u treatment was lowest. No difference in ƒõw between the 7th and 14th true leaves was detectable. Experiment 2. Diurnal changes of fruit and leaf water status Diurnal changes of fruit and leaf ƒõw were shown in Fig. 4. Fruit ƒõw was minimal at 2 PM and at maximum at 2 AM in all treatments. From Fig. 3. Biweekly changes in water potential, ƒõw, in leaves of cv. Cherry cherry tomato Sun collected from plants grown in concentrations of three nutrient solution. Vertical indicate bars error of the mean. zthe nutrient.0 u is 8 AM to 5 PM, fruit ƒõw in the 2.0 u plot was lower than those in the other 2 plots. However, between 5 PM and 8 AM, no difference in fruit ƒõw 7L indicates y seventh true leaf, 14L indicates fourteenth true leaf. was apparent among the three treatments. Leaf Fig. 2. Weekly changes in soluble solids content and water potential, Ww, in cherry tomato cv. Sun Cherry grown in three concentrations of nutrient solution. Vertical bars indicate error of the mean. `The nutrient solution concentration; 1.0 u is Fig. 4. Diurnal changes in water potential (ƒõw) of fruits and leaves of cherry tomato cv. Sun Cherry harvested from three concentrations of nutrient solution. Vertical bars indicate error of the mean. The z nutrient solution concentration; 1.0 u is

4 814 K. Ohta, N. Ito, T. Hosoki, K. Inaba and T. Bessho day leaf ƒõw were similar in the 3 treatments. Both fruit and leaf ƒõ w changed largely as the nutrient solution concentrations were elevated. As the nutrient solution concentrations became higher, fruitƒõw and ƒõs decreased considerably during the day (2 PM). The value of fuit ƒõs decreased more than that of fruit W w, hence fruit p increased (Fig. 5). At night (2 AM), fruit ƒõw ƒõ did not differ among 3 treatments. Fruit Ws at night decreased as it did during the day. Therefore, fruit ƒõp increased markedly as the nutrient solution concentrations became higher. Compared to the daytime values, both fruit ƒõw and ƒõp at night were higher. Experiment 3. Fruit and leaf ƒõw in different weather On a rainy day both fruit and ƒõw increased markedly compared to those on a dry day (Fig. 6). The differences in fruit ƒõw on rainy versus sunny days increased in the 1.0 u and 2.0 u plots. At the higher concentrations, the fruit and leaf ƒõw decreased markedly on dry or rainy days. Discussion As the nutrient solution concentrations was increased, the percentage of cracked fruits increased. This result was similar to that of the previous study (Ohta et al., 1993). Ohta et al. (1991a) reported that at high concentration of the nutrient solution fruit weight decreased, whereas fruit soluble solids content increased. When the fruit and leaf Ww decreased, the moisture status of fruit and leaf was low, the suction forces of fruit and leaf developed from a relatively early growth stage. Therefore, when concentration of the nutrient solution was high, water uptake by the fruit was suppressed, so that fruit growth was retarded; hence, the soluble solids content became concentrated. In Experiment 2, we found that the changes in fruit and leaf Ww influenced their moisture status. That is, because the moisture status was low during the day and high at night, water is imported by the fruit and leaf at night. This result was also recognized in sweet cherry (Tvergyak and Richardson, 1979). In this study, these trends were larger at 2.0 u than at 0.5 u. In this case, as in the nighttime relative humidity was thought to be high (Ohta et al., 1991b), it was anticipated that transpiration from leaf was suppressed. Therefore, it was suggested that excessive water uptake by cherry tomato plant induced fruit cracking. Furthermore, from 8 AM to 2 PM fruit Vi w was higher than leaf Ww, and at 5 AM fruit!ww was lower than leaf W w in all treatments. These results suggested that in the daytime more water flowed into leaves than into fruits, while the flow was reversed toward morning. Milad and Shackel Fig. 5. Water status of cherry tomato cv. Sun Cherry fruits harvested from three concentrations of nutrient solution. Vertical bars indicate error of the mean. The nutrient z solution concentration; 1.0 u is 'Day indicates y daytime (2 PM). Night indicates nighttime (2 AM). Fig. 6. Water potential (Ww) of fruits and leaves of cherry tomato cv. Sun Cherry grown in three concentrations of nutrient solution and harvested on dry and rainy days. Vertical bars indicate error of the mean. 'The nutrient solution concentration; 1.0 u is

5 J. Japan. Soc. Hort. Sci. 62(4) : (1992) attributed the cracking of efrench' prune to the high fruit ƒõp. In this study, it was recognized that the clear relationships of fruit ƒõp with fruit cracking existed. The reason why fruit cracking increased in the high concentration of nutrient solution was probably due to the decreased fruit ƒõs with increased p. On a rainy day the increasement in ƒõ fruit ƒõw was high with increasing the nutrient solution concentration compared to a dry day. This result suggested that on a rainy day fruit ƒõp at 2.0 u was higher than that at 0.5 u. Thus, it was clarified that cherry tomato fruit grown in the high concentration of nutrient solution was likely to crack through the increased fruit ƒõp, which was caused by excessive water uptake followed by decrease in fruit ƒõw in the daytime. Literature Andersen, P. C. and D. G. Richardson A rapid cited method to estimate fruit water status with special reference to rain cracking of sweet cherries. J. Amer. Soc. Hort. Sci. 107: Araki, Y. and Y. Gotoo Application of the pressure chamber method to tomato leaflets for determination of water potential. J. Japan. Soc. Hort. Sci. 56 : (in Japanese with English summary) Boyer, J. S Measurement of the water status of plants. Ann. Rev. Plant Physiol. 20 : Considine, J. A. and P. E. Kriedemann Fruit splitting in grapes: Determination of the critical turgor pressure. Aust. J. Agric. Res. 23 : Elfving, D. C. and M. R. Kaufmann Diurnal and seasonal effects of environment on plant water relations and fruit diameter of citrus. J. Amer. Soc. Hort. Sci. 97 : Fukumoto, Y., S. Okamoto and K. Kojima Studies on the plant growth and fruit yield of cherry tomato in different cultivation style. Bull. R. I. Sys. Hort. Fac. Agr. Kochi Univ. 7 : (in Japanese) Ito, H., M. Murakami and S. Kawai Swelling cracks in cherry tomatoes (Lycopersicum esculentum var. cerasiforme Alef.). I. Influence of cultivar, method of watering and environmental factors on fruit cracking. Res. Bull. Aichi Agric. Res. Ctr. 22 : (in Japanese) Milad, R. E. and K. A. Shackel Water relations of fruit and cracking in French prune (Prunus domestica L. cv. French). J. Amer. Soc. Hort. Sci. 117 : Murase, H Fruit water potential change related to tomato fruit cracking. Bull. Univ. Osaka Pref., Ser. B. 33 : Murase, H., H. Yamada, Y. Nishiura and N. Honami Finite element analysis of fruit cracking in cherry tomato. SHITA JOURNAL 4 : (in Japanese) Ohta, K., N. Ito, T. Hosoki and H. Higashimura. 1991a. Influence of the concentrations of nutrient solution and salt supplement on quality and yield of cherry tomato grown hydroponically. J. Japan. Soc. Hort. Sci. 60 : (in Japanese with English summary) Ohta, K., N. Ito, T. Hosoki and Y. Sugi. 1991b. Influence of relative humidity on fruit cracking of cherry tomato grown on hydroponic culture and its control. J. Japan. Soc. Hort. Sci. 60 : (in Japanese with English summary) Ohta, K., N. Ito, T. Hosoki, K. Endo and 0. Kajikawa Influence of the nutrient solution concentrations on cracking of cherry tomato fruit grown hydroponically. J. Japan. Soc. Hort. Sci. 62 : Tvergyak, P. J. and D. G. Richardson Diurnal changes of leaf and fruit water potentials of sweet cherries during the harvest period. HortScience 14 : Yamamoto, T., M. Kudo and S. Watanabe Fruit cracking and characteristics of fruit thickening in 'Satonishiki' cherry. J. Japan. Soc. Hort. Sci. 59 : Yamamura, H., R. Naito and H. Tamura Effects of light intensity and humidity around clusters on the formation of surface wax and the resistance to berry splitting in 'Delaware' Grapes. J. Japan. Soc. Hort. Sci. 55 :

6 816 K. Ohta, N. Ito, T. Hosoki, K. Inaba and T. Bessho