Mill.) was collected in the daytime and the nighttime, and dependence of calcium uptake on water absorption and respiration in the tomato roots is examined by analyzing exudation rate CJw; ,uL S-I), calcium concentration ((Ca2+J ; mmol L-I) in the xylem sap and root calcium uptake rate CJCa; nmol S-I) in the root exudation. lw from the stem stump was about one third of transpiration rate from the whole shoot before decapitation and was kept two to five times higher in the daytime than in the nighttime. The xylem sap (Ca2+J was about 3 to 4.5 times higher than that of the nutrient solution in the hydroponic pot, and the xylem sap (Ca2+J in the daytime was 1.5 times higher than that in the nighttime. Consequently, lca in the daytime was 3 to 5.5 times higher than that in the nighttime. The daytime higher lea was depressed in the restrictedly water absorbing plant, and the restriction of root respiration in the daytime lowered the xylem sap (Ca2+J, which resulted in significant depression in lea. Furthermore, the lower lea in the nighttime was not enhanced by activating the nighttime root respiration. Thus, the daytime root calcium uptake was regulated by both of the water absorption and the respiration in roots, and the nighttime root respiration was not a rate-limiting factor for the lower calcium uptake in the nighttime. The observed dependence of calcium uptake on water absorption and respiration in roots was explained in relation to the important role of the root endodermis.

KITANO M., ARAKI T. and ECUCHI H. Temperature dependence of postphloem transport regulated by respiration in tomato fruit. BIOTRONICS 27. 33-39, 1998. Temperature effect on postphloem transport in tomato fruits was analyzed by measuring fruit growth rate, pedicel sugar flux and fruit respiratory CO, efflux under changes in air temperature around fruits. Dynamic responses of fruit growth rate and pedicel sugar flux to temperature change around fruits were clearly found to be associated with change in fruit respiration. Fruit growth rate and pedicel sugar flux were remarkably enhanced with fruit respiration by temperature rise around fruits, where those &lo values between 20°C and 30°C distributed around 2.3. These enhancements in fruit growth and sugar translocation by the temperature rise were not found in the truss with the respiration-inhibited fruits. From these results, it can be suggested that respiration in tomato fruits contributes to the temperature effects on the expansive growth and the sugar accumulation through regulation of the energy-dependent process of the postphloem sugar transport in the fruits.

EGUCHI T., KIT ANO M. and EGUCHI H. Growth of sweetpotato tuber as affected by the ambient humidity. BIOTRONICS 27, 93-96, 1998. A tuber of sweetpotato plants (Ipomoea batatas Lam. cv. Koganesengan) was grown in the air space of a hydroponic system, where relative humidity around the tuber was controlled at 50, 70 or 90%RH under an air temperature of 28°C. Diurnal variation of the tuber volume was measured on-line by using a laser micrometer system, and effect of the ambient humidity on the tuber growth was analyzed. In all of the humidity conditions, the larger increase in the tuber volume was found during the nighttime. The nighttime growth rate was clearly affected by the humidity around the tuber, which became higher in the order of 90, 50 and 70%RH.

EGUCHI, H., YOSHIDA, S., TOH, K., HAMAKOGA, M. and KITANO, M. Growth of lettuce plants (Lactuca sativa L.) under variable-value control of air temperature by using natural light intensity as feedback signal. BIOTRONICS 26, 13-20. 1997. Lettuce plants (Lactuca sativa L.) were grown under different regimes of variable-value control of air temperature, where the set values of air temperature increased quadratically with the natural light intensity in the different dynamic ranges. Under the regime of lower night temperature and larger dynamic range of air temperature, succulent growth was prevented, and leaf fresh and dry weights per unit leaf area became larger because of leaf thickening with well developed spongy layer. The results suggest that the variable-value control of air temperature by using the natural light intensity as a feedback signal can improve plant growth under controlled environment.

EGUCHI T., KITANO M. and EGUCHI H. Measurement of diurnal change in tuber growth of sweet potato plants. BIOTRONICS 26, 67-72, 1997. Tuber volume of sweet potato plants (Ipomoea batatas Lam.) was measured in course of time by applying an on-line laser micrometer eLM) system, and diurnal change in tuber growth was analyzed. Tuber growth rate fluctuated synchronizing with the photoperiod, where the growth rate in the light was kept lower than that in the dark. Rapid increase and decrease in the growth rate were occurred after darkening and lightening, respectively. These results suggest that tuber growth of sweet potato plants responds to changes in the shoot environment, and the growth response was considered to be related to leaf transpiration through dynamics of plant water balance. Thus, diurnal pattern of tuber growth in sweet potato plants was revealed clearly by using the LM system.

KITANO M., YOKOMAKURA F. and EGUCHI H. Interactive dynamics of fruit and stem growth in tomato plants as affected by root water condition. II Relation with sucrose translocation. BIOTRONICS 25, 77-84, 1996. Dynamics of sucrose translocation in hydroponic tomato plants (Lycopersion esculentum MilL) were analyzed with reference to fruit and stem growth as affected by water relations. Sucrose flux through a pedicel was evaluated by bathing the cut end of the pedicel into a chelating agent of ethylenediaminetetraacetic acid (EDTA) solution under on-line measurement of fruit and stem growth. Sucrose flux and fruit and stem growth were affected by change in root water conditions and appeared in different patterns dependent on change in xylem water potential during dewatering. In the case of larger decrease in xylem water potential and significant stem shrinkage during dewatering, fruit growth was kept higher with decrease in sucrose flux, but rewatering induced immediate swelling of stem and sap backflow from the fruit. On the other hand, the smaller decrease in xylem water potential during dewatering resulted in highly enhanced sucrose flux and fruit growth after rewatering. These results suggest that fruit growth and sucrose translocation can be controlled by the root water condition through interactive dynamics with water relations of translocation path responding to change in xylem water potential.

EGUCHI T., KITANO M. and EGUCHI H. Effect of air humidity around tuberous root on sink strength in sweet potato prants grown in a solution-air culture system. BIOTRONICS 24, 45-49, 1995. Sweet potato plants (Ipomoea batatas Lam.) were grown in a solution-air culture system, where the tuberous root was kept in an air space above a nutrient solution. Effect of air humidity in the air space on sink strength of tuberous root was examined under the respective humidity conditions of 50, 70 and 90±8%RH at a root temperature of 24 ± O. 5°C. Fresh weight of tuberous root became higher at higher humidities. Dry weight was lowest at 50%RH and almost the same at 70% and 90% RH. At 90% RH, however, the larger part of dry matter was partitioned to adventitious buds than to tuberous root. Sink strength of tuberous root, which was estimated by dry weight per unit leaf area, was found to be maximized at 70%RH.

EGUCHI T,. KITANO M. and EGUCHI H. Effect of root temperature on sink strength of tuberous root in sweet potato plants (Ipomoea batatas Lam.). BIOTRONICS 23, 75-80, 1994. Eflect of root temperature on sink strength of tuberous root in sweet potato plants was examined at root temperatures of 20 to 32°C under a constant air condition of 28°C and 70% RH. Dry weight, volume and dry matter content of tuberous root became higher at root temperatures of 24 to 26°C. However, sink strength of tuberous root, which was estimated by its dry weight per unit leaf area, was highest at a root temperature of 24°C possibly because of lower sink activities at lower root temperatures and lower sink capacities with higher respiratory loss at higher root temperatures.

KITANO M., HAMAKOGA M. and EGUCHI H. Control of evaporative demand on transpiring plants m. Transpiration and growth of cucumber under controlled evaporative demand. BIOTRONICS 23, 105-111, 1994. The Control of evaporative demand on transpiring plants was performed in natural light growth chambers, and transpiration, stomatal conductance and dry matter production of cucumber seedling (Cucumis sativus L.) were analyzed under different conditions of the controlled evaporative demand. Under the lower evaporative demand, transpiration was extremely depressed, and stomatal conductance and turgor-driven leaf expansion were enhanced. These effects of the lower evaporative demand brought the higher photosynthetic dry matter production with the higher water use efficiency. From the results, it is suggested that the control of evaporative demand can be a reliable measure to manipulate water use and dry matter production of plants.

CHIKUSHI J. and EGUCHI H. A model of leaf growth responding to air temperatures. BIOTRONICS 20, 65-71, 1991. A hysteresis model was applied to estimate leaf growth curve of cucumber leaf exposed to changing air temperature. Cucumber plants were treated with low temperature of 15°C for different periods, and thereafter grown at 25°C in a growth chamber. Observed data of leaf growth curves were fitted by the Richards equation, and were compared with the curves estimated by the model. It was demonstrated that the hysteresis model can be useful for estimating the curves of leaf growth responding to the low temperature treatment.