The stomatal response to evaporative demand depending on air humidity and wind was analyzed in an intact cucumber leaf (Cucumis sativus L.) exposed to different conditions of air humidity and wind velocity in a leaf cuvette. The evaporative demand on the transpiring leaf was evaluated on the basis of the environmental factors within the leaf cuvette and was set at different values by changing the saturation vapor deficit and wind velocity within the leaf cuvette. Using a model leaf of wetted filter paper, a constant positive linear relationship was found between the evaporation rate and the evaporative demand even under different conditions of air humidity and wind velocity. On the other hand, the relationship between gas exchange parameters in the cucumber leaf (i.e., stomatal conductance, transpiration rate and photosynthetic rate) and the evaporative demand was discontinuously shifted due to the change in wind velocity even under the same humidity condition. These differences in the stomatal behaviors in relation to the evaporative demand, given by the respective changes in air humidity and wind velocity, were not attributed to the feedback stomatal response to the intercellular CO2 concentration in the leaf. The mechanism of stomatal response to the evaporative demand, given by the respective changes in air humidity and wind velocity, was explained on the basis of the antagonism relationship between the guard and epidermal cell turgors that are directly affected by the leaf surface humidity and impact of the evaporative demand through water balance within the stomatal complex.
Nutrient solution supplied to cucumber (Cucumis sativus L.) cuttings during low air temperature storage was warmed for 1 day to reduce water stress of cuttings during storage and advance their rooting after storage. Cuttings were stored for 7 days in air temperature of 12-14°C with photosynthetic photon flux density of 12 μmol m-2 s-1. Nutrient solution was supplied to the cuttings through the hypocotyl cut-ends during storage. The nutrient solution temperature was maintained at 28°C for 1 day after starting of storage or before end of storage. The nutrient solution temperature was maintained at 14°C on other days. During storage, fresh weight and relative chlorophyll content of the cuttings treated in nutrient solution of 28°C for 1 day after the starting of storage was maintained higher than those that were untreated. Three days after planting the cuttings following storage, root fresh weight of the cuttings treated in nutrient solution of 28°C for 1 day after the starting storage or before the ending storage was 1.7-1.8 times as large as those that were untreated. Treatment using the warming nutrient solution increased water absorption rate and transpiration rate of cuttings ; moreover, it reduced wilting of cuttings during storage. These results indicate that application of nutrient solution of about 28°C for 1 day after the starting storage reduced the water stress of the cuttings, maintained high chlorophyll content, and advanced rooting after the end of storage in comparison with nutrient solution of about 14°C during storage. As a result of applying the treatment at various temperatures, the rooting after storage was most promoted at 29-36°C.
The objective of this study was to develop a practical diagnosis method of indoor trees based on laser induced chlorophyll fluorescence. We have suggested that two parameters, MM-gradient and MM-distance, could be used to analyze induction kinetics curve. Induction kinetics data of trees with low-irradiance stress, water stress, long-darkness-stress and short-darkness-stress were used for analyses by the two parameters, and a criterion based on the two parameters for judging whether the tree was stressed or not, was derived. Though the judgment using the criterion we found was not perfectly correct, it reflected the stress imposed on trees with a high probability and can be used in practical situations.
We examined the relationship between the timing of heating the greenhouse in autumn and winter period and flowering of Disa orchid as part of efforts to develop and establish a stable method of growing with the suitable cultivars at the Yatsugatake Farm of the Yamanashi Agricultural Research Center (955 m above sea level, Takane, Hokuto) . In the 2001 experiment, flowering were promoted by rising the night temperatures from February 8. Heating treatment hastened flowering by about 20 days in D. Kewensis and about 40 days in D. Helmut Meyer. Flower stalks of the two cultivars were longer in heat-treated plants than in control plants. The number of flowers per flower stalk was not affected by the heating treatment except for D. Helmut Meyer which had fewer flowers in treated plants than in control. In the 2003 experiment, heating the greenhouse at night hastened the flowering in D. Cardior × D. uniflora and D. Helmut Meyer, but not affected in D. uniflora and D. Helmut Meyer. Only in D. uniflora, the length of flower stalk was shortened by earlier heating. The other three cultivars, (D. Cardior × D. uniflora, D. Margaret Ann Rundle and D. Helmut Meyer), were not affected by heating.