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Seong-Hee Lee, Soon-Ho Ha, and Gap-Chae Chung

In order to diagnose the nutritional disorders caused by various environmental stress, biochemical test, xylem sap analysis and colorimetric petiole analysis were used to assay symptoms well before the severe development. Among the various enzymatic analysis, alkaline phosphatase activity was highly specific to calcium deficiency while in vivo nitrate reductase activity was not stable parameter in response to nitrogen deficiency. Determination of nitrogen, phosphorus and magnesium by colorimetric petiole analysis was sensitive to induced deficiencies. The status of potassium in the plant, however, could be better determined with the xylem sap analysis. Salinity stress induced by low osmotic potential of the nutrient solution increased the activity of alkaline phosphatase, showing similar results as calcium deficiency. Magnesium and phosphorous contents by the colorimetric petiole analysis were particularly low when the roots in anoxia.

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Kyong Ju Choi, Gap Chae Chung, and Sung Ju Ahn

Cucumber (Cucumis sativus L.) seedlings were grafted onto cucumber-(CG) or figleaf gourd (FG, Cucurbita ficifolia Bouche) seedlings in order to determine the effect of solution temperature 12, 22, and 32C) on the mineral composition of xylem sap and plasma membrane K+–Mg++–ATPase activities of the roots. Low solution temperature (12C) lowered the concentration \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{H}_{2}\mathrm{PO}_{4}^{-}\) \end{document} in xylem sap of CG plants, but not of FG plants. Concentrations of K+, Ca++, and Mg++ in xylem sap were less affected than anions by solution temperature. The plasma membrane of FG plants grown in 12C solution temperature showed the highest K+–Mg++–ATPase activity at all ATP concentrations up to 3 mM and at low reaction temperature up to 12C, indicating resistance of figleaf gourd to low root temperature.

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Yong In Kuk, Jae Hong Lee, Han Yong Kim, Soon Ju Chung, Gap Chae Chung, Ja Ock Guh, Hee Jae Lee, and Nilda R. Burgos

To determine whether chilling tolerance is related to cold acclimation, changes in physiological responses and activity of antioxidative enzymes were investigated in leaves of cucumber (Cucumis sativus L.) grown in controlled environments. Plants were exposed to 15 °C (cold-acclimated) or 25 °C (nonacclimated) for 3 days, under 50 μmol·m-2·s-1 photosynthetic photon flux and 70% relative humidity. Plants were then exposed to 8 °C chilling temperature for 3 days, and allowed to recover in a growth chamber at 25 °C for 3 days. Measurements of leaf water content, cellular leakage, lipid peroxidation, chlorophyll a fluorescence, and quantum yield showed that cold-acclimated leaves were less affected by chilling compared to nonacclimated leaves. Cold-acclimated leaves recovered faster than nonacclimated leaves with regard to all variables examined. Catalase and ascorbate peroxidase activities were induced in cold-acclimated leaves, but not in nonacclimated leaves. These data indicate that cold acclimation increased chilling tolerance of cucumber in association with antioxidative enzymes.