Physiological responses of grafted-cucumber leaves and rootstock roots affected by low root temperature

Different root temperatures were imposed on cucumber plants (Cucumis sativu s L. cv. Chung-Jang), and figleaf gourd plants (Cucurbita ficifolia Bouche) , and cucumber (as scion) grafted onto figleaf gourd (as rootstock). Physio logical parameters such as dry weight, leaf area, chlorophyll fluorescence, leaf temperature, photosynthesis and stomatal resistance showed that own-r ooted figleaf gourd plants had a high capacity to grow at a relatively low root temperature of around 15 degrees C. However, own-rooted cucumber plant s suffered seriously at root temperatures below 20 degrees C. The leaf temp erature measured by infra-red thermometry was the most sensitive of the par ameters investigated. Electrophoretic patterns of own-rooted cucumber and f igleaf gourd root systems showed an increase in polypeptide level of 100 kD a in both plants, coinciding with the H+-ATPase activity of the root plasma membrane. Physiological differences between scion leaves and rootstock roo ts at low root temperatures and own-rooted scion and rootstock are discusse d. (C) 1999 Elsevier Science B.V. All rights reserved.