Effect of Root Temperature on Cytokinin Activity in Root Exudate of Vitis vinifera L.

Root exudates of plants of Vitis vinifera L. cv. Thompson Seedless, grown in nutrient cultures with root temperatures maintained at either 20 degrees or 30 degrees and with shoots at a common air temperature, were assayed for cytokinin activity. After chromatography of freeze-dried sap on paper with n-butanol/acetic acid/water (4:1:1). activity was detected with a soybean callus assay. For both root temperatures, major activity appeared between R(F) 0.6 and R(F) 0.8, at about the same concentration in each case. The major difference between the 2 samples was the presence of activity at R(F) 0.1 to 0.2 in the 20 degrees sample and its absence in the 30 degrees sample.The higher root temperature resulted in increased shoot and root elongation, increased dry matter accumulation by both shoots and roots, and also altered the morphological appearance of the roots.