The Relationship Between the Effects of CCC on Root Growth and Cytokinin Levels in the Bleeding Sap ofVitis viniferaL.

Abstract

The growth retardant (2-chloroethyl)trimethylammonium chloride (CCC) induced swollen root tips on seedlings of grape vines (Vilis vinifera L.) as well as on plants grown from cuttings. In both cases CCC had to be applied to the growth medium for the response to be expressed; spraying the shoots reduced stem growth without inducing swollen roots. N-dimethylarminosuccinamic acid (B995) was ineffective in causing these root symptoms on grapes, nor did root swellings appear on five other species treated with CCC. On the other hand, kinetin resulted in grape roots which in some respects resembled those treated with CCC. Two regions of cytokinin activity were detected on chromatograms of bleeding sap from grape-vines grown in serated nutrient culture solutions compared with only one region in sap from plants grown in soil or other solid media. Activity of a region of high mobility was increased by CCC applications to the culture solutions; effects of CCC on a region of low mobility, which may be a bound derivative of the other, were variable. Both the concentration and absolute amounts of cytokinin activity in the sap were increased by CCC, indicating that this retardant probably affected cytokinin synthesis by the root tip. The effect of CCC on cytokinin levels in the sap diminished during the bleeding period. The results are interpreted to indicate that in grapes, CCC acts directly on the root meristem to increase cytokinin production. Swelling of the tips is probably a consequence of the elevated cytokinin levels in this region.