Gibberellin and Auxin-Induced Berry Enlargement inVitis ViniferaL.

Publisher Website
Google Scholar
Abstract
Gibberellic acid (GA) and the auxin, 4 chlorophenoxyacetic acid (CPA), differ in their effects upon berry enlargement in two seedless varieties of Vitis vinifera L., cv. Black Corinth and Thompson Seedless. Although initially both substances cause nearly equal increases in berry growth rates, at maturity GA-treated berries far surpass those treated with CPA. The growth rate of CPA-treated berries declines, relative to that of the GA group, two to seven days after treatment. The results of experiments in which berries received treatment with both GA and CPA show that CPA may act as an inhibitor of GA-induced expansion, particularly during the later stages of enlargement. Also, GA-treated berries have a greater length-to- width ratio than CPA-treated berries. Thus, there are apparently qualitative differences in mode of action between the two substances. Increase in berry size, regardless of treatment, is the result of water uptake accompanied by solute storage and synthesis of cell components. Histological studies reveal that berry enlargement is the result of tissue growth in a region of the pericarp between the locule and peripheral vascular tissues. This tissue increases in size within 48 hours after treatment with GA or CPA. In GA- treated berries there is a 10-fold increase in parenchyma cell diameter in this tissue between anthesis and maturity. New cell formation in the pericarp of the GA-treated berries may also occur. GA has a more pronounced effect upon enlargement of distal than of proximal parenchyma tissues in the Black Corinth variety. Tissue expansion in CPA-treated berries, as well as those on girdled vines, was approximately equal at both poles. Such differential effects upon expansion at the proximal and distal poles may account for the difference in shape between GA- and CPA-treated berries.