Evaluation of the role of Gibberellin and Cytokinin in Regulation of Seed Setting and Seed Filling in Sunflower plant (Helianthus annuus L.)

Abstract

Sunflower yield is determined by seed (kernel) number / m –2 and by achene (fruit) weight. Two pot experiments were carried out during two successive seasons to investigate localized effect of GA, Kinetin or mixture of both on sink site and filling in tow cultivars of sunflower plant. The experiment was laid out in a completely randomized block design in a factorial arrangement with tow cultivars (Flame and Euroflore) and four plant growth regulators treatments ( (Control , GA3 ,Kinetin and ( GA3 +Kinetin) ) with four replications . GA 200 ppm, Kinetin 200 ppm and (GA 200+Kinetin 200) ppm each were applied to the buds at opening stage (45 after sowing). Comparable plants in control were treated with distilled water. At maturity, heads were divided into four equal parts across the center. Each of these four parts was further divided into 1 /3 equal portions i. e. peripheral, middle and central. Data were recorded on seed weight, number of total seeds and filled seeds for each portion, then percent increase in number of seed, percent increase in number of filled seed و percentage of filled seed and mean weight of seed were calculated. For both cultivars plant growth regulator (PGRs) applications gave higher number of total seeds, number of filled seeds and percentage of filled seed in all the three portions and improved mean of seed weight in both seasons and as a mean of seasons as compared to their respective controls. The most effective treatment was (GA 200 + Kinetin 200) ppm. Flame cultivar was superior over Euroflore in number of total seeds, number of filled seeds and percentage of filled seeds in all the three portions and in mean of seed weight in both seasons and as a mean of seasons.