A NEW CHEMICAL BRASSINOLIDE IN COMBINATION WITH FERTILIZER LEVELS TO IMPROVE THE SEED SETTING PERCENTAGE IN SUNFLOWER
Poor seed set and filling is one of the most common problems encountered in sunflower cultivation. The yield of sunflower could be increased to a considerable extent by using brassinolide, a plant growth promoting substance, isolated from the pollen of rape, which prevents the formation of empty achenes, thus increasing the number of filled seeds. Field experiments were carried out at Tamil Nadu Agricultural University, Coimbatore, India during the summer (March–May) and South West Monsoon (June– September) seasons of 1997 to study the effect of brassinolide and NPK levels on the yield and yield attributes of sunflower. The experiments were laid out in a split plot design. The main plots were treated with five levels of fertilizer (N:P:K), namely 40:20:20, 50:25:25, 60:30:30, 70:35:35 and 80:40:40 kg ha -1, while the subplots consisted of seed setting treatments: hand pollination, 0.2% borax + 2% diammonium phosphate spray and 1 ppm brassinolide spray at the ray floret opening stage, together with a control. Yield attributes: head diameter, number of seeds head –1, seed filling percentage and 100 seed weight, were significantly influenced by NPK levels. Among the seed setting treatments, brassinsolide 1 ppm spray at the ray floret opening stage was found to be superior in enhancing the seed setting percentage. The application of N:P:K at 80:40:40 kg ha –1 was found to be optimum for higher seed yield in sunflower.