Influence of Benzyladenine on Leaf Senescence and Photosynthesis in Sunflower (Helianthus annuus L.)

The effect of foliar application of benzyladenine on sunflower leaf senescence, photosynthesis, RuBP carboxylase activity and diffusion resistance was investigated. A considerable drop in photosynthetic rate and rise in diffusion resistance were noted dunng the seed filling period. Benzyladenine application maintained the chlorophyll content and chlorophyll a : b ratio at higher level, enhanced RuBP carboxylase activity and net photosynthesis in both upper and lower leaves. A lower level of diffusion resistance was also observed by benzyladenine application during seed filling period. The results suggested that application of benzyladenine at 30, 60 and 90 days after sowing could help to maintain photosynthesis and assimilate supply to the developing seeds of sunflower.