Efficacy of indol-3-yl acetic acid on improvement of some biochemical and physiological aspects of wheat flag leaf during grain filling

Flag leaf area, leaf fresh and dry matter show two phases of development du ring grain filling in Triticum aestivum. The initial large increase in leaf size is mainly due to water intake. Chlorophylls, reducing sugars, sucrose , Hill activity and photosynthetic activity appeared to be stimulated durin g leaf growth; thereafter, a noticeable decline in these parameters was man ifested particularly throughout leaf senescence. The maximum accumulation o f polysaccharide and protein occurred at the beginning of grain set followe d by continuous decline in these absolute values during grain filling. Grain priming with IAA at 25 ppm stimulated flag leaf growth by increasing its fresh and dry matter as well as its area. Furthermore, the stimulatory effect was mainly due to the increase in pigment production which, in turn, increase the photo synthetic activity of the wheat flag leaf during grain filling. On the other hand, the higher dose of IAA (50 ppm) attenuated the growth and physiological activity of the wheat flag leaf through its inhibi tory action on leaf fresh weight, dry weight, leaf area, pigment content, c arbohydrate and protein formation as well as its effect on (CO2)-C-14 assim ilation.