effect of dichlorophenyl dimethylurea (dcmu) on source strength and remobilization of stem water-soluble carbohydrates in wheat under terminal drought

in order to study the role of photosynthetic tissues on grain filling and remobilization of stem reserves under terminal drought, a pot experiment as semi-field was conducted as two-factor factorial in complete randomized design with three replicates at research farm of agriculture college of vali – e – asr university of rafsanjan during january to june 2012 . first factor was source strength reduction in three levels as control, inhibition of flag leaf photosynthesis and inhibition of photosynthesis of leaves below flag leaf. the second factor was watering regime including normal watering and water withholding after flowering. photosynthesis inhibition was applied by dcmu. results showed that only inhibition of flag leaf photosynthesis decreased starch content but increased grain protein content. however mean grain weight was not significantly affected by this treatment. at maturity and in normal watering regime, stem water soluble carbohydrates (wsc) content was not significantly affected by source strength reduction treatments, while water withholding significantly increased it. the highest wsc content was observed in inhibition of photosynthesis of leaves below flag leaf.  on the other hand, neither source strength reduction treatments nor watering regimes, had significant effect on stem nitrogen content. results suggest that source strength reduction induced by inhibition of photosynthesis may lead to decreased sink demand for photoassimilate and nitrogen and consequently decreased remobilization efficiency.