Wheat (Triticum aestivum L.) grain filling and dry matter partitioning responses to source:sink modifications under postanthesis water and nitrogen deficiency

Abstract

Re-translocation of stem and spike reserves was investigated in source: sink restricted wheat subjected to water and nitrogen deficiency during seed filling. Either sink or source restriction significantly decreased the amount of current photosynthesis and its contribution to grain yield and Source limitation increased stem and spike reserves contribution to seed filling process. More amount of stem reserve mobilization in source restricted vs. control and sink restricted plants indicates that at rapid grain filling stage (14 days after anthesis to physiological maturity), stem dry matter decrease to provide assimilates for kernel after defoliation. In spike halved plants, drought stress significantly decreased grain yield indicates that when the sink is restricted, postanthesis water deficiency can increase sink limitation through lower grain filling rate and dry matter allocation to grain two weeks after anthesis at beginning of rapid grain filling stage. In other hand, in spike halved plants, more nitrogen supply at anthesis increased grain yield because more dry matter allocation to grain not more current photosynthesis, But When the all leaves removed except flag leaf, more postanthesis nitrogen could not increase dry matter allocation to grain filling process, it show that postanthesis nitrogen supply increase grain yield through decrease in sink limitation than increase in source strength. Key words:, Current photosynthesis, Dry matter allocation, Grain filling rate, Stem reserves, Wheat (Triticum aestivum L.)