Abstract
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.)
Highlights
Improving the capacity for supporting grain filling by stem and spike reserves is an important physiological trait and breeding target in wheat (BLUM)Acta Scientiarum
Amount of current photosynthesis for grain filling (t ha-1) = grain yield (t ha-1) − amount of stem and spike reserves mobilization to grain yield (t ha-1); 6
This confirmed the hypothesis that photosynthetic rate is apparently underutilized in modern cultivars and that radiation use efficiency (RUE) during grain filling can be increased through increasing number of grains per spike
Summary
Improving the capacity for supporting grain filling by stem and spike reserves is an important physiological trait and breeding target in wheat (BLUM)Acta Scientiarum. Improving the capacity for supporting grain filling by stem and spike reserves is an important physiological trait and breeding target in wheat (BLUM). Postanthesis nitrogen and drought stress decrease grain yield of wheat through sink strength and source capacity (YANG et al, 2002; SCHAPENDONK et al, 2007). Wheat breeding programs for developing wheat genotypes that can recover from postanthesis stresses require improved understanding of source:sink relationship physiological process and modeling research on source:sink interactions that determine the magnitude of multiple stresses on grain growth (SPIERTZ et al, 2006; GARCIA DEL MORAL et al, 2007). On the other hand, narrowing the gap between genetic potential and phenotypic expression need knowledge about the effects of source:sink manipulation on net photosynthetic rate and photosynthate partitioning during grain filling in winter wheat (BARNABAS; FEHER, 2008; REYNOLDS; TRETHOWAN, 2007)
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