Senescence‐related translocation of nonstructural carbohydrate in rice leaf sheaths under different nitrogen supply

Abstract

The translocation of nonstructural carbohydrates (NSC) from leaf sheaths to filling grains after anthesis contributed greatly to the grain yield of cereal crops. In this study, the effect of nitrogen (N) supply levels on the accumulation and translocation of NSC in leaf sheath tissues and its relationship with the initiation and progression of leaf senescence during grain filling was investigated using two rice (Oryza sativa L.) genotypes, namely, premature flag leaf senescence mutant (psf) and its wild‐type. Three N treatment levels were used to examine N‐supply induced alteration in the activities of several key enzymes involved in NSC translocation and N assimilation in different leaf sheaths. The results show that the NSC translocation rate in leaf sheaths under low nitrogen (LN) treatment was significantly higher than those under normal nitrogen (NN) and high nitrogen (HN) treatments. However, the positive effect of LN on the NSC translocation in leaf sheath was closely associated with its negative effect on grain yield, due to accelerated leaf senescence and shortened leaf longevity. Comparatively, the upper‐positional sheath had a lower NSC amount and higher NSC translocation rate than the lower‐leaf sheaths after heading. High N suppressed sucrose‐phosphate synthase (SPS) activity in leaf sheaths, but enhanced the activity of key enzymes involving in N assimilation in leaf sheaths. The upper sheath had higher activity of sucrose‐metabolizing enzymes and lower activity of N‐assimilating enzymes. Hence, the upper‐leaf sheath had a relatively weak N assimilation and stronger NSC translocation than the lower‐leaf sheaths.

Senescence-Specific Expression of RAmy1A Accelerates Non-structural Carbohydrate Remobilization and Grain Filling in Rice (Oryza sativa L.)

“…Previous studies have demonstrated that NSCs accumulated in rice stems prior to heading play an important role in yield formation which can later be mobilized to supplement photosynthetic production during grain filling (Pan et al, 2010 ; Wang et al, 2016 ; Zakari et al, 2020 ). Pre-anthesis NSC reserves in the stem are also closely associated with the sink strength during grain-filling of rice (Fu et al, 2011 ).…”

“…Grain filling is a significant and dynamic process for the final yield of rice. Previous studies have shown that the assimilates required for grain filling are primarily supplied by leaf photosynthesis and non-structural carbohydrates (NSCs) reserved in leaf sheaths and stems before anthesis (Schnyder, 1993 ; Samonte et al, 2001 ; Xie et al, 2015 ; Zakari et al, 2020 ). NSCs can contribute to 10–40% of final grain yield, depending on the variety and environmental conditions (Takai et al, 2005 ; Yang and Zhang, 2010 ).…”

“…Several physiologists and breeders propose that improving the remobilization and transport efficiency of NSCs stored in rice source organs during vegetative growth could be an efficient way to improve the rice grain-filling rate and yield (Fu et al, 2011 ; Wang et al, 2016 ; Zakari et al, 2020 ). However, most of the previous studies have focused on adjusting traditional cropping strategies (Pan et al, 2010 ; Chen et al, 2019 ).…”

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“…Previous studies have demonstrated that NSCs accumulated in rice stems prior to heading play an important role in yield formation which can later be mobilized to supplement photosynthetic production during grain filling (Pan et al, 2010;Wang et al, 2016;Zakari et al, 2020). Pre-anthesis NSC reserves in the stem are also closely associated with the sink strength during grain-filling of rice (Fu et al, 2011).…”

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“…Grain filling is a significant and dynamic process for the final yield of rice. Previous studies have shown that the assimilates required for grain filling are primarily supplied by leaf photosynthesis and non-structural carbohydrates (NSCs) reserved in leaf sheaths and stems before anthesis (Schnyder, 1993;Samonte et al, 2001;Xie et al, 2015;Zakari et al, 2020). NSCs can contribute to 10-40% of final grain yield, depending on the variety and environmental conditions (Takai et al, 2005;Yang and Zhang, 2010).…”