ABSTRACT.
Shading stress after heading enhances the remobilization of nonstructural carbohydrates in rice under different ecological conditions

Yuling Zeng1, 2, Qiuping Li1, 2, Hong Chen1, 2, Bo Li1, 2, Xiaoyuan Zhong1, 2, Zhenzhen Li1, 2, Hui Lu1, 2, Li Wang1, Wanjun Ren1, 2, and Fei Deng1, 2*
 
Low light levels during rice (Oryza sativa L.) growing seasons may lead to significant reductions in grain yield and quality. The effect of shading stress on remobilization of nonstructural carbohydrates (NSC) from the stem plus sheath (SPS) to the grain, a process crucial to rice grain formation, wasi nvestigated. Field shading experiments were conducted in Hanyuan and Wenjiang, China, using two rice varieties (Huanghuazhan and Guichao II) subjected to shading stress after heading. Stored NSC of 60.00-159.15gm-2 werere mobilized from SPS after heading, contributing 9.63%-23.63% to grain dry weight at maturity. Shading stress resulted in the 23.99%-50.30% and 31.65%-61.33% reduction in NSC content of SPS at 20 d after heading (DAH20) and maturity stages, respectively. This contributed to the 13.80%-89.00% increase in the remobilization of stored NSC from SPS to the grain (RASN) and 15.86%-73.30% increase in remobilization percentage of removed NSC from SPS to the grain (RPRN). The effect of shading stress on remobilization differed between sites and varieties. Owing to a greater sink capacity, shading stress led to a higher RASN and RPRN fromheading to DAH20 for ‘Huanghuazhan’ in Hanyuan. To compensate for photosynthate deficiency under shading stress, rice is adapted to remobilize stored NSC during early grain filling stages. Consequently, grain yield loss caused by shading could be reduced by increasing the SPS remobilization ability (especially in low light areas). Increasing NSC accumulation in SPS before heading for later remobilization may be a feasible way to alleviate rice yield loss under adverse light conditions.
Keywords: Nonstructural carbohydrates, Oryza sativa, remobilization characteristics, shading stress, yield.
1Sichuan Agricultural University, College of Agronomy, Key Laboratory of Crop Ecophysiology and Farming System in Southwest China of Ministry of Agriculture, Chengdu 611130, China.
2Crop Ecophysiology and Cultivation, Key Laboratory of Sichuan Province, Chengdu 611130, China.
*Corresponding author (ddf273634096@163.com).