Effects of shading stress after heading on the accumulation and remobilization characteristics of non-structural carbohydrates in internodes of indica hybrid rice

This study was performed to investigate the dynamic changes of non-structural carbohydrate (NSC) content and accumulation, as well as the redistribution characteristics of NSC in different internodes of hybrid Indica rice. A field experiment with 53% shading treatment was conducted using the Indica rice hybrids ‘Yixiangyou 2115’ and ‘C Liangyouhuazhan’. The results showed that the NSC content in the lower internodes rapidly decreased after heading, which resulted in faster remobilization of stored NSC in the lower internodes. Meanwhile, the remobilization of the stored NSC in the upper internodes was slower than that in the lower internodes. In addition, some of the upper internodes continued to accumulate NSC after heading. Compared with the control, the shading treatment significantly decreased the NSC content in each internode of by 20.98% to 95.45% at the maturity stage (P<0.05), and increased the remobilization amount of stored NSC in each internode by 3.37% to 453.70%, as well as the remobilization rate and contribution rate of remobilized stored NSC in each internode by 3.25 to 325.07 and 0.63 to 9.18 percentage points, respectively. With the exception of neck internodes, the content and accumulation of NSC, as well as the remobilization amount and contribution rate of stored NSC in each internode was greater in ‘Yixiangyou 2115’ than in ‘C Liangyouhuazhan’. Compared to ‘C Liangyouhuazhan’, ‘Yixiangyou 2115’ exhibited lower reduction of both seed-setting rate and grain yield under shading stress, which was attributed to the greater NSC accumulation before heading and remobilization amount of stored NSC after heading in each internode. Correlation analysis indicated that the difference in grain yield between the control and shading treatments was significantly negatively correlated with the difference in NSC accumulation in the third and fifth internodes, but significantly positively correlated with the differences in remobilization amount of stored NSC and the remobilization rate within these internodes. In conclusion, rice could reduce the adverse effects of shading stress on grain yield by enhancing the remobilization of stored NSC in internodes (especially the third and fifth internodes) after heading. Therefore, the selection of rice varieties with high NSC accumulation before heading and high NSC remobilization after heading is helpful in relieving the harm caused by shading stress.