Varietal difference in dynamics of non-structural carbohydrates in nodal segments of stem in two varieties of rice (Oryza sativa L.) at pre- and post-heading stages

ABSTRACT The non-structural carbohydrate (NSC) stored in rice stems (culm plus leaf sheaths) at pre-heading stage is one of the major carbon sources for grain filling. In this study, we conducted field experiments in 2018 and 2019 using two varieties, Momiroman (japonica-dominant) and Teqing (indica), which have different accumulation and remobilization patterns of NSC in the stems. We analyzed NSC dynamics of each of the five nodal segments of internodes and leaf sheaths at pre- and post-heading stages. The dynamics of NSC at pre- and post-heading stages differed among segments. The lower segments of internodes and leaf sheaths accumulated more NSC at pre-heading stage compared to the upper segments in both varieties. The lower internodes in Teqing were morphologically larger than in Momiroman and would be able to store more NSC. However, the upper parts of the stems required biomass for development and formation at the stage of NSC accumulation in stems. Momiroman had longer upper internodes and leaf sheaths and required more biomass than Teqing. The NSC remobilization was later in the upper than the lower internodes for both varieties, which led to the delay of NSC remobilization in the entire culm after heading. These results indicated that ideal morphology of stems, to maximize the potential contribution of stem NSC as the carbon source for grain filling, is large lower internodes and short upper internodes and leaf sheaths. Graphical Abstract