Response of Rice with Overlapping Growth Stages to Water Stress by Assimilates Accumulation and Transport and Starch Synthesis of Superior and Inferior Grains

Abstract

Drought stress at jointing–booting directly affects plant growth and productivity in rice. Limited by natural factors, the jointing and booting stages of short-growth-period rice varieties are highly overlapped in high-latitude areas, which are more sensitive to water deficit. However, little is known about the dry matter translocation in rice and the strategies of starch synthesis and filling of superior and inferior grains under different drought stress was unclear. In this study, the rice plants were subjected to three degrees of drought stress (−10 kPa, −25 kPa, −40 kPa) for 15 days during the jointing–booting stage; we investigated dry matter accumulation and translocation, grain filling and enzyme activities to starch synthesis of superior and inferior grains in rice with overlapping growth stages from 2016 to 2017. The results showed that drought stress significantly reduced dry matter accumulation in the stems and leaves. Mild and moderate drought increased dry matter translocation efficiency. However, severe drought stress largely limited the dry matter accumulation and translocation. A large amount of dry matter remains in vegetative organs under severe drought stress. The high content in NSC in stem and sheath plays a key role in resisting drought stress. The drought stress at jointing–booting directly caused a change in the grain filling strategy. Under moderate and severe drought, the grain-filling active period of the superior grains was shortened to complete the necessary reproductive growth. The grain-filling active period of the inferior grains was significantly prolonged to avoid a decrease in grain yield. The significant decrease in the grain-filling rate of the superior and inferior grains caused a reduction in the thousand-grain weight. In particular, the influence of the grain-filling rate of inferior grains on the thousand-grain weight was more significant. Drought stress changed the starch synthesis strategies of the superior and inferior grains. Soluble starch synthase and starch branching enzyme activities of inferior grains increased significantly under drought stress. GBSS activity was not sensitive to drought stress. Therefore, amylose content was decreased and amylopectin synthesis was enhanced under drought stress, especially in inferior grains.

Rice Growth and Leaf Physiology in Response to Four Levels of Continuous Drought Stress in Southern China

“…The reduction in the number of tillers and the number of grains in the spike resulted in yield loss, which is consistent with the results of this study. Studies have reported that drought stress at the jointing-booting stage can lead to stagnant growth, limited photosynthesis, reduced accumulation of photosynthetically active products, and impeded nutrient translocation, thereby reducing rice yield and quality [8,49]. In this study, the P3 treatment had the lowest thousand grain weight and fruiting rate because continuous drought stress from the heading-flowering stage affects the development and functioning of the reproductive organs of rice [50].…”

Assessing Grain Quality Changes in White and Black Rice under Water Deficit

“…The TGW-Pa values obtained under flooded and AWD conditions exceeded those reported for pigmented rice by Rungrat and Poothab [ 30 ] by 11.2% and 5.5%, respectively. Furthermore, a two-year study conducted by Wang et al [ 31 ] evaluated two japonica rice varieties under water deficit, reporting average values for TGW-Pa ranging from 23.6 to 25.2 g and from 22.9 to 24.4 g under mild and severe drought stress, respectively. These values were notably lower than those obtained in the present study.…”

Metabolomics and Physiological Methods Revealed the Effects of Drought Stress on the Quality of Broomcorn Millet during the Flowering Stage

“…In the booting stage, flowering stage and filling stage, mild drought increased the starch content of rice (NJ9108) by 1.11%, 2.52% and 3.54%, while severe drought decreased the starch content by 12.49%, 8.87% and 5.86% [19]. Severe drought at the jointing stage reduced the amylose content of rice (SJ6) by 15.61% and increased amylopectin content by 7.21% [20]. Moderate drought stress increased the accumulation of Arabidopsis proline by 6.4 times, anthocyanin by 2.9 times and soluble sugar by 1.7 times [21].…”