Table_1_Effects of water stress on starch synthesis and accumulation of two rice cultivars at different growth stages.doc

Rice is a water intensive crop and soil water conditions affect rice yield and quality. However, there is limited research on the starch synthesis and accumulation of rice under different soil water conditions at different growth stages. Thus, a pot experiment was conducted to explore the effects of IR72 (indica) and Nanjing (NJ) 9108 (japonica) rice cultivars under flood-irrigated treatment (CK, 0 kPa), light water stress treatment (L, -20 ± 5 kPa), moderate water stress treatment (M, -40 ± 5 kPa) and severe water stress treatment (S, -60 ± 5 kPa) on the starch synthesis and accumulation and rice yield at booting stage (T1), flowering stage (T2) and filling stage (T3), respectively. Under LT treatment, the total soluble sugar and sucrose contents of both cultivars decreased while the amylose and total starch contents increased. Starch synthesis-related enzyme activities and their peak activities at mid-late growth stage increased as well. However, applying MT and ST treatments produced the opposite effects. The 1000-grain weight of both cultivars increased under LT treatment while the seed setting rate increased only under LT3 treatment. Compared with CK, water stress at booting stage decreased grain yield. The principal component analysis (PCA) showed that LT3 got the highest comprehensive score while ST1 got lowest for both cultivars. Furthermore, the comprehensive score of both cultivars under the same water stress treatment followed the trend of T3 > T2 > T1, and NJ 9108 had a better drought-resistant ability than IR72. Compared with CK, the grain yield under LT3 increased by 11.59% for IR72 and 16.01% for NJ 9108, respectively. Overall, these results suggested that light water stress at filling stage could be an effective method to enhance starch synthesis-related enzyme activities, promote starch synthesis and accumulation and increase grain yield.

稻米为需水量极高的作物，土壤水分状况对稻米产量与品质产生显著影响。然而，关于不同生长阶段下，不同土壤水分条件下稻米淀粉合成与积累的研究尚显不足。鉴于此，本研究通过盆栽实验，探讨了在淹灌处理（CK，0 kPa）、轻度水分胁迫处理（L，-20 ± 5 kPa）、中度水分胁迫处理（M，-40 ± 5 kPa）以及重度水分胁迫处理（S，-60 ± 5 kPa）下，IR72（ indica）与Nanjing 9108（japonica）稻种在拔节期（T1）、抽穗期（T2）和灌浆期（T3）的淀粉合成与积累以及稻米产量。在LT处理条件下，两种稻种的总可溶性糖和蔗糖含量降低，而支链淀粉和总淀粉含量增加。淀粉合成相关酶活性及其在中后期生长阶段的峰值活性也有所上升。然而，实施MT和ST处理则产生了相反的效果。在LT处理下，两种稻种的千粒重均有所增加，而仅LT3处理下的结实率有所提高。与CK相比，拔节期水分胁迫降低了稻米产量。主成分分析（PCA）显示，LT3处理获得了两种稻种最高的综合评分，而ST1处理获得了最低的综合评分。此外，在相同的水分胁迫处理下，两种稻种的综合评分呈现出T3 > T2 > T1的趋势，且Nanjing 9108的耐旱能力优于IR72。与CK相比，IR72在LT3处理下的产量提高了11.59%，而Nanjing 9108提高了16.01%。总体而言，这些结果提示，在灌浆期施加轻度水分胁迫可能成为提升淀粉合成相关酶活性、促进淀粉合成与积累以及提高稻米产量的有效途径。