Abstract:

【Objective】 The objective of this study was to investigate the effects of different planting methods on starch formation and key enzyme activities in rice grains, aiming to provide insights for improving direct seeding techniques for rice cultivation in Ningxia Hui Autonomous Region.【Methods】 The experiment was conducted at the original seed farm of Ningxia Hui Autonomous Region from 2020 to 2021. Fuyuan 4 (FY4), Ningjing 28 (NJ28), Ningjing 43 (NJ43), and Ningjing 50 (NJ50) were selected as experimental materials. Soil moisture conservation, dry direct seeding (Z1), watering after sowing (Z2), and transplanting (Z3) were chosen as planting methods. A split-zone design was employed to study the effects of planting methods on rice yield, starch content, and key enzyme activities.【Results】 Under different planting methods, direct-seeded rice exhibited higher amylose content and total starch content, while transplanted rice showed higher amylopectin content. The total starch content followed the order: Z2 > Z1 > Z3, while the amylopectin content followed the order: Z3 > Z2 > Z1. In 2021, the highest amylose content of NJ28 under Z1 planting mode was 21.90%, while the highest amylopectin content of NJ28 under Z3 planting mode was 51.64%. Starch synthesis and accumulation in grains are primarily influenced by the activity of key enzymes in starch synthesis. Compared to Z3, Z1 and Z2 significantly reduced the activities of AGP and GBSS. Transplanting notably increased UGP and SBE activities of FY4 and NJ43, while direct seeding increased UGP and SBE activities of NJ28 and NJ50. Additionally, under different planting methods, Z1 significantly increased the activity of SSS enzyme. Under Z3 planting mode, the maximum AGP activity of NJ43 was 28.53 U·g^-1·min^-1, which was 4.1% and 8.4% higher than that of Z2 and Z1, the maximum GBSS activity of NJ28 was 10.36 U·g^-1·min^-1, which was 11.2% and 13.5% higher than that of Z2 and Z1 treatment respectively. Similarly, under Z1 planting mode, the maximum SSS activity of NJ50 was 20.05 U·g^-1·min^-1. Moreover, compared to transplanted rice, the 1000-grain weight and seed setting rate of directly seeded rice were significantly higher, although the panicle length and grain number were lower. Consequently, the yield of transplanted rice was significantly higher than that of directly seeded rice. In 2020, the yield of NJ50 under Z3 planting mode reached 898 kg/666.7 m², which was 30.7% and 39.4% higher than that of Z1 and Z2, respectively.【Conclusion】 The findings indicate that while the yield of rice under direct seeding was lower compared to transplanting, the 1000-grain weight and seed setting rate were significantly increased by direct seeding. Additionally, direct seeding led to higher activity of key enzymes involved in starch formation and increased amylose content in rice grains, consequently enhancing the total starch content in rice grains.

Key words: rice, direct seeding, starch, key enzymes of starch synthesis, yield

摘要：

【目的】研究不同种植方式对水稻籽粒淀粉形成及关键酶活性的影响，为宁夏水稻直播栽培技术提供参考。【方法】2020－2021年在宁夏回族自治区原种场，选取富源四号(FY4)、宁粳28号(NJ28)、宁粳43号(NJ43)和宁粳50号(NJ50)为试验材料，设置保墒旱直播(Z1)、旱播后上水(Z2)以及插秧(Z3)三种种植方式，采用裂区设计，研究不同种植方式对水稻产量、淀粉含量及关键酶活性的影响。【结果】不同种植方式下，直播稻具有更高的直链淀粉和总淀粉含量，插秧稻具有更高的支链淀粉含量，总淀粉含量表现为Z2>Z1>Z3，支链淀粉含量表现为Z3>Z2>Z1。2021年Z1种植方式下 NJ28直链淀粉含量最高达到21.90%，Z3种植方式下 NJ28支链淀粉含量最高达到51.64%。籽粒淀粉合成积累主要与淀粉合成关键酶活性有关，与Z3相比，Z1和Z2显著降低了AGP和GBSS活性；插秧显著提高了FY4和NJ43的UGP和SBE活性，直播显著提高了NJ28和NJ50的UGP和SBE活性；不同种植方式下，Z1对SSS活性的提高更显著。在Z3种植方式下，NJ43的AGP活性最大值为28.53 U/(g·min)，较Z2和Z1提高了4.1%和8.4%，NJ28的GBSS活性最大值为10.36 U/(g·min)，较Z2和Z1处理提高了11.2%和13.5%。在Z1种植方式下，NJ50的SSS活性最大值为20.05 U/(g·min)。与插秧稻相比，直播稻千粒重和结实率显著高于插秧稻，但直播稻穗长和穗粒数显著降低，使得插秧稻产量均显著高于直播稻。2020年Z3种植方式下NJ50 产量高达898 kg/666.7m²，较Z1和Z2高了30.7%和39.4%。【结论】与插秧种植相比直播方式下水稻产量降低，但直播处理显著提高千粒重以及结实率，同时直播方式可以提高水稻籽粒淀粉形成关键酶的活性，增加直链淀粉含量，使得水稻籽粒总淀粉含量增加。

关键词: 水稻, 直播, 淀粉, 淀粉合成关键酶, 产量