Effect of non-flooded cultivation patterns for the seedling-raising and -transplanting of rice on grain quality and its relations with the concentrations of hormones in grains

صينى. 探讨育苗移栽水稻在不同旱种方式下米质形成的特点及其与籽粒激素浓度的关系。试验以镇稻88（粳稻）和扬稻6号（籼稻）为材料，进行无覆盖旱种（裸种，BN）、地膜覆盖旱种（PM）和麦秸秆覆盖旱种（SM）处理，以常规水种（TF）为对照。与TF相比，BN和PM显著降低了产量，SM的产量与TF无显著差异。SM显著降低了垩白米率、垩白度和消减值，显著增加了胶稠度、碱消值和崩解值。BN和PM对上述稻米品质的影响与SM的相反。稻米直链淀粉含量和蛋白质含量在各处理间无显著差异。两品种表现一致。结实期籽粒吲哚-3-乙酸（IAA）、赤霉酸（GA1＋GA4）、玉米素（Z）＋玉米素核苷（ZR）浓度在灌浆早期处理间差异很小，在灌浆中、后期则表现为SM＞TF＞PM＞BN，乙烯释放速率则表现为BN＞PM＞TF＞SM。籽粒脱落酸（ABA）浓度在SM、PM和TF之间无显著差异。在各处理中，BN籽粒ABA浓度在灌浆前期最低，灌浆中后期则最高。灌浆中后期籽粒IAA和GA1＋GA4、灌浆前中期籽粒ABA及灌浆各期籽粒Z＋ZR浓度与粒重、出糙率、精米率和崩解值呈显著或极显著正相关（r=0.71*～0.96**），与消减值呈显著或极显著负相关(r=-0.76*～-0.91**)。灌浆后期籽粒IAA和Z＋ZR浓度与垩白粒率和垩白度呈显著或极显著负相关（r=-073*～-0.85**）。灌浆各期籽粒乙烯释放速率与粒重、出糙率、精米率、碱消值和崩解值呈显著或极显著负相关（r=-0.71*～-0.91**），与垩白粒率、垩白度和消减值呈显著或极显著正相关（r=0.73*～0.93**）。覆草旱种可以改善稻米品质，裸地旱种和覆膜旱种则使品质变差；促进型激素浓度的降低和乙烯产生的增加是裸地旱种和覆膜旱种稻米加工品质和外观品质较差的重要原因。

إنجليزي. The purpose of this study was to investigate the grain quality under different non-flooded cultivations for seedling-raising and -transplanting rice and its relationship with the concentrations of hormones in grains during grain filling. Two rice cultivars, Zhendao 88 (japonica) and Yangdao 6 (indica), were used as materials. Four treatments, traditional flooding (TF), bare and non-flooded cultivation (BN), non-flooded plastic film mulching (PM) and non-flooded wheat-straw mulching (SM), were conducted during the whole growth season. Compared with TF, both BN and PM significantly reduced grain yield, whereas there was no significant difference in the yield between TF and SM. SM significantly reduced the percentage of chalky kernels, chalkiness and setback value, while markedly increased gel consistency, alkali spreading value and breakdown value. The effects of BN and PM on the above quality traits were opposite to those of SM. No significant differences were observed in amylose content and protein content among the four treatments. The two cultivars behaved the same. Concentrations of indole-3-acetic acid (IAA), gibberellins (GA1+GA4) and zeatin (Z) + zeatin riboside (ZR) in grains differed little among the treatments at the early grain filing stage, and showed SM＞TF＞PM＞BN at the mid and late filling stages. Ethylene evolution rate of grains exhibited BN＞PM＞TF＞SM. There were no significant differences in abscisic acid (ABA) concentrations in grains among the TF, PM and SM during the grain filling period. BN had the lowest ABA concentration at the early filling stage, whereas had the highest concentration at the mid and late filling stages among the all treatments. Concentrations of IAA and GA1 + GA4 at the mid and late filling stages, ABA concentrations at the early and mid filling stage and Z + ZR concentrations during the whole grain filling period significantly or very significantly and positively correlated with grain weight, brown rice, milled rice and breakdown value (r = 0.71*-0.96**), and negatively correlated with setback value (r =－0.76*-－0.91**). Concentrations of IAA and Z + ZR at the late filling stage significantly or very significantly and negatively correlated with the percentage of chalky kernels and chalkiness (r =－073*-－0.85**). The ethylene evolution rates at each filling stage significantly or very significantly and negatively correlated with grain weight, brown rice, milled rice, alkali spreading value and breakdown value (r = －0.71*-－0.91**), and positively correlated with the percentage of chalky kernels, chalkiness and setback value (r = 0.73*-0.93**). The results demonstrate that SM improves, whereas BN and PM degrade, rice quality. Decrease in the concentration of promotive hormones and increase in ethylene production in grains during grain filling account for the poor milling quality and appearance quality under BN and PM conditions.