结实期灌溉方式对水稻品质和不同器官镉浓度与分配的影响

旨在探讨在土壤镉（Cd）污染条件下，能否通过合适的灌溉方式改善稻米品质并减少Cd在籽粒中的分配。盆栽扬粳9538（粳稻）和扬稻6号（籼稻），于移栽前加Cd 150 mg kg-1（Cd处理），以未加Cd为对照（CK）。自抽穗后7 d至成熟设置3种灌溉方式，即保持水层(WW)；轻干-湿交替灌溉(MD，土壤落干至土壤水势为－20 kPa时复水)；重干-湿交替灌溉(SD，土壤落干至土壤水势为－40 kPa时复水)。结果表明，在土壤Cd浓度相同条件下，与WW比较，MD显著增加结实率、千粒重、产量、稻米的出糙率、精米率和整精米率，显著降低垩白度，SD的结果则相反。Cd处理对结实率、千粒重和稻米品质各指标无显著影响。在Cd处理条件下，与WW相比，MD和SD显著增加Cd在根系的浓度和分配比例，降低Cd在茎叶的浓度和在籽粒的分配比例。籽粒和精米中Cd浓度，SD显著高于WW，MD与WW无显著差异。Cd在精米的分配比例则SD显著低于MD和WW。两品种结果趋势一致。说明结实期轻干-湿交替灌溉可以增加产量、改善稻米的加工和外观品质，并可不增加甚至降低Cd在籽粒中的浓度及分配比例。从根系活性、叶片光合特性以及Cd的转运等方面分析了在不同灌溉方式下产量、品质及不同器官Cd浓度与分配差异的原因。

Effects of Irrigation Regimes during Grain Filling on Grain Quality and the Concentration and Distribution of Cadmium in Different Organs of Rice

The objective of this study was to investigate whether the grain quality could be improved and the proportion of cadmium (Cd) be reduced in grains through a proper irrigation regime when rice was planted in Cd-contaminated soil. Two rice cultivars of Yangjing 9538 (japonica) and Yangdao 6 (indica) were pot-grown. 150 mg kg-1 Cd was added into pots before seedling transplanting (Cd treatment), and no Cd addition was taken as control (CK). Three irrigation regimes, well-watered (WW), moderate dry-wet alternate irrigation (MD, soil was re-watered when soil water potential reached at –20 kPa), and severe dry-wet alternate irrigation (SD, soil was re-watered when soil water potential reached at –40 kPa), were imposed from 7 d after heading to maturity. The results showed that under the same Cd concentration in soil and when compared to WW, MD significantly increased, whereas SD significantly reduced, seed-setting rate, 1 000-grain weight, grain yield, brown rice rate, milled rice rate, and head rice rate. MD markedly reduced, while SD increased, chalkiness. There were no significant differences in the seed-setting rate, 1000-grain weight, and each index of rice quality between the Cd treatment and the control. Under the Cd treatment and compared to WW, MD and SD significantly increased the concentration and proportion of Cd in roots, while significantly reduced Cd concentration in stems and leaves and reduced Cd proportion in grains. Cd concentrations in grains and milled rice were significantly higher under SD than under WW, and exhibited no significant difference between MD and WW. SD showed lower proportion of Cd in milled rice, when compared to MD or WW. The two cultivars behaved the same. The results indicate that a moderate dry-wet alternate irrigation during grain filling could increase grain yield, improve milling and appearance quality and not increase Cd concentration or even reduce Cd proportion in grains. Reasons for variations in grain yield, quality, and the concentration and proportion of Cd under different irrigation regimes were analyzed from the aspects of root activity, photosynthetic characters, and Cd translocation.