水稻花后叶面锌和尿素配施对稻米锌营养的影响

为研究水稻花后单独叶面施锌及配施尿素对不同品种糙米和精米锌含量及生物有效性的影响及其原因，以11个种子锌含量不同的水稻品种为试验材料，于开花期、花后6 d和12 d叶面分别喷施0.5% ZnSO₄（ZnSO₄）和0.5% ZnSO₄+1%尿素（ZnSO₄-Urea），同期喷施等量清水作为对照，测定各品种成熟期糙米和精米的锌营养指标及花后剑叶气孔相关性状。结果表明：与精米相比，糙米的锌含量、植酸含量和植酸与锌摩尔比平均分别极显著增加31%、222%和151%。ZnSO₄、ZnSO₄-Urea处理使糙米锌含量较对照分别极显著增加28.2%和31.5%，精米锌含量分别极显著增加22.2%和27.6%。ZnSO₄、ZnSO₄-Urea处理对糙米、精米植酸含量均没有影响，但植酸与锌摩尔比均极显著降低，其中糙米两处理下均降低24.3%，精米则分别降低17.2%、20.3%。锌处理与品种或部位的互作对稻米锌含量有极显著影响，锌处理与部位的互作对植酸与锌摩尔比亦有极显著影响。相关分析表明，糙米及精米锌含量在叶面施锌后的增幅与开花期气孔导度均呈极显著正相关，而与稻米本身的锌含量呈显著负相关。由此可知，花后叶面施锌处理使稻米锌营养水平明显增加，增幅总体表现为籼稻大于粳稻，糙米大于精米，叶面锌肥与尿素配施效果更好；水稻种子锌水平低及其叶片气孔导度大均有利于叶面锌肥的吸收。

Effects of the post-anthesis foliar application of zinc and urea on zinc nutrition of rice grains

This study aimed to investigate the effects of foliar zinc application alone or combination with urea on zinc concentration and bioavailability in brown and milled rice of different rice cultivars, and to explore the physiological mechanisms for genotypic differences in grain zinc nutrient enhancement. Eleven rice cultivars with different seed zinc concentrations were subjected to two foliar zinc fertilizer treatments:0.5% ZnSO₄ alone(ZnSO₄)or 0.5% ZnSO₄ plus 1% urea(ZnSO₄-Urea). For each foliar zinc treatment, zinc fertilizer was sprayed three times:at anthesis and 6 days and 12 days after anthesis, and water was sprayed at the same time as the control. The stomatal characteristics of flag leaves of each rice cultivar were determined after anthesis. Grain zinc nutritional indexes of brown and milled rice were measured at plant maturity. The averages across all rice cultivars and foliar zinc applications for grain zinc concentration, phytic acid concentration, and molar ratio of phytic acid to zinc of brown rice were significantly higher than those of milled rice by 31%, 222%, and 151%, respectively. Compared with the foliar spray of water, foliar spray of ZnSO₄ and ZnSO₄-Urea significantly increased the zinc concentrations of brown rice by 28.2% and 31.5%, and those of milled rice by 22.2% and 27.6%, respectively. In contrast, foliar ZnSO₄ and ZnSO₄-Urea treatments had no significant effect on grain phytic acid concentrations for both brown and milled rice, but the molar ratio of phytic acid to zinc decreased significantly, in which the ratio decreased by 24.3% for both ZnSO₄ and ZnSO₄-Urea treatments in brown rice, whereas in milled rice, it decreased by 17.2% with ZnSO₄ treatment and by 20.3% with ZnSO₄-Urea treatment. Significant zinc treatment by rice cultivar interactions(P<0.01)were detected in zinc concentration of rice, and significant interactions(P<0.01)between zinc treatment and grain were detected in the zinc concentration of rice and molar ratio of phytic acid to zinc. The increases in zinc concentration in brown and milled rice by foliar zinc application was positively correlated(P<0.01)with leaf stomatal conductance at anthesis, but negatively correlated(P<0.05)with seed zinc concentration of rice cultivars. Thus, the zinc nutrient levels of rice grains were significantly enhanced by foliar zinc application after anthesis, and the increases were greater in brown rice than those in milled rice. Indica rice were generally more responsive to foliar zinc application than japonica rice. ZnSO₄ in combination with urea was more effective than ZnSO₄ alone in rice grain zinc nutrient enhancement. Biofortification through foliar zinc fertilizer is relatively simple in rice cultivars characterized with low seed zinc level and high leaf stomatal conductance.