叶面施锌对不同水稻品种稻米锌营养的影响及其机理

研究水稻灌浆早期叶面施锌对稻米锌浓度及其生物有效性的影响及其与叶片气孔特征的关系,旨在为稻作生产上生物强化策略的制订提供参考依据。2016—2017年在土培条件下,以6个水稻品种为供试材料,于抽穗期、抽穗后6 d和12 d叶面喷施0.2%ZnSO_4共3次,以喷施等量清水为对照,抽穗灌浆期测定剑叶气孔导度和气孔结构,成熟期测定产量性状、糙米锌浓度、植酸浓度和植酸与锌的摩尔比。结果表明,尽管叶面施锌对水稻籽粒产量无显著影响,但显著改变稻米的锌含量水平。与对照相比,锌处理使两年所有品种糙米锌浓度平均增加27.9%(P0.01)。锌处理对各品种糙米植酸浓度没有影响,但使植酸与锌摩尔比平均下降23.4%(P0.01)。灌浆期叶面施锌对糙米锌浓度、植酸与锌摩尔比的影响因品种而异,表现在锌处理与品种间存在明显的互作效应,其中3个低锌水稻品种的响应明显大于3个高锌水稻品种。相关分析表明,叶面施锌导致糙米锌浓度的增幅与灌浆早期气孔导度呈显著正相关,但与气孔长度和密度相关不密切。水稻灌浆初期叶面施锌可大幅增加糙米锌浓度及其生物有效性,增幅因品种不同而异;水稻本身锌水平低,叶片气孔导度大均有利于叶面锌肥的吸收。

Effect of foliar zinc application on zinc nutrient levels of different rice cultivars

The effects of foliar Zn application during the early grain-filling stage on Zn concentration and Zn bioavailability in rice and its relationship with leaf stomata characteristics were studied to provide a scientific basis for effective Zn biofortification in rice production. Six rice cultivars with different seed Zn contents were grown under soil culture conditions from 2016-2017. Foliar Zn spray(0.2% ZnSO₄) was applied at heading, 6 d after heading(DAH), and 12 DAH, and the same amount of water was sprayed as the control. The stomatal conductance and stomatal structure of flag leaves were measured at the heading and early grain-filling stages. The yield traits, Zn concentration, phytic acid concentration, and molar ratio of phytic acid to Zn in brown rice were determined at plant maturity. Although foliar Zn application had no significant effect on the grain yield of rice, it significantly changed the Zn nutrition level of brown rice. Averaged over 2 a, Zn application increased the Zn concentration in brown rice by 27.9%(P<0.01). Zn application did not affect the phytic acid concentration of brown rice, but molar ratio of phytic acid to Zn decreased by 23.4%(P<0.01)on average. The effects of foliar Zn application during the early grain-filling stage on the Zn concentration, phytic acid concentration, and molar ratio of phytic acid to Zn in brown rice varied with cultivars, as shown by the significant Zn treatment by cultivar interactions. The responses of the three cultivars with low seed Zn content were significantly greater than those of the three cultivars with high seed Zn content. The correlation analysis showed that the increment of Zn concentration in the brown rice due to foliar Zn application was significantly positively correlated with the stomatal conductance at the early grain-filling stage, but not related to the stomatal length or density. In conclusion, foliar Zn application during the early grain-filling stage can significantly increase the Zn concentration and bioavailability in brown rice, and the increment varied with cultivars.The low level of seed Zn and the large stomatal conductance of leaves may be beneficial for the absorption of Zn fertilizer into rice leaves.