大气CO_2浓度升高和叶面施锌对武运粳23稻米不同部位锌浓度和有效性的影响

Effects of Elevated CO_2 Concentration and Foliar Zn Application on Zn Concentration and Bioavailability in Different Parts of Grains of Rice Wuyunjing 23

2013年利用稻田FACE(Free Air CO2Enrichment)平台,以武运粳23为供试材料,主区CO2处理分别设置环境CO2浓度(Ambient)和高CO2浓度[比Ambient高(200±40)μL·L-1]两个水平,裂区锌处理分别设置对照(不施锌)和叶面施锌(齐穗后每隔5 d喷施0.2%ZnSO4,共3次)处理,研究常规粳稻籽粒不同部位锌浓度、植酸浓度以及[植酸]/[Zn2+]摩尔比值对CO2和锌处理的响应。结果表明,籽粒不同部位的锌浓度、植酸浓度以及[植酸]/[Zn2+]摩尔比均表现为精米<糙米<糠层,糠层部位分别是精米部位的4.8、45.3倍和9.6倍。大气CO2浓度升高对精米、糙米和糠层部位锌浓度均无显著影响,但锌处理使对应部位锌浓度平均分别增加8.5%、17.1%和22.7%,均达显著或极显著水平。CO2和锌处理对稻米各部位植酸浓度均无显著影响。大气CO2浓度升高对稻米各组分[植酸]/[Zn2+]摩尔比均无显著影响,但锌处理使精米、糙米和糠层[植酸]/[Zn2+]摩尔比平均分别下降5.2%、12.9%和18.7%,糙米和糠层部分达显著水平。方差分析表明,锌处理与部位间的互作对锌浓度、[植酸]/[Zn2+]摩尔比的影响达极显著和显著水平。糙米和糠层中[植酸]/[Zn2+]摩尔比与对应部位锌浓度均呈极显著负相关,但与植酸浓度相关不密切。以上数据说明,高浓度CO2环境下武运粳23稻米不同部位锌浓度及有效性无显著变化,但结实期叶面喷施锌肥,可改善该品种稻米不同部位特别是外层的锌营养水平。

Elevated CO2 concentrations enhance plant growth and biomass production, but may also decrease concentrations of elements in plants, thus reducing rice quality. In this study, a conventional japonica rice variety Wuyunjing 23 was grown under two levels of CO2concentrations[ambient and（200±40）μL·L^-1 higher than ambient] in a Free Air CO2Enrichment（FACE）facility installed in a paddy field. Foliar Zn applications（0.2% ZnSO4）were performed for 3 times at 5-day interval right after flowering. Rice seeds were divided into milled rice, brown rice and bran and subjected to analysis of Zn and phytate（PA）concentrations. Zinc and PA concentrations and PA to Zn molar ratios in different parts of rice grains were all in order of milled rice brown rice bran, and they were respectively 4.8 times, 45.3 times and 9.6 times higher in the bran than in milled rice. Elevated CO2 had no significant effects on Zn concentrations in different parts of rice grains; while foliar Zn applications significantly increased Zn concentrations of milled rice, brown rice and bran by 8.5%, 17.1% and 22.7%,respectively. Phytate concentrations of milled rice, brown rice and bran were not affected by either CO2 or Zn treatments. The molar ratio of PA to Zn in different parts of rice grains was not affected by elevated CO2, but decreased by Zn applications by 5.2% in milled rice, 12.9%（P〈0.05）in brown rice and 18.7%（P〈0.05）in bran. Zinc treatment and seed part interaction had significant effects on Zn concentrations and PA to Zn molar ratios. The molar ratio of PA to Zn in brown rice or bran was negatively correlated with Zn concentration, but not with PA concentration. Our results indicate that content and bioavailability of micronutrient Zn in edible part of rice Wuyunjing 23 were not affected by elevated CO2, while foliar Zn application during grain-filling could improve Zn nutrition of rice grains, particularly in outer layer of rice grains.