大气CO2浓度升高对矿质元素在水稻中分配及其根际有效性的影响

在开放式空气CO_2浓度升高(free-air CO_2 enrichment, FACE)条件下,研究了籼稻IIY084与粳稻WYJ23根际土壤矿质元素(Fe、Mn、Cu、Zn、Ca和Mg)有效态含量及其在水稻各组织中的吸收与分配,结合前期稻米矿质元素含量下降的研究结果,探讨了其下降的机制。结果表明:大气CO_2浓度升高,显著增加水稻穗、茎、根和整株生物量,两个品种平均增加19.4%、9.3%、23.4%、16.0%;根际土壤中矿质元素的有效态含量大体呈增加趋势;除Ca吸收量增加外,水稻其他矿质元素总吸收量未发生显著变化;显著促进大部分矿质元素在穗中的吸收与分配,而降低其在茎中的分配比;在穗内有增加大部分矿质元素在壳梗中滞留的趋势,相应地减少其在糙米中的分配比。品种效应分析显示,IIY084的茎和整株生物量,以及穗中Fe、Mn、Cu,叶中Zn、Mg,茎中Cu的吸收量与分配百分数均显著高于WYJ23,而叶中Mn、茎中Fe和根中Cu、Zn则呈相反趋势。可见,大气CO_2浓度升高条件下,碳水化合物与矿质元素从植株营养器官到籽粒的不平衡转运以及在壳梗中的滞留可能是导致两水稻品种糙米中矿质元素含量降低的重要原因。

Effects of Free-air CO2 Enrichment(FACE) on Mineral Element Partitioning and Rhizosphere Availability of Rice (Oryza sativa L.)

A previous investigation had demonstrated that mineral (Fe, Mn, Cu, Zn, Ca and Mg) concentrations in brown rice of indica IIY084 and japonica WYJ23 (Oryza sativa L.) were significantly reduced by elevated CO2]. However, the underlying mechanisms were known little. Thus, a field experiment was conducted to investigate the mineral partitioning and availability in rhizospheric soil of IIY084 and WYJ23 with a Free-air CO2 enrichment (FACE) in Eastern China. The results showed that regardless of cultivars, the biomass of panicles, stems, roots and whole plants were significantly stimulated by elevated CO2] with average increase of 19.4%, 9.3%, 23.4% and 16.0%, respectively. Generally, elevated CO2] trended to raise the bio-available contents of minerals in the rhizosphere soils. Except for the enhanced accumulation of Ca, most of mineral accumulations in the whole plants were unchanged under elevated CO2]. However, elevated CO2] significantly increased mineral uptake and distribution in panicles, and declined them in stems. Interestingly, most of mineral distributed in husk and stalk were detained, while those in brown rice were reduced by elevated CO2]. In the case of cultivar effects, the biomass of stems and whole plants, the accumulation and distribution of Fe, Mn and Cu in panicles, Zn and Mg in leaves, and Cu in stems were much greater in IIY084 than in WYJ23. However, the accumulation and distribution of Mn in leaves, Fe in stems and Cu, Zn in roots showed an opposite trend. In short, the mineral decline in brown rice may mainly attribute to the unbalanced stimulations on the translocations of mineral elements and carbohydrates from vegetative parts to the grains under elevated CO2],as well as to more retention in husks and stalks of rice panicles.