不同锌效率基因型水稻籽粒中矿质元素的原位微区分布研究

 采用同步辐射（SRXRF）结合ICP MS研究了足Zn条件下不同锌效率水稻籽粒中Zn及其他矿质元素的微区分布特征。结果表明SRXRF技术可高效分析水稻籽粒锌等矿质元素的微区分布特征。水稻籽粒中K和Ca元素的分布特征与其余4种元素相关不显著，而Zn、Fe、Cu、Mn元素的含量分布相互间则显著相关；水稻籽粒中K含量最高，移动性也最强，精米中K含量可达颖壳的52.6%~90.6%，而Ca在颖壳中含量最高。其余矿质元素含量最高值均出现在糊粉层；Zn、Fe等元素主要集中在水稻籽粒的胚及糊粉层等外层功能组织，在胚乳中由外向里呈递减趋势。此外，锌高效基因型IR8192在水稻籽粒各部位的Zn含量均低于锌低效基因型二九丰。可见，与锌低效品种相比，锌高效品种仅在低Zn水平下表现出更高的锌吸能力及利用效率，在足Zn条件下并无籽粒富锌特征。

in situ Micro-distributions of Mineral Elements in Rice Grains with Different Zinc Efficiency

The concentrations of Zn and other mineral elements and in situ spatial distribution patterns were analyzed by  combing ICP MS  with synchrotron radiation X ray fluorescence (SRXRF). The results showed that SRXRF was a reliable technique to investigate the element micro distribution in rice grains. Significantly positive correlations between elemental distribution of Zn, Fe, Cu and Mn were observed in rice grains, while there was no such pronounced correlation for K and Ca. Among the minerals, potassium is of the highest concentration and mobility in rice grains, being up to 52.6-90.6% in polished rice of that in the hulls. Highest Ca concentration was observed in the hulls, while the other five elements were preferentially distributed in the outer layer, such as embryo and aleuronic layer. The contents of Zn and other mineral elements in the endosperm decreased rapidly from the outer layers to the central parts. Both XRF mapping and ICP MS analysis showed that Zn level in rice grains of Zn inefficient genotype (Erjiufeng) was significantly higher than that in grains of Zn efficient genotype (IR8192). This indicated that the Zn efficient genotype IR8192 was not able to accumulate higher Zn in grains when exposed to sufficient Zn levels, despite of its high efficient uptake and utilization of Zn under Zn deficient conditions.