Semiquantitative estimates of Al and other cations in the leaf tissues of some Al-accumulating species using electron probe microanalysis

Electron probe microanalysis of transverse sections was used to provide semiquantitative estimates of Al and other cations in the leaf tissues of some Al-accumulating plants of the cerrado vegetation of central Brazil. Concentrations of Al were generally higher than those of other cations in the phloem elements of these plants growing on dystrophic as well as fertile acid soils. When one of the Al-accumulating species,Vochysia thyrsoidea, was grown in a calcareous soil, the concentration of Al in the phloem elements of leaves was lower than that of Ca and K though the cotyledons showed higher concentrations of Al than those of other cations.     

Rapid changes in levels of mineral nutrients in root-tip cells following short-term exposure to aluminium

We investigated the rapid modification of plasma membrane and changes in mineral nutrients in root-tip cells of Al-tolerant rice and Al-sensitive barley following short-term exposure to Al (20 M Al, 1 h). The plasma membrane of the barley cells was significantly permeabilized when re-elongated in an Al-free Ca solution following a 1-h pre-treatment with Al, while that of rice cells was not affected at all. The elemental distribution and concentration in a 2-mm portion of the root apex were determined by electron probe X-ray microanalysis. Al was localized primarily to the epidermis and outer cortex cells in both species, and was much more abundant in barley than in rice. Al increased and decreased remarkably the intracellular K concentration in whole root-tip cells of rice and barley, respectively. In barley, the decrease in the concentration of Ca coincided with the accumulation of Al. Conversely, the intracellular concentration of P in the surface layers of root-tip cells increased with the accumulation of Al. The distribution and concentration of Ca and P in rice did not change after 1-h treatment with Al. These results suggest that the rapid modification of the plasma membrane of root-tip cells induced by Al affects the nutritional homeostasis in the cells.     

基于耳石微化学的长江安徽和县江段刀鲚生境履历重建

为了解长江刀鲚(Coilia nasus)的“生境履历”, 利用电子探针微区分析技术研究了2015年5月17日在长江安徽和县江段捕获的刀鲚短颌鲚与长颌鲚类型耳石Sr和Ca微化学特征。短颌鲚的耳石Sr/Ca值变化动态为2类, 一类比值稳定在2.00左右(1.65±0.87—2.03±0.96), 反映了其纯淡水的生境履历; 另一类比值波动显著, 不仅具有对应淡水生境的低值(2.39±1.18—2.63±0.85), 还具有对应半咸水生境的高值(3.22±1.17—3.29±1.14), 显现了其江海生活的生境履历。长颌鲚耳石的Sr/Ca值均波动显著, 同时具有对应淡水生境的低值(1.35±1.07—2.37±1.04)和半咸水、海水生境的高值(3.47±1.09—8.35±1.25), 表现了其均为溯河洄游的生境履历。Sr面分析结果也与上述Sr/Ca值的结果相印证。长江安徽和县江段刀鲚资源组成复杂, 群体可由纯淡水型和江海生活型的个体共同组成。