Sugar concentrations along and across the Ricinus communis L. hypocotyl measured by single cell sampling analysis
Sugar concentrations along and across the Ricinus communis L. hypocotyl measured by single cell sampling analysis
复制标题
通过单细胞采样分析测量蓖麻下胚轴沿线和整个下胚轴的糖浓度
DOI：
10.1007/s00425-006-0309-x
复制
发表时间：
2006
期刊：
影响因子：
4.3
通讯作者：
E. Komor
中科院分区：
文献类型：
--
作者：
Jutta Verscht;D. Tomos;E. Komor
单细胞汁液取样和分析被用来测量纵向和径向分布的蔗糖，葡萄糖和果糖在顶端细胞分裂区和在基部，延长区的蓖麻下胚轴。蔗糖和己糖的浓度从苗轴的顶端到基部增加。在细胞分裂区，皮层和髓中的己糖和蔗糖浓度较低，髓细胞中的己糖浓度略高。筛管和韧皮部的蔗糖浓度远高于皮层和髓细胞。在下胚轴的基部区域，韧皮部、皮层和髓中的蔗糖水平较高，因此认为不可能有径向的、扩散的蔗糖流离开韧皮部。有人建议，径向流动的生长水的下胚轴周边一起下调的蔗糖转运蛋白在韧皮部导致优先蔗糖流量扩大皮层。髓细胞，不经历生长水的流动，可能没有足够的蔗糖供应从韧皮部最终导致细胞死亡，随着植物的生长。实验中通过去除胚乳来减少蔗糖供应，导致髓中的蔗糖水解。其他组织中蔗糖水平下降较少，看来髓细胞液开始水解为己糖是为了维持渗透值。据推测，在细胞中的高己糖水平是指示通过韧皮部和髓细胞的蔗糖供应不足，在早期幼苗发育过程中面临的情况。
Single cell sap sampling and analysis were used to measure the longitudinal and radial distribution of sucrose, glucose and fructose in the apical cell division zone and in the basal, elongated zone of the Ricinus hypocotyl. Sucrose and hexose increased in concentration from the apex to the base of the seedling axis. In the cell division zone low hexose and sucrose concentrations prevailed in cortex and pith, with a slightly higher hexose concentration in pith cells. The sucrose concentrations in sieve tubes and in phloem were much higher than in the cortex and pith cells. In the basal zone of the hypocotyl high levels of sucrose in phloem, cortex and pith were found, therefore radial, diffusional sucrose flow away from the phloem was considered unlikely. It is proposed that radial flow of growth-water to the hypocotyl periphery together with the down-regulation of a sucrose transporter at the phloem leads to a preferential sucrose flow to the expanding cortex. The pith cells, which do not experience flow of growth-water, are probably insufficiently supplied with sucrose from the phloem resulting eventually in cell death as the plant grows. Shortage of sucrose supply, experimentally achieved by removal of the endosperm, led to sucrose hydrolysis in the pith. The sucrose levels in the other tissues decreased less. It appears that the hydrolysis to hexose was initiated to maintain the osmotic value in the pith cell sap. It is speculated that high hexose levels in the cells are indicative of insufficient sucrose supply via the phloem and that the pith cells are confronted with that situation during early seedling development.