Seasonal changes in the efflux of sugars from parenchyma cells into the apoplast in poplar stems (Populus × canademis “robusta”)
Seasonal changes in the efflux of sugars from parenchyma cells into the apoplast in poplar stems (Populus × canademis “robusta”)
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杨树茎中糖从薄壁细胞流入质外体的季节性变化（杨 × canademis “robusta”）
DOI：
10.1007/bf00202379
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
J. Sauter
中科院分区：
文献类型：
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作者：
J. Sauter
本文研究了加拿大“罗布斯塔”杨木材薄壁细胞糖外流到质外体的过程及其与组织糖水平和气管液中糖含量的关系。杨树气管液的春季最大含糖量显然不是冬季持续渗出的结果，而是在春季很短的时间内达到的。描述了木材中淀粉和糖含量以及管液中糖含量的季节模式。组织切片中糖的流出量在一年中变化很大，从0.3DWT g mgμ−到8.3DWT day−1。总体来说，秋季和冬季糖流出量较高，春末和夏季较低。然而，高组织糖水平并不总是与高外排速率或气管汁液中的高糖水平相关，这表明糖在细胞内的区域化、它们被动和催化释放到质外体中以及它们从质外体重新吸收都是决定汁液实际含糖量的基本因素。蔗糖在冬季(pH 7.0-7.5)和在pH 7.5的外排实验中是气管液中的主要糖，而在春季(pH约5.5)和在pH 5.6的外排实验中，蔗糖是占主导地位的己糖，它被认为优先在杨树中释放并被胞外降解。对树种间差异的原因进行了讨论。
SummaryThe efflux of sugars from parenchyma cells into the apoplast has been studied in the wood of Populus × canadensis “robusta” in relation to the sugar level of the tissue and the sugar content of the tracheal sap during all physiological stages of the year. In poplar, the spring maximum in sugar content of the tracheal sap is clearly not the result of continuous exosmosis during winter but is reached within a short period in spring. The seasonal patterns of starch and sugar content of the wood and of the sugar content of the tracheal sap are described. The efflux of sugars from tissue sections changes drastically over the year, i.e., from 0.3 to 8.3 μg mg−1DWT day−1. In general, it is high in fall and winter, and low during late spring and summer. However, high tissue sugar levels proved not always to be correlated with high efflux rates or with high sugar levels in the tracheal sap, indicating that the intracellular compartmentalization of sugars, their passive and catalysed release into, and their re-uptake from the apoplast are all essentially involved in determining the actual sugar content of the sap. Sucrose, which is the dominant sugar in the tracheal sap during winter (pH 7.0–7.5) and in the efflux experiments at pH 7.5, in contrast to the hexoses which prevail in the spring sap (pH around 5.5) and also in the efflux experiments at pH 5.6, is considered to be preferentially released in poplar and to become extraplasmatically hydrolysed. The reasons for tree-specific differences are discussed.