Minchin Peter E H, Lacointe André
The New Zealand Institute for Plant and Food Research Ltd (PFR), 412 No. 1 Rd, Te Puke 3182, New Zealand.
UCA, INRA, UMR PIAF, F-63000 Clermont-Ferrand, France.
Funct Plant Biol. 2017 May;44(5):507-514. doi: 10.1071/FP16354.
It is now accepted that the transport phloem, linking major sources and sinks, is leaky, and this leakage can be considerable. Hence for phloem transport to function over the long distances observed, a large fraction of this unloaded photosynthate must be reloaded. A fraction of this unloaded solute is used to maintain tissues surrounding the phloem, as well as being stored. Also, pathway unloading/reloading acts as a short-term buffer to source and sink changes. In this work we present the first attempt to include both pathway unloading and reloading of carbohydrate in the modelling of pressure driven flow to determine if this has any significant effect upon source-sink dynamics. Our results indicated that the flow does not follow Poiseuille dynamics, and that pathway unloading alters the solute concentration and hydrostatic pressure profiles. Hence, measurement of either of these without considerable other detail tells us very little about the flow mechanisms. With adequate reloading along the pathway, the effects of pathway unloading can completely compensate for, making the entire system look like one with no pathway unloading.
现在人们普遍认为，连接主要源库的运输韧皮部是有渗漏的，而且这种渗漏可能相当可观。因此，要使韧皮部运输在观察到的长距离上发挥作用，很大一部分卸载的光合产物必须重新装载。这部分卸载的溶质有一部分用于维持韧皮部周围的组织，以及用于储存。此外，途径卸载/重新装载作为源库变化的短期缓冲。在这项工作中，我们首次尝试在压力驱动流模型中纳入碳水化合物的途径卸载和重新装载，以确定这是否对源库动态有任何显著影响。我们的结果表明，流动并不遵循泊肃叶动力学，并且途径卸载会改变溶质浓度和静水压力分布。因此，在没有相当多其他细节的情况下，对其中任何一个进行测量，都很难让我们了解流动机制。沿着途径进行充分的重新装载后，途径卸载的影响可以完全得到补偿，使整个系统看起来就像一个没有途径卸载的系统。
