渗透驱动的管流及其与植物糖运输的关系
Osmotically driven pipe flows and their relation to sugar transport in plants
摘要：
在植物中，被认为是糖在管状韧皮部细胞网络中易位的原因，跨越植物的整个长度。在本文中，我们提出了一个实验和理论研究的瞬态驱动流通过管道的半渗透壁。我们通过提供一个更精确的实验版本，使之与理论更好地进行比较，从而扩展了埃弗雷特、埃弗雷特和杨\cite []{埃弗雷特：1972}的实验工作。在实验中，我们测量的动态和结构的“糖前”，即运输和衰减的突然加载的糖在管道是封闭的两端。我们包括膜管内部的压力测量，使我们能够直接将实验与理论进行比较，特别是定量地确认封闭管中前沿的指数衰减。在一个新颖的设置中，我们能够测量糖前沿移动时的整个浓度分布。与以前的研究相比，我们发现实验和理论之间非常好的协议。在低轴向阻力的限制（有效的在我们的实验中，以及在许多情况下，在植物），我们表明，方程可以精确地解决的方法的特点，产生，在一般情况下，一个隐式的解决方案。此外，我们表明，在更一般的条件下，运动方程可以重写为一个单一的积分微分方程，这可以很容易地解决数值。我们的结果对植物的适用性进行了讨论，它表明，这是可能的，压力流假说可以解释短距离运输的糖在植物中。
英文摘要：
In plants, osmotically driven flows are believed to be responsible for translocation of sugar in the pipe-like phloem cell network, spanning the entire length of the plant. In this paper, we present an experimental and theoretical study of transient osmotically driven flows through pipes with semipermeable walls. We extend the experimental work of Eschrich, Evert and Young \cite[]{Eschrich:1972} by providing a more accurate version of their experiment allowing for better comparison with theory. In the experiments we measure the dynamics and structure of a "sugar front", i.e. the transport and decay of a sudden loading of sugar in a pipe which is closed in both ends. We include measurements of pressure inside the membrane tube allowing us to compare the experiments directly with theory and, in particular, to confirm quantitatively the exponential decay of the front in a closed tube.In a novel setup we are able to measure the entire concentration profile as the sugar front moves. In contrast to previous studies we find very good agreement between experiment and theory. In the limit of low axial resistance (valid in our experiments as well as in many cases in plants) we show that the equations can be solved exactly by the method of characteristics yielding, in general, an implicit solution. Further we show that under more general conditions the equations of motion can be rewritten as a single integro-differential equation, which can be readily solved numerically. The applicability of our results to plants is discussed and it is shown that it is probable that the pressure-flow hypothesis can account for short distance transport of sugar in plants.
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