XYLEM, PHLOEM AND TRANSPIRATION FLOWS IN A GRAPE - APPLICATION OF A TECHNIQUE FOR MEASURING THE VOLUME OF ATTACHED FRUITS TO HIGH-RESOLUTION USING ARCHIMEDES PRINCIPLE
XYLEM, PHLOEM AND TRANSPIRATION FLOWS IN A GRAPE - APPLICATION OF A TECHNIQUE FOR MEASURING THE VOLUME OF ATTACHED FRUITS TO HIGH-RESOLUTION USING ARCHIMEDES PRINCIPLE
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DOI：
10.1093/jxb/40.10.1069
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发表时间：
1989-10-01
影响因子：
6.9
通讯作者：
THORPE, MR
中科院分区：
文献类型：
--
作者：
LANG, A;THORPE, MR
葡萄浆果每小时体积的微小变化是在现场使用现成的廉价实验室设备和现代电子天平非破坏性地测量的。该方法基于阿基米德原理，甚至适用于小水果（约10克），通过测量浆果浸入水中时所经历的浮力向上推力，分辨率约为1千分之一。体积数据控制，花梗蒸，分离浆果被用来计算的幅度和方向的流体流发生通过茎的韧皮部和木质部流，并通过皮肤的蒸腾流。在果实发育的后期，在成熟开始后，葡萄的净体积增长或多或少停止，尽管它们的糖输入率最高。体积增长的停止是因为韧皮部中含糖水的强烈流入部分地被通过皮肤的蒸腾水分损失和部分地被木质部水回流到母藤中而紧密平衡。这种木质部回流似乎持续整个昼夜循环。木质部流的净回流方向，以及韧皮部流不能携带某些离子（特别是钙），可以解释一些矿物质不平衡障碍如何出现在果实发育的后期。在葡萄属中，结实库与营养库竞争的激烈方式可以用质外体的分解来解释：浆果中的共质体区室化发生在成熟开始的时候。破裂将浆果的终端筛管暴露于高度负水势的环境，用于增加易位流的速度和浓度。
The minute changes in volume of a grape berry which occur from hour to hour were measured non-destructively in the field using readily available and cheap laboratory equipment and a modern electronic balance. The method, applicable even to small (approximately 10 g) fruits, is based on Archimedes'' principle and gave a resolution of about 1 part in 1,000 by measuring the buoyant upthrust experienced by a berry when immersed in water. Volume data from control, pedicel-steamed, and detached berries were used to calculate the magnitudes and directions of the fluid flows which took place through the stalk of the phloem and xylem streams and through the skin in the transpiration stream. In the latter stages of fruit development, after the onset of ripening, net volume growth more or less ceases in grapes although their rate of sugar import is at its strongest. Cessation of volume growth comes about because the strong inflow of sugary water in the phloem is closely balanced in part by transpirational water loss through the skin and in part by the backflow of xylem water to the parent vine. This xylem backflow appears to persist throughout the diurnal cycle. The net backflow direction of the xylem stream, together with the inability of the phloem stream to carry certain ions (notably calcium), may explain how some mineral imbalance disorders arise in the later stages of fruit development. The intense manner in which fruiting sinks compete with vegetative sinks in Vitis finds its explanation in the breakdown of apoplast:symplast compartmentation in the berry which occurs around the time of onset of ripening. The breakdown exposes the terminal sieve tubes of the berry to a highly negative water potential environment, serving to increase both the speed and the concentration of the translocation stream.