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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Pressure Flow Hypothesis ： ウィキペディア英語版 Pressure Flow Hypothesis The Pressure Flow Hypothesis, also known as the Mass Flow Hypothesis, is the best-supported theory to explain the movement of sap through the phloem.〔(Translocation of Food )〕 It was proposed by Ernst Munch, a German plant physiologist in 1930.〔 〕 A high concentration of organic substances, particularly sugar, inside cells of the phloem at a source, such as a leaf, creates a diffusion gradient (osmotic gradient) that draws water into the cells from the adjacent xylem. This creates turgor pressure, also known as hydrostatic pressure, in the phloem. Movement of phloem sap occurs by bulk flow (mass flow) from ''sugar sources'' to ''sugar sinks''. The movement in phloem is bidirectional, whereas, in xylem cells, it is unidirectional (upward). Because of this multi-directional flow, coupled with the fact that sap cannot move with ease between adjacent sieve-tubes, it is not unusual for sap in adjacent sieve-tubes to be flowing in opposite directions. ==Sources and sinks== A sugar source is any part of the plant that is producing or releasing sugar. During the plant's growth period, usually during the spring, storage organs such as the roots are sugar sources, and the plant's many growing areas are sugar sinks. After the growth period, when the meristems are dormant, the leaves are sources, and storage organs are sinks. Developing seed-bearing organs (such as fruit) are always sinks. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pressure Flow Hypothesis」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.