Toko K, Iiyama S, Tanaka C, Hayashi K, Yamafuji K, Yamafuji K
Department of Electronics, Faculty of Engineering, Kyushu University 36, Fukuoka 812, Japan.
Biophys Chem. 1987 Jul;27(1):39-58. doi: 10.1016/0301-4622(87)80045-5.
The electric spatial pattern and invertase activity distribution in growing roots of azuki bean (Phaseolus chrysanthos) have been studied. The electric potential near the surface along the root showed a banding pattern with a spatial period of about 2 cm. It was found that the enzyme activity has a peak around 3-7 mm from the root tip, in good agreement with the position of the first peak of the electric potential, which is located a little behind the elongation zone. An inhomogeneous distribution of ATP content was also detected along the root. Experiments on the electric isolation of the elongation zone from the mature zone and acidification treatment showed that H+ is transported from the mature-side to elongation-side regions, causing tip elongation through an acid-growth mechanism. Both acidification and electric disturbance on growing roots affected growth significantly. Simultaneous measurements of electric potential and enzyme activity clearly showed a good correlation between these two quantities and growth speed. From an analogy with the Characean banding, the spatio-temporal organization via the cell membrane in electric potential and enzyme activity can be regarded as a dissipative structure arising far from equilibrium. These experimental results can be interpreted with a new mechanism that the dissipative structure is formed spontaneously along the whole root, accompanied by energy metabolism, to make H+ flow into the root tip.
对小豆（Phaseolus chrysanthos）生长根中的电空间模式和转化酶活性分布进行了研究。沿根表面的电势呈现出一种带状模式，空间周期约为2厘米。研究发现，酶活性在距根尖约3 - 7毫米处有一个峰值，这与电势的第一个峰值位置高度吻合，该电势峰值位于伸长区稍后方。还检测到沿根的ATP含量分布不均匀。对伸长区与成熟区进行电隔离以及酸化处理的实验表明，H⁺从成熟侧区域运输到伸长侧区域，通过酸生长机制导致根尖伸长。对生长根进行酸化和电干扰均显著影响生长。同时测量电势和酶活性清楚地表明这两个量与生长速度之间具有良好的相关性。类比轮藻的带状现象，电势和酶活性通过细胞膜的时空组织可被视为一种远离平衡态产生的耗散结构。这些实验结果可用一种新机制来解释，即沿着整个根自发形成耗散结构，伴随着能量代谢，使H⁺流入根尖。
