Métraux J P, Taiz L
Proc Natl Acad Sci U S A. 1977 Apr;74(4):1565-9. doi: 10.1073/pnas.74.4.1565.
The giant internode cells of Nitella axillaris exhibit acid-induced growth similar to that found in higher plants. The threshold pH is 4.5, with a maximum at 3.5. The acid growth effect is transient, lasting no more than 32 min. Extensibility measurements of isolated cell walls showed a similar pattern of acid enhancement. Prolonged boiling in water (12 hr) only partially inhibited the acid-induced wall extensibility and actually increased the extensibility at pH 6. It was concluded that physical, rather than enzymatic, processes were responsible for acid-enhanced continuous extension ("creep") in Nitella walls. A complex cation-sensitive mechanism that affects extensibility was also characterized. Among the stimulatory (wall-softening) cations, divalents were generally more effective than monovalents, with magnesium being the most stimulatory. The inhibitory (wall-hardening) cations included divalents and trivalents, aluminum being the most inhibitory. Ionic effects on extensibility were even less sensitive to prolonged boiling in water than acid effects.
腋生茨藻的巨大节间细胞表现出与高等植物中相似的酸诱导生长。阈值pH为4.5，在pH 3.5时达到最大值。酸生长效应是短暂的，持续不超过32分钟。对分离细胞壁的伸展性测量显示出类似的酸增强模式。在水中长时间煮沸（12小时）仅部分抑制了酸诱导的细胞壁伸展性，实际上还增加了pH 6时的伸展性。得出的结论是，物理过程而非酶促过程是茨藻细胞壁中酸增强的持续伸展（“蠕变”）的原因。还对一种影响伸展性的复杂阳离子敏感机制进行了表征。在刺激性（细胞壁软化）阳离子中，二价阳离子通常比一价阳离子更有效，其中镁的刺激性最强。抑制性（细胞壁硬化）阳离子包括二价和三价阳离子，铝的抑制作用最强。离子对伸展性的影响对在水中长时间煮沸的敏感性甚至比对酸的影响更低。
