METABOLIC AND PHYSICAL CONTROL OF CELL ELONGATION RATE - IN-VIVO STUDIES IN NITELLA
METABOLIC AND PHYSICAL CONTROL OF CELL ELONGATION RATE - IN-VIVO STUDIES IN NITELLA
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DOI：
10.1104/pp.47.3.423
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发表时间：
1971-01-01
期刊：
影响因子：
7.4
通讯作者：
BUGGY, J
中科院分区：
文献类型：
--
作者：
GREEN, PB;ERICKSON, RO;BUGGY, J
几个层次的控制伸长速率揭示了通过详细的研究的响应的Nitellainternode突然转移膨压。直接反应反映了细胞的物理状态，可用公式r =（P-Y）m近似描述，其中r为速率，P为压力，Y为细胞壁的屈服阈值，m与细胞壁的表观流动性（倒数粘度）有关。因为PandY在5至6个大气压的范围内，并且（P-Y）大约为0.2个大气压，所以延伸率最初对P的变化极其敏感。（0.7个大气压）停止增长，而类似的上升大大加速了它。（15分钟）由Y的变化补偿。明显的代谢依赖性反应（叠氮敏感）降低Y;应变硬化这两个相反的过程，作用于Y，作为（P-Y）的调控器，这种代偿能力本身是膨压的一个功能。随着膨压福尔斯从5个大气压下降到约2个大气压，生长似乎不再恢复，膨压逐步下降的补偿越来越少，导致速率降低。这是可达到的最低屈服值Y1。补偿的膨压依赖性反映了Y降低（“壁软化”）过程的膨压要求。因此，稳态rs和膨压之间的关系是一种间接的关系，来源于细胞壁随时间的变化。这个关系式表面上类似于瞬时有效的关系式，大致上是rs=（P-Y1）ms。然而，Y1和ms的值比Yandm小得多。伸长率与生长率关系的双重性和阴调节率的突出作用是丽藻生长控制的主要特点。
Several levels of control of elongation rate are revealed through the detailed study of responses of theNitellainternode to abrupt shifts in turgor. The immediate response, which apparently reflects the physical state of the cell, is approximately described by the equationr= (P — Y)mwhereris rate,Pis pressure,Yis the wall's yielding threshold, andmis related to the wall's apparent fluidity (reciprocal viscosity). BecausePandYare in the range 5 to 6 atmospheres, and (P — Y) is roughly 0.2 atmosphere, elongation rate is initially extremely sensitive to changes inP.A small step-down in turgor (0.7 atmosphere) stops growth, and a similar rise greatly accelerates it. These initial responses are, however, soon (15 minutes) compensated by changes inY.An apparent metabolism-dependent reaction (azide-sensitive) lowersY; strain hardening (azide-insensitive) raises it. These two opposing processes, acting onY, serve as a governor on (P — Y), tending to maintain it at a given value despite changes inP.This ability to compensate is itself a function of turgor. Turgor step-downs are less and less well compensated, leading to lower rate, as turgor falls from 5 atmospheres to about 2 atmospheres where growth appears not to resume. This is the lowest attainable yield value,Y1. The turgor dependency of compensation reflects a turgor requirement of theY-lowering (“wall-softening”) process. Thus the relation between steady state,rs, and turgor is an indirect one, derived from time-dependent alterations of the cell wall. This relationship superficially resembles the instantaneously valid one in that, roughly,rs= (P—Y1)ms.Y1andms, however, have much lower values thanYandm. The duality of the elongation rateversusturgor relation and the prominent role ofYin regulating rate are the major features of growth control inNitella.