Gamow R I, Böttger B
J Gen Physiol. 1982 May;79(5):835-48. doi: 10.1085/jgp.79.5.835.
If a mature sporangiophore is placed next to a barrier that is moving in a clockwise direction, it grows both away from the barrier and into the wind; the wind is generated by the moving barrier itself. When the barrier is moving in a counterclockwise direction, the sporangiophore grows towards both the barrier and the wind. The net direction of growth appears to be the vector sum of the rheotropic response and the avoidance aiming error and does not involve the classic stationary-barrier avoidance response. Our experiments all support the suggestion that the avoidance response, the rheotropic response and the variety of reported wind responses can be explained by the presence of a self-emitted, growth-simulating avoidance gas. We present data that suggest that it is the direction of the net flux (mass transfer) of this gas that determines both the direction and the magnitude of the sporangiophore growth. We further suggest that the region of the cell wall showing maximum mass transfer will show a minimum growth rate, i.e., the direction of growth will always be in the direction of maximum transfer. If water is the avoidance gas, then it would follow that the total hydration of the cell wall in an aqueous salt solution should result in cell wall softening; cell wall softening has been correlated directly to cell wall growth. Using the Instron technique, we now show that submerging the entire sporangiophore in an aqueous salt solution for 4 min causes an increase in cell wall extensibility.
如果将一个成熟的孢子囊柄放置在一个沿顺时针方向移动的障碍物旁边，它会朝着远离障碍物并迎着风的方向生长；风是由移动的障碍物自身产生的。当障碍物沿逆时针方向移动时，孢子囊柄会朝着障碍物和风的方向生长。生长的净方向似乎是向流性反应和避障瞄准误差的矢量和，并不涉及经典的固定障碍物避障反应。我们所有的实验都支持这样一种观点，即避障反应、向流性反应以及各种已报道的风反应都可以用一种自身释放的、模拟生长的避障气体的存在来解释。我们提供的数据表明，正是这种气体的净通量（质量传递）方向决定了孢子囊柄生长的方向和幅度。我们进一步表明，细胞壁显示出最大质量传递的区域将显示出最小的生长速率，也就是说，生长方向将始终朝着最大传递的方向。如果水是避障气体，那么可以推断，在盐水溶液中细胞壁的完全水合作用应该会导致细胞壁软化；细胞壁软化与细胞壁生长直接相关。使用英斯特朗技术，我们现在表明，将整个孢子囊柄浸入盐水溶液中4分钟会导致细胞壁伸展性增加。
