Research on the role of microtubules in stomatal function

利用免疫荧光显微镜研究了诱导气孔关闭的植物激素脱落酸（阿坝）对蚕豆保卫细胞微管阵列的影响。用10 μ M阿坝处理表皮条1小时，导致保卫细胞中微管的破坏，伴随气孔的关闭。阿坝的这种作用是可逆的，并且微管阵列在去除阿坝后1 h内重组。0.1 M甘露醇处理引起的气孔关闭与微管的破坏无关。微管的破坏之前，气孔关闭时施加阿坝和propyzamide，微管聚合的抑制剂，微管的解聚，不诱导气孔关闭。这些观察结果表明，微管在保卫细胞中的破坏可能不是直接由气孔关闭。在自然条件下，微管阵列的变化在保卫细胞中进行了检查，从清晨一天。气孔开度逐渐增大，至中午达到最大值。之后，规模再次变小，并最终在0：00至3：00达到最小值。保卫细胞中的微管在6：00时排列不规则，部分呈分节状态。然后它们在12：00至15：00相对于细胞的长轴优先横向排列。此后，微管逐渐分段并在约3：00时破裂。因此，微管阵列的变化不仅反映了气孔开度的昼夜节律，也反映了气孔开度的昼夜节律。这些结果表明，气孔孔径的大小和微管阵列之间的一些平行。

Effects of abscisic acid (ABA), which is a kind of phytohormone known to induce stomatal closure, was investigated on the arrays of microtubules in guard cells of Vicia faba by immunofluorescence microscopy. Treatment of epidermal strips for 1 h with 10muM ABA resulted in disruption of microtubules in the guard cells with concomitant closure of stomata. This effect of ABA was reversible, and arrays of microtubules were reorganized within 1 h after the removal of ABA.Stomatal closure caused by treatment with 0.1 M mannitol was not, however, associated with the disruption of microtubules. The disruption of microtubules was preceded by stomatal closure when ABA was applied and the depolymerization of microtubules by propyzamide, an inhibitor of the polymerization of microtubules, did not induce stomatal closure. These observations suggest that the disruption of microtubules in guard cells is probably not directly necessiated by stomatal closure.In natural conditions, changes in the arrays of microtubules in guard cells were examined during a day from an early morning. The size of stomatal aperture gradually increased till noon, when the size attained the maximum. The size became smaller again after then and ultimately got the minimum at 0 : 00 to 3 : 00. The microtubules in guard cells were aligned at random and some of them were in the segmented state at 6 : 00., and then they were aligned preferentially transversely with respect to long axis of the cell at 12 : 00 to 15 : 00. Thereafter, the microtubules were gradually segmented and disrupted at about 3 : 00. Thus, the change of arrays of microtubules showed circadian rhythm as well as the stomatal aperture. These results suggest some parallelism between the size of stomatal aperture and the arrays of microtubules.