Research on the role of microtubules in stomatal function

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(ABA)对蚕豆保卫细胞微管的影响。用10muM ABA处理表皮条1h，保卫细胞微管断裂，气孔关闭。ABA的这种作用是可逆的，在去除ABA后1h内微管排列重组，然而，0.1M甘露醇治疗引起的口闭合与微管的破坏无关。当ABA处理时，微管的破裂发生在气孔关闭之前，而微管聚合的抑制剂丙氨酰胺解聚微管不会导致气孔关闭。这些观察结果表明，保卫细胞微管的破坏可能不是气孔关闭的直接原因。在自然条件下，从清晨开始的一天中观察保卫细胞微管排列的变化。气孔大小逐渐增大，直到中午达到最大值。之后尺寸再次变小，最终在0：00到3：00达到最小。保卫细胞微管呈随机排列，6：00部分微管呈分段排列状态，12：00~15：00保卫细胞微管相对于细胞长轴优先横向排列。此后，约3：00左右，微管逐渐分段并破裂。因此，微管排列的变化表现出昼夜节律和气孔开度的变化。这些结果表明，气孔大小和微管排列之间存在一定的平行关系。

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.