乙酰胆碱与蚕豆气孔运动的关系

在蚕豆（ViciafabaL）幼苗中，很尖的切除可以引起植株蒸腾速率的逐渐下降；而在这一过程中植株地上部水势保持不变；外施乙酰胆碱可以使蒸腾速率基本恢复到断根前的水平。利用气质联动技术对乙酰胆碱的内源性进行了鉴定，结果表明蚕豆的类乙酰胆碱提取物具有与人工合成的乙酰胆碱和高等动物脑组织中类乙酰胆碱提取物相同的质谱谱线，说明乙酰胆碱是蚕豆中的一种内源物质。为了对乙酰胆碱进行快速而准确的测定，建立了测定乙酰胆碱的热裂解的气相色谱法。利用这种方法测定的结果表明，在从根的切除到不定根重新长成的整个过程中，叶片下表皮中乙酰胆碱的含量与叶片的蒸腾速率及根的存在和生长状态密切相关，表明内源的乙酰胆碱可能参与调控植物的气孔行为；这一推论又为乙酰胆碱对表皮条中气孔开度的刺激效应和乙酰胆碱酯酶抑制剂neostig－mine可以增加气孔对乙酰胆碱的敏感性的实验进一步证实。

Relationship Between Acetylcholine and Stomatal Movement in Vicia faba

In Vicia faba L., root excision could cause a gradual decrease of the transpiration rate without affecting the shoot water potential, provided water could be supplied by other means. The lowed transpirationrate could be restored by acetylcholine. To evaluate the role of acetylcholine in this process, endogenousacetylcholine was identified by field desorption spectroscopy coupled with gas chromatography. It is shown thatthe acetylcholine-like substance isolated from Vicia faba seedlings exhibited a spectroscopic spectrum similar tothat of the authentic acetylcholine and an extract of rat brain. These results demonstrated that acetylcholine isan endogenous substance of Vicia faba seedlings. In addition, a method of pyrolysis gas chromatography wasestablished for determining the concentrations of acetylcholine in plants. It was found that aretylcholine contents in the abaxial epidermis exhibited a close relationship with the leaf transpiration rate and the root statues.It is speculated that acetylcholine may play an important role in the regulation of stomatal movement. This hypothesis was confirmed by the finding that acetylcholine has a stimulatory effect on stomatal aperture in theabedal epidermis and the acetylcholine esterase inhibitor, neostigmine could increase the susceptibility ofstomata to acetylcholine.