【作者】 孙青；

【导师】 沈繁宜；

【作者基本信息】 北京林业大学 ， 植物学， 2006， 硕士

【摘要】 空穴化发生之后，栓塞化的导管(或管胞)能够修复。空气的溶解被认为是日常栓塞修复的主要机制，但这一学说不能解释较低负压下的栓塞修复。郭锐用几种裸子植物做的实验中，得出气体的移动是切片样品栓塞修复的主要原因。为进一步寻找活体植物中栓塞气体的去向，我用几种被子植物和裸子植物的切片做实验，在显微镜下观察样品失水空穴化和复水后栓塞修复的过程，寻找有无大导管(管胞)中的气泡长大的现象。 实验中观察到，切片样品复水达到相对稳定状态后，小导管中的气泡一直缩小，回缩成半径越来越小的球形泡并最终消失，同时，半径较大的导管(管胞)中的长形泡在不断的长大，不过随着时间的推移，长大的长形泡也会逐渐的回缩并最终消失。复水达到稳定状态后，胞外球形泡逐一出现，我们看到胞外球形泡主要从木射线的横断面出来，并且随着导管(管胞)中长形泡的回缩，球形泡逐渐长大。在复水的不同时期比较一个视野内导管内外气体的量时，通过计算，导管内外气体的量基本相等，说明修复完全后，栓塞导管中的气体绝大部分进入了胞外球形泡。 通过进一步的分析，除了气体的移动外，我们认为气体的溶解也是导致栓塞修复的一个原因。无论是气体的移动还是气体的溶解，气体的去向都是由半径小的地方到半径大的地方，半径小的最后消失，而半径大的则长大。切片样品中，半径较小的导管(管胞)中的气体通过两种方式从木射线进入半径较大的导管(管胞)和胞外球形泡，同理，大导管(管胞)中的气体也可以进入球形泡。所以修复完全后，栓塞导管中的气体绝大部分进入了胞外球形泡，导管内外气体的量基本相等，进一步证明了此结论。栓塞修复是由于气体的移动和气体的溶解扩散。 由于气体的移动和溶解均可为低压下的运动，据此推测在活体植物中，半径较小的导管(管胞)中的气体通过气体的移动和溶解扩散进入大导管(管胞)和木射线，木射线中的气体横向运输到压强更小的髓心区域，导致活体植物的栓塞修复。 此外，由于各树种空穴化和栓塞修复的时间各不相同，对它们的接触角进行了测量。结果证明接触角小，栓塞修复就快，反之，栓塞修复就慢。更多还原

【Abstract】 Cavitation and embolism are common events in plants and water stress is the most common of which induce cavitation. Cavitation is induced by air seeding, which can occur through the pores of pit membranes. It might also be caused by tiny air bubbles adhering to cracks in vessel walls.Following daily cavitation the refilling of embolized conduits is common in both woody and herbaceous plants even when the water in neighboring conduits is under tension. Dissolution of gas is regarded as the primary mechanism of daily embolism repair.We did experiments with several woody plants (angiosperm and gymnosperm plants). In our experiments there are not only phenomena that bubbles in small conduits kept contracting but also bubbles in big conduits kept expanding, some times later, it contracted too. Spherical bubbles mainly emerged from place where woody rays existed, and grew up continually. When we compare the amount of the gas in and out conduits in one view , the amount of the gas was equal in different periods of rewetting, air in the embolismed conduits entered the spherical bubbles at the end.According to the analysis, air dissolution and air transfer were both accounted for the embolism repair at the beginning, but at the end there was only air dissolution. Air in small conduits entered big conduits and spherical bubbles in out sections, and air in big conduits could came into spherical bubbles too. Air in embolismed conduits entered the spherical bubbles at the end. According to this, we can deduce that in alive trees air moved from embolismed conduits (tracheids) to pith, air transfer and air dissolution maybe both accounted for embolism repair.According to the conception of contact angle, it maybe has some relation with embolism repair. We drew and measured different plant’s contact angle, the results showed that they were indeed different in different trees. In different seasons, the contact angle was different too. In summary it was big in winter and spring, small in summer and autumn. When the angle is small, embolism repair time is short, and when it is big, embolism repair time is long. So contact angle maybe one of reasons that cause embolism repair.更多还原