Effect of diurnal change of turgor pressure on wood formation

本研究的目的是建立一种利用应变计检测树木活细胞中膨胀压力日变化的方法，并了解膨胀压力与树木次生生长的关系。测量了树皮内切向应变的日变化，得到如下结果：1、在自然光条件下，树干内侧树皮的切向应变在下午两点左右收缩最大，下午晚些时候逐渐扩大，直至夜间。在黎明前观察到最大的膨胀，在白天期间，当阳光开始时，突然收缩。在人工光照控制下的生长室中测量的切向应变表明，应变的日变化与光照的变化一致。2、切向应变与叶片水势有较高的相关性。在最大收缩条件下观察到的切向应变，在去叶或浇头时突然释放。切向应变随水应力增大而收缩。在萎凋过程中，当水势低于-1.5MPa时，即使补水，收缩应变也无法恢复。切向应变的收缩过程分为两个阶段。菌株收缩到原生质分离发生的点，细胞停止收缩，并通过进一步干燥重新开始收缩。4、由以上结果可知，切向应变的日变化是由于蒸腾和吸胀两种作用引起的负压变化引起的活细胞胀压的变化。5、根据树皮内切向应变和杨氏模量数据计算，活细胞的膨胀压力为0.3 ~ 0.4 mpa。膨压的日变化量估计在16-88Kpa。本研究提出了一种与水势相关的活细胞膨胀压力的连续测量方法。进一步的研究将有助于了解木材物理性质的产生过程与细胞壁形成的关系。少

The aim of this research was to establish a method of detecting the diurnal change of turgor pressure in the living cells of tree by using the strain gage and also to understand the relation between the turgor pressure and the secondary growth of the tree.The diurnal change of the tangential strain in the inner bark was measured, leading to the following results.1, Under the natural light condition, the tangential strain in the inner bark of the tree trunk showed a maximum shrinkage at about two o'clock in the afternoon, expanding gradually later in the afternoon until night-time. The maximum expansion was observed before the daybreak and during the day period a sudden shrinkage was appreciated at the same time when the sunshine started.The tangential strain measured in a growing chamber with controlled artificial lighting made clear that the diurnal change of the strain coincided with the change of sunlight illumination.2, The tangential strain had a high correlation with the water po … More tential measured in the leaves measured with a psychrometer.3, The tangential strain observed under the maximum shrinkage condition, was suddenly released when the leaves were removed or topping was done. Tangential strain shrinks corresponding to large water stress.During the process of withering, the shrunk strain did not recover even after water was supplied once the water potential became less than -1.5MPa. Two steps were recognized in the shrinkage process of the tangential strain. The strain shrunk up to the point when protoplasm separation would be occurred in the cell stops to shrink and start again to shrink by further drying.4, From the above results, it was clear that the diurnal change of tangential strain was due to the change in turgor pressure of living cells generated by the change in negative water pressure induced by both, transpiration and imbibition.5, The calculation made from the data of tangential strain and Young's modulus of the inner bark gave a value of 0.3-0.4MPa as the turgor pressure of living cells. The amount of diurnal change of the turgor pressure was estimated at 16-88Kpa.In this research, a method of continuous measurement of turgor pressure of living cells related to water potential was developed.Further research will enable to understand the generation process of the physical properties of wood in relation to the cell wall formation. Less