水稲下位節間の挫折抵抗力に関する組織形態学的研究 : 第5報研磨切片法による節間挫折過程の組織学的観察

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This report presents a result of histological observations on breaking process and slip planes formation in the fourth internode of rice culm, var. Koshihikari, with a polished thin section method. This method was devised in order to prepare microscopic thin sections of hard plant tissues with no artifact. The procedure is described as follows. Small specimens were dehydrated through ethanol series, and the ethanol was substituted with methyl methacrylate, which was polymerized later in gelatin capsule. Then, one side of the embedded specimen was disclosed with a grinder and emery papers, and was polished with abrasive cloth soaked in chromium oxide suspension. Subsequently, the polished side was stuck on a slide glass with epoxy resin, which was polymerized later, and the specimen was thinned to 5-20 μm thick, and was polished by the same means as mentioned above. Breaking process of the internode observed with the polished thin sections and a polarizing microscope is shown as follows. In the concave side of bent internodes, (1) first of all, a small number of slip planes arise in the cell walls of the cortical fibers (Fig. 1), (2) subsequently, many small creases and several chaps appear on the internodal surface (Figs. 2 and 3), (3) the cortical fiber cells begin to bend and the slip planes increase notably (Fig. 4), and when the internodes are broken, (4) the cortical fiber cells bend remarkably and separate from each other at middle lamella, and at the same time, the epidermal cells separate from the cortical fibers (Figs. 5 and 6), and (6) fundamental parenchyma cells are broken lastly (Fig. 5). The slip planes in the wall of the cortical fiber cells were formed on S helices crossing at almost right angles with Z helices of cellulose microfibrils in the S_2 layer, which run parallel to the long axes of pits (Figs. 7 and 8). It is considered, therefore, that the slip planes of the internode are microscopic folds or crinkles in the S_2 layer of secondary cell wall caused by compressive stress of bending load, as previously reported on wood cell walls by WARDROP et all and KEITH et al. The number of slip planes increased gradually with repeat of culm bending by wind and rain in the ripening period (Table 1). It is supposed, therefore, that the slip planes, small creases and chaps are the important factors of so-called fatigue of the lower internodes, and that thc short cells and large papillae on the epidermis function as the powerfull resistants to bending stress. From these results, the following conclusion can be deduced that the thickness of epidermis-cortical fiber compound and its cell walls, fiber cell length and sufficient depositions of silicic acid and lignin are the important factors to increase breaking resistance of the lower internodes.
日本作物学会の論文
1983-12-05

水稲下位節間の挫折抵抗力に関する組織形態学的研究 : 第5報研磨切片法による節間挫折過程の組織学的観察

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水稲下位節間の挫折抵抗力に関する組織形態学的研究 : 第5報 研磨切片法による節間挫折過程の組織学的観察

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水稲下位節間の挫折抵抗力に関する組織形態学的研究 : 第5報研磨切片法による節間挫折過程の組織学的観察