竹の切断試験 : 地下茎または幹と枝葉の切断が竹の生育におよぼす影響について

Abstract

The cutting of bamboo culm head (or the end) is sometimes called "URADOME", and has been widely applied in the field of bamboo sprout. Cutting of the rhizome is also a significant problem on the planting of young bamboo plants. The cutting of bamboo culm head is represented by the cutting of branches and leaves, while the cutting of rhizome is represented by the limitation in reserving the nutriments. In order to investigate the physiological and ecological influences on bamboo, this experiments were carried out by cutting bamboo culms, branches, leaves and rhizomes in various degree of cutting parts. A. MOSOCHIKU (Phyllostachys edulis Riv.), a species of bamboo, was used as the material for the cutting of bamboo culm head. The cutting degrees were classified in four: I. Large cutting, II. Relatively large cutting, III. Relatively small cutting, IV. Uncut (Control). The following results were obtained by a experimental comparison. 1) The ratio in the number of leaves at one leaf-sheath base showed the large cutting (I) the highest and it was followed by II and III cutting procedures respectively. 2) The larger in cutting the larger became the number of leaves between the same number of nodes. 3) When the degree of cutting is larger, increasing in the number of leaves at one leaf-sheath base is inversely proportional to the leaf area per leaf. The bamboo was treated with the procedure III showed similar state to that of the control. However, the average leaf area per leaf had the order, IV<III<II<I, respectively. The leaf area which was lost has relatively recovered by the treatment of the procedure III although the total leaf area per bamboo was not completely recovered until the initial state. 4) Although one leaf-sheath base was increased by "URADOME", any difference in the weight of the leaf dried in air was not recognized. However, in a case of cutting the water content in a leaf decreased. From the above results the branches and leaves of the bamboo should be left more than 18 nodes, around 28 cm. of the girth breast height, so that the bamboo recovers to its uncut state. B. Two species of bamboos, MOSOCHIKU (Phyllostachys edulis Riv.) and MADAKE (Phyllostachys reticulata C. Koch) were used for the cutting test of the rhizomes. The MADAKE is composed of bamboo thicket of slender culms. Rhizomes for the experiment were cut as follows: I. 1 meter, II. 2 meter, III. 3 meter, IV. Uncut (Control). The results are as follows. 1) The shorter in length of the rhizome, the worse in growth of the culm and in development of the root, especially it was remarkable in MOSOCHIKU. The position of the maximum internode length also was changed by the cutting of rhizomes. 2) The relation between the fresh weight of culms and the fresh weight of branches and leaves shows the shorter the rhizome is cut, the heavier becomes the fresh weight of culms of MOSOCHIKU and the lighter in that of MADAKE. 3) The content of soluble nitrogen in MOSOCHIKU was much less than that of MADAKE. The content of reducing sugar increased largely in longer rhizomes of MOSOCHIKU, while the reducing sugar in shorter rhizomes of MADAKE decreased. It is assumed that the least needed length of the young rhizomes of MOSOCHIKU and MADAKE to secure their thriving power is 5-6 and 4 meter respectively, although the necessary length of rhizomes for the normal growth varies according to their thickness and ages.