Studies on the Stiffness of Culms in Barley Plants (Hordeum sativum, JESSEN) : 15. Physiological studies on the stiffness of culms by ¹⁴C-tracer method(2)

Abstract

A brittle culm variety, Sekitorisai-No. 1 and three stiff culm varieties, Haganemugi, Mitake, and Dorirumugi were used. The present studies were carried out in attempt to get background information on the mechanical properties of brittle and stiff culms. Haganemugi and Mitake, as compared with other varieties, were found to be superior in respect of the moment of inertia of cross sectional area of the culm. On the other hand, Dorirumugi showed a higher value in YOUNG's modules than other varieties. In Haganemugi and Mitake, the dry weight was higher and the amounts of assimilated-¹⁴C, cellulose, and silica accumulated in the culms were more than those in other varieties. Therefore, Haganemugi and Mitake are considered to be superior to other varieties in respect of culm growth, as they have large culm diameters and thick culm walls. Dorirumugi was found to be superior to other varieties, so far the number of vascular bundles per unit area of cross section of the culm is concerned. The greater mechanical culm strength in Dorirumugi variety was therefore supposed to be the contribution of the higher number of vascular bundles in unit area corresponding to those in other varieties. Based upon the above facts, the culm stiffness, which is significantly ascribed to the increase in YOUNG's modules or moment of inertia of cross sectional area of the culm, is considered as one of the most important factors for resistance against lodging. Therefore, it might be concluded that the shorter the culm becomes, to a certain extent, the more the buckling load is increased.