A New Method for Tracing of Internode Length in Wheat

Abstract

Experiments were carried out on the new method for tracing of internode length in wheat. Measurements were made on the process of the elongation in leaf sheath, spike and internode, and the process of the height in lamina joint and spike tip. Leaf sheaths, spike and internodes were beyond the sweep of the eye, since these organs were covered by the alien organs. Soft X-rays, therefore, were applied to tracing the lenght of these organs. The heights from the ground surfacc to lamina joint and spike were traced, after these organs had come into sight from the lower lamina joints. These measurements were carried out for the main stem of the single plant. S₁:S₂:..., I₁:I₂:... indicated the order of leaf sheaths and internodes from the uppermost to the lower ones, the spike being indicated as S₀ (Fig. 1), respectively. 1. The elongation process of respective organs showed the S-shaped curves (Fig. 2). The main elongating periods differed with organs and node order. The dates of the highest activity of the elongation were repeated regularly from the lower to the upper. The dates occured at intervals of a week as a general rule, however, the dates of I₀ and I₁ were nearly the same (Table 1). 2. Immediately after the end of the main elongating period of leaf sheaths, the beginning of the main elongating period of internodes started in the same order. The date of emergence of lamina joints was synchronously observed with the end of the main elongating period of leaf sheaths in the same order (Table 2). These facts showed that the growth of the lamina joint height was due to the elongation of the internodes in the same order. The interdode length, therefore, is related to the leaf sheath or the spike lenght and the lamina joint or the spike tip height as follows: I_{n, t}= (L_{n, t}-S_n)-(L_{n+1, t}-S_n+1) [1] where, I_{n, t} is the n-th internode length at the time t; L_{n, t} is the n-th lamina joint height or the spike tip at the time t; S_n is the final length of the n-th leaf sheath or the spike. 3. The estimates of the internode length applied to the formula [1] agreed well with the measurements by using X-rays, exclusive of the starting phase in elongation. Supposing we applied the formula [1], we would be able to perform for tracing of the elongation of internode (Table 3). Judging from previous studies of rice, it should be possible to apply this formula derived from wheat to the investigation of internode length of rice.