抄録
Rice plants, cv. Nipponbare were grown under three temperature conditions with day/night temperature(°C) of 33/27(H), 29/23(M) and 25/19(L) during the young panicle development (from the initiation to the full heading). Using the main stems of plants, the effects of temperature on growth of panicle, leaf blade, leaf sheath and internode at each position of the main stem were examined. The results are summarized as follows : 1. Effects of temperature on growth of plant parts varied depending on the ontogenic stage of development. At the early stage of development, elongation was strongly accelerated with increase in temperature. However, after rapid growth had started, temperature had no strong accelerative effect on elongation (Figs. 1-3). In the case of panicle, the difference between L and H in the period from the initiation to 1 cm-stage was 8 days while from the 1 cm-stage to the full length, it was only 1 day (Fig. 4). Thus, it seemed that the growth of plant organs or their parts is sensitive to temperature at the early stage of development but becomes less sensitive at later stages. 2. Since temperature affects growth of every organ or its part evenly, synchronous relations in elongating processes among definite combinations of plant parts were maintained irrespective of temperature conditions. For example, panicle, leaf sheath of the flag leaf and the third internode (counted from the top) grew synchronously (Fig. 6). 3. The effect of temperature on final length of plant parts was different depending on the kind of organ and the position of the part. Leaf blade of the uppermost three leaves was longer under higher temperature (Fig. 7). With rise in temperature, the uppermost internode was lengthened while the penultimate, the third and the fourth internode were shortened (Fig. 8). Thus, culm length was almost constant in the temperature range applied. Similarly, panicle length was little affected by temperature (Fig. 9).
