抄録
The effects of rhizosphere temperature during about 40 days after seeding upon the growth of some autumn soybean varieties and rhizobial infection or nodule formation and their subsequent development were studied, especially, from the viewpoint of the "leguminous plant-Rhizobium symbiotic complex". For the experiments, following plots were designed: HH…about 27°C throughly; LL…about 22°C throughly; HL and LH…about 27°C (vs. 22°) for 15 days after seeding land 22°(vs. 27°) for the rest. The data were obtained in '58 and '59 under the green house condition by quarz sand culture containing no nitrogen fertilizer and inoculated with the rhizobia. 1) It was observed that the period from the emergence to falling-off of cotyldons in the LL-plot plants were about 3 days longer than that in the HH-plot ones, and the development of both aerial and subterranean parts of the former were inferior to those of the latter (Fig. 2∼5 and Tab. 1). 2) Effects of lower rhizosphere temperature upon the top growth of soybean may be characterized into two types; (i) the direct reduction or shortening in size or length of some organs or portions of the plant (e.g., hypocotyl length, size of primary and foliage leaves when they expanded entirely, and their petiole length etc.) and (ii) mere delaying or lag of growth stge (e. g., inferiorities in plant length, number of leaves, and total leaf area per plant etc.). 3) With regard to the number of nodules formed on the LL-plot plants, irregularities were found, while the dry matter weight of nodules was inferior respectively to the HH-plot ones. The value of "nodule d. m. w./total plant d. m. w." (Relative ammounts of nodule formation) of the LL-plot was decidedly larger than that of the HH-plot (Table 1). In connection with the carbohydrate supply by host plant to the symbiont, these results may suggest that the "symbiotic effects" may vary under the different conditions of rhizosphere temperatures.
