Abstract
The effect of temperature on mineral N absorption and symbiotic N fixation by Desmodium intortum cv. Greenleaf (De) was studied using ^<15>N. To study this effect, three different temperature conditions of 20℃, 25℃ and 30℃ were imposed on the seedling of De inoculated and applicated with starter N. Plants were harvested 8 times at 5 day intervals commencing in 8 days after the germination. Items studied were DM yield, leaf area, nodule number, nodule weight, total N and the proportions of N originated from N fertilizer and symbiotically fixed N. Results obtained were as follows: 1) DM yield was higher in order of 30℃>25℃>20℃ with wider difference between 25℃ and 20℃. 2) Better nodulation was seen at higher temperature. White nodule increased at lower temperature. Nodule weight per leaf area showed similar trend to nodule number. Nodule number per root weight was higher at 30℃, followed by 25℃ and 20℃ without any significant difference between 25℃ and 20℃. 3) N content was higher at higher temperature and wider differences between tem-temperatures were recognized in the plant top. Total N yield and the portion of N originated from nodule was higher at higher temperature. The N originated from nodule out-yielded that from fertilizer at 25℃ and 30℃, but not at 20℃. The N fixed per nodule weight at 25℃ and 30℃ doubled that at 20℃. 4) The basic mechanism in which starter N affects the seedling growth of De and N fixation might be identical at all temperature conditions to those described in the previous paper. However, N fixation played a more significant role at higher temperature, and N absorption at lower temperature.
