Studies on the Responses of Pasture Grasses to Nitrogen Fertilization : III. Effect of nitrogen fertilizer rate, leaf nitrogen concentration and chlorophyll content on photosynthetic activities of some subtropical grass species

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  • 施肥窒素に対する牧草の反応に関する研究 : III.数種暖地型牧草の光合成作用に及ぼす窒素施肥量,葉身窒素含有率およびクロロフィル含有量の影響
  • 施肥窒素に対する牧草の反応に関する研究-3-数種暖地型牧草の光合成作用に及ぼす窒素施肥量,葉身窒素含有率およびクロロフィル含有量の影響
  • セヒ チッソ ニ タイスル ボクソウ ノ ハンノウ ニカンスルケンキュウ 3

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The experiment was carried out to clarify the effect of nitrogen fertilizer rate, leaf nitrogen concentration and chlorophyll content on photosynthetic activities of some subtropical grass species. Species used were rhodesgrass (Chloris gayana KUNTH.), dallisgrass (Paspalum dilatatum POIR.) and bahiagrass (Paspalum notatum FLUGGE). Results obtained were as follows: 1. Photosynthetic rate per plant (P) under low nitrogen fertilizer treatment showed the lowest in rhodesgrass at the weeks of advanced growth. This seemed to be caused by the remarkable drop in photosynthetic rate per unit leaf area (P_0) which resulted from the marked decrease of leaf nitrogen concentration due to the serious nitrogen deficiency in rhodesgrass plot. In contrast, rhodesgrass showed the highest P value followed by dallisgrass and bahiagrass under high nitrogen fertilizer treatment. This specific difference was considered to be based on the difference in their ability of leaf area expansion. 2. The three species equally increased their P_0 as leaf nitrogen concentration increased up to about 3% and their P_0 reached 60mg CO_2/dm^2, hr. But, beyond this nitrogen level their P_0 were independent of leaf nitrogen concentration. 3. The three species contained about 4.5mg chlorophyll per dm^2 leaf area at 3% leaf nitrogen concentrations. Positive correlation between their chlorophyll contents and P_0 were observed within the range of up to about 4.5mg/dm^2 chlorophyll, but beyond this value their P_0 were independent of chlorophyll contents.

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