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A greenhouse pot experiment was conducted to study the effects of nitrogen fertilization on Calophyllum inophyllum seedlings grown with 0, 50, 100, 150,200, 300, 400 and 600 mg N per seedling according to exponential functions. Seedling height, root collar diameter, leaf area and total biomass increased with increasing fertilization from 0 to 200 mg N per seedling and decreased with further increase in fertilization from300 to 600 mg N per seedling. The net photosynthetic rate,stomatal conductance, intercellular CO_2 concentration and transpiration rate of C. inophyllum seedlings showed a unimodal parabolic trend, with peak values of7.29 mmol·m~(–2)·s~(–1), 0.071 mol·m~(–2)·s~(–1), 220 mmol·mol~(–1) and 1.34 mmol·m~(–2)·s~(–1), respectively, when the rate of fertilization was 200 mg N per seedling. Photosynthetic gas exchange parameters were significantly different among nitrogen treatments. Based on the critical values of leaf N and P concentration and N/P ratio, the optimum amount of nitrogen of C. inophyllum seedlings was 200–400 mg per seedling for leaf N and P concentration, and100–400 mg per seedling for N/P ratio. It was concluded that 200–400 mg N per seedling was the most suitable nitrogen range for C. inophyllum seedlings.
A greenhouse pot experiment was conducted to study the effects of nitrogen fertilization on Calophyllum inophyllum seedlings grown with 0, 50, 100, 150, 200, 300, 400 and 600 mg N per seedling according to exponential functions. and total biomass increased with increasing fertilization from 0 to 200 mg N per seedling and decreased with further increase in fertilization from 300 to 600 mg N per seedling. The net photosynthetic rate, stomatal conductance, intercellular CO 2 concentration and transpiration rate of C. inophyllum seedlings showed A unimodal parabolic trend with peak values of 7.29 mmol · m -2 · s -1, 0.071 mol · m -2 · s -1, 220 mmol · mol ~ (-1) -1) and 1.34 mmol · m -2 (-2) · s -1, respectively, when the rate of fertilization was 200 mg N per seedling. Photosynthetic gas exchange parameters were significantly different among nitrogen treatments. Based on the critical values of leaf N and P concentration and N / P ratio, the optimum amount of nitrogen of C. inophyllum seedlings was 200-400 mg per seedling for leaf N and P concentration, and 100-400 mg per seedling for N / P ratio. It was noted that 200-400 mg N per seedling was the most suitable nitrogen range for C. inophyllum seedlings.