Effects of N supply level on leaf photosynthesis in rice seedlings.

Rice plants (cv. Shanyou 63 and Yangdao 6) were supplied with N at three different levels (low: 20 mg L−1 N, intermediate: 40 mg L−1 N, and high: 100 mg L−1 N). Data are means ± SD of more than 20 individual chloroplasts for their length and thickness, and 5 individual plants for other variables.
Notes: Significant differences (P<5%) between N supplies or varieties were indicated by different lowercase letters or different uppercase letters, respectively. A, gs, gm, N, Rubisco and PNUE represent leaf photosynthetic rate, stomatal conductance to CO2, mesophyll conductance to CO2, leaf nitrogen content, leaf Rubisco content, photosynthetic N-use efficiency, respectively.