. 2013 Apr 19;8(4):e62036. doi: 10.1371/journal.pone.0062036

Table 2. Effects of N supply level on leaf photosynthesis in rice seedlings.

Variables	Shanyou 63			Yangdao 6
	Low-N	Int.-N	High-N	Low-N	Int.-N	High-N
A (µmol CO₂ m⁻² s⁻¹)	16.32±0.09^b	18.76±2.88^ab	22.68±0.86^a	10.33±2.32^c	15.56±2.80^b	23.36±2.89^a
g_s (mol CO₂ m⁻² s⁻¹)	0.16±0.03^a	0.19±0.04^a	0.18±0.03^a	0.10±0.04^b	0.13±0.02^b	0.21±0.03^a
g_m _(Harley)	0.18±0.05^b	0.21±0.07^ab	0.25±0.03^a	0.11±0.03^c	0.18±0.02^b	0.26±0.05^a
(mol CO₂ m⁻² s⁻¹)
g_m _(Ethier)	0.21±0.05^b	0.24±0.02^ab	0.28±0.04^a	0.13±0.01^c	0.19±0.03^b	0.28±0.08^a
(mol CO₂ m⁻² s⁻¹)
Г* (µmol CO₂ mol⁻¹)	38.29±0.24^b	40.80±1.05^ab	42.26±1.89^a	38.53±0.68^b	39.91±1.34^ab	42.58±1.23^a
R_d (µmol CO₂ m⁻² s⁻¹)	1.00±0.05^a	0.67±0.026^b	0.61±0.06^b	1.37±0.06^a	1.23±0.17^a	0.83±0.09^b
N (mmol m⁻²)	87.14±0.93^c	106.43±4.14^b	143.57±0.50^a	61.43±4.29^c	92.14±2.86^b	139.29±8.57^a
NO₃ ⁻ (mmol m⁻²)	0.20±0.02^b	0.27±0.07^b	0.60±0.06^a	0.20±0.06^b	0.30±0.07^b	0.42±0.04^a
Relative Rubisco content	35.89±2.32^c	46.79±2.32^b	61.79±4.29^a	26.61±2.86^c	40.89±2.68^b	60.71±4.11^a
(µmol m⁻²)
Chloroplast length	4.20±0.59^b	4.69±0.62^b	5.55±0.82^a	4.51±0.61^a	4.72±0.63^a	4.87±0.67^a
(µm)
Chloroplast thickness	1.84±0.33^c	2.34±0.34^b	3.03±0.49^a	2.40±0.44^a	2.30±0.45^a	2.33±0.46^a
(µm)
Initial Rubisco activity	1.05±0.12^a	0.87±0.04^b	0.67±0.10^c	0.69±0.11^a	0.77±0.21^a	0.83±0.18^a
(mol mol⁻¹ Rubisco s⁻¹)
Max Rubisco activity	1.41±0.13^a	1.29±0.13^ab	1.07±0.23^b	1.31±0.36^a	1.38±0.25^a	1.17±0.06^a
(mol mol⁻¹ Rubisco s⁻¹)
A/Rubisco	0.45±0.03^a	0.40±0.04^ab	0.36±0.05^b	0.36±0.06^a	0.35±0.05^a	0.38±0.04^a
(mol CO₂ mol⁻¹ Rubisco s⁻¹)
PNUE (A/N)	190±9^a	178±23^ab	164±5^b	154±51^a	171±27^a	168±24^a
(µmol CO₂ mol⁻¹ N s⁻¹)
Chloroplast volume	7.44	13.44	26.67	13.59	13.07	13.84
(V_chl, µm³)
Chloroplast surface area	18.43	27.33	43.16	27.54	26.82	27.87
(S_chl, µm²)
g_m/Rubisco_(Harley)	5.02	4.49	4.05	4.13	4.4	4.28
(mol CO₂ mmol⁻¹ Rubisco s⁻¹)
g_m/Rubisco _(Ethier)	5.85	5.13	4.53	4.89	4.65	4.61
(mol CO₂ mmol⁻¹ Rubisco s⁻¹)

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, g_s, g_m, 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.