Table 1.

Effects of salt stress on the photosynthesis in the rapeseed seedlings under different N levels.

Salt	N rate (g kg−1)	Pn (μmol CO2 m−2 S−1)	Gs (mol H2O m−2 S−1)	Ci (μmol CO2 m−2)	Tr (mmol H2O m−2 S−1)	CE
S0	N0	11.09 ± 1.02f	0.15 ± 0.01cd	299.17 ± 18.93b	2.77 ± 0.12e	0.037 ± 0.006f
	N1	16.21 ± 0.53d	0.16 ± 0.01c	245.13 ± 15.23d	3.06 ± 0.27d	0.066 ± 0.003d
	N2	23.84 ± 0.79a	0.23 ± 0.01a	221.13 ± 5.33e	3.99 ± 0.21b	0.108 ± 0.006a
	N3	24.22 ± 1.00a	0.24 ± 0.01a	224.05 ± 7.20e	4.31 ± 0.11a	0.108 ± 0.008a
S1	N0	8.85 ± 0.20g	0.11 ± 0.01e	338.03 ± 11.04a	2.05 ± 0.12f	0.026 ± 0.001g
	N1	14.13 ± 1.21e	0.14 ± 0.02d	274.27 ± 10.68c	2.88 ± 0.26de	0.052 ± 0.005e
	N2	21.51 ± 1.17b	0.19 ± 0.01b	250.78 ± 9.36d	3.81 ± 0.17b	0.086 ± 0.008b
	N3	19.49 ± 0.95c	0.18 ± 0.01b	255.20 ± 5.72d	3.52 ± 0.12c	0.076 ± 0.005c
ANOVA
Salt		**	**	**	**	**
N		**	**	**	**	**
Salt x N		**	**	ns	*	*

Data are mean ± SE (n = 6). S0 and S1 respectively represent salinity levels of 0 and 3 g NaCl kg⁻¹ soil. N0, N1, N2, and N3 respectively represent N rate levels of 0, 0.1, 0.2, and 0.3 g N kg⁻¹ soil. Different letters within a column indicate significant differences at p = 0.05. Probability levels are indicated by ns, *, and ** for not significant, 0.05, and 0.01, respectively.

Pn, net photosynthetic rate; Gs, stomatal conductance; Ci, intercellular CO₂ concentration; Tr, transpiration rate; CE, instantaneous carboxylation efficiency.