Effects of saline and alkaline stresses on the germination, growth, photosynthesis, ionic balance and anti-oxidant system in an alkali-tolerant leguminous forage Lathyrus quinquenervius

Figures & data

Figure 1 Effects of saline and alkaline stress on the (A) rate of germination and (B) rate of recovery germination in Lathyrus quinquenervius seeds. The L. quinquenervius seeds were treated with saline stress (NaCl : Na2SO4 = 9:1; pH 6.44–6.65) and alkaline stress (NaHCO3 : Na2CO3 = 9:1; pH 8.71–8.89) for 10 days to assess the rate of germination, and then the ungerminated seeds were transferred to distilled water for another 10 days to assess their rate of recovery germination. In each column, the data markers identified with the same letters are not significantly different (P < 0.05) according to a least significant difference test. The error bars represent ± standard error (n = 4) of four replicates.

Figure 2 Effects of saline and alkaline stress on the (A) relative growth rate (RGR) and (B) activity of the root system in Lathyrus quinquenervius shoots. The 8-week-old L. quinquenervius seedlings were treated with saline stress (NaCl : Na2SO4 = 9:1; pH 6.44–6.65) and alkaline stress (NaHCO3 : Na2CO3 = 9:1; pH 8.71–8.89) for 10 days. In each column, the data markers identified with the same letters are not significantly different (P < 0.05) according to a least significant difference test. The error bars represent ± standard error (n = 4) of four replicates.

Figure 3 Effects of saline and alkaline stress on (A) net photosynthetic rate (PN), (B) transpiration rate (E), (C) stomatal conductance (gS), (D) chlorophyll (Chl) a, (E) chlorophyll (Chl) b and (F) carotenoids (Car) in Lathyrus quinquenervius leaves. The 8-week-old L. quinquenervius seedlings were treated with saline stress (NaCl : Na2SO4 = 9:1; pH 6.44–6.65) and alkaline stress (NaHCO3 :  Na2CO3 = 9:1; pH 8.71–8.89) for 10 days. In each column, the data markers identified with the same letters are not significantly different (P < 0.05) according to a least significant difference test. The error bars represent ± standard error (n = 4) of four replicates. FW, fresh weight.

Figure 4 Effects of saline and alkaline stress on the amount of (A) malondialdehyde (MDA), (B) H2O2, (C) superoxide dismutase (SOD), (D) catalase (CAT), (E) ascorbate peroxidase (APX) and (F) electrolyte leakage rate (ELR) in Lathyrus quinquenervius leaves. The 8-week-old L. quinquenervius seedlings were treated with saline stress (NaCl : Na2SO4 = 9:1; pH 6.44–6.65) and alkaline stress (NaHCO3 :  Na2CO3 = 9:1; pH 8.71–8.89) for 10 days. In each column, the data markers identified with the same letters are not significantly different (P < 0.05) according to a least significant difference test. The error bars represent ± standard error (n = 4) of four replicates. SOD, CAT and APX were expressed relative to the control value of 100%. FW, fresh weight.

Figure 5 Effects of saline and alkaline stress on (A) Ca2+, (B) Mg2+, (C) Fe2+, (D) Na+, (E) K+ and (F) Na+/K+ ratio in Lathyrus quinquenerviu shoots. The 8-week-old L. quinquenervius seedlings were treated with saline stress (NaCl : Na2SO4 = 9:1; pH 6.44–6.65) and alkaline stress (NaHCO3 : Na2CO3 = 9:1; pH 8.71–8.89) for 10 days. In each column, the data markers identified with the same letters are not significantly different (P < 0.05) according to a least significant difference test. The error bars represent ± SE (n = 4) of four replicates. DW, dry weight.

Figure 6 Effects of saline and alkaline stress on (A) Cl− , (B) NO3–, (C) H2PO4−, (D) SO42− and (E) organic acid in Lathyrus quinquenervius shoots. The 8-week-old L. quinquenervius seedlings were treated with saline stress (NaCl : Na2SO4 = 9:1; pH 6.44–6.65) and alkaline stress (NaHCO3 : Na2CO3 = 9:1; pH 8.71–8.89) for 10 days. In each column, the data markers identified with the same letters are not significantly different (P < 0.05) according to a least significant difference test. The error bars represent ± SE (n = 4) of four replicates. DW, dry weight.

Figure 7 Effects of saline and alkaline stress on the tissue pH in Lathyrus quinquenervius shoots. The 8-week-old L. quinquenervius seedlings were treated with saline stress (NaCl : Na2SO4 = 9:1; pH 6.44–6.65) and alkaline stress (NaHCO3 : Na2CO3 = 9:1; pH 8.71–8.89) for 10 days. In each column, the data markers identified with the same letters are not significantly different (P < 0.05) according to a least significant difference test. The error bars represent ± SE (n = 4) of four replicates.

Table 1 Percentage of the contribution of various anions to the total negative charge (ion balance) in Lathyrus quinquenervius shoots under saline and alkaline stresses

	Salinity (mmol L^−1)	Cl^− (%)	NO3 ^− (%)	H2PO4 ^− (%)	SO4 ^2− (%)	Organic acid (%)
Saline stress	Control	6.63	3.90	29.29	5.14	55.04
	30	19.43	1.28	25.56	6.61	47.12
	60	30.09	0.47	20.53	6.17	42.75
	90	38.21	0.35	15.20	6.73	39.52
Alkaline stress	30	6.59	1.06	17.68	6.16	68.52
	60	4.08	0.05	8.80	3.63	83.44
	90	1.83	0.09	3.86	1.72	92.50
Eight-week-old seedlings were subjected to saline (NaCl : Na2SO4 = 9:1) or alkaline (NaHCO3 : Na2CO3 = 9:1) stress for 10 days.