Germination, growth, osmotic adjustment and ionic balance of wheat in response to saline and alkaline stresses

Figures & data

Table 1 Electrical conductivity (EC) and osmotic potential of the stress treatment solutions

Salinity (mmol L^−1)	EC (dS m^−1)	Osmotic potential (MPa)
Control	2.17	−0.05
Salt stress
30	5.62	−0.25
60	8.90	−0.43
90	11.86	−0.60
120	14.58	−0.79
150	17.32	−0.95
Alkali stress
15	3.00	−0.14
30	4.40	−0.23
45	5.85	−0.32
60	7.15	−0.40
75	8.25	−0.50

Figure 1 Effects of salt and alkali stresses on the ionic activities (IA) and free concentrations (FC) of macronutrients in the nutrient solutions (percentage is calculated according to the mean value of every treatment). (a) Ca2+, (b) Mg2+, (c), K+, (d) SO²⁻ ₄ and (e) NO⁻ ₃.

Figure 2 Effects of salt stress and alkali stress on the activities of (a) PO³⁻ ₄, (b) HPO²⁻ ₄, (c) H2PO⁻ ₄, and (d) the total ionic activities (IA) in the nutrient solutions.

Figure 3 Effects of salt and alkali stresses on (a) under ground and (b) above ground relative growth rate (RGR), (c) water content, (d) electrolyte leakage, (e) chlorophyll a, (f) chlorophyll b, (g) carotenoid content and (h) root system activity. Salt stress: NaCl : Na2SO4 = 1:1, pH 6.6–6.95; alkali stress: NaHCO3 : Na2CO3 = 1:1, pH 9.77–9.96. The values are the means of five replicates. Means followed by different letters in the same curve are significantly different at P ≤ 0.05 according to a least significant difference test. FW, fresh weight.

Table 2 Regression equation between the relative growth rate (RGR) and the salt concentration

	Regression equation	R ^2	Decrease in RGR for a 100 mmol L^–1 increment of salinity
RGR of shoot	YSalt = −0:0003x + 0.079	0.9563	0.03
	YAlkali = −0:0004x + 0.076	0.9483	0.04
RGR of root	YSalt = −0:0004x + 0.090	0.9437	0.04
	YAlkali = −0:0001x + 0.098	0.9743	0.10

Figure 4 Effects of salt and alkali stresses on the contents of (a) Na+, (b) K+, (c) free Fe2+, (d) free Mg2+ and (e) free Ca2+ in the wheat shoots. Salt stress: NaCl : Na2SO4 = 1:1, pH 6.6–6.95; alkali stress: NaHCO3 : Na2CO3 = 1:1, pH 9.77–9.96. The values are the means of five replicates. Means followed by different letters in the same curve are significantly different at P ≤ 0.05 according to a least significant difference test. DW, dry weight.

Figure 5 Effects of salt and alkali stresses on the contents of (a) Cl−, (b) SO42−, (c) NO3− and (d) H2PO4− in the wheat shoots. Salt stress: NaCl : Na2SO4 = 1:1, pH 6.6–6.95; alkali stress: NaHCO3 : Na2CO3 = 1:1, pH 9.77–9.96. The values are the means of five replicates. Means followed by different letters in the same curve are significantly different at P ≤ 0.05 according to least significant difference test. DW, dry weight.

Figure 6 Effects of salt and alkali stresses on the contents of (a) proline, (b) soluble saccharides, (c) betaine and (d) organic acid in the wheat shoots. Salt stress: NaCl : Na2SO4 = 1:1, pH 6.6–6.95; alkali stress: NaHCO3 : Na2CO3 = 1:1, pH 9.77–9.96. The values are the means of five replicates. Means followed by different letters in the same curve are significantly different at P ≤ 0.05 according to least significant difference test. DW, dry weight.

Figure 7 Effects of salt and alkali stresses on (a) the rate of germination and (b) the recovery germination of wheat. Salt stress: NaCl : Na2SO4 = 1:1, pH 6.66–7.01; alkali stress: NaHCO3 : Na2CO3 = 1:1, pH 9.83–10.03. The values are the means of five replicates. Means followed by different letters in the same column are significantly different at P ≤ 0.05 according to least significant difference test.

Table 3 Percentage of each solute molarity to the total molarity

Salinity (mmol L^− ^1)	Na^+ (%)	K^+ (%)	Fe^2+ (%)	Mg^2+ (%)	Ca^2+ (%)	Cl^− (%)	SO^2− 4 (%)	NO^− 3 (%)	H2PO^− 4 (%)	Proline (%)	SS (%)	Betaine (%)	OA (%)
Control	1.549	40.172	0.007	0.282	0.058	3.486	1.279	31.369	4.394	0.065	1.495	1.678	14.165
Salt stress
30	4.725	39.512	0.008	0.244	0.048	7.785	1.608	24.268	4.159	0.126	1.505	1.812	14.199
60	6.237	37.739	0.007	0.288	0.046	11.282	2.462	21.099	3.353	0.173	2.334	2.501	12.479
90	8.330	34.037	0.006	0.271	0.040	17.274	3.335	15.185	2.821	0.227	3.063	3.491	11.918
120	11.421	27.571	0.006	0.226	0.036	23.259	4.09	12.302	2.668	0.463	3.407	3.644	10.907
150	15.009	19.105	0.006	0.208	0.026	30.699	4.695	9.934	2.438	0.598	3.948	3.400	9.935
Average	7.879	33.023	0.007	0.253	0.042	15.631	2.912	19.026	3.306	0.275	2.625	2.754	12.267
Alkali stress
15	7.887	37.282	0.008	0.442	0.061	5.863	1.347	20.726	4.220	0.134	1.983	3.168	16.881
30	16.280	34.167	0.010	0.459	0.067	5.554	1.275	12.824	4.323	0.205	3.069	3.160	18.608
45	28.786	24.928	0.010	0.560	0.062	4.724	0.956	9.190	3.279	0.332	2.948	3.505	20.720
60	39.103	20.001	0.011	0.605	0.064	4.031	0.672	6.391	2.636	0.605	2.654	3.283	19.944
75	49.160	8.369	0.009	0.540	0.060	3.235	0.638	4.163	1.921	0.626	2.147	5.943	23.188
Average	28.243	24.949	0.010	0.521	0.063	4.681	0.978	10.659	3.276	0.380	2.560	3.812	19.868
OA, organic acid; SS, soluble sugar; 100% is the sum of all solute values.