Research on modeling germination response to salinity of barley seeds

doi:10.3724/SP.J.1258.2012.00849

Abstract

Abstract:

Aims Salinization is a worldwide problem, and some researchers focus on the effect of salt on seed germination. The results are variable, and quantifying germination response to salt is significant. Furthermore, seed germination is affected by salinity, as a result of both osmotic and ion effects. How the two effects act together is unclear. Thus our objectives are to propose a model to accurately describe the effect of salt on seed germination and to clarify the role of the osmotic and the ion effect act under different salinities.
Methods Two varieties of barley (Hordeum vulgare) seeds (‘Cask’ and ‘County’) were cultured in five binate iso-osmotic polyethylene glycol (PEG) and NaCl solutions (-0.45, -0.88, -1.32, -1.76 and -2.20 MPa, distilled water as the control) at four constant temperatures of 5, 12, 20 and 27 °C. Germination time courses were recorded and germination rates (the reciprocal of germination time) were calculated. The hydrotime model and the new salinity model were used to calculate the parameters and test which was the better fit.
Important findings Results indicated that not only were seeds in saline conditions able to germinate at lower osmotic potentials than seeds germinating in an isotonic PEG-6000 solution, but that they were also able to do so faster. The hydrotime parameters of the NaCl treatments had great differences with the isotonic PEG treatments, which indicated the hydrotime model cannot describe salt effects on seed germination well. Barley seed germination rates in salt solutions were negatively linear with salinity. We proposed a salinity model to quantify germination response to salt. The germination time calculated from the salinity model approached the real data, compared to that calculated from the hydrotime model. Differences of germination rates in NaCl and the isotonic PEG treatments increased and then decreased with decreasing water potential. We suggest three situations of function mode by the osmotic and ion effects of salt. First, at low salinities the osmotic effect acts as the main negative role. Second, at medium salinities the two effects act together, with the positive ion effect stronger than the negative osmotic effect. Third, at high salinities the ion effect begins to harm the germination process.

Key words: barley (Hordeum vulgare), ion effect, model, osmotic effect, salinity, seed germination

ZHANG Hong-Xiang, TIAN Yu, ZHOU Dao-Wei, ZHENG Wei, WANG Min-Ling. Research on modeling germination response to salinity of barley seeds[J]. Chin J Plant Ecol, 2012, 36(8): 849-858.

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Figures/Tables 7

Fig. 1 Germination courses for two varieties of barley ‘Cask’ and ‘County’ cultured in isotonic NaCl and polyethylene glycol (PEG) solutions at four temperatures.

Table 1 Parameter estimate of hydrotime model for seed germination of two varieties of barley under different salinities, polyethylene glycol (PEG) solutions and four temperatures

品种 Variety	温度 Temperature (℃)	渗透调节物质 Osmotica	水势常数 θ_H (MPa·h)	最低水势 Ψ_b (50) (MPa)	误差 σ_Ψ_b (MPa)	R²
‘Cask’	5	NaCl	428	-2.51	0.63	0.83
		PEG	208	-1.22	0.61	0.66
	12	NaCl	115	-1.70	0.71	0.85
		PEG	65	-0.77	0.22	0.89
	20	NaCl	73	-1.72	1.09	0.84
		PEG	52	-1.23	0.64	0.68
	27	NaCl	36	-0.56	1.21	0.73
		PEG	34	-0.65	0.87	0.67
‘County’	5	NaCl	355	-2.55	0.83	0.58
		PEG	184	-1.32	0.56	0.62
	12	NaCl	115	-1.93	1.18	0.65
		PEG	63	-0.86	0.55	0.57
	20	NaCl	36	-1.35	0.72	0.73
		PEG	29	-1.01	0.49	0.67
	27	NaCl	20	-0.80	0.65	0.70
		PEG	30	-1.16	0.74	0.51

Fig. 2 Germination rate plotted against external salinity concentration for two varieties of barley ‘Cask’ and ‘County’ at four temperatures (mean ± SE).

Table 2 Parameter estimate of salinity model for seed germination of two varieties of barley under different salinities and four temperatures

品种 Cultivar	温度 Temperature (℃)	萌发率 Germination (%)	盐度常数 θ_S (mmol·L^-1·d^-1)	最高盐度 S_m (mmol·L^-1)	R²	p
‘Cask’	5	1	3 333.3	621.3	0.99	0.000 8
		50	5 000.0	712.0	0.98	0.000 8
	12	1	833.3	552.8	0.98	0.001 0
		50	909.1	392.6	0.98	0.093 4
	20	1	500.0	612.4	0.99	0.000 6
		50	1 000.0	573.0	0.99	0.039 5
	27	1	416.7	609.6	0.99	0.000 7
		50^*
‘County’	5	1	3 333.3	796.0	0.99	0.000 3
		50	3 333.3	638.0	0.94	0.006 7
	12	1	769.2	600.3	0.96	0.003 1
		50	1 000.0	558.5	0.89	0.015 6
	20	1	357.1	528.9	0.96	0.003 5
		50	370.4	382.9	0.99	0.067 2
	27	1	227.3	390.9	0.88	0.223 7
		50^*

Fig. 3 Comparison of germination time between the real data (50% germination) and the data predicted by hydrotime model and salinity model for two varieties of barley.

Fig. 4 Difference of germination rate between binate iso-osmotic NaCl and polyethylene glycol (PEG) plotted against external water potential for two varieties of barley ‘Cask’ and ‘County’ at four temperatures.

Fig. 5 Three situations of salt effect on seed germination (germination rate of varieties ‘Cask’ at 5 °C, for example).

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