Physiological Response of Salt‐Tolerant and Nontolerant Alfalfa to Salinity during Germination¹

Abstract

Identification of the physiological processes involved in salt tolerance is required to develop appropriate selection criteria for breeding salt‐tolerant crops. For this purpose selected physiological characteristics were evaluated in five alfalfa (Medicago sativa L.) populations selected for NaCl tolerance during seed germination and the source population, 'Mesa‐Sirsa'. Seed of the populations (Syn‐1) was germinated in distilled water and solutions of NaCl, NaNO3, KC1, KNO3, and mannitol ranging from −1.0 to −1.6 MPa osmotic potential. The mean difference in percent germination between Mesa‐ Sirsa and ‘AZST1982’, the most salt‐tolerant population, was greater in the NaCl solutions than the other salt solutions (P < 0.01). Seed from AZST 1982 also had higher percent germination than Mesa‐Sirsa in mannitol solutions (90.6 and 2.8%, respectively, at −1.6 MPa osmotic potential). Mesa‐Sirsa had higher (P < 0.01) average seed respiration rate than AZST 1982 between 3 and 24 h of germination in NaCl solutions of −0.6 to −3.0 MPa osmotic potential. There was no significant difference between Mesa‐Sirsa and AZST 1982 for Na+ or Cl− accumulation after 48 h of germination in NaCl solutions of −0.6 to −1.8 MPa osmotic potential, or absorption of tritiated water after 6 and 12 h of germination in NaCl solutions of −1.3 and −2.0 MPa osmotic potential. Selection for NaCl tolerance in germinating alfalfa seed results in two separate types of tolerance: tolerance of an inhibitory effect specific to NaCl and tolerance of lowered water potential. Selection for NaCl tolerance of alfalfa during germination does not appear to influence ion accumulation or the rate of imbibitional water uptake.

Effect of salt and osmotic stresses on the germination of pepper seeds of different maturation stages

“…(Table 1). Both the osmotic and toxic effects of the salts have been implicated in the inhibition of the germination (Allen et al, 1986, Machado Neto et al, 2004. Higher germination percentages obtained from NaCl compared to those of PEG at the same concentrations in the same harvest period proved that the adverse effect of PEG on the germination was due to an osmotic effect rather than specific ion accumulation.…”

Effect of Salt Stress on Germination and Seedling Growth of Barley (Hordeum vulgare L.)

“…These results are in close conformity with the earlier findings of Alka et al (1981) and Iqbal et al (1998) in which they reported that increasing salinity decreased percent germina on in wheat, barley and triticale. Allen et al (1986) proposed that the reduction in germination percentage under same conditions might be due to the ion toxicity and reduced uptake of water, which affected the physiological and biochemical activities through inhibition of the anabolic or stimulation of catabolic processes (Corchete and Guerra, 1986). As in the germination percentage, there was also a considerable decrease in root and shoot length of both barley varieties with increasing salinity levels of the growth medium.…”

Screening of tropical maize for salt stress tolerance

“…However, two different mechanisms of salt tolerance enable seeds to germinate at high salt concentrations. Seeds can tolerate the effects of a lower water potential in the substrate (Allen et al 1986) or they may present specific tolerance to the inhibitory effect of NaCl (Rumbaugh et al 1993). In some cases, germination inhibition of Eucaliptus grandis was higher in NaCl than in PEG 6000 solutions at equal osmotic potential (Souza and Cardoso 2000).…”