Abstract
The study investigated the physiological behaviors and antioxidant responses ofMedicago sativa, Melilotus officinalis and Astragalus adsurgens to saline environment during seed germination stage. At 300 mM NaCl treatments, the final germination percentage of M. officinalis was much higher than that of M. sativa and of A. adsurgens and the initiation of germination process of A. adsurgens was 5 days later than the others. Moreover, after being treated in 300 mM NaCl, much weaker catalase (CAT) activity in seed of M. officinalis, peroxidase (POD) activity in seed of A. adsurgens and glutathione reductase (GR) activity in seed of M. sativawere found in the controls and salt treatments. Thus, oxidative stress could be an influential component of salt stresses on plant seeds during seed germination stage. Key words: Germination, Medicago sativa, Melilotus officinalis, Astragalus adsurgens, osmotic stress, malondialdehyde, antioxidant enzymes.
Highlights
High salinity is the most widespread abiotic stress and constitutes the most stringent factor that limits plant growth and development (Vernon and Bohnert, 1992)
The final germination percentages of seeds of the three legume species were over 89% in distilled water, but the percentages decreased with the increasing NaCl concentration (Figure 1)
In the 50 mM NaCl concentration treatment, final germination percentage for M. sativa seeds was significantly decreased by 8.7%, while for M. officinalis and A. adsurgens, the decrease was 7.3 and 0.5%, respectively
Summary
High salinity is the most widespread abiotic stress and constitutes the most stringent factor that limits plant growth and development (Vernon and Bohnert, 1992). Germination is a key stage in the life cycle of plants in saline environments as it determines whether or not the plants can establish successfully in certain areas (Ungar, 1991). Studies on salt stress in seed germination have shown that during this stage the seeds are sensitive to saline environments (Bewley and Black, 1982). Some halophytes can complete their life cycle under hypersaline conditions (McKell, 1994), while glycophytes, though generally more sensitive to saline stress, range widely between species and even among varieties in their tolerances (Tobe et al, 2001). Non-halophytes and halophytes respond to salinity in a similar way during the germination stage; in some species, the initial germination process is often delayed under salt stress (Keiffer and Ungar, 1997; Khan and Ungar, 1997). The effect of salinity on seed germination can be attributed to an osmotic effect and/or specific ion toxicity, depending on the plant species (Petruzzelli et al, 1992; PoljakoffMayber et al, 1994)
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