Abstract:

The aim of this study was to determine the growth and physiological characteristics of Echinochloa frumentacea seedlings under different degrees of salt stress （NaCl and Na₂SO₄）. We determined growth and development indexes （plant height， root length， fresh weight∶dry weight ratio）， contents of photosynthetic pigments and osmoregulation substances （proline， soluble sugars）， malondialdehyde and activities of antioxidant enzymes （superoxide dismutase， peroxidase， catalase） under two types of salt stress. The results showed that the threshold for growth and development of E. frumentacea seedlings was 50 mmol·L^-1 NaCl or Na₂SO₄. The highest chloroplast pigment contents were in the 50 mmol·L^-1 NaCl and 75 mmol·L^-1 Na₂SO₄ treatments. The proline content was significantly higher in all the salt treatments than in the control （P<0.05）. The thresholds for increases in proline content were 100 mmol·L^-1 NaCl and 125 mmol·L^-1 Na₂SO₄. The highest malondialdehyde contents were in the 100 mmol·L^-1 salt treatments （NaCl and Na₂SO₄）. The highest soluble sugars content and catalase activity were in the 75 mmol·L^-1 NaCl and 100 mmol·L^-1 Na₂SO₄ treatments， respectively. The activity of superoxide dismutase increased as the NaCl and Na₂SO₄ concentrations increased， and it was significantly higher than that of the control （P<0.05） when the concentration of either salt was greater than or equal to 50 mmol·L^-1. Therefore， our results show that NaCl and Na₂SO₄ can promote E. frumentacea growth at lower concentrations but inhibit its growth at higher concentrations， and the inhibitory effect of NaCl is stronger than that of Na₂SO_4.

Key words: Echinochloa frumentacea, seedlings stage, salt stress, physiological property