ABSTRACT
OBJECTIVE:To study the resistance physiological responses of seedling of Scrophularia ningpoensis to the stress caused by saline and alkali at different concentrations. METHODS:The seedling of S. ningpoensis was placed in the illumination in-cubator,in which the temperature was maintained at(20±2)℃,light-dark cycle at 13 h/11 h and illumination intensity at 2 000 lx. The alkali (NaHCO3) of 50,100,150,200 and 250 mmol/L and the saline (NaCl) of 50,100,150,200 and 250 mmol/L were poured once every 4 days for 16 consecutive days. The growth indexes(plant height,fresh weight,dry weight),chlorophyll (Chl) content,antioxidative indexes [superoxide dismutase (SOD),catalase (CAT),peroxidase (POD),hydrogen peroxide (H2O2),malonaldehyde (MDA),membrane penetration (RMP)],and osmotic regulation physiological indexes [soluble sugar (SS),soluble protein(SP)and proline(Pro)] of the seedling were determined. There set a blank control group(distilled water). RESULTS:For saline concentration higher than 50 mmol/L and alkali concentration higher than 150 mmol/L,the seedling height, fresh weight and Chl content were lower;for saline concentration higher than 100 mmol/L and alkali concentration higher than 150 mmol/L,the dry weight of the seedling was lower. For saline concentration of 50 mmol/L and alkali concentration of 150 mmol/L, the activities of SOD and POD were the strongest;for saline concentration of 150 mmol/L and alkali concentration of 50 mmol/L, the activity of CAT was the strongest. The contents of H2O2 and MDA increased and the content of SP decreased with the increase in saline-alkali concentration. The level of RMP increased therewith,that is to say,membrane stability decreased. For saline concen-tration higher than 100 mmol/L and alkali concentration higher than 150 mmol/L,the accumulation of SS terminated;for saline and alkali concentrations higher than 100 mmol/L,the accumulation of Pro terminated,however,the content of Pro was markedly high-er in the above-said alkali concentration than in that saline concentration. CONCLUSIONS:Saline-alkali stress causes the tissues of S. ningpoensis to produce active oxygen and its cytoplasmic membrane system to be damaged. Chl,enzymatic antioxidants such as SOD,CAT and POD,and osmoprotectants such as Pro and SS can buffer saline-alkali stress to some degree. The maximum concen-trations of NaCl and NaHCO3 that seedling of S. ningpoensis can tolerate are 50 mmol/L and 150 mmol/L respectively.