The Growth And Physiological Response Of Several Willows To NaCl Salt Stress

In this paper,S.linearistipularis?Franch.?Hao,S.matsudana Koidz.,S.psammophila,S.integra Thunb.,S.Chosenial Nakai.,S.matsudana f.pendula Schneid.and S.fragilis L.cutting seedlings were used as materials,and the method of applying a single neutral salt Na Cl solution was tendered in the self-controlled greenhouse.The growth status and growth index of the trees were measured.The Na Cl concentration of the dead willow was screened,and the resistance of seven willows to different concentrations of Na Cl stress was summarized.The growth and physiological responses of willows to NaCl stress were studied to provide basis for the willow planting and research in saline-alkali area.The main findings are as follows:?1?With the aggravation of Na Cl stress,the growth of the seven willows all deteriorated.The browning of the shoots was aggravated,and the S.Chosenial Nakai.was browned under 400 mmol/L NaCl stress;the leaves became yellow and fell,the number of leaves decreased,and the total area of the leaves decreased.The total length of roots,root surface area and root tips all showed a downward trend,and the total lengths of roots of the S.linearistipularis?Franch.?Hao.and the S.psammophila became shorter and the average root diameter increased,that is,the roots became shorter and thicker.Compared with the control,the above-ground biomass of seven willow species showed a downward trend.Except for S.Chosenial Nakai.,S.integra Thunb.,S.matsudana f.pendula Schneid.and S.psammophila biomass of roots increased at a low concentration?100 mmol/L NaCl?,and the high-concentration root biomass decreased.The other three root biomass showed a downward trend.300 mmol/L Na Cl was the lethal concentration of willow,and 200 mmol/L NaCl was the limiting concentration of willow growth.?2?With the increase of Na Cl stress,the photosynthetic rate,transpiration rate,and stomatal conductance of the willow increased.The PSII light quantum yields showed a downward trend.But there was no significant difference.Under the 100 mmol/L NaCl stress,the actual light quantum yields of four willow leaves were compared with those of the control.The difference was not obvious.Under 200 mmol/L NaCl stress,the actual photo-quantity of PSII in leaves of S.integra Thunb.,S.linearistipularis?Franch.?Hao and S.fragilis L.were lower than that of the control.?3?The MDA concentration of four kinds of willow leaves kept rising;the soluble sugar content of S.fragilis L.increased first and then decreased,and the soluble sugar content of S.linearistipularis?Franch.?Hao.and S.psammophila decreased;The soluble sugar content of S.integra Thunb.was decreased first and then increased;the soluble protein content of S.psammophila decreased;except for the increase of free proline content in S.fragilis L.leaves,the other three responses to salt stress vary;the SOD activity of S.integra Thunb showed an upward trend;the CAT activity of S.linearistipularis?Franch.?Hao increasd;The response of four kinds of willow POD activity to salt stress vary.The content of H₂O₂ in S.linearistipularis?Franch.?Hao and S.psammophila showed an upward trend,the other two responses to salt stress vary.It is speculated that changes in the antioxidants of willows have regulatory effects on the maintenance of plant osmotic stability,and that the increase of antioxidant enzyme activity plays an important role in resisting the damage of active oxygen to cell membranes.?4?With the increase of NaCl stress,the potassium content of four willow roots showed a downward trend,and the leaf potassium content showed an upward trend.And the leaf potassium content was higher than the root potassium content.Under 200mmol/L NaCl stress,the contents of sodium in the leaves of the S.linearistipularis?Franch.?Hao,S.fragilis L.,and S.psammophila are higher than those in the roots.It is assumed that the sodium transport from the root to the leaves increased,the plants absorb the roots and transport the ions upwards,reducing the sodium content in the soil,willow has a certain role in improving the saline soil.?5?Based on the analysis of growth index,photosynthetic parameters,fluorescence parameters,antioxidants and antioxidant enzymes,the order of resistance of the four willows under the growth limiting concentration of 200 mmol/L NaCl was assessed by membership function:S.fragilis L.>S.integra Thunb.>S.psammophila>S.linearistipularis?Franch.?Hao.