| In this thesis,two-year-old seedlings of Salix linearistioularis are used as research objects.Two kinds of neutral salts,NaCl,Na2SO4 and two kinds of basic salts.NaHCO3 and Na2CO3,are mixed in different proportions.Twelve kinds of saline-alkali mixed conditions were simulated,and the Salix linearistioularis seedlings were subjected to stress treatment with different salt concentrations and alkali concentrations.The dynamic changes of various physiological indicators of Salix linearistioularis under salt-alkali stress were studied.The main findings are as follows:1.The effect of saline-alkali interaction stress on the growth and development of two-year-old seedlings of Salix linearistioularis can be directly reflected by the salt damage symptoms in leaves.Under low-concentration salt stress,Salix linearistioularis leaves showed no obvious symptoms of salt damage,With the increase of treatment time and the intensification of saline-alkali interaction stress,Salix linearistioularis leaves show obvious salt damage symptoms,most of the leaves have dropped,It shows that high concentration saline-alkali interaction stress has strong stress effect on Salix linearistioularis.2.The effects of saline-alkali interaction on physiological and biochemical indexes of Salix linearistioularis biennial seedlings have varying degrees.Under low-salt(50 mmol/L)stress,the contents of malondialdehyde and osmolytes increased slightly compared with the control.With the increase of salt concentration,the contents of malonaldehyde and osmolytes both increased;Under low salt(50 mmol/L)and low pH(7.93)stress,the antioxidant enzyme activity and total chlorophyll content of the leaves were higher than those of the control.As the salt concentration and pH value increased,it showed a downward trend;Salt concentration stress has less damage to the growth of Mongolian willow.With the increase of salt concentration and pH value,the damage to the plasma membrane of Salix linearistioularis leaves will increase,and the ability to remove active oxygen or peroxide free radicals will weaken,Inhibits chlorophyll synthesis to a certain extent.3.Under salt-alkali interaction stress,photo synthetic parameters are an important indicator of plant salt tolerance.Under low salt(50 mmol/L)and low pH(7.93)stress,the net photosynthetic rate and water use efficiency of Salix linearistioularis were higher than those of the control.With the increase of salt concentration and pH value,the photosynthetic rate showed a downward trend.The utilization rate is similar to the trend of photosynthetic rate.The intercellular CO2 decreases first and then increases,and the stomatal conductance and transpiration rate decrease.These results indicate that low-salinity-alkali stress is beneficial to the synthesis of photosynthetic pigments in Salix linearistioularis.4.Low-concentration saline-alkali stress had little effect on the epidermal stomata morphology and internal structure of Salix linearistioularis biennial seedlings.With the increase of salt concentration and pH value,it was stressed at high salt(200 mmol/L)and high pH(9.72)The stomata of the Salix linearistioularis leaves have a small opening,most of the stomata are closed,and the chloroplast ultrastructure of the leaves is deformed and distorted.This indicates that low-salt stress has a slight effect on the structure of Salix nearistioularis leaves,and high-salt concentration and high pH stress seriously damage the stomata morphology and ultrastructure of Salix linearistioularis leaves.In summary:under the stress of low salt(50 mmol/L)and low base(pH value is 7.93),the effect on Salix linearistioularis is relatively small,and some physiological indexes also show a promoting effect.With the increase of salt concentration and pH value,when the salt concentration reaches 200 mmol/L、pH to 9.72,it has obvious inhibitory effect on Salix linearistioularis,but it can still maintain its life vitality,indicating that Salix linearistioularis has a certain salt alkali tolerance. |
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