Response Of Annual Plant Bassia Dasyphylla To Salt-alkaline Stress

Soil salinize-alkalization is one of the major environmental problems that affect the world,and the major abiotic stress factors that affect the ecological security and sustainable development of agriculture in China.The annual plant is an important part of the saline alkali land flora,and also the main pioneer plant in the saline alkali land,which plays an important role in the composition of the saline alkali land ecosystem.The adaptability of annual plants to saline alkali habitats is the result of long-term evolution and natural selection.The adaptation mechanism of plants to saline alkali habitats is an important prerequisite for the treatment and recovery of saline alkali land,but at present,the research on the primary plants of saline alkali land is still a blank to study the mechanism of environmental adaptation.In this experiment,Bassia dasyphylla,typical annual herbaceous plants of saline alkali land was used as the test material.The germination indexes of germination rate,germination speed,germination index,seeding vigor index and growth indices of shoot length,root length,fresh weigh were determined.The indexes of seed germination,immature embryo growth,photosynthetic pigment content,photosynthetic gas exchange parameters,chlorophyll fluorescence characteristics,osmotic regulation substance content,superoxide anion production rate,H₂O₂ content,cell membrane peroxidation degree,antioxidant enzyme activity,phenotypic plasticity were determined,proved its adaptation mechanism of B.dasyphylla to saline alkali habitats.The main results and conclusions are as follows:1.Under the condition of salt-alkaline stress,germination rate,germination speed,germination index,seeding vigor index,germination rate index of treatment group were significantly lower than control group,were both decreased with increasing salinity and pH,and were found significant different?P<0.05?from the negative control group.At the same time,shoot length,root length,fresh weigh were significantly inhibited.Seed germination stage is more sensitive to salt-alkaline stress than immature embryo growth stage.Salinity was the dominant factor for seed germination under mixed salt-alkaline stress conditions,and pH changed into the dominant factor for seedling establishment2.Under the condition of salt-alkaline stress,the chlorophyll a?Chla?,chlorophyll b?Chlb?,and carotenoids?Caro?contents,net photosynthetic rate?P_n?,stomatal conductance?G_s?,intercellular CO₂ mole fractions?C_i?,transpiration rate?T_r?,PSII potential efficiency?F_v/F₀?,maximal photochemical efficiency?F_v/F_m?,PSII actual quantum yield??PSII?,apparent electron-transfer rate?ETR?,and photochemical quenching?qP?indexes of the treatment group were significantly lower than that of the control group;both reduced with increasing salinity and pH;and were significantly different?P<0.05?from the negative control group.Steady state fluorescence?F_s?result indicates the variation trendency of"M-type"with increasing salinity and pH,which is firstly increased and then decreased,followed the similar trendency again.Water use efficiency?WUE?and non-photochemical quenching?NPQ?showed irregular change with increasing salinity and pH.The correlation coefficient between salt ions and the photosynthetic characteristics showed that the rejection capability of sodium salts was Na₂CO₃>NaHCO₃>NaCl>Na₂SO₄in the photosynthetic pigment content index and gas exchange parameters.The effect of salt ions and chlorophyll fluorescence parameters was comparatively complex.This study suggests that salt-alkaline environments inhibited the photosynthetic system of B.dasyphylla,and negatively affected several physiological responses.3.Under the condition of salt-alkaline stress,soluble sugar,soluble protein,proline,betaine,O₂^-·production rate,H₂O₂ content,MDA content and cell membrane permeability were both decreased with increasing salinity and pH,and were found significant different?P<0.05?from the negative control group.The activity of SOD,POD and APX increased first and then decreased,and the activity of CAT increased steadily.The results showed that salt-alkaline stress increased osmotic pressure in B.dasyphylla and induced a large amount of active oxygen in the body.By increasing the content of osmotic substances and increasing the activity of antioxidant enzymes,maintains the normal osmotic pressure and water absorption and water retention in the cells,which consumes the excessive accumulation of active oxygen in the body,protects the complete structure and function of the cell membrane,and relieves the damage caused by the salt-alkaline coercion on the normal physiological activities of B.dasyphylla.4.Under the condition of salt-alkaline stress,plant height,main root length,stem diameter,branch number,lateral root number and biomass of each part were significantly lower than control group?P<0.05?.In biomass allocation,the ratio of root biomass to biomass increased,while the ratio of stem biomass to leaf biomass decreased.The results showed that salt-alkaline stress changed the phenotypic plasticity of B.dasyphylla,which is mainly manifested in the inhibition of morphological indexes.B.dasyphylla could adapt to the salt-alkaline stress environment by adjusting the proportion of the biomass of each part5.Salt-alkaline stress inhibited the normal growth of B.dasyphylla.The overall inhibition effect of different properties of salt composition on the antifreeze was Na₂CO₃>NaHCO₃>NaCl>Na₂SO₄,indicating that the effect of alkaline salt stress on the B.dasyphylla was greater than that of neutral salt stress.6.Under the condition of simulated salt-alkaline stress,B.dasyphylla showed strong adaptability,indicating that it had good adaptability in the natural saline alkali habitats of different saline alkali types and degrees.It could be used for ecological treatment and vegetation restoration in saline alkali land,and can be used as model plant to dig its salt tolerance mechanism and potential.It provides an alternative approach for crop improvement.