| Soil salinization is a global problem affecting the ecological environment,and in the case of China,there are more than 100 million hm2 of various saline lands in the country,including about 37.3 million hm2 of modern saline soils.84 K poplar wild type（WT）is an important tree species for afforestation and protection forestry projects worldwide because of its fast growth and high yield.In this study,we investigated the photosynthetic characteristics of poplar seedlings under stress with CK as the control group and 10 m M Ca Cl2 added to 50 m M,100 m M and 150 m M NaCl in NaCl stress,and determined the photosynthetic characteristics,chlorophyll fluorescence and biochemical The photosynthetic,chlorophyll fluorescence and biochemical characteristics of poplar seedlings under NaCl stress were determined.The study of photosynthetic characteristics of poplar seedlings under NaCl stress and the addition of exogenous Ca2+ can provide a reference for providing a more salt-tolerant and mitigating method for poplar under NaCl stress.The main findings of this study are as follows:（1）The net photosynthetic rate（Pn）,transpiration rate（Tr）and stomatal conductance（Gs）of poplar seedlings showed a decreasing trend and the intercellular CO2 concentration（Ci）showed an increasing trend with the increase of NaCl concentration,which indicated that NaCl stress inhibited photosynthesis of poplar seedlings.After the addition of 10 m M Ca Cl2,Pn,Tr and Gs increased and Ci decreased compared with plants without 10 m M Ca Cl2,and the degree of mitigation by 10 m M Ca Cl2 varied at different NaCl concentrations.Pn,Tr and Gs increased by 30.61%,6.63% and 40.11%,respectively,while Ci decreased by 5.14%.All of these indicate that the addition of exogenous Ca2+ mitigated the photosynthesis of poplar seedlings under NaCl stress.（2）With the increase of NaCl concentration,the maximum fluorescence（Fm）,maximum photochemical efficiency（Fv/ Fm）,potential photochemical efficiency（Fv/Fo）,actual photochemical efficiency（ΦPSII）and photochemical burst coefficient（q P）of poplar seedlings showed a decreasing trend,while the initial fluorescence（Fo）and non-chemical burst coefficient（NPQ）showed an increasing trend,and the photosynthetic The photosynthetic system of poplar seedlings was injured by NaCl stress.After adding 10 m MCa Cl2,Fm,Fv/Fm,Fv/Fo,ΦPSII and q P in the leaves of poplar seedlings were alleviated and elevated,while Fo and NPQ were decreased.The degree of alleviation by 10 m MCa Cl2 varied at different NaCl concentrations,and the most significant alleviation effect was observed at the concentration of100 m M,with Fm,Fv/Fm,Fv/Fo,ΦPSII and q P increased by 2.52%,2.23%,11.35%,6.89% and13.24%,respectively,while Fo and NPQ decreased by 7.84% and 16.09%,respectively.All of these indicate some mitigation of the damage to the photosynthetic system of poplar seedlings under the addition of exogenous Ca2+.（3）With the increase of NaCl concentration,malondialdehyde（MDA）content of poplar seedling leaves began to increase,ascorbate peroxidase（APX）,peroxidase（POD）,soluble sugars and soluble proteins showed a tendency to rise and then fall,and root vigor decreased.Poplar seedlings were subjected to ionic toxicity of NaCl stress and responded to it through the regulation of osmoregulation and antioxidant system.After adding 10 m M Ca Cl2,MDA,APX and POD decreased,soluble sugar and soluble protein contents increased,and root vigor rose.The degree of alleviation by 10 m M Ca Cl2 varied at different NaCl concentrations,and the most significant alleviation effect was observed at 100 m M concentration,with MDA and APX decreasing by 21.16% and 22.61%,and soluble sugar and soluble protein contents increasing by 12.22% and 6.28%,respectively.However,POD decreased by 16.36% and root vigor increased by 6.9% in the addition of 10 m M Ca Cl2 at 50 Mm NaCl concentration.The injury suffered by poplar seedlings under NaCl stress was regulated by enhancing the efficiency of osmoregulation and antioxidant system,which had some relief in maintaining cell membrane stability and metabolic homeostasis.Poplar seedlings were subjected to the addition of exogenous Ca2+,which acted as a plant resistance response mechanism to induce a series of physiological responses to resist NaCl stress,thereby improving the salt tolerance of plants... |
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