| Nitraria sibirica Pall.It is a deciduous shrub of the genus Nitraria,in the family Nitrariaceae.In salt-alkali,dry-cold,poor soil and other adversity environment,it can show good adaptability,and it is an excellent plant resource for repairing saline-alkali land.In this paper,the seeds and seedlings of N.sibirica were treated with different levels of salt stress and cultured in different substrates.The aim of this study was to find out the optimum conditions for seed germinatio n and seedling growth of N.sibirica.The following conclusions have been reached:(1)The germination rate,germination energy and germination index were increased at low salinity(100 mmol ·L-1),but the relative salt damage was decreased.After Na Cl > 100 mm ol ·L-1,the germination rate,germination potential and germination index began to decrease,and the germination rate,germination potential and germination index began to decrease after Na Cl > 100 mmol ·L-1.The relative salt damage rate increased.When there was no stress,germination percentage,germination energy and germination index were the best under the substrate of garden soil: river sand = 1:0.The Na Cl level was 100 mmol ·L-1,the germination rate of garden soil: river sand = 1:0,the relative salt damage was the least,the garden soil: river sand = 1:1,the germination index of 1:2 was the best.When Na Cl > 100 mmol ·L-1,the comprehensive performance of garden soil: river sand = 1:4 is the best.It can be concluded that the low level of Na Cl p romotes germination,whereas the high level of Na Cl can inhibit the germination.It can be concluded that the same ratio of garden soil and river sand under low salt condition is moderate in water holding capacity and air permeability,which promotes germination and strong respiration of seeds under high salinity.Therefore,the substrate with strong permeability is more favorable for seed germination.(2)With the increase of Na Cl level,the relative water content and chlorophyll of prickly leaf in different substrate culture increased first and then decreased,and reached the peak at Na Cl level of 100 mmol ·L-1.However,there was no significant difference in relative water content between each group and other Na Cl levels.Under the same salt concentration,the content of chlorophyll reached the peak in the garden soil: river sand = 1:1,,and then decreased,and the relative water content of the plant was the best.The exosmosis rate and MDA content of white prickly electrolyte increased with the increase of Na Cl concentration.There was no significant difference between different substrate without salt stress.100 ~ 400 mmol ·L-1,The electrolyte exudation rate and MDA content of garden soil: river sand = 1:1 and 1:2 were lower than that of garden soil: river sand = 1:0,and the treatment of garden soil: river sand = 1:4 increased significantly.The results indicated that reasonable proportion of substrate culture could increase the relative water content,increase chlorophyll content and decrease the permeabilit y of cell membrane and the accumulation of MDA content in plant leaves under white prickly salt stress.(3)Under the same substrate,Na Cl stress could affect the gas exchange parameters,Na Cl > 100 mmol ·L-1,net photosynthetic rate,stomatal conductance,tra nspiration rate decreased,and intercellular CO2 concentration increased significantly.With the increase of salt concentration,the maximum photochemical efficiency,the actual photochemical efficiency and the photochemical quenching coefficient of PSII increased first and then decreased,while the non-photochemical quenching coefficient decreased first and then increased,the fluorescence parameters were obviously affected by the changes of each index.The results show that when the Na Cl level in the environment exceeds the acceptable reasonable range,the gas exchange decreases,the utilization rate of CO2 decreases,and the carbon cycle pathway is destroyed.(4)Under the same salt stress,different substrates could increase net photosynthetic rate,stomatal conductance and transpiration rate,and significantly reduce intercellular CO 2 concentration.The results showed that the suitable substrate culture was beneficial to its growth,and could promote the stomatal opening of leaf epidermis,increase the excha nge of gas with the outside world,and improve the photosynthetic efficiency.The substrate(garden soil: river sand = 1:4)had obvious effects on the gas exchange parameters of N.sibirica.Under this substrate,the maximum photochemical efficiency of each Na Cl concentration was found to be higher than that of the substrate,and the maximum photochemical efficiency of the substrate was higher than that of the control group.The actual photochemical efficiency and the photochemical quenching coefficient were significantly lower than those of the control,while the non-photochemical quenching coefficient increased.The results showed that the reasonable proportion of substrate could increase the photochemical efficiency of N.sibirica. |
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