| With the change of global climate and the frequent occurrence of extreme climate,the increasing soil salinization has seriously affected plant growth and reproduction.The breeding and utilization of salt-tolerant plants is a direct and powerful measure to improve the productivity and utilization rate of saline soil.Lycium ruthenicum is a unique halophyte in the desert area of Northwest China.It has strong drought resistance,cold resistance,saline-alkali tolerance capacity,strong tillering resistance,poor soil resistance and high nutritional value.It is a pioneer tree species in saline-alkali land management,and has broad economic value and development potential.In this paper,in order to provide theoretical reference for the adaptation mechanism of Lycium ruthenicum in halophytic environment,pot experiments were carried out with 1-year-old Lycium ruthenicum seedlings of Golmud in two periods of 15 and 30 days under different NaCl concentrations.By measuring the effects of the morphological characteristics,physiological characteristics and leaf structure characteristics under NaCl stress was discussed.The following results were obtained:1.Under the condition of NaCl stress,the relative height growth,relative ground diameter,leaf water content,leaf volume,leaf number and leaf biomass of Lycium ruthenicum showed a trend of first increasing and then decreasing after 30 days treatment,and the difference was significant compared with other control?p<0.05?,but not significant after 15 days of treatment.The density of fresh leaves and dry leaves increased first,then decreased and then increased with the increase of NaCl concentration.Meanwhile,the leaf water content,leaf volume,leaf number and leaf biomass were all maximized at NaCl medium concentration(150 mmol·L-1).on the contrary,under the condition of high concentration(250 mmol·L-1),its were decreased compared with the control.Regression analysis of leaf biomass and other ecological indexes showed that leaf water content,leaf volume and leaf number were significantly correlated with leaf biomass,while the correlation between other indexes and leaf biomass was not significant.Through principal component analysis,leaf volume,dry leaf density,leaf number and leaf water content were selected as the reference indicators to evaluate the response of morphological characteristics of Lycium ruthenicum to salt stress.2.Under the condition of NaCl stress,superoxide dismutase,catalase,soluble sugar and soluble protein in leaves of Lycium ruthenicum increased first and then decreased with the increase of NaCl concentration.The peroxidase,malondialdehyde and chlorophyll decreased with the increase of NaCl concentration.The proline and relative conductivity increased with the increase of NaCl concentration.With the prolongation of treatment time,the changing trend of each index did not change,but the degree of expression increased.Na+and K+contents in organs showed the rule of leaf>stem>root after 15 or 30 days of NaCl treatment;Na+contents in leaves and stems increased with the increase of NaCl concentration,while K+contents showed a downward trend,but the changes of Na+and K+contents in roots had no obvious regularity.Through correlation analysis and principal component analysis of physiological indices of Lycium ruthenicum,it can be concluded that six indices,including the malondialdehyde,chlorophyll,soluble sugar content,POD activity,CAT activity and K+content in stem,can be used as main reference indices to evaluate the response of physiological characteristics of Lycium ruthenicum to salt stress.3.Under the condition of NaCl stress,the leaf thickness,palisade tissue thickness and tissue structure tightness of Lycium ruthenicum increased with the increase of NaCl concentration,and increased with the extension of stress time.The leaf spongy tissue thickness and tissue structure looseness decreased with the increase of NaCl concentration,and decreased significantly with the extension of stress time.The upper epidermal thickness,the length,width and the length-width ratio of epidermal stomata increased first and then decreased with the increase of salt solution concentration.When NaCl concentration was 150 mmol·L-1,the values of each index reached the maximum value.When NaCl concentration was more than 150 mmol·L-1,the stomatal length and width decreased significantly,the stomatal openness decreased,and the stomatal opening was closed or semi-closed.The trend was unchanged with the prolongation of stress time.Through correlation analysis and principal component analysis of each structural characteristic index of Lycium ruthenicum leaves,the leaf thickness,palisade tissue,sponge tissue,tightness of leaf tissue structure,looseness of leaf tissue structure and stomatal size can be used to evaluate the response of leaves structural characteristics of Lycium ruthenicum to salt stress.4.The results showed that Lycium ruthenicum.exhibited strong adaptability to NaCl stress and could adapt to a certain concentration of halophytic environment.Lycium ruthenicum is resistant to salt stress through the coordination and interaction of its own morphological characteristics,physiological characteristics and leaf structure. |
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