Study On Physiological Responses Of Elaeagnus Angustifolia From Different Provenances To Saline-alkali Stress

Elaeagnus angustifolia is deciduous tree belonging to Elaeagnaceae Elaeagus,which has the characteristics such as resistance to drought,barren soil and easy management,and is used as an important pioneer tree species in wasteland and saline-alkali land.The branches,leaves,flowers and fruits of E.angustifolia have high ornamental,economic and medicinal value.Through the study of saline-alkali resistance of E.angustifolia,discussed it’s saline-alkali adaptation mechanism and selected high-quality germplasm resources,which is of great significance to the introduction and cultivation of E.angustifolia,the improvement of plant landscape in saline-alkali rich areas and the ecological environment.This paper,taking seeds and 2-year-old’s seedlings from Ningxia,Gansu provenances of E.angustifolia as testing material,with artificial simulated saline-alkali stress environment,respectively study the V（Na Cl）:V（Na₂SO₄）=1:1 neutral salt（A）,V（Na Cl）:V（Na₂SO4）:V（Na HCO₃）:V（Na₂CO₃）=1:1:1:1 mixed saline-alkali（B）and V（Na HCO₃）:V（Na₂CO₃）=1:1 alkaline salt（C）on seed germination,seedling growth and development of E.angustifolia.The salt concentration gradients of0.3%,0.6%,0.9%,1.2%were set and repeat three times in each treatment group,starting with a 15-day seed germination test and a 40-day seedling stress test.The physiological response mechanism of E. angustifolia to saline-alkali stress was discussed from the aspects of seed germination indexes,seedling growth characteristics,antioxidant system and osmotic regulatory substances.Main results of this research were summarized as following:1.Examination on seed Germination:（1）Under neutral salt stress（A）and mixed saline-alkali stress（B）,salt concentration was 0.3%,the germination rate,germination potential and germination index of E.angustifolia seeds from two provenances were the higher than the control treatments,salt concentration was greater than 0.3%,the germination indexes decreased,showed‘promote at low concentration and restrained at high concentration’.under alkaline salt stress（C）,the germination indexes of two provenances decreased,and the inhibition increased with the increase of salt concentration.（2）Through the comprehensive comparison of the germination potential,germination rate,germination index and vital index of the seeds from Ningxia and Gansu provenances under saline-alkali stress,the results showed that the saline-alkali tolerance ability of the seeds from Gansu provenances was higher than that of the seeds from Ningxia provenances.The inhibition degree of the three types of saline-alkali stress on the seed germination of E.angustifolia was in order:alkali stress>saline stress>saline-alkali stress.2.Examination on saline-alkali stress of seedling:（1）The effects of three types of saline-alkali stress on the growth characteristics of two provenances of E.angustifolia showed that:with the increase of salt concentration,the growth of leaf length,leaf width,new shoot and ground diameter of E.angustifolia decreased;The seedling growth of Ningxia provenance was greatly affected by stress;Under alkali stress（C）,the growth of E.angustifolia seedlings from two provenances was inhibited greatly.（2）The effects of three types of saline-alkali stress on membrane systems of two provenances of E.angustifolia showed that:with the increase of salt concentration and the prolongation of stress time,the membrane permeability and MDA content showed an upward trend;In the early stage of salt damage,membrane permeability and MDA content under low concentration treatment showed no significant difference compared with the control group,while in the later stage of stress,both of them increased significantly,indicating that the membrane system of E.angustifolia was damaged to some extent.（3）The effects of three types of saline-alkali stress on osmotic adjustment substances of two provenances of E.angustifolia showed that:with the increase of salt concentration and the prolongation of stress time,proline content and soluble sugar content showed an upward trend as a whole,which the proline content and soluble sugar content in Ningxia provenance was higher than those in Gansu provenance;with the prolongation of stress time,the soluble protein content showed first increased and decreased then upward trend,indicating that Pro,SS and SP alternately accumulated play the role of osmotic regulation to balance the osmotic potential of cells under saline-alkali stress,so as to improve the saline-alkali tolerance of E.angustifolia.（4）The effects of three types of saline-alkali stress on protective enzyme system of two provenances of E.angustifolia showed that:with the prolongation of stress time,SOD activity and POD activity showed first upward and then downward trend as a whole,the variation amplitude was different under different salt concentrations,indicating that under short-term stress,protective enzymes could cooperate with each other to reduce oxidative damage,but with the prolongation of stress time,the protective enzyme system was damaged.（5）The effects of three types of saline-alkali stress on the photosynthesis o of two provenances of E.angustifolia showed that:at the early stage of low concentration stress,chlorophyll content increased,but with the increase of salt concentration and the prolongation of stress time,and the decline of Ningxia provenance was lower than that of Gansu provenance;With the increase of salt concentration,the net photosynthetic rate（Pn）,stomatal conductance（Gs）and transpiration rate（Tr）showed a downward trend,which the intercellular CO₂concentration（Ci）showed an upward trend;The decline of photosynthesis was influenced by stomatal and non-stomatal factors.（6）E.angustifolia seedling’s salt tolerance threshold was the salt concentration when the shoot growth decreased by 50%,under neutral salt stress、mixed saline-alkali stress and alkali stress,the salt tolerance threshold of E.angustifolia from Ningxia provenances were 1.088%、1.138%、0.917%,respectively;the salt tolerance threshold of E.angustifolia from Gansu provenances were 1.153%、1.001%、0.966%,respectively.The tolerability of E.angustifolia from the same provenances to three types of saline-alkali was different.（7）Seedling tolerance ability of E.angustifolia from two provenances was assessed by principal component analysis,and the sequence were as following:Under neutral salt stress,the salt-tolerance capacity of Gansu provenance was higher than that of Ningxia provenance;Under mixed saline-alkali stress,the salt-tolerance capacity of Ningxia provenance was higher than that of Gansu provenance;Under alkali stress,the salt-tolerance capacity of Gansu provenance was higher than that of Ningxia provenance,which was consistent with the salt tolerance threshold of E.angustifolia from two provenances.（8）Through stepwise regression analysis,soluble protein content,MDA content,POD activity and transpiration rate（Tr）were selected as the main identification indexes for the saline-alkali resistance evaluation of E.angustifolia from two provenances.