| Land salinization is a common problem worldwide today,and saline land has great potential as a backup land.The’Zizhi’series of roses are large and double-petal,and can be used for flower viewing in three seasons.In order to study the morphological,physiological,and photosynthetic response of’Zizhi’series roses under salt stress and salt-alkali mixed stress,understand the differences in salinity tolerance among varieties,and compare the effects of salt stress and saline-alkali mixed stress on plants.In this study,we mainly used annual cuttings of three varieties（’Zizhi’,’Fenzizhi’,and’Baizizhi’）from the’Zizhi’series as the test materials.Na Cl+Na HCO3 treatments were used to determine the water physiological indexes,photosynthetic capacity characteristics,cytoplasmic membrane stability,osmoregulatory substances,antioxidant enzyme activities and ion balance,and were comprehensively evaluated using principal component analysis as well as affiliation functions.The main results of the study are as follows:1.Effects of salt stress and saline-alkali mixed stress on phenotypic and water physiological indicators of three rose species:With the extension of salt stress and saline-alkali mixed stress,the leaf phenotypes of the three rose species showed more obvious injury performance and an overall decreasing trend of relative water content.The phenotypic injury of the plants under salt stress conditions was significantly less than that of the mixed salt and alkaline stresses,and no significant differences were observed among the rose varieties under salt stress conditions,but the relative water contents of’Fenzizhi’and’Baizizhi’under the mixed salt and alkaline treatments were significantly lower.The relative water content of’Zizhi’did not show significant differences.Under both stress conditions,the phenotypic performance of’Zizhi’leaves was relatively better,and the decrease in relative water content was significantly smaller than that of’Fenzizhi’and’Baizizhi’.2.Effects of salt stress and saline-alkali mixed stress on photosynthetic characteristics of the three rose species:net photosynthetic rate（Pn）,dark respiration rate,saturated light intensity,maximum photochemical efficiency（Fv/Fm）,actual photochemical efficiency（ФPSII）,electron transfer efficiency（ETR）,potential photochemical efficiency（Fv/Fo）,photochemical quenching coefficient（q P）,photosynthetic pigment content（Chl）all decreased and the light compensation point increased,and the changes of each index were relatively larger under mixed salinity stress.Under the two stress conditions,the changes of each photosynthesis-related index of’Zizhi’were relatively small,and it was able to maintain a high photochemical efficiency to adapt to the saline-alkali mixed stress by effectively using and capturing light energy.3.The effects of salt stress and saline-alkali mixed stress on the osmoregulatory system of the three rose species:under salt stress and saline-alkali mixed stress conditions,the proline content increased continuously,and soluble sugars and soluble proteins showed a trend of first increasing and then decreasing.It showed that the rose balanced the osmotic potential by increasing the organic small molecules in osmoregulation and attenuated the effect of salinity on the normal life of the plant.Throughout the process,’Zizhi’showed the greatest rise compared to’Fenzizhi’and’Baizizhi’.4.The effects of salt stress and saline-alkali mixed stress on the cell membrane stability and ion homeostasis of the three rose species:under salt stress and saline-alkali mixed stress conditions,the cell stability of all three rose species was disrupted,and the relative conductivity,MDA content and Na+content were significantly increased and K+content was significantly decreased,among which’Zizhi’showed the smallest change in each The relative conductivity,MDA content and Na+content were significantly increased and K+content was significantly decreased.This indicates that the cell membrane of’Zizhi’is relatively the most stable and more tolerant to salinity under both stresses.5.Effects of salt stress and mixed salinity stress on the activities of antioxidant enzymes of the three rose species:under both salt stress and mixed salinity stress,superoxide dismutase（SOD）showed a trend of increasing and then decreasing,while catalase（CAT）kept increasing.Peroxidase（POD）gradually increased under salt stress conditions and increased then decreased under saline-alkali mixed stress conditions.It showed that all three varieties of roses under saline mixed stress conditions could effectively eliminate excess reactive oxygen species（ROS）by increasing the activity of peroxidase,thus avoiding serious damage to plant photosynthesis caused by excess ROS.6.The results of this study showed that’Zizhi’was more tolerant to salinity under both salt stress and saline-alkali mixed stress conditions.Combining the phenotypic changes of the three rose varieties,the calculation of the comprehensive evaluation of the salinity tolerance of the three rose varieties by the principal component analysis method and the affiliation function method can be obtained in the order of the size of the salinity tolerance of the three rose varieties:’Zizhi’,’Fenzizhi’,and’Baizizhi’. |
