Analysis And Comparison Of Salt Tolerance Among Three Island Plants In Eastern Zhejiang

As an important biological genebank in China,island plants have the great significance for diversity conservation and the mining of stress-resistant plant resources.In recent years,although a large number of high-quality island plants have been continuously applied in urban landscaping,agricultural production,and ecological protection,the majority of them are in a bad status due to lack of understanding of their characteristics.Toexplore the adaptation of island plants to soilswithsaltandthen to discover salt-tolerant species,two-year-old potted seedlings of three excellent island plants in eastern Zhejiang(Cinnamomum japonicum var.chenii,Viburnum japonicum,Rhaphiolepis umbellate)were selected as experimental materials.Then,the potted seedlings were treated with salt stress(salt mass concentration 0.3%,0.6%,0.9%)and a control group(0%;CK)in GP8432 Multi-span film greenhouse.Thechanges ofphotosynthetic characteristics parameters,chlorophyll fluorescence parameters,osmotic regulation substance content,antioxidant enzyme activities,plant growth and morphological traits were analyzed to compare salt tolerance.Themain research results of this study are as follows:(1)After salt stress,the content of main photosynthetic pigments of the three plants remained basically stable under the treatment of ≤0.6%Na Cl,but after the treatment of 0.9%Na Cl,C.japonicum var.chenii decreased significantly compared with the control(P<0.05),V.japonicum remained stable compared with the control,and the carotenoid of R.umbellate increased nutrient content;The changes of photosynthetic gas exchange parameters showed that both C.japonicum var.chenii and V.japonicum continued to decrease with the increase of Na Cl concentration and treatment time,while R.umbellate showed an upward trend;The/8)and / of C.japonicum var.chenii and V.japonicum both increased first and then decreased after Na Cl treatment,while the /8)of R.umbellate remained stable,but the /continued to increase with the treatment time,and reached a significant level under 0.9% Na Cl treatment(P<0.05).(2)After salt stress,the MDA content of C.japonicum var.chenii and V.japonicum increased first and then decreased with the increase of Na Cl concentration,and the MDA content of R.umbellate decreased to different degrees after salt stress at different concentrations,but began to increase at 50 days after treatment;The POD activities of the three plants all showed a trend of first increasing and then decreasing after Na Cl treatment,but only C.japonicum var.chenii decreased significantly compared with the control at50 d of treatment;the SOD activities of the three plants remained basically stable during the salt stress process of the three plants.(3)After 0.9%Na Cl treatment,the salt damage index of the three plants all reached the maximum value,and the salt damage index of V.japonicum was the largest(11.67%);With the increase of Na Cl concentration,the seedling height increments of the three plants all increased first and then decreased,but the change rule of the ground diameter increments showed that C.japonicum var.chenii continued to decrease,V.japonicum continued to increase,and R.umbellate increased first and then decreased;The fresh weight ratio(above/underground)and dry weight ratio(above/underground)of C.japonicum var.chenii and V.japonicum decreased after each concentration of Na Cl treatment,while R.umbellate increased;The trypan blue staining and the morphological changes of leaves and roots of the three plants were basically the same,which showed that with the increase of Na Cl concentration,leaf cell death increased,leaves became smaller,and fibrous roots decreased.(4)The comprehensive analysis showed that the concentration thresholds of soil salinity tolerance for C.japonicum var.chenii,V.japonicum and R.umbellate were 0.6%,0.6%,and 0.9%,respectively.The membership function values of the seven main salt tolerance evaluation indexes,including Pn,Gs,/8),/,SOD activity,fresh weight ratio(above/underground),and dry weight ratio(above/underground),were calculated from 18 indexes.The salt tolerance was in the order of R.umbellate>V.japonicum>C.japonicum var.chenii.In conclusion,this study indicated that the three island plantsin eastern Zhejianghave high salt toleranceandpotential application in saline soil cultivation.