Effects of Salt Stress on Seed Germination and Seedling Physiology of Avicennia marina
[Objective]The aim of this study is to explore the effects of different salt concentrations on the germination of Avicennia marina seeds and the physiology of seedlings.[Method]The experiment was conducted using controlled variable method to investigate the effect of different saline concentrations on the growth of A.marina in sand substrate.The experimental groups were set with artificial seawater salinity levels of 5,10,15,and 20,while distilled water was used as the control group.The plants were cultivated for 120 days,and various growth parameters including root germination rate,development time of true leaves,leaf quantity,plant height,net photosynthetic rate,chlorophyll content,biomass,and stress resistance were measured.[Result]The germination rates of A.marina seeds were(90.3±0.3)%,(94.3±1.2)%,and(91.6±1.5)%in the 0,5,and 10 salinity treatment groups,respectively,which were significantly higher than the salinity 15 treatment group's(75.3±3.5)%and salinity 20 treatment group's(62.3±2.5)%(P<0.05).There was no significant difference in leaf development time and leaf number between the salinity 0,5,and 10 treatment groups(P>0.05).However,in the salinity 15 and 20 treatment groups,the leaf development time was significantly delayed compared to the low salinity treatment group(P<0.05),and the leaf number showed a decreasing trend.The plant height of the groups treated with salinity levels of 0,5,and 10 was significantly higher than the groups treated with 15 and 20(P<0.05).The basal stem diameter of the salinity 5 treatment group was significantly thicker than the salinity 20 treatment group(P<0.05).Among them,the plant height of the salinity 5 treatment group was the highest(33.7±0.8)cm.The total chlorophyll content of the salinity 5 treatment group was significantly higher than the salinity 10,15,and 20 treatment groups,while the salinity 0 and 10 treatment groups were significantly higher than the salinity 15 and 20 treatment groups(P<0.05).The net photosynthetic rate of the salinity 5 treatment group was significantly higher than the other treatment groups,while the salinity 0 and 10 treatment groups were significantly higher than the salinity 15 and 20 treatment groups(P<0.05).Among them,the salinity 5 group had the highest total chlorophyll content and net photosynthetic rate,which were(2.67±0.10)mg/g and(10.32±0.20)μmol·m2·s-1,respectively.The dry mass of leaves,stem,roots,and total biomass of A.marina seedlings in the salinity 5 and 10 groups were significantly higher than those in the salinity 0,15,and 20 groups(P<0.05).Among them,the dry mass of various organs reached the highest value under the salinity 5 condition,significantly higher than other groups(P<0.05).The membrane permeability,malondialdehyde content,proline content,and superoxide dismutase activity in the leaves of A.marina seedlings were significantly higher in the salinity 15 and 20 groups compared to other groups(P<0.05),while these four stress resistance physiological indicators were the lowest in the salinity 5 group,significantly lower than all other groups(P<0.05).[Conclusion]A.marina seeds exhibited high germination rate and good seedling growth under low salinity conditions(0-10),with the most suitable condition observed at salinity 5.However,germination and growth of A.marina were significantly inhibited at salinity levels of 15 and 20.
salt stressAvicennia marinamangrove plantsgrowth indicatorsphysiological indicators
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