Effect Of Drought And Salinity Stress On Germination And Seedling Viability In Ceratoides Arborescens

Desert ecosystems is the harshest and most vulnerable areas of terrestrial ecosystems which is account for about 60% of the grassland area.Ceratoides arborescens is a desert xeric perennial semi-shrub of the genus Ceratoides widely distributed in desert areas.C.arborescens not only utilizes the advantages of long years,but also is an excellent forage semi-shrub with sand fixation.Understanding the factors impacting seed germination in desert areas is needed to accelerate the restoration process.The objective of this paper was to determine the influence of seed size(small seed,large seed),seed coat impacted seed germination and seedling growth in wet-dry cycle,salinity and water stress.Germinating seeds and seedlings have dehydration tolerance.Germination percentage were almost 100% with wet-dry cycle treatments.However,wet-dry cycle treatments decreased seedling survival percentage.Our results showed that the point of no recover for C.arborescens was 30 days for 2–3 mm root lengths below which seedlings have the ability to survive and re-grow.The seed coats have a separation effect during the germination under the salinity stress,and have the effect of increasing the osmotic potential under drought stress,in order to ensuring the growth of the seedlings.The seed coats delayed and inhibited the germination of the seeds in the salt stress.The germination percentage of the seeds without coats were 17% higher than seeds with coats,and seed coat delayed the mean germination day(0.8 d).However,the radical length,shoot length and seedling vigor index of seeds with coats were higher than seeds without coats,especially under high salt stress,which indicated that the presence of coats enhanced the salt tolerance of seeds and protected the seed embryo structure during germination.Under sufficient water conditions,large seeds gave full play to their advantages,while small seeds reduced the demand for water under insufficient water conditions and increased the elongation of radicle as soon as possible to ensure recruitment of population.Although the presence of coats increased the water potential of seed germination,it had a positive effect on seed germination and seedling growth under water stress.The presence of coats makes the seed germination irregular,because after the coats were removed,all the seeds germinated one day,and the seedling growth were all concentrated,which may lead to collective death.The presence of coats distracts the risk of collective death of seedlings.The relative embryo length is positively correlated with the germination speed.The large seeds had higher relative embryo length than the small seeds.The advantages of large seeds in the germination and seedling growth stages are not only from the advantages of large seeds,but also because they had larger relative embryo lengths.Through this study,first we revealed how the seeds of C.arborescens could adapt to low water availability and salinity stress through the characteristic plasticity of germination and seedling growth.Secondly,demonstrated the effects of morphological characteristics of desert species in desert,which will contribute to the ecological restoration and provide a theoretical basis for sustainable development of desertification areas.