Influence Of Saline And Alkali Stresstes On Seed Germination And Seedling Growth Of Three Species Of Psammophytes

Soil salinization is the most common type of land degradation in arid area in Northern China.It affects the distribution of plant population and the construction of ecosystem and limits the development of agricultural productivity.Ammopiptanthus mongolicus(Maxim,ex Kom.)Cheng f.(Am),Ammopiptanthus nanus(M.Pop.)Cheng f.(An),Caragana korshinskii Kom.(Ck)are the common psammophytes in arid desert in Northern China Which have a greater ability to adapt and improve environment.Little is known about the adaptive mechanisms to saline-alkail enviroment of these psammophytes,especially in the stage of seed germination and seedling growth.The contents of this study were:(1)the characteristics of seed biology and seed coat structure of three species of psammophytes;(2)the responses to saline-alkail stress of seed germination of three species of psammophytes;(3)the responses to saline-alkail stress of seedling growth of three species of psammophytes.The main results were shown below:1.The seed shape of Am and An deviated from round,the mass were heavier.The testa of three species of psammophytes were sclereid layer which contributed to keeping the seed vigor.The mesosperm and endopleura were loose and with cavity,which helped to imbibe moisture.2.Proper saline-alkail treatment was good to seed imbibition.Under the same concentration,NaOH solution had more roles on promoting seed imbibition than NaCl solution.3.Low concentration of NaCl solution was good to seed germination of Ck.When saline-alkail stress enhanced,the germination capacities of three species of psammophytes declined sharply.When the concentration of NaOH was 80mM,Am and Ck were no germination;when the concentration of NaOH was 100mM,An was no germination.Under the same concentration,NaOH solution had more roles on depressing seed germination than NaCl solution.4.Low concentration of NaCl solution was good to radicle growth of Ck and the biomass accumulation of three species of psammophytes.When saline-alkail stress enhanced,the growth of radicle and germ with the biomass accumulation of three species of psammophytes were depressed.When the concentration of NaOH was 120mM,the seedlings had no radicles.In the same concentration,the inhibition of NaOH solution to seedling growth was heavier than NaCl solution.The sensibility of radicle to the change of NaOH solution concentration was stronger than germ in Ck,the sensibility of radicle to the change of NaOH solution concentration was weaker than germ in An.Before germination,the embryos were hurted irreversiblely by salt-alkali stress.5.Under the same concentration,the relative conductivity of three species of psammophytes under alkali stress were higher than under salt stress and the relative water content were lower than under salt stress.When the concentration of NaOH was 120mM,Ck died;when the concentration of NaOH was 120mM,Am and An died.The adaptability to salt stress of Ck was the strongest and the adtability to alkali stress of Am and An were stronger than Ck.When the content of neutral salt in soil is higher,we can plant Ck to improve the edatope;when the content of alkali salt in soil is higher,we can plant Am and An to improve soil environment.