Study On Physiological Response Of Quercus Nuttallii To Salt Stress And Alleviating Effect Of Gibberellin

Quercus nuttallii is a deciduous tree of the genus Quercus in the Fagaceae.It has upright trunk,tower-like crown,bright red or red-brown autumn leaves,strong adaptability,strong resistance to water and humidity,strong resistance to urban pollution,strong adaptability to climate,and good ornamental effect,it is a kind of plant which is seldom used in gardens,but has potential development.The study on its growth and adaptive mechanism in saline soil of different composition and concentration is of great significance to the selection of salt-tolerant plants,the popularization of the wide application of Q.nuttallii in gardens and the improvement of its economic benefits.Exogenous gibberellin can obviously improve the adaptability of plants and alleviate the salt injury of plants.The physiological responses of one-year-old Q.nuttallii to salt stress were studied under 0.5%,0.8%and 1.1%NaCl.NaCl+Na2SO4 and other(1:1)mixed salt treatments,after that,1.1%NaCl stress was relieved by exogenous gibberellin(the concentration of exogenous gibberellin was 0,100,200,300mg/L)to study the relieving effect of exogenous gibberellin on salt stress of nuttallii.By measuring the growth,physiology and photosynthesis of the plant,the results were as follows:(1)NaCl、NaCl+Na2SO4 and other salt mixtures had significant effects on the growth characteristics,osmotic adjustment,oxidase system,chlorophyll,fluorescence parameters and photosynthesis of Q.nuttallii.(2)Under salt stress,plant height,stem diameter,leaf width,chlorophyll content,carotenoid content,Fv/Fm、ETR、qP、Fv’/Fm’,maximum net photosynthetic rate,light saturation point,transpiration rate were decreased,SOD,soluble protein,soluble sugar,first up and then down,qN,MDA,light compensation point increased.(3)The salt tolerance of Q.nuttallii was strong.Under 0.5%salt treatment,Q.nuttallii grew well,and there were no significant differences in growth,physiology and photosynthesis between the control and Q.nuttallii has certain adaptability to 0.5%NaCl.NaCl+Na2SO4 salt,and can ensure normal growth and development.(4)By measuring the growth,physiological and photosynthetic indexes of Q.nuttallii under salt stress after applying exogenous gibberellin,after applying gibberellin,the plant height,stem diameter,leaf width,chlorophyll content,Fv/Fm、ETR、qP and other indexes of Q.nuttallii increased in different degrees,and the parameters of qN and MDA decreased in different degrees,the exogenous gibberellin could effectively improve the indexes of Q.nuttallii under salt injury,and could effectively alleviate the damage of Q.nuttallii under salt.According to the comprehensive evaluation model,it was found that gibberellin of T3>T4>T2>T1,T3(200 mg/L)had the best effect to alleviate the harm of salt to Q.nuttallii.(5)Under the condition of soil salinity less than 0.5%,nata oak showed good tolerance,so it could be cultivated under the condition of moisture and low salt.When the salinity is 0.5-1.1%,the experiment can be carried out in the salinized areas,such as the coastal saline-alkali land,and some gibberellin can be used as exogenous reducing agent to improve its salt resistance...