| Alstonia scholaris have the characteristics of the fast-growing,strong adaptability,high survival rate,anti pollution,it usually not only regards as the subtropical and tropical tree,but also as the garden tree;Alstonia scholaris secondary metabolites such as alkaloids had important medicinal value,its bark and leaf extract contains anticancer activity.The article analysis the different light intensity(T0100?95%,T180?75%,T260?55%,T330?25%,T410?5%)and different temperature(15?,20?,25?,30 ?,35 ?)of the influence of the growth and physiological indexes of Alstonia scholaris seedling,aiming at cultivating seedlings and provide reference for Alstonia scholaris seedling.The results are as follows:(1)Seedling height increment(?H)of T2 light tretment was 1.5 times that of T0,which was 2.8 times of T4,ground diameter increment(?D)was 1.2 times that of T0,which was 1.3 times that of T4,indicating the appropriate decrease of light significantly promoted the Alstonia scholaris seedling height,ground diameter growth;with the light lower,the total dry weight of Alstonia scholaris seedlings decreased,the root shoot ratio of Alstonia scholaris seedling firstly decreased and then increased,water content increased;the total root length,root surface area with decreasing light intensity changed little,the average root diameter,root volume was significantly lower than that in T0 treatment and other light treatment.(2)Soluble sugar content and soluble protein content of Alstonia scholaris seedling decreased with light intensity decreased,the conductivity,malondialdehyde,proline content decreased with increasing illumination increased firstly and then decreased,reached the lowest in T2 treatment;under different illumination,SOD enzyme activity of Alstonia scholaris seedling changed small,POD enzyme activity of Alstonia scholaris seedling on T2 treatment was significantly higher than other treatments,respectively was 2.5 times of To treatment and 1.5 times of T4 treatment,with the decrease of light intensity,Chla,Ch1b,Chla+b content and Chla/b numerical of Alstonia scholaris seedling firstly decreased and then increased,the chlorophyll content of the growth of fast processing was low;with the decreasing of light intensity,net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)of Alstonia schoaris seedling firstly increased and then decreased,intercellular CO2 concentration(Ci)showed a trend of decrease,T2 treatment Pn respectively was 1.6 times of T0 treatment and 10.7 times of T4 treatment,F0 and Fm of T0 treatment were both the smallest,with the decrease of light,Fv/Fm firstly increased and then decreased,but in To treatment was minimum,that indicated full sunlight treatment can mostly cause decline in plant potential photosynthetic rate;with decreasing light,qN firstly increased and then decreased,but To treatment was significantly higher than other light treatment,indicating the decrease of light intensity,significantly decreased plant heat dissipation capacity;T2 treatment of Y(II)respectively was 1.1 times of T0,3.1 times of T4;with the decreasing of light intensity,Y(NPQ)had a downward trend,Y(NO)had a rising trend,with the decrease of light intensity,that indicated Alstonia scholaris seedling light protection ability decreased,regulating energy conversion and self protection ability were getting worse,and more and more difficult to excess light energy to heat dissipation.(3)Under 5 kinds of temperature treatment,with the temperature rising,seedling height and ground diameter change quantity of Alstonia scholaris seedling,firstly increased and then decreased,the seedling diameter growth of 15? treatment was the lowest;with the increase of temperature,the root dry weight ratio of Alstonia scholaris seeding firstly increased and then decreased,the stem dry weight ratio decreased,the leaf dry weight ratio gradually increase and the total dry weight also increased first and then decreased;with increasing temperature,root shoot ratio firstly increased and then decreased,the water content of plants increased gradually with the increase of temperature;the temperature is not obvious different on the average root diameter of Alstonia scholaris seedling,the root length,root surface area and root volume were significantly affected,the root length,root surface area,root volume of Alstonia scholaris seedling at 30? treatment were 3.1 times,4.6 times,5.9 times of 15?treatment,and were 1.2 times,2.1 times,2.6 times of 35? treatment.(4)Soluble sugar and soluble protein content of Alstonia scholaris seedling were increased with the temperature firstly decreased and then increased,with the increase of temperature,the conductivity,malondialdehyde,proline content were firstly decreased and then increased,three of 15?treatment were all significantly higher than that of the other 4 treatments,the results showed that low temperature was the most serious,with the increase of temperature,SOD and POD enzyme activity of Alstonia scholaris seedling were firstly increased and then decreased,and there was significant difference among treatments;with temperature increased,Alstonia scholaris seedling Chla,Chlb,~Chla+b content firstly increased and then decreased,and Chla contents among treatments were significant difference,Chla/b was lowest at 15?,however,Chla/b of which the plants grow more faster at 25?and 30?was relatively.low,with the change of temperature,chlorophyll synthesis and decomposition of Alstonia scholaris seedling in the growth process were adjusted,with the increase of temperature,Alstonia scholaris seedling net photosynthetic rate(Pn)firstly increased and then decreased,stomatal conductance(Gs)and transpiration rate(Tr)were both increased,intercellular CO2 concentration(Ci)firstly decreased and then increased,net photosynthetic rate Pn of Alstonia scholaris seedling at 30? was 7.6 times of 15? treatment,1.1 times of 3 5 ? treatment;F0,Fm of chlorophyll fluorescence at 30?reached the maximum,Fv/Fm at 35 ? 15 ? were lower,that indicated the stress of Alstonia scholaris seedling at 15 ?and 35 ? were greater than other temperature processing;with the increase of the temperature,qN gradually decreased;with the increase of temperature,Y(II)and rETR showed firstly increase and then decrease;plant actual quantum yield at 25?was maximum,but Y(NPQ),Y(NO)was not the smallest,plant optical protection ability and light damage of 15? treatment respectively was maximum and minimium,plant optical protection ability and light damage of 30? respectively was minimum and maximum,however,the actual photosynthetic quantum yield is not the lowest,this indicated that plants can use different regulatory mechanisms for self-regulation and physiological compensation in different temperature conditions. |
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