| In recent years,soil acidification and soil salinization had become well-known environmental problems.With the development of industry,urban development and incorrect irrigation and fertilization,soil acidification and alkalization were becoming more and more serious.At the same time,Jianghan Plain was an alluvial plain,and its soil was acidic.Most of the southwest China and the Yangtze River Basin were also the hardest hit areas of acid rain.This series of reasons caused soil acidification,and it was difficult for plants to adapt it.The coastal areas,industrial restoration sites and other areas of the soil were suffering alkali damage,resulted in poor growth of plants.Based on this environment,this paper studied the adaptability of Cinnamomum bodinieri Levl.and Phoebe bournei(Hemsl.)Yang.to environmental pH.Under this background,in this stduy,the river sand was used as the matrix to plant C.bodinieri and P.bournei,and HCl and NaOH was used to regulate the pH value of 1 times Hoagland solution,and the pH values of solution was regualated to 4.0,5.0,6.0,7.0,8.0,8.5 and 9.0 as 7 different irrigation treatment.Then used the different treatment irrigated C.bodinieri and P.bournei,by analysing their growth index,photosynthetic pigment and photosynthetic characteristics,plasma membrane stability,the content of osmotic adjustment substance,as the 4 aspects,analyzed the growth situation of C.bodinieri and P.bournei in different pH treatment,analyzed the tolerance of acid and alkali stress of C.bodinieri and P.bournei.The results of showed that:(1)The growth of acidic environment under the condition of p H4.0~pH6.0 had some positive effects to P.bournei seedling growth,in acid conditions,seedlings in the light energy utilization rate was higher,thus,the the growth of P.bournei was promoted,also showed that the P.bournei seedlings had acid resistant ability.Under the alkaline environment of pH8.0~pH9.0 treatment,the growth of P.bournei seedlings was inhibited,and the damage degree of P.bournei seedlings was increased with the increase of pH.Under the acidic environment of pH4.0 treatment and strong alkali environment of pH8.5 and pH9.0 treatment,all the growth of C.bodinieri seedlings was inhibited in different degrees,but did not stop the normal physiological and developmental activities of C.bodinieri seedlings.C.bodinieri showed no phenomenon of damage under different treatments.(2)The photosynthesis index :the photosynthetic pigment contented in P.bournei seedling reached the highest level under the treatment of pH4.0,while the pH5.0 and pH9.0 treatment in the next.The lowest level of the photosynthetic pigment contented in P.bournei was under the pH7.0 treatment;and the photosynthetic pigment contented in C.bodinieri seedlings reached the highest level in pH6.0 and pH8.5,and in pH4.0,pH5.0 and pH9.0 treatment,the photosynthetic pigment contented in C.bodinieri seedlings significantly inhibited.As the influences of different pH values on photosynthetic parameters of P.bournei seedling was different under rifferent treatment.Pn and Tr reached the highest level under the pH6.0 treatment,Gs and Ci was highest under the treatment of pH4.0.Besides,under the treatment of pH9.0 all the light and the parameters were in low level,amnog that,Pn and Gs were at the lowest level under the pH4.0 treatment;Pn of C.bodinieri seedlings reached the maximum value in the treatment of pH4.0;Tr,Gs and Ci of C.bodinieri reached the maximum under the treatment of p H5.0 and pH8.5,what's more,the light and the parameters under the treatment of pH8.0 reached the lowest level.(3)Membrane permeability: the membrane stability and active oxygen dynamic balance of P.bournei seedlings had been seriously affected under the growth environment of pH9.0 and pH8.5.As SOD activity decreased rapidly at the end of the experiment,P.bournei seedlings under alkaline stress accumulated lots of free radicals,which was beyond its limits.It reflacted that P.Bournei seedlings was not tolerance to the environment of p H9.0 and pH8.5;but showed good tolerance under pH4.0 treatment.The membrane permeability of C.bodinieri seedlings,which was under pH4.0 treatment and pH9.0 treatment,were damaged certainly,but was still within the tolerance range,C.bodinieri seedlings still could effectively remove excess free radicals to improve antioxidant activity,maintain the stability of plasma.(4)The content of osmotic substances: the RWC of P.Bournei seedlings under pH4.0 was at highest level,combined with the content of TSS,SP,Pro analysing,by the accumulation of osmotic substances,P.Bournei maintained the positive pressure of the cell effectively,reduced the external osmotic potential,to make the RWC of plant leaves staing at the highest level,these showed that the P.Bournei seedling under the treatment of pH4.0 could maintain normal cell osmotic potential;and in the alkaline treatment,especially under pH8.5 and pH9.0 treatments,seedlings of P.Bournei failed to maintain the osmotic potential of cells by increasing the content of TSS and SP,and then decreased its RWC;in the late phase,the content of Pro reduced greatly,indicated that the P.Bournei seedlings were damaged severely under the alkali stress,the normal physiological activity was inhibited,and Pro accumulation process blocked.Only under pH4.0 treatment,the RWC of C.Bodinieri seedlings was at low level,C.Bodinieri seedlings under other treatments were maintained normal cell osmotic potential by increasing TSS and SP content,and by produced Pro to scavenge free radical,and maintained the normal physiological activity.By analysising the growth and physiological indexes of P.Bournei seedlings in each period,It was found that P.Bournei seedlings,which were under the treatment of pH4.0~pH6.0,had grew well and had good tolerance to acidic environment,besides,the acidic environment of pH4.0 was within its tolerance range,and significantly promoted the growth of seedlings;but pH8.0 and above conditions would inhibit the growth of P.Bournei seedlings.C.Bodinieri seedlings could grow normally in the range of pH4.0~pH9.0,but the strong acid and strong alkali environment such as the treatment of pH4.0 and pH9.0,were not enough to stop the growth and development of.C.Bodinieri seedlings,but they could inhibit the physiological activities to some extent. |
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