Effect Of Physiological Characteristics Of Phyllostachys Edulis Forest Under Drought Stress

Phyllostachys edulis?Carr.?H.de Lehaie is long-growing,the most extensive and the most important economic value of bamboo species in China.Drought is one of the disaster-prone disasters in China,which directly affects the growth and development of bamboo and the economic benefits of bamboo producing areas.In order to understand the photosynthetic physiological changes of Phyllostachys edulis under drought stress,the study was conducted with 1-3 years Phyllostachys edulis and based on the platform of Qianjiangyuan Forestry Ecosystem Research Station,State Forestry Administration.It mainly studied the photosynthesis and related physiological indexes in the natural?control?and drought environment,comparing from different canopies and seasonal variation.The main results were showed as follows:1.Light response characteristics of Phyllostachys edulis forestThe maximum net photosynthetic rate(P_nmax)of each year was showed that P_nmax was decreased with the decrease of canopy height.In the natural environment,P_nmax,LSP and LCP of one year were higher,while P_nmax,LSP and LCP of three-year were lower in the upper canopy.In the lower canopy,P_nmax and LSP of one-year were higher,LCP was lower,while P_nmax and LSP of three year were lower,LCP was higher.The photosynthetic pigment content of one year was the highest in the upper canopy,while the photosynthetic pigment content of two-year was the highest in the lower canopy.LMA of each canopy was two-year> three-year> one year.The values of P_nmax under drought stress were higher than those under the control treatment,except P_nmax of two-year was not significant?P>0.05?.P_nmax in the upper canopy of one year and the three-year under drought stress in natural environment were respectively 15.86% and 63.35% higherer than that in natural environment?P<0.05?,while P_nmax in the lower canopy of one year and the three-year under drought stress were respectively 33.51% and 82.76% higher than that in natural environment?P<0.05?.In general,drought treatment improved the ability of using the weak light in the upper canopy,reduced the dark respiration rate.It also improved the dark respiration rate and light energy efficiency in the lower canopy.The photosynthetic pigment content and LMA were not significantly different between control and drought treatments?P>0.05?.2.Response to CO₂ of Phyllostachys edulis forestThe net photosynthetic rate of Phyllostachys edulis was high light> low light.In the natural environment,P_nmax of each year under high irradiance was significantly higher than that under low irradiance?P<0.05?,which was 50.74%,43.39% and 98.12% higher than that under low irradiance.In general,One year and three-year under high irradiance?1500?mol·m-2·s-1?had higher CSP and lower CCP than that under low irradiance?200?mol·m-2·s-1?.Two-year under high irradiance?1500?mol·m-2·s-1?had higher P_nmax and CE than that under low irradiance?200?mol·m-2·s-1?.Under low irradiance,the values of P_nmax and CE under drought stress were higher than those under the control treatment,except P_nmax of two-year was lower than that under the control treatment and CCP was lower than that under the control treatment.Under high irradiance,the values of P_nmax?Rp and CE under drought stress were higher than those under the control treatment,and CSP and CCP under drought stress were lower than those under the control treatment.However,the change of two-year under drought stress was inconsistent.The values of P_nmax and CE under drought stress were lower than those under the control treatment,and CSP?CCP and Rp under drought stress were higher than those under the control treatment.3.Seasonal variation of photosynthetic physiology of Phyllostachys edulis forestThe seasonal changes of each index was similar under drought and control condition.Pn?LSP and AQY were higher and LCP was lower in summer.The total chlorophyll content of each year was higher in autumn and winter,and was lower in spring and summer.The seasonal variation of LMA was Spring> Winter> Autumn> Summer.The seasonal variation of leaf water content of each year was Summer> Autumn> Winter> Spring.The activity of SOD?POD and CAT were higher in autumn and winter,and was lower in spring and summer.The content of MDA was showed that it increased first and then decreased and increased.The seasonal variation of MDA was Summer>Winter>Spring>Autumn.The content of souble protein was higheat in autumn.P_nmax of one year in Spring under drought stress was 25.63% higher than that in the control condition significantly?P<0.05?,while P_nmax in Summer and Winter was 20.04% and 53.02% lower than that in the control condition significantly?P<0.05?.The P_nmax of two-year in each season under drought treatment was lower than that of the control condition,which was 57.16%,15.80%,21.53 %,39.90% lower than that of the control condition?P<0.05?.The P_nmax of three-year in Summer?Autumn and Winter under drought stress was 8.86%,57.27%,27.27% higher than that of the control condition significantly?P<0.05?,while the difference of P_nmax in Spring was not significant between control and drought treatment.There were no significant differences in photosynthetic pigment content of each year between control and drought treatment.The LMA under drought stress was higher than those in control condition,and the leaf water content under drought stress was lower than those in control condition.In general,the activity of SOD?POD and CAT and the content of MDA of each year under drought stress were lower than those in control condition.The content of soluble protein under drought stress was higher in Spring and Autumn and was lower in Summer and Winter.Through the analysis of physiological and biochemical indexes,LMA?leaf water content and MDA content were closely related to the changes of Pn.Due to photosynthesis as an important metabolic process of plant growth,it could also provide some theoretical reference for drought resistance research of Phyllostachys edulis.