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Shanxi University (2021)

Diurnal Variation in Net Photosynthetic Rate and Main Influencing Factors of Populus Euphratica in Extremely Arid Region of the Lower Heihe River

李雪娇

Titre : Diurnal Variation in Net Photosynthetic Rate and Main Influencing Factors of Populus Euphratica in Extremely Arid Region of the Lower Heihe River

Auteur : 李雪娇

Grade : Master 2021

Université : Shanxi University

Résumé
Ejina Oasis is the second largest Populus euphratica forest reserve in our country.Since the 1960s,excessive water use in the middle reaches of the Heihe River led to insufficient water supply and ecological imbalance in Ejina.In order to prevent the desertification of vegetation caused by desertification,the national and local governments have adopted a series of measures to greatly improve the ecological environment of the downstream,mainly for the Heihe water diversion project started in 2000.Photosynthesis is the most important characteristic and the basic unit of material accumulation metabolism of plants,the basis of plant growth and development and the decisive factor of productivity,the rate of net photosynthesis is the main index of plant photosynthesis.To restore vegetation in the desert area,the photosynthetic parameters represented by the net photosynthetic rate(Pn)are of great research significance.In this paper,the Pnof the main tree species—P.euphratica and the main influencing factors were explored.The typical sunny weather in the main growing season of P.euphratica from June to September 2016was selected,and the physiological factors of P.euphratica leaves were measured using the Li-COR 6400 portable photosynthesis measurement system.Combined with the weather station set up in the reserve to detect environmental factors,analyze the daily changes of each factor,and conduct correlation,multiple stepwise regression and path analysis of P.euphratica leaf Pnwith other physiological and environmental factors to clarify the main influencing factors of Pn.The results showed that :(1)The daily variation of Pnof P.euphratica in the extreme arid area showed an overall upward trend and then a downward trend.In the experiment,the Pnof P.euphratica reached up to 30.27 mmol·m-2·s-1(13:00 on August 24).At noon when the temperature is high,the relative humidity is low and the radiation is strong,the leaves of P.euphratica appear obvious"midday depression of photosynthesis"(appears around 15:00).Pnmay decrease slightly near noon due to insufficient supply of basic photosynthesis(10:00 on August 24) ;(2)Pnand transpiration rate(Tr),stomatal conductance(gs)and environmental factors:incident photosynthetically active radiation(PAR),air temperature(Ta),leaf water vapor pressure difference(VPD)showed a very significant positive correlation(the correlation coefficients are respectively:0.641**、0.316**、0.819**、0.424**and 0.378**),showing a very significant negative correlation with the atmospheric CO2concentration(Ca)and leaf surface CO2concentration(Cs)(P :-0.602**,-0.352**) ;(3)From the results of multiple stepwise regression and path analysis,PAR is the main determining factor(R2path=0.638),followed by Tr(R2path=0.372),but Tralso affects Pnthrough PAR.The main limiting factor is Ta(R2path=-0.931).However,the effect of Tathrough other factors is positive,and the comprehensive effect is shown as promotion.The photosynthesis of P.euphratica is the result of the mutual influence and joint action of various factors,and the most important influencing factors are light and temperature.This research aims to clarify the main influencing factors of P.euphratica Pnin extreme arid areas,explore ways to improve P.euphratica photosynthesis,and provide a scientific theoretical basis for vegetation restoration in oasis and desert areas.

Mots clés : Net photosynthetic rate ;Multiple stepwise regression analysis ;Path analysis ;Populus euphratica ;

Présentation (CNKI)

Page publiée le 19 novembre 2021