Studies On The Photosynthetic Physiological Characteristies And Drought Resistance Of Three Cultivars Of Penstemon

Three species of Penstemon spp which belong to Family scrophulariaceae, is a perennial herbaceous plant. In this article,one-year old of three species of Penstemon (Penstemon'Purple Passion', Penstemon digutalis'Husker Red', Penstemon barbatus'Rondo') were used as materials to study its photosynthetic physiological characteristics and drought tolerance in natural,the results indicated that:(1) The photosynthetic capacity of three species of Penstemon is different,the order was as follows: Penstemon'Purple Passion' > Penstemon barbatus'Rondo' > Penstemon digutalis'Husker Red';Photosynthetic characteristic parameters of three species of Penstemon were different, they all had different abilities of using strong light and different light adaptation range,the order was as follows: Penstemon'Purple Passion'>Penstemon barbatus'Rondo'>Penstemon digutalis'Husker Red';by comparison of the apparent quantum yield,the light percent conversion register as Penstemon'Purple Passion'>Penstemon barbatus'Rondo'>Penstemon digutalis'Husker Red'.The curves diurnal variation of net photosynthetic rate of three different Penstemon presented two peaks, there was obvious photosynthetic depression.The curves diurnal variation of transpiration rate and water use efficiency also presented two peaks.The interrelation between the net photosynthetic rate of three different Penstemon and the affecting factors is not same,and the main factors was as follows:photosynthetically active radiation, stomatal conductance ,air relative humidity. the chlorophyll fluorescence of three different Penstemon showed that the chlorophyll fluorescence of the three cultivars reached significant level or extremely significant level. The values of Fv, Fv/Fm, Fv/Fo, Yield, ETR, qP, NPQ of the Penstemon'Purple Passion'were the highest, followed by the Penstemon barbatus'Rondo', and those of the Penstemon digutalis'Husker Red'were the lowest。Correlation analysis among photosynthetic parameters showed that there were significant or extremely significant positive correlations between Fo and Fm, qP and Fm, qP and Fv, Yield and ETR, Fm and Fv, Fo and F, Fm and Yield; significantly or extremely significantly negative correlations between Fo and ETR, Fv/Fo and Yield. the photosynthetic physiological functions of three species of Penstemon is different,the order was as follows:Penstemon'Purple Passion'>Penstemon barbatus'Rondo'>Penstemon digutalis'Husker Red'.(2) Compared ability of drought tolerance according to the changes of physiological and biochemical parameters and chlorophyll fluorescence parameters during the drought stress on three different Penstemon,the results indicated that:the MDA content,antioxidant enzymes activity and Soluble protein content showed"first and decreased afterwards"with deeper drought stress,the changes of physiological and biochemical indexes during drought stress of three different Penstemon were different. chlorophyll fluorescence parameters were affected by drought stress,while the change range was ditterent,Initial fluorescence(Fo),Variable fluorescence(Fv),Maximal PSⅡefficiency(Fv/Fm),chemical quenching coefficient(qP),non-chemical quenching coefficien(tqN)and others could be used to compare the drought-tolerance ability of different Penstemon.According to the parameter changes,the drought-tolerance ability of different Penstemon in drought stress condition by the comprehensive appraisal index as follows: Penstemon digutalis'Husker Red'>Penstemon'Purple Passion'>Penstemon barbatus'Rondo'.