Studies On The Photosynthetic Physiological Characteristics And Drought Resistance Of Three Species Of Coreopsis

Three species of Coreopsis which belong to Family Asteraceae, is a perennial herbaceousplant,were used widely in garden.In this article, one-year old of three species of Coreopsis (Coreopsisgrandiflora、Coreopsis lanceolata、Coreopsis rosea ’Heaven’s Gate’) were used as materials to study itsphotosynthetic physiological characteristics with the LI-6400photosynthesis system analyzer anddrought tolerance using potted water control methods. The results indicated that:(1) The light compensation point and light saturation point of three species of Coreopsis weredifferent. The sequence of their light adaptive range was Coreopsis lanceolata＞Coreopsis grandiflora＞Coreopsis rosea ’Heaven’s Gate’ and the order of their abilities of using strong light was Coreopsislanceolata＞Coreopsis rosea ’Heaven’s Gate’＞Coreopsis grandiflora. The diurnal variation of netphotosynthetic rate （Pn） of three species of Coreopsis displayed double-peaked curves which hadgreater initial peaks and obviously photosynthetic noon break. Transpiration rate （Tr） and stomatalconductance （Cond）had similar change trends with Pn, however, the intercellular carbon dioxideconcentration （Ci） had the opposite change compared with Pn. The water use efficiency （WUE） ofthree species of Coreopsis was different with sequence of Coreopsis grandiflora＞Coreopsis lanceolata＞Coreopsis rosea ’Heaven’s Gate’.The interrelation between the net photosynthetic rate of three species of Coreopsis and theaffecting factors was not same.(2) Under drought stress, the changes of physiological and biochemical parameters of three kindsof Coreopsis reflect their drought tolerance. The results indicated that: the leaf water potential and thecontent of chlorophyll kept decreasing, and the relative electric conductivity continued to rise, the moreleaf water potential and Chlorophyll decreased, relative electrical conductivity rised, the weaker itsdrought resistance was. The relative electric conductivity、the MDA content、the activities of SOD andPOD can be used to sequence the plants’drought resistance. (3) Changes in chlorophyll fluorescence parameters of three kinds of Coreopsis, indicating droughtstress have a significant impact on the chlorophyll fluorescence parameters of Coreopsis, the range ofchanges of chlorophyll fluorescence parameters of different species of Coreopsis was different, Initialfluorescence (Fo)、Variable fluorescence (Fv)、Maximal PSⅡ efficiency (Fv/Fm)、chemical quenchingcoefficient (qP)、non-chemical quenching coefficient (qN) could be used as a reference indicator ofdrought resistance of Coreopsis.(4) According to the parameter changes, the drought-tolerance ability of different Penstemon indrought stress condition by the comprehensive appraisal index as follows: Coreopsis grandiflora＞Coreopsis lanceolata＞Coreopsis rosea ’Heaven’s Gate’.