Abstract
The common bean，Phaseolus vulgaris L（Pv），is sensitive to heat and drought stress，and its yield is significantly reduced under these conditions；Phaseolus acutifolius A.Gray., tepary bean （Pa） is well adapted to hot and arid environment and might be a valuable source of traits to improve the adaptation of the common bean to drought. Therefore many researchers have devoted much attention to their physiological differences in physiology and stress tolerance. However，their photosynthesis，one of the most important physiological process，has never been systematically studied. Our work focused on the differences in of the two plants withstanding unfavored conditions and the subsequent adjustment，the resistance to photoinhibition and it’s protective mechanism，and their antioxidant systems involve in the process after acclimation to varied stress，including high temperature and double stress state－drought plus high temperature. After getting used to the given stress conditions，we explore photosynthetic activities of plants via chlorophyll fluorescence，we found that the improvement of Pv in PSII activity，thermal dissipation and electron flow process etc were greater than those of Pa. This suggests that Pv owns a better capability of self-adjustment. In study of the effect of photoinhibition and it’s protective mechanism，we discovered that the extent of damage to photosynthetic apparatus by excessive light could significantly be alleviated a lot in Pv after acclimation tothe given stress. Besides，the induction of xanthophyll cycle －the general belived photoprotection mechanism under high light intensity－was more complete in Pv. From this result，we suggest that acclimation to stress condition would confer Pv with more resistance to strong light. As regards the role of antioxidant systems，more SODs（superoxide dismutase）were induced in Pv，and we have identified it as Cu-Zn SOD. However，glutathione peroxidase，no difference was found between Pa and Pv. maybe in terms of the expression of GPx， clearance of H2O2 is through an alternative pathway. With concerning to protein compositions，due to no high sensitivity of detective tools in hand，we cannot assure any heat-tolerance related proteins to involve in，but we found the amounts of large subunit of the Rubisco decayed with the stringent condition and the extent of reduction was less in Pv. In summary，these studies demonstrated that Pv have a greater plasticity. During acclimation to high temperature and double stress state，Pv may continue to adjust its physiological state to accommodate unfavored condition and reach a level comparable to that of Pa