Daily Variation Characteristics of Photosynthesis and Chlorophyll Fluorescence in Dahlia Leaves under Water Stress
The effects of different levels of water stress on daily variation of photosynthesis and chlorophyll fluorescence characteristics of ‘Fenxishi’ plant were studied by pot experiments. With the increasing extent of drought stress,the daily means of Pn ,Tr and Gs of Dahlia decreased;the daily means of Ci increased under light and moderate stress while decreased under severe stress. The main reason of the reduction of Pn in Dahlia leaves was stomatal limitation under light and moderate stress while the main reason was nonstomatal factors under severe stress. The daily curve of the net photosynthesis rate changed from single zenith to double zenith with the influence of water stress, appeared “nap” phenomenon. Daily variation curve of Tr and Gs under water stress were the consistent with Pn. Contrary to Pn, daily variation of Ci was smooth.With the increasing extent of drought stress, the daily means of F0 in Dahlia increased and its daily changed curve appeared “V” type. Response center in PS Ⅱ could be damaged or had reversible inactivation; the daily means of Fm, Fv/Fm and φPSⅡ decreased and the daily changed curves appeared “V” type. Water stress deepened the degree of photoinhibition, curbed the photochemical activity in PS Ⅱ and reduced the light part used in photochemical reactions and actual photochemical efficiency. The results of study showed that photosynthesis occured photoinhibition in Dahlia‘Fenxishi ’ under different levels of water stress, making the net photosynthetic rate reduced. Photosynthetic institutions in Dahlia might have reversible deactivation to adapt to light and moderate stress, not suffered irreversible damage. The activity of photosynthetic institutions decreased by the severe water stress which also increased the severity of photoinhibition and limited the normal process of photosynthesis. So the appropriate relative water content in soil for Dahlia was more than 30％ of maximal water content in field.
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NSTL
万方数据
维普
