P hotosynthetic Characteristics of Five Catalpa duclouxii Seedling Clones
We used two-year-old Catalpa duclouxii seedlings by grafting to compare their differences of the photosynthetic charac-teristics in Jianghan Plain under drought stress.Drought inhibited the seedling growth severely, and there were no signifi-cant differences in growth traits of August and December between different clones of C.duclouix i ( P>0.05) .Photosynthetic characteristics of the clones were no longer apparent unimodal or bimodal curves, the maximum net photosynthetic rate (Pn) occurred at 7:00 AM in 8-14μmol· m-2· s-1, plummeted after 7:00 AM, and maintained in 2-6μmol· m-2· s-1 low ground.The order of the day total Pn was 008-1>Y011-1>Y023-2>Y020-6>8402>Y011-4>YN014-5, the or-der of the daily average of instantaneous water use efficiency ( WUE ) was 008-1>Y011-4>YN014-5>Y020-6>Y011-1>Y023-2>8402.The light saturation point (LSP) and the maximum net photosynthetic rate (Pnmax) of these clones were be-tween 324-796μmol·m -2 · s-1 and 4.58-8.17μmol· m-2 · s-1 , respectively, and they were far below than the trait val-ues under the normal water supply.By correlation analysis, WUE was both significant correlated with the growth traits and photosynthetic characteristics (P<0.05).When the seedlings subjected to drought stress, WUE became important particu-larly.According the growth performance, WUE and photosynthetic characteristics, Y011-4 had stronger growth potential and photosynthetic capacity among five clones in Jianghan Plain.
Catalpa duclouxiiDrought stressDiurnal changes of photosynthesisPhotosynthesis-light response curves
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