Studies on the Photosynthetic Characteristics of Extremely Small Population of the Plant Madhuca pasquieri at Different Growth Stages
In order to investigate the photosynthetic characteristics of Madhuca pasquieri,which is a key wild plant under State Class Ⅱ protection and a very small population wild plant,a portable photosynthesizer(Li-6400)was used to determine the photosynthetic parameters of Madhuca pasquieri seedlings,juvenile trees,and adult plants in this study.The results showed that:①The right-angle hyperbola correction model was the best model for fitting the light response of seedlings,juvenile and adult plants of Madhuca pasquieri;②the daily change of net photosynthetic rate of adult Madhuca pasquieri leaves had an obvious"lunch break"phenomenon,and the daily change curves of leaf transpiration rate,stomatal conductance and air temperature were similar to each other,and all of them showed a bimodal curve.The maximum peaks of net photosynthetic rate and transpiration rate ap-peared at 10:00-11:30,with 9.223 μmol/(m2·s)and 1.979 mmol/(m2·s),respectively;the maximum peak of stomatal conductance appeared at 14:30-16:00 0.285 mmol/(m2·s);③the apparent quantum efficiency(AQE),maximum net photosynthetic rate(Pnmax),light saturation point(LCP)and light compensation point(LSP)of leav-es of seedlings,juvenile,adult plants were significant and rate of dark respiration(Rd)(P＜0.05).The net photo-synthetic rate,stomatal conductance,and transpiration rate of Madhuca pasquieri increased with increasing light intensity within a certain range of light intensity,but then showed photoinhibition under strong light;④total chlo-rophyll was significant(P＜0.05)in Madhuca pasquieri seedlings,juvenile and adult plants.In conclusion,Madhu-ca pasquieri has higher Pnmax and LSP,while LCP and AQE are lower,and it is heliophyte.Adult plants of Madhu-ca pasquieri had higher adaptability to light than juvenile plants and seedlings;juvenile plants had higher adapta-bility to light than seedlings.
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