Studies On Photosynthetic And Physiological Characteristics Of Phoebe Bournei In Different Provenances

In this paper,the gas exchange parameters were measured by LI-6400 portable photosynthesis apparatus,and the chlorophyll fluorescence parameters were measured by using MINI-PAM portable fluorescence spectrometer for five provenances of Phoebe bournei sapling.The changes of photosynthesis and fluorescence of provenances in Mingxi,Jindong,Yanling,Taining and Taigong were studied,and the environmental factors affecting photosynthesis of them were explored.The correlation analysis was made with increments and functional traits the provenances of provenances and functional traits.And provide reference for the selection of fine provenances and the improvement of plant productivity.The main findings are as follows:（1）The diurnal variation of provenances in the Meixi and Jindong species was bimodal,the peak appears at 10:00 and 14:00,with the maximum net photosynthetic rate at 10:00 am,Mingxi 10.31 μmol·m-2.s-1,Jindong 10.96 μmol·m^-2·s^-1.The daily variation of Pn in three provenances of Yanling,Taining and Taigong is single peak.The correlation analysis showed that Pn was positively correlated with photosynthetically active radiation in a certain range and positively correlated with leaf temperature（P>0.05）.The daily average net photosynthetic rate of the various sources showed a single peak type,and the peak values were in September.The Pn values of the Mingxi and Jindong provenances in July to August were significantly higher than those in the others.The diurnal variation of transpiration rate of Mingxi and Jindong provenances was bimodal,and the transpiration rate was significantly reduced at 12:00,which was beneficial to the preservation of water at high temperature.Yanling,Taining and arch were single peak type,Most of the peak values of transpiration occurred at 14:00 pm;the average monthly variation of transpiration rate decreased from July to November month by month.The mean diurnal variation of stomatal conductance and intercellular CO₂ concentration showed a large difference with the change of light intensity and ambient temperature,and the high temperature time was maintained in a relatively stable state.The monthly variation trend of stomatal conductance and transpiration rate did not show a positive correlation The main influencing factors of transpiration rate are not only the stomatal conductance,but also the ambient temperature and humidity are the main influencing factors affecting the transpiration rate.（2）Response curve analysis:the maximum net photosynthetic rate Pnmax showed Jindong and Mingxi larger,respectively 11.62 μmol·m^-2·s^-1 and 10.73μmol·m^-2·s^-1.The results of apparent quantum efficiency（AQY）showed that Yanling and Mingxi were larger.Jindong got a great adaptability to the strong light,and the provenances of the Mingxi provenance could reach the saturated net photosynthetic rate under the weak light intensity.Under the saturated light intensity and control environment CO₂ concentration,Taigong’s maximum photosynthetic rate of the highest proven photosynthetic capacity can reach 24.55 μmol·m^-2·s^-1.（3）PS Ⅱ photochemical quantum efficiency Fv/Fm average,the maximum value of Mingxi 0.81,the minimum Yanling 0.75.Mingxi,Jindong provenances had strong photosynthesis and plant growth were better than the others in July to September period.The results showed that with the increase of light intensity,the regulated dissipation Y（NPQ）of Mingxi and Jindong provenances were higher than that of other provenances.The ability to disperse excess light which indicated that the light dissipation was stronger than that of other provenances,that is,the ability of light protection was stronger than that of other provenances,and Yanling,Taining and Taigong were relying on increasing photosynthesis to dissipate excess light.（4）The ground diameter and height of the Mingxi were the highest,the diameter was 14.28 mm,the height of the tree was 90.97 cm,and the growth of Yanling was the smallest.The leaf area index（LAI）of Mingxi was the largest,2.13±0.24,and Yanling was the smallest,1.47±0.13.The maximum of chlorophyll was Yanling 2.54±0.54 mg/g and the lowest was Jingdong 2.05±0.50mg/g.There was a significant positive correlation between leaf area index LAI and ground diameter growth for Phoebe bournei（P<0.05）.The chlorophyll had no significant correlation with the growth of ground diameter.The net photosynthetic rate Pn was positively correlated with the growth of ground diameter（P<0.05）,and was correlated with the growth of height.the leaf area index LAI was significantly positively correlated with the growth of ground diameter（P<0.01）.There was no significant correlation between chlorophyll content and photosynthetic rate,ground diameter growth,height growth.