Study On Photosynthesis,Carbon Sequestration And Other Ecological Characteristics Of Six Endangered Magnoliaceae Species Plants

In this thesis,we selected grafted plants of Michelia shiluensis,Magnolia sirindhorniae,Michelia ingrata,Manglietia aromatic,Manglietia lucida,Manglietia kaifui as our targets to do measuring and research about their light response characteristic,cholrophyll,diurnal change characteritic of gas-exchange and the factors that make influence,as well as estimating their carbon sequestration capacity,cooling and humidification capaciry on the level of unit leaf area.The achievement of our research will provide theoretical basis to the endangeredMagnoliaceae's conservation and cultivation management.Result of research is as follow:?1?The diumal variation curves of six species that participated in the research all displayed a bimodal curve or a unimodal curve.They all displayed a bimodal curve with an obvious midday depression on July.The maximum of the six species'net photosynthetic rate apear between 6:00 and 8:00.The diumal variation curves of net photosynthetic rate of six species that participated in the research displayed a unimodal curve on October with a maximun of net photosynthetic rate appearing between 8:00 and 12:00.The diumal variation curves of net photosynthetic displayed a bimodal curve or a unimodal curveon January and April.The daily net photosynthetic rate mean of M.sirindhorniae on July was highest compared with other threemonths while the other were highest on October.Three species of Michelia's daily net photosynthetic rate mean in January are lowest compared with other threemonths,and three species of Manglietia's were lowest on July.Correlation analysis between net photosynthetic rate and environment factors that make an impact to photosynthesis indicated that net photosynthetic rate of three species of Michelia exhibited very significant positive correlation with atmosphere temperature and photosynthetically active radiation?P<0.01?while net photosynthetic rate of M.lucida and M.kaifui exhibited very significant positive correlation with photosynthetically active radiation?P<0.05?.Atmosphere temperature made a greater incidence to Michelia's photosynthesis than Manglietea's.M.sirindhorniae(6.69?mol·m^-2·s^-1)has the highest mean diurnal variation of net photosynthetic rate in the three Michelia species and M.ingrate(4.54?mol·m^-2·s^-1)has the lowest one;that of was:M.kaifui(5.88?mol·m^-2·s^-1)has the highest mean diurnal variation of net photosynthetic rate in the three Manglietiaspecies and M.lucida(4.10?mol·m^-2·s^-1)has the lowest one.According to the synthetic analysis,photosynthetic capacity of Michelia was better than Manglielia.?2?Transpiration rate'sdiurnal variation of six species was similar to the diurnal variation of their net photosynthetic rate,which displayed a bimodal curve or a unimodal curve.The maximum of the six species'transpiration rate apear between10:00 and 12:00.The transpiration rate of six species was significantly higher on July rather than other months,which indicated atmosphere temperature was one of the most significant factors that makes an impact to transpiration rate.The mean diurnal variation of transpiration rate of Michelia was:M.sirindhorniae(3.02 mmol·m^-2·s^-1)has the highest mean diurnal variation of transpiration rate in the three Michelia species and M.ingrate(1.61 mmol·m^-2·s^-1)has the lowest one;M.kaifui(2.30mmol·m^-2·s^-1)has the highest mean diurnal variation of transpiration rate in the three Michelia species and M.lucida(1.59 mmol·m^-2·s^-1)has the lowest one.The synthetical transpiration rate of Michelia was higher than Manglielia.?3?Light response curves of six species of Magnoliaceae display similar variation,photoinhibition phenomenon after reaching the maximum of net photosynthetic rate in light saturation was not obvious.Four models were used to simulate the light response models of six species of Magnoliaceae,and the result showed that modified rectangular hyperbola model fit light response of photosynthesis best compared with the other three models.M.kaifui has the maximum light saturation point of 2261?mol·m^-2·s^-1 compared with the other species,and it has the best ability of utilizing high light.M.ingrata has the minimum light saturation point of 992?mol·m^-2·s^-1which has the worst ability of utilizing high light.M.kaifui has the maximum light compensation point of 13.34 and maxmumdark respiration rate of0.88,and it had the worst ability of utilizing weak light.M.aromatic has the minimum light compensation point of 6.21?mol·m^-2·s^-1 and the minimum dark respiration rate of 0.15?molCO₂·m^-2·s^-1,so it has the best abilitiy of utilizing weak light.The order of the net photosynthetic ratemaximum of six species in light saturation from large to smallwas:M.kaifui(10.34?mol·m^-2·s^-1),M.shiluensis(8.03?mol·m^-2·s^-1),M.lucida(6.55?mol·m^-2·s^-1),M.aromatic(6.30?mol·m^-2·s^-1),M.sirindhorniae(5.09?mol·m^-2·s^-1)and M.ingrata(2.76?mol·m^-2·s^-1).We evaluate the ability of light utilizing through principal component analysis,and the order of the ability of light utilizing from large to small was:M.aromati,M.shiluensis,M.lucida,M.kaifui,M.sirindhorniae and M.ingrata.?4?The order of annual mean leaf unit area net sequestered carbon from large to small was:M.sirindhorniae(11.20 g·m^-2·d^-1),M.shiluensis(10.07 g·m^-2·d^-1),M.kaifui(9.72g·m^-2·d^-1),M.aromatic(7.50 g·m^-2·d^-1),M.ingrata(7.44 g·m^-2·d^-1),M.lucida(6.66g·m^-2·d^-1).?5?M.aromatic had the best cooling and humidification capacity on October,and that of the other species were on July.The seasonal variation of six species'cooling and humidification capacity on January,April and October didn't show an obvious rule.The order of Michelia'cooling and humidification capacity from large to small was:M.sirindhorniae,M.shiluensisand M.ingrate;that of Manglietia was:M.kaifui,M.aromatic and M.lucida.Michelia had a generally better cooling and humidification capacity rather than Manglielia.