High Temperature Index Of Quercus Variabilis Leaves And Its Mechanism Study Of Photosynthesis Response To High Temperature Stress

Quercus variabilis, the genera of Fagaceae oak(Quercus), is one of the most important afforestation tree species in China. The temperature is the main environmental factors affecting plant growth and development. As the global temperature rising, the influence of heat stress on plant has become increasingly significant. using chlorophyll fluorescence instrument Mini-PAM, the paper measured the Quercus variabilis leaves maximal and actual chlorophyll fluorescence quantum yield of photo system II、 maximum quantum yields 、Photochemical quenching and Non-photochemical quenching, in order to study the temperature of photo system II inactivation of Quercus variabilis leaves on high temperature stress in different seasons. The results of the study are as follows:(1)Chlorophyll fluorescence parameters is important means to study the impact of high temperature stress, and heat stress significantly affect quercus variabilis photosynthesis. because of chlorophyll, photosynthesis on the chlorophyll fluorescence have sensitive reaction under high temperature stress, fluorescence and photosynthesis parameters become the means of high temperature stress research.Especially the high temperature stress under drought condition.(2) both Fv/Fm and Y(II) decreased with increase of heat stress temperature and increase of high temperature treating time; and the process of that ΔF/Fm’ decreased could be simulated with Logistic Curves; Y(II) simulation curve showed decreased with increasing temperature, and reduce speed slow at different seasons, then speed up early, to a certain temperature and slow.(3) Photochemical quenching under high temperature stress q P is on the decline, the photochemical quenching q N and NPQ is on the rise, but more than 45 ℃, these parameters are declining, this may be because the temperature is too high, cork oak leaf inactivation. Trials, photochemical quenching q P to high temperature stress with the increase of time, temperature falling rather than photochemical quenching parameters q N and NPQ under 35 to 45 ℃, as the temperature rises; Up 45 ℃, and decreased with the increase of temperature and these parameters tend to zero, this is likely to be plants at high temperature, plant leaves has lost its vitality, life in a state of death, so I showed a trend of decrease.(4) the damage to the photosynthetic institutions were significantly positive related to the intensity of high temperature stress. Green fluorescence in the parameters, the PS(II) the actual quantum yield Y(Ⅱ), maximum quantum yield Fv/Fm in the role of 41 and 35 ℃ ℃, the slow decline trend, and under the effect of 47 ℃, the decreasing speed significantly greater than 35 ℃and 41 ℃, this fully shows that with the increase of high temperature stress, the chlorophyll fluorescence parameters also present obvious positive correlation tendency.(5) high temperature stress clearly influenced photosynthesis of Quercus Variabilis Leaves; the temperature of that Y(II) decreased 50%(T50) was limit temperature index of photo system II inactivation, and could be taken as characteristic point of high temperature stress; the high temperature tress index of Quercus variabilis was determined as 40 ℃in different sesons. This paper is useful for analyzing the intensity and lasting time of high temperature stress of Quercus variabilis leaves, and providing methods of determining agricultural meteorology index of other plants.