Photosynthetic And Transpiration Characteristics Of Eucommia Ulmoides

Photosynthesis is the fundamental way of the biological community to obtain energy, food and oxygen. Transpiration can not only enable the plant to absorb water, inorganic salts and other nutrients from the soil, but also maintain the cell and plant morphology, ensure the normal plant metabolism and regulate the plant body temperature. The experiment selects Eucommia ulmoides in Anhui Vocational&Technical College of Forestry as the tested material, and makes girdling and non girdling treatment respectively. For both of the two treatments, the author uses the LI-6400portable photosynthetic apparatus produced by the American LI-COR to measure the net photosynthetic rate, transpiration rate and its related physiological ecological factors in spring, summer and autumn. Then by using Excel and DPSv7.05edition, the net photosynthetic rate, transpiration rate and its influencing factors in different seasons are analyzed to draw out the following conclusion:1. Comparing the light response curves of two different treatments in different seasons, the author observes that in spring and summer, the girdled plant’s light compensation point (that are8.73μmolm^-2s^-1 and10.06μmolm^-2s^-1 in spring and summer respectively) is lower than the non-girdled plant’s(that are9.87μmolm^-2s-1and11.32μmolm^-2s^-1 in spring and summer respectively), and concludes that the girdled Eucommia ulmoides have higher ability of using weak light and a certain shade tolerance at the primary stage. The girdled plant’s light saturation point drops in the later stage, and the ability of synthesize photosynthetic products declines accordingly.2. Under natural conditions, the diurnal variation of net photosynthetic rate of Eucommia ulmoides in the two treatments shows a single-peak curve in spring and a double-peak curve in summer and autumn when the photosynthetic "lunch break" occurs. The variation rule of non-girdled Eucommia ulmoides’ photosynthetic rate is summer> spring> autumn, while the variation rule of girdled Eucommia ulmoides’ is spring>summer> autumn. Through path analysis and stepwise regression analysis, the author finds that the transpiration rate （Tr）, photosynthetic active radiation （PAR）, stomatal conductance （Cond）, and atmospheric temperature （Ta） are the main factors impacting the net photosynthetic rate in each season and the influencing factors exert different comprehensive effects in different seasons.3. In spring and autumn, the diurnal variation of transpiration rate for both girdling and non-girdling is a single-peak curve. The spring peaks for these two treatments are 2.897mmolm^-2s^-1 and3.312mmolm^-2 s^-1, and the autumn peaks are4.577mmolm^-2s^-1 and5.077mmolm^-2s^-1. In summer, it is a double-peak curve, with the summer average transpiration rate being the maximum. The transpiration rates for the two treatments of girdling and non-girdling are4.023mmolm^-2s^-1 and4.399mmolm^-2s^-1. In the spring, summer and autumn, transpiration rate of Eucommia ulmoides in the two treatments is in a positive relation with photosynthetic active radiation, air temperature, leaf temperature and stomatal conductance.4. In spring and autumn, the water use rate curve of the two treatments rises first and then falling, presenting a single peak curve. The water use rate curve in summer has no obvious rules. Overall, the light utilization efficiency of Eucommia ulmoides in different seasons changes as autumn> spring> summer.