Characteristics Of Photosynthetic Ecophysiology Of Four Medical Plants

Eriobotrya japonica (Thunb.) Lindl,Magnolia officinalis Rehd. et Wils,Eucommia ulmoides Oliv and Rosa rugosa Thunb are four medical plants with high values of exploitation and utilization. To confirm the growth status of E. japonica (Thunb.) Lindl and M. officinalis Rehd. et Wils which were introduced into the local place and compare to E. ulmoides Oliv and R. rugosa Thunb, Using LI-6400 portable photosynthesis system, the net photosynthetic rate and transpiration rate of these four plant were measured in different periods of the growing season. The related mathematical models about the response characteristics of photosynthesis to the light and CO2 were established. The corresponding ecophysiological factors responsible for photosynthesis and transpiration of the four plant species were analyzed via Stepwise Multi-variable regression methods. The results are as follows:1 The diurnal changes of photosynthetic active radiance were single peak type in sunny days of their vegetal environment and more change scope occurred in their prosperous growth period, and less change in the last growth period. The diurnal changes of air temperature showed a gentle single peak curve. The diurnal changes of relative humidity generally showed a pattern of upside-down parabolas. Daily changes of carbon dioxide concentration were remarkable during the summer, but much less so in autumn.2 The seasonal changes of air temperature showed a pattern of single peak and got the lowest point at the end of the growing season. Carbon dioxide concentration varied remarkably in different seasons and had the lowest value in the midseason.3 The diurnal courses of photosynthesis were main double peaked curves and there were remarkable midday depression. But single curves were also found in the end of the growing season. The seasonal variation of photosynthesis of four plants showed consistent trends, and the two peaks appeared in July and August respectively. The photosynthetic rate in the early growing period of these plants was higher than that in the late period. Photosynthetic rate of these four plants was related to the photosynthetic active radiance, stomatal conductivity and ambient CO2 concentration. The effects of ecological factors, such as air temperature, air humidity, vapor wane and so on on photosynthesis were depend on different plant species and different periods. The annual average net photosynthetic rate of E.japonica (Thunb.) Lindl was higher than E. ulmoides Oliv, then R. rugosa Thunb, and M. officinalis Rehd. et Wils was lowest.4 The stomatal conductivity and vapor wane were the main factors that influenced the transpiration rate, besides, the effects of the photosynthetic active radiance, air temperature and relative humidity on transpiration rate were depend on different plant species and different periods. The annual average transpiration rate of E. japonica (Thunb.) Lindl was higher than E.ulmoides Oliv, then M. officinalis Rehd. et Wils, and R. rugosa Thunb was lowest. But water use efficiency of R. rugosa Thunb was highest, then M. officinalis Rehd. et Wils, and E. japonica (Thunb.) Lindl was lowest. This indicated that E. japonica (Thunb.) Lindl is a type of high transpiration and low water use efficiency plant.5 According to parameters of the established response characteristic curve of photosynthesis to the light, we can know that the photosynthesis capability of four plants was: E. japonica (Thunb.) Lindl>M. officinalis Rehd. et Wils>E. ulmoides Oliv>R. rugosa Thunb. According to parameters of the CO2 response characteristic curves to the double increasing CO2 concentration and common CO2 concentration, we can know that the photosynthetic rate of four plants all remarkably increased, and light saturation point and apparent quantum yield also increased. But light compensation point,dark respiration rate decreased.