Study On Photosynthetic Ecophysiological Characteristics Of Wild Vetiver In Western Guangdong

Diurnal dynamic of photosynthesis and responses of the photosynthesis characteristics tothe enhanced photosynthetic radiation in different CO₂ concentrations of wild Vetiver grass inwestern Guangdong were studied in this experiment by Li-6400 Portable PhotosynthesisSystem. Results were indicated that:The diurnal curve of net photosynthetic rate of wild Vetiver grass was a single-peakedpattern in spring and summer, which was different from the two-humped curve in autumn.There was an obviously decrease at noon. Non-stomatal limitation, Carboxyl-efficiency wasthe main causes of the depression. Net photosynthetic rate (Pn), transpiration rate (Tr) andstomatal conductance (gs) were affected by various environmental factors. Variousenvironmental factors mutual restraint each other. The influence of environmental factor onthe Pn, Tr and gs was different. In this period, photosynthetic active radiation (PAR), whichwas significantly (P<0.01) correlative with Pn and Tr were (P<0.01), was the most intensiveeffect on the photosynthesis of Vetiver. Among Pn, Tr and gs, gs was one of the most obviouseco-physiological factors that were hardly affected by environmental factors. In badenvironment, the gs changes weavers leaves little opening for the physical activity to maintainsurvial;In a good environment, the gs increases with the increasing of PAR to enhance the Pn,and accelerat growth. The rainy season is the rapid growth period in Vetiver grass.Physiological factors of Vetiver leaves with the enhanced PAR were significantlycorrelative (P<0.01). Physiological factors in the case of double CO₂ concentration were of nosignificant differences. The light compensation point of Vertiver leaves was about 50μmol·m^-2·s^-1 and the light saturation point was more than 2600μmol·m^-2·s^-1 in experimentalconditions. Vetiver grass is a typical sun plant. gs of Vetiver leaves resulted in the changes ofTr in a certain range, and water vapour play an important role in limiting the rate oftranspiration. Water use efficiency of Vetiver decreased in response to the increasing of thewater vapour pressure.