Photosynthesislight response characteristics of five tropical forage cultivars

Photosynthetic rate (Pn),transpiration rate(Tr), stomatal conductance(Gs) and water use efficiency(WUE) of 5 tropical forage cultivars were measured by using LI6400 portable photosynthesis system in Guilin. The results were as follows:1) The Pn, Tr and Gs of the five cultivars were increased with the enhancement of the PAR, and the WUE of the 5 cultivars were firstly increased and then decreased as the PAR was gradually enhanced. Guimu No.1 (Pennisetum purpureum cv.Mott) (P. americanum P. purureum) reached the maximum WUE at 1 500 mol/（m2s） while the others at 600 mol/（m2s）. 2) The maximum photosynthetic rate (Amax) and the light saturation point (LSP) of 3 hybrid cultivars were significantly higher than that of the two Paspalum cultivars, and it was same for net Pn and Tr. It could be concluded that the tested 5 cultivars were well adapted to the local environment.