Photosynthesis, transpiration, and water use efficiency of two Puccinelliaspecies on the Songnen grassland, northeastern China

The intra- and inter-specific variations in net photosynthetic (P-N) and tr anspiration (E) rates and water use efficiency (WUE) of Puccinellia tenuifl ora and Puccinellia chinampoensis leaves were compared. The two species exp erienced a similar habitat, but differed in leaf area, leaf colour, and nit rogen contents. Leaf P-N and E for both reproductive and vegetative shoots of the two species declined with leaf age. P-N for reproductive shoots was less than for vegetative shoots, but their E was greater than that of veget ative shoots in the dry season. The average P-N and E for reproductive shoo ts of P. tenuiflora were lower than those of P chinampoensis, but higher fo r vegetative shoots.