Abstract: We measured the seasonal changes of photosynthetic and transpiration characters of Puc-cinellia tenuiflora, both natural growth and one to three-year planted P. tenuiflora on alkalized Songnen grassland. The curve of seasonal changes of photosynthetic rate of P. tenuiflora is one-peaked. The pohotosynthetic rate at heading stage is the maximum. The transpiration rate of P. tenuiflora decreased with the progress of fertility period, but the curve of transpiration rate of P. tenuiflora population per unit grassland area is one-peaked. The maximum values of one-year, two-year and three-year P. tenuiflora are in florescence, the maximum value of natural growth P. tenuiflora is at heading stage. The seasonal changes of water use efficiency of P. tenuiflora is one-peaked curve, the maximum values are at heading stage.

Key words: Puccinellia tenuiflora, Grown years, Photosynthetic and transpiration characters, Seasonal changes