Abstract: This study was conducted at research and experimental areas of Bahri Dagdas International Agricultural Research Institute. For the experiment, 8 forage plants were used (all plants with a C3 type of photosynthesis and they were grown under some conditions). The experiment was laid out Randomized Complete Block design with four replications. We analyze importance of the growth parameters Relative Growth Rate (RGR), Net Assimilation Rate (NAR), Leaf Area Rate (LAR), Leaf Weight Rate (LWR) and Root Weight Rate (RWR). A large variation in physiological characters between species was observed. Slow-growing species had a constant RGR, NAR and LAR in early stages. Genotypic variation in physiological characters may be an explanation for the observed.