Comparative Studies on the Biology of Upland Grasses: I. Rate of Dry Matter Production and its Control in Four Grass Species

The growth of four grass species, Lolium perenne S.24, Agrostis tenuis, Sieglingia decumbens and Nardus stricta is described and compared. The species were grown as spaced plants under both fertile and infertile soil conditions. Their growth was studied using the technique of growth analysis. The results showed that there were large differences in total dry matter production, relative growth rates, leaf area ratios, net assimilation rates and shoot: root ratios. The species fall into two groups with Agrostis and Lolium in one and Nardus and Sieglingia in the other. The species in the first group produce more dry matter and have higher relative growth rates than those in the second. The growth rates of Lolium and Agrostis are reduced on the infertile soil, but there is no such reduction in Sieglingia and Nardus. It is concluded that the differences found in the relative growth rates are brought about mainly in response to differences in leaf area ratios rather than net assimilation rates. Of the four species studied, the ones which show the lowest rates of dry matter production are normally associated with the poorest soils. This evidence lends support to the view that slow growth rates may be of adaptive significance to plants indigenous to soils of low fertility.