THE CHEMICAL-COMPOSITION AND ANATOMICAL STRUCTURE OF LEAVES OF GRASS SPECIES DIFFERING IN RELATIVE GROWTH-RATE

To arrive at a better understanding of variation in specific leaf mass (SLM, leaf weight per unit leaf area), we investigated the chemical c omposition and anatomical structure of the leaves of 14 grass species varying in potential relative growth rate. Expressed on a dry weight b asis, the fast growing grass species with low SLM contained relatively more minerals and organic N-compounds, whereas slow-growing species w ith high SLM contained more (hemi)cellulose and lignin. However, when expressed per unit leaf area, organic N-compounds, (hemi)cellulose, to tal structural carbohydrates and organic acids increased with increasi ng SLM. For the 14 grasses, no trend with SLM was found for the leaf v olume per unit leaf area. Leaf density was positively correlated with SLM. Variation in density was not caused by variation in the proportio n of intercellular spaces. The proportion of the total volume occupied by mesophyll and veins did not differ either. A high SLM was caused, at least partly, by a high proportion of non-veinal sclerenchymatic ce lls per cross-section. The epidermal cell area was negatively correlat ed with SLM. We conclude that the differences in SLM and in the relati ve growth rate (RGR) between fast- and slow-growing grass species are based partly on variation in anatomical differentiation and partly on chemical differences within cell types.