LEAF MORPHOLOGY AND ANATOMY IN TWO CONTRASTING ENVIRONMENTS FOR C3 AND C4 GRASSES OF DIFFERENT INVASION POTENTIAL

Leaf morphology, coarse structure and anatomy were compared for two invasive C4, two non-invasive C4, and two expanding native C3 grass species grown in their original, high-light semiarid temperate habitat, and in a growth room under variable moderate light and favourable supply of water and nutrients. It was hypothesised that (H1) among C4 grasses leaf structural response will be greater for invasive than for non-invasive species, and (H2) for plants of high spreading capacity C4 species will be less responsive than C3 spe-cies. Leaf mass per area was lower in the growth room than in the field by 43.4–54 % and 5.7–21.2 % for grasses of high spreading capacity and for non-invasive C4 species, respec-tively. Little or no response was observed in the proportion of epidermis and mesophyll, but the proportional area of veins plus sclerenchyma was greater in the field than in the growth room for the invasive C4 Sorghum halepense, and the spreading C3 Bromus inermis and Calamagrostis epigeios, while it did not differ for the two non-invasive C4 grasses and the invasive C4 Cynodon dactylon. Leaf intervenial distance was invariant for C4 grasses (except for the non-invasive Chrysopogon gryllus) and the C3 C. epigeios, but changed by 25.1 % for the C3 B. inermis. These results suggest that among C4 grasses invasive species exceed non-inva-sive ones in the plasticity of leaf coarse structure, but not that of leaf morphology and anat-omy. However, leaf structure was not less plastic in invasive C4 than in expanding C3 grasses except for intervenial distance