Leaf morphology and anatomy in two contrasting environments for C₃and C₄grasses of different invasion potential

Abstract

Leaf morphology, coarse structure and anatomy were compared for two invasive C 4 , two non-invasive C 4 , and two expanding native C 3 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 (H 1 ) among C 4 grasses leaf structural response will be greater for invasive than for non-invasive species, and (H 2 ) for plants of high spreading capacity C 4 species will be less responsive than C 3 species. 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 C 4 species, respectively. 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 C 4 Sorghum halepense, and the spreading C 3 Bromus inermis and Calamagrostis epigeios, while it did not differ for the two non-invasive C 4 grasses and the invasive C 4 Cynodon dactylon. Leaf intervenial distance was invariant for C 4 grasses (except for the non-invasive Chrysopogon gryllus) and the C 3 C. epigeios, but changed by 25.1% for the C 3 B. inermis. These results suggest that among C 4 grasses invasive species exceed non-invasive ones in the plasticity of leaf coarse structure, but not that of leaf morphology and anatomy. However, leaf structure was not less plastic in invasive C 4 than in expanding C 3 grasses except for intervenial distance.