Leaf Micro-Morphology in Two Ecotypes of Ashleaf Maple Adaptated to Different Survival Environments

Through one hundred years of adaptation in China, The Acer negundo Linn. (ashleaf maple), originally grown in North America, has developed morphological characteristics to cope the severe situation of its habitats. Two ecotypes from different vegetation belts in the ecotone of eastern Inner Mongolia Autonomous Region were detected. Although there was no macroscopic difference, contrasting micro-characteristics had been observed between the two sources. The leaves from more drought and warmer zone were found with more trichomes, more and smaller stomata, larger subsidiary cells, thicker palisade and flatter epidermal wax than those of leaves from the more humid and colder zone. Microstructures of the leaves from xeric sources can more effectively reduce leaf temperature and conserving water than those of mesic sources. Intra-species difference of the two ecotypes is the result of adaptation in different environments. This should be considered when characteristics of foliage are used as characters of species in taxonomy.