Leaf epidermis morphological differentiation between Tamarix africana Poir. and Tamarix gallica L. (Tamaricaceae) with ecological remarks

Tamarix L. is a taxonomically difficult genus since species identification is based on hard to see floral characters, which can be observed only during the very short spring bloom. In order to find new and always accessible tools for species identification, leaf epidermis characters were analyzed. During spring 2008, flowers and green twigs were collected in four natural tamarisk populations of Southern Italy. The flowers were used for species identification, while leaf imprints were examined for stomata and salt glands traits. Tamarix africana Poir. and Tamarix gallica L. were the most widespread species in the studied populations. T. africana showed longer guard cells, and lower stomatal and salt gland density compared to T. gallica. These differences were more significant than intraspecific ones. Moreover, the interspecific leaf micromorphological differentiation was found to be consistent across the populations. These results suggest the efficacy of the use of leaf morphological traits as a new tool for identification of the two main South European Tamarix species. Ecological implications of leaf micromorphology have also been discussed and the distance from the river had the major effect on plant phenotypic plasticity.