Microscopical investigation of the leaf architecture in greenhouse-cultivated Ficus (Moraceae)

Abstract

A high diversity of leaf structural traits in the genus Ficus is often argued with regard to its taxonomic implications. Greenhouse-cultivated plants of Ficus are in special need of identification based on the vegetative organs since they rarely produce flowers. We studied the leaf anatomy in 33 Ficus species of six subgenera and 12 sections grown under greenhouse conditions, using light microscopy and SEM. A great between-species variation of the leaf traits was revealed as opposed to their stability within each species. Qualitative leaf traits were found useful for distinguishing species and some higher taxa of Ficus. Namely, the features of epidermis, mesophyll, and vein anatomy were characteristic at the level of sections and subsections. Quantitative parameters of stomata and glandular trichomes, as well as the thickness of lamina and its inner layers, separated well the species and subgenera of Ficus. The classification of the species based on the quantitative leaf parameters revealed several groups of related species, which are placed close in the existing system of the genus. New data on Ficus leaf architecture were obtained, including the presence of branched trichomes, the features of vein anatomy, and the diagnostic value of laminar hydathodes. The study shows that many characters of Ficus leaf architecture are of taxonomic value and provide support to the existing classification of the genus. The leaf anatomical and surface features analyzed may facilitate a proper identification of the species and higher taxa of Ficus if considered together in a complex.