Comparative leaf and root anatomy of two Dendrobium species (Orchidaceae) from different habitat in relation to their potential adaptation to drought.

Dendrobium capraand Dendrobium arcuatumare closely related in phylogeny, but they have very contrasting vegetative morphology and habitats. D. caprais known as a species that is well-adapted to dry lowland teak forest habitat in East Java, where most trees drop their leaves in summer, while D. arcuatumhas adapted to mid or high land moist forest at elevation up to 800 m dpl. In order to investigate their potential adaptation to drought stress in the climate change era, we have compared and analyzed the leaf and root anatomical characteristics of both species. Transversal sections were made using hand mini microtome, dehydrated in graded alcohol series and stained with safranin 1 % and fastgreen 1 %. Leaf scraping technique has been used to prepare paradermal sections, and then dehydrated in graded alcohol series and stained with safranin 1 %. Quantitative anatomical characteristics between D. capra and D. Arcuatum have been compared using a t-test. The result showed that there were significant differences on anatomical characters between both species. Compared to D. arcuatum, D. caprashows more developed anatomical features for adapting to drought and dry condition. These anatomical features were a thicker cuticle, thicker epidermis, presence of hypodermis, thicker mesophyll, broader primary vascular bundle, well developed xylem’s sclerenchyma, lower stomatal density, thicker and high proportion of velamen.