Peculiarities of Leaf Epiderma in Orchid Bletilla Striata under Ex Vitro Adaptation

Bletilla striata ((Thunberg) H. G. Reichenbach) a member of the Orchidaceae Juss. family is grown in greenhouse culture as an ornamental plant, and it is also valuable as a raw material for medicinal products. In this regard, the development of B. striata cultivation and propagation technologies is relevant. The aim of the work was to find out the peculiarities of the leaf stomata of B. striata plants based on the micromorphological structure of their surface during adaptation to the ex vitro conditions. The leaf epidermis structure was used as a biological marker of plant adaptation to assess the influence of in vitro and ex vitro growing conditions. Plants were propagated in vitro and transferred ex vitro to outdoors conditions (Kyiv, Ukraine). The structure of the leaf epidermis formed in vitro and ex vitro was studied using optical microscopy. We found that the leaves of B. striata are amphistomatic, but stomata rarely occur on the adaxial surface. The density of stomata on the abaxial surface is on average 70–85 pcs/mm2, their dimensions according to the guard cells are 36.16 × 29.61 μm, the stomatal pores are 22.83 × 10.89 μm. Morphometric parameters of the stomatal apparatus revealed statistically significant differences in the shape parameters of the stomata between plants cultivated in vitro and grown outdoors. A statistically significant increase of the stomata density on the abaxial leaf surfaces and a decrease in the number of epidermal cells on the adaxial surface of ex vitro grown plants were also established. So, the changes in growing conditions were reflected in the structure of the leaf epidermis. This indicated the success of plant adaptation and favorable cultivation conditions.