The role of leaf epidermis in providing buoyancy to Hydrocharis morsus-ranae (Hydrocharitaceae)

The leaf micromorphology and ultrastructure of Hydrocharis morsus-ranae leaves were examined using light microscopy, scanning electron microscopy, and laser confocal microscopy. We used also the Pascal program (LSM 5) for detected of fluorescence intensity chlorophylls and intensity of fluorescence intensity of monolignols, and also for to calculate the area of the periclinal walls of the epidermis as well as the volume of air occupied by the deepening cushions formed by the main cells of the lower epidermis. The study found that buoyancy affects the micromorphology of the upper and lower epidermis, the formation of aerenchyma between the mesophyll and epidermis, and the presence of air space under the cells of the lower epidermis. Differences in the ultrastructure of the upper and lower epidermis walls and the presence of silicon only on the upper epidermis suggest different functions for these tissues. The content of polysaccharides and monolignols in the leaves depends on the type of epidermal cells and the walls that form air cushions under the leaf blade. The study discusses the role of the air cushion and the involvement of monolignols and callose in plant adaptation to buoyancy. The article also explores the functional role of anticlinal wall projections on the leaf surfaces, which help the leaves float and stay on the water.