Lotus leaf does not get wet due to our layers of cells in the epidermal layer of leaves. They contain cellulose, which get converted to cutin by the process of cutinization and form an impermeable membrane on the cell wall known as cuticle.
Cuticle is a layer of wax-like substances which are simple lipids containing one molecule of fatty acids esterifies with one molecule of long-chain alcohols instead of glycerol. A molecule of wax consists of odd number of carbon atoms ranging from C25 to C35. These are highly insoluble in water and chemically inert because these do not have double bonds in their hydrocarbon chains. Hence waxes form a protective covering. The formation of wax will be more in lotus leaf and hence being impermeable, it won’t allow the leaf to get wet.
The epidermal cells of the aerial parts of the plant very often deposited with a layer of fatty material called cutin on their exposed wall surface. It is actually made up of two layers namely inner cutinized layer, a layer of cellulose encrusted with cutin and outer cuticularised layer, a layer consisting of cutin ad crusted on the cell wall. When the cuticle is of considerable thickness, its chemical nature often varies in different plants, at least proportionally and may include cutin and wax. Since this layer is resistant to decay, and to microbes, in all the land plants it may have protective function and also prevent surface evaporation. In the case of aquatic plants like lotus, in the outer surface of the upper epidermis of floating leaves there is a conspicuous deposit of wax.
It is found as a thick layer on the surface of the cuticle. It is this wax that gives the bloom to these glaucous leaves and also resists wetting. So when water is spilled over this surface it will roll down and will not form a film over the leaf surface. If this unwetting property is not found, this film of water when happens to cover the leaf surface will close all the stomata, which will affect the gaseous exchange in this floating leafed plant, which has stomata only on the upper surface of the leaves. It is one kind of Hydrophytic adaption.
The unwettability prevents the retention of water on the leaf surface and thereby reduce the water weight which otherwise cause the submerging of the leaf instead of floating.