All the aerial parts of the plantbody without exception transpire; but their efficiency will vary. However the chief transpiring organ is leaf, ever though stomata etc., are the chief places where water loss occurs. Similarly in the stems transpiration takes place through lenticels. Based on these, transpiration is divided into three categories viz., Cuticular transpiration. Lenticular transpiration and Stomatal transpiration.
The surface of leaves and very often stems are covered by a waxy coating called cuticle which is actually a layer that is supposed to prevent loss of water. That is why in plants exposed to sunlight, the deposition of cuticle is heavy, while in plants of the shaded area it is thin: However, water still evaporates through the cuticle and it is known as cuticular transpiration.
Cuticular water loss however is not much when compared with the overall rate of transpiration. In barely it amounts to about 3-10% of total transpiration. When compared with the overall rate of transpiration.
In woody plants, after the secondary growth, the epidermis is replaced by periderm whose outer layers are composed of dead cells (cork). In order to provide aeration to the inner living tissues, at certain places the cork tissue opens out and forms small slits called lenticels. Transpiration taking place through these lenticles is called lenticular transpiration. In comparison with other types of transpiration, this is very insignificant as it amounts to only 0.1% of the total.
Stomata are small openings present on lower, upper or both the surfaces of the leaf. By and large most of the water loss in Plants (90-95%) is stomatal transpiration. Transpiration through stomata is known to occur in two stages. First, water evaporates from the moist cell walls of mesophyll cells into the intercellular spaces and secondly from the intercellular spaces into the exterior through the stomata. Various aspects of stomatal distribution, morphology etc will affect the rate of transpiration.