BOTANY WITH BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

VII. PLANT TISSUES

Dermal Tissues

Cork

The secondary dermal tissue, cork (phellem), develops from a secondary lateral meristem known as the cork cambium (phellogen). Cork is primarily a protective tissue found on woody stems, as well as in the ROOT conduction zone of Secondary Structure in dicotyledonous and gymnosperm plants.

Unlike the epidermis, cork is always multilayered. Its Cells are dead, tightly packed together, and their inner Cell walls are impregnated with suberin and wax. The cells are arranged in regular radial and tangential rows.

The cork cambium consists of a single layer of dividing cells that originates from the epidermis, subepidermal layer, or deeper cortical layers. Phellogen cells divide by tangential walls into two cells. Over time, the outer cell becomes suberized, dies, and transforms into cork. The cells deposited by the phellogen inward remain living and form an assimilatory or storage tissue known as phelloderm.

The activity of the cork cambium results in The formation of a complex tissue called periderm. It is composed of cork (phellem), cork cambium (phellogen), and phelloderm. The protective function is performed by the cork, the thickness of which can reach 15-20 cm in the cork oak. It is used for sealing bottles and containers. Various substances, such as Tannins, resins (e.g., betulin in birch cork), and salt crystals, may be deposited within cork cells.

The Functions of gas exchange and Transpiration in cork are carried out by lenticels—Pores in the cork layer filled with rounded complementary (filling) cells and well-developed intercellular spaces. Complementary cells form beneath the epidermal Stomata As a result of the intensive division of phellogen cells originating from the primary cortex. The walls of these complementary cells quickly suberize, and their protoplasts die; the dead cells are then pushed outward by newly formed cells. For the winter period, lenticels are sealed by a special cork layer, which ruptures in the spring under the pressure of new complementary cells produced by the phellogen.