Botany - B.E. Yakubenko 2017

Part One. Plant Anatomy and Morphology
Chapter II. Histology
2.7. Secretory Tissues

The elimination of Water and various substances that in some cases solidify (or even crystallize) is carried out by excretory Tissues. Secretory tissues are divided into external and Internal secretory tissues. The former include hydathodes, glandular hairs, osphores, and nectaries. To rid itself of excess water, a plant releases it not only in a gaseous state but also as liquid droplets. This function is performed by hydathodes (water Stomata) located at the tips of leaves. The phenomenon of a plant's leaves excreting water droplets under certain meteorological conditions is called guttation.

Glandular hairs consist of one or many Cells that accumulate and secrete various substances, mostly Essential Oils used in perfumery. In carnivorous plants (such as sundew), glandular hairs contain digestive Enzymes.

Nectaries, appearing as glands, plates, or discs, are found in flowers and secrete nectar.

Osphores are specialized Organs that secrete essential oils from the Cells of the perianth epidermis to attract pollinating insects.

Internal secretory tissues accumulate metabolic products inside plant organs within specialized reservoirs. These include cavities and laticifers. Cavities are referred to as schizogenic if they form As a result of cells moving apart; resin accumulates within them in the bark and wood of most conifers, as well as secretions in the rhizomes of Apiaceae and the Vegetative organs of many Representatives of the Hypericaceae and Myrtaceae families. Substances accumulated in schizogenic cavities are used in the chemical and pharmaceutical industries.

Other cavities are called lysogenic; they form as a result of the accumulation of excretory substances in a Cell or groups of cells followed by the dissolution of their cell walls. Such cavities are found in the pericarp and leaves of mandarins, oranges, and other citrus fruits.

Laticifers are formed by living cells and accumulate milky sap or latex. Structurally, laticifers are classified as articulate and non-articulate. Articulate (or compound) laticifers consist of A large number of cells and form a branched system. They permeate all plant organs, and in the Pará rubber tree (Hevea brasiliensis), they are mostly concentrated in the bark. Hevea latex was once used to obtain natural rubber. Articulate laticifers are characteristic of poppies, dandelions, and lettuces.

Non-articulate (or simple) laticifers originate as early as the Embryonic Stage and grow along with the plant. They are found in castor bean and spurges.