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

VII. PLANT TISSUES

Secretory (Excretory) Tissues

Individual Cells and groups of cells that isolate various chemical substances inside plant Organs or excrete them into the external environment constitute the plant's secretory system. This group of Tissues is highly diverse in its Structure and localization within plant organs, as well as in the Chemical Composition and functional purpose of the substances it produces.

The excretion of substances can be either passive or active. Waste products are eliminated passively along with dead cells and organs (such as the ROOT cap, epiblema, primary root cortex, and leaves)—these include Amino Acids, CARBOHYDRATES, Vitamins, Alkaloids, and Glycosides that influence the microflora surrounding the plant. Active excretion (carried out by specialized glandular cells) involves the release of Water, salts, sugars, mucilage, Enzymes, and Essential Oils by the plant.

Active secretion can occur through three pathways: extrusion (where Golgi vesicles filled with secretion approach the Plasmalemma, fuse with it, and release their contents, which are then forced outward through The Cell wall); active Transport of substances across the Cytoplasm via carrier Proteins; and filtration along a concentration gradient, facilitated by the increased permeability of the cytoplasmic membrane adjacent to the opposing cell wall.

Substances may be secreted externally by exocrine tissues or remain within plant organs, accumulating in Internal Secretory Tissues.