Cells with similar functions aggregate into tissues, which are broadly categorized into three fundamental systems: dermal, ground, and vascular. The serves as the protective interface between the plant and its environment. In primary (non-woody) growth, it is represented by the epidermis, a single layer of tightly packed cells often covered by a waxy cuticle to prevent desiccation. Specialized epidermal cells include guard cells, which form stomata for gas exchange, and root hair cells, which vastly increase the surface area for water and mineral absorption. In secondary (woody) growth, the protective epidermis is replaced by the periderm (bark), composed of cork cells impregnated with suberin.
Beneath the dermis lies the , which fills the interior of the plant and performs metabolic support functions. It comprises three cell types: parenchyma, collenchyma, and sclerenchyma. Parenchyma cells are thin-walled, living, and versatile; they are the sites of photosynthesis (chlorenchyma), storage, and secretion. Collenchyma cells have unevenly thickened primary walls and provide flexible support in growing stems and leaves. Sclerenchyma cells, including fibers and sclereids, possess thick, lignified secondary walls and are dead at maturity, providing rigid, durable structural support. plant anatomy
The is the primary organ of photosynthesis. Its flattened blade optimizes surface area for light absorption. The leaf's anatomy is a masterpiece of physiological engineering: an upper and lower epidermis (with cuticle and stomata primarily on the lower surface) sandwiching the mesophyll, a photosynthetic ground tissue differentiated into palisade and spongy parenchyma. A network of veins (vascular bundles) provides both hydration and a means to export sugars. Cells with similar functions aggregate into tissues, which