Plant “filler” tissue also runs photosynthesis and storage
Ground tissue is everything in a plant that is neither dermal skin nor vascular plumbing—one of three main tissue systems. Its living parenchyma often looks like soft filler, yet it stores food, repairs wounds, and builds the photosynthetic mesophyll inside leaves.
Plants run on three tissue systems: a protective skin that limits water loss, vascular tissue that moves water and molecules between organs, and ground tissue, which makes up most of the body in between. Its jobs range from strength and support to metabolism, storage and photosynthesis. Botanists split it by cell wall into parenchyma, collenchyma and sclerenchyma.
Parenchyma cells are large, thin-walled and usually alive at maturity, with big central vacuoles that hold water, ions and waste. They fill the cortex and pith of stems, the cortex of roots, fruit pulp and seed endosperm, and they can divide again when stimulated, which lets them repair wounds. In leaves they form the palisade and spongy mesophyll just below the epidermis; these chloroplast-rich chlorenchyma cells make food and manage gas exchange. Spongy cells can be loose spheres or star-shaped cells joined arm to arm, as in the red kidney bean. Parenchyma also stores starch, protein and oil in potatoes, cereal grains and peanut cotyledons, lines resin ducts, and in water plants becomes aerenchyma, whose air cavities help the plant float.
Collenchyma is living tissue with unevenly thickened walls of cellulose and pectin that props up growing shoots and leaves; the tough strands in celery stalks are an example. Its walls respond to stress: in plants shaken to mimic wind they grew 40 to 100 percent thicker. The name was coined by Link in 1837 for a sticky coating on orchid pollen, and Schleiden mocked the choice two years later.
Sclerenchyma supplies stiffness through fibres and sclereids whose walls contain lignin, and the cells often die once mature. In apple stalks, experiments showed fibres keep the stalk stiff and strong under tension, while sclereids resist bending and damp wind-driven swaying, so the stalk carries swelling fruit without snapping. The same fibres give us flax, hemp, jute and ramie.
Source: Ground tissue
