A plant cell is surrounded by a membrane and wall, which protects the cell, while allowing chemicals to pass. The nucleus is located in the middle of the cell and contains strands of DNA that control cell metabolism and synthesizes protein. Organelles are small structures in the middle of the cell that perform other necessary functions, such as produce energy, help digest nutrients and other materials, and transport chemicals. Plant cells develop into three types of plant tissue.
Dermal tissue protects soft plant parts and controls the plant's interaction with its environment. The epidermis covers young parts of a plant and secretes a waxy cuticle to prevent water loss. Epidermal hairs also slow water loss by deflecting air from the surface of the plant. Root hairs in the epidermis of the roots increase the surface area of the roots and help the plant gather more water. Glandular hairs in the epidermis store chemicals that are toxic to insects.
Ground tissue consists of three types of cells--parenchyma, collenchyma and sclerenchyma. Parenchyma cells are generalized cells that make up the bulk of ground tissue. They absorb light for photosynthesis, transport material laterally through wooden stems and store materials. Collenchyma cells have thick walls to help support the plant. The cells are usually in strands in the growing region of the plant. Sclerenchyma cells have rigid, thick secondary walls to support the plant.
Vascular tissue transports water, food, nutrients and minerals throughout the plant. The majority of the cells in vascular tissue are parenchyma cells, with other types of cells called xylem, phloem and cambium. Parenchyma cells have the same function in vascular tissue as they do in ground tissue--photosynthesis, transportation and storage. Xylem cells are tubes of long tapered cells or short wide cells that transport water and nutrients from the root cells to the leaves. Phloem cells move food from the leaves to the rest of the plant. Cambium cells between the xylem and phloem promote secondary growth of transport cells, while cambium cells between the phloem and cork (outer layer of stem) develop into the outer bark of the plant.
A vascular bundle is a group of xylem, phloem and cambium cells. In grasses and grass-type plants, vascular bundles are scattered throughout the plant. New vascular bundles develop as new plant growth occurs. In herbaceous (soft, non-woody plants) and woody plants, vascular bundles are arranged in a ring around the pith at the center of the plant. As the plant grows, the vascular bundles get larger but no new bundles develop. The vascular bundles in herbaceous plants remain separated, but the bundles in woody plants merge together to form a complete ring around the pith. The vascular bundles in woody plants also develop rays that transport nutrients from the phloem to the pith.