epithelium diffusion xylem phloem vascular tissue vascular bundle endodermis meristem cell pericycle cambium cortex photosynthesis sieve tube element companion cell lignin parenchyma pits lumen mitochondrion plasmodesmata A tissue that covers the outside of a structure The net movement of molecules or ions in a gas or liquid from an area of high concentration to an area of lower concentration. A plant tissue containing xylem vessels and other cells, that are used to transport water in a plant and provide support A tissue in plants that is used to transport dissolved sugars and other substances, made up of sieve tube elements and companion cells. The transport tissue in a plant, usually found as a bundle containing both xylem and phloem A collection of xylem and phloem tissues. A ring of cells between the cortex of a root and the area housing the xylem and phloem Undifferentiated plant cells capable of rapid cell division A layer of cells in the root that lies just inside the endodermis. It usually consists of meristematic cells whose division gives rise to lateral roots. Plant tissue in the stem and root that contains dividing cells Tissue in plant roots and stems between epidermis and vascular tissue The process by which plants, some bacteria make food using carbon dioxide, water and energy from sunlight. A cell found in phloem tissue through which sap containing sucrose is transported. It has very little cytoplasm, no nucleus, and non-thickened cellulose cell walls, with the end walls perforated to form sieve plates through which the cell sap passes from element to element. A cell in the phloem involved in actively loading sucrose into the sieve tube elements. The companion cell is closely associated with a phloem sieve tube element to which it is linked by many plasmodesmata. A waterproofing substance that impregnates the wall of the xylem tissue. Lignin gives wood its strength. Relatively unspecialised plant cells. They have living contents and thin, permeable cellulose cell walls. They may be able to photosynthesise, store food or support young plants. Thin areas of the lignified walls of xylem tissue cells that allow communication between adjacent cells. A cavity surrounded by a cell wall in cells, such as xylem vessels, which have lost their cell contents. The organelle found in cells in which most of the ATP synthesis occurs. It is the site of aerobic respiration. A fine strand of cytoplasm that links the protoplasm of adjacent plant cells through a thin area of cell wall called a pit.