Vascular and Nonvascular Plant Structures and Functions
Stomata
Openings in the outer cell layer of leaf surfaces and some stems that allow the exchange of water, carbon dioxide, oxygen, and other gases between a plant and its environment.
Vascular Tissue
Specialized tissue that transports water, food, and other substances in vascular plants and can also provide structure and support.
Vascular Plant
Type of plant with vascular tissues adapted to land environments; most widely distributed type of plant on Earth.
Nonvascular Plant
Type of plant that lacks vascular tissues, moves substances slowly from cell to cell by osmosis and diffusion, and grows only in a damp environment.
Seed
Adaptive reproductive structure of some vascular plants that contains an embryo, nutrients for the embryo, and is covered by a protective coat.
Thallose
Liverwort with a fleshy, lobed body shape.
Strobilus
Compact cluster of spore-bearing structures in some seedless vascular plant sporophytes.
Epiphyte
Plant that lives anchored to an object or to another plant.
Rhizome
Fern’s thick underground stem that functions as a food-storage organ.
Sporangium
Sac or case in which fungal spores are produced.
Sorus
Fern structure formed by clusters of sporangia, usually on the undersides of a frond.
Cotyledon
Seed structure that stores food or helps absorb food for the sporophyte of vascular seed plants.
Cone
Feature that contains male or female reproductive structures of cycads and other gymnosperms.
Annual
Plant that completes its life span in one growing season or less.
Biennial
Plant with a two-year life span.
Perennial
Plant that can live for several years.
Parenchyma Cell
Spherical, thin-walled cell found throughout most plants that can function in photosynthesis, gas exchange, protection, storage, and tissue repair and replacement.
Collenchyma Cell
Often elongated plant cell that provides flexibility for the plant, support for surrounding tissues, and functions in tissue repair and replacement.
Sclerenchyma Cell
Plant cell that lacks cytoplasm and other living components when mature, leaving thick, rigid cell walls that provide support and function in transport of materials.
Meristem
Region of rapid cell division in plants; produces cells that can develop into many different types of plant cells.
Vascular Cambium
Thin cylinder of meristematic tissue that produces new transport cells.
Cork Cambium
Meristematic tissue that produces cells with tough cell walls that form the protective outside layer on stems and roots.
Epidermis
Dermal tissue that makes up a plant’s outer covering.
Guard Cell
One of a pair of cells that function in the opening and closing of a plant’s stomata by changes in their shape.
Xylem
Vascular plant tissue that transports water and dissolved minerals away from the roots throughout the plant and is composed of vessel elements and tracheids.
Vessel Element
Elongated, tubular plant cell that forms xylem strands (vessels) and conducts water and dissolved substances.
Tracheid
Long, cylindrical plant cell in which water passes from cell to cell through pitted ends.
Phloem
Vascular plant tissue composed of sieve tube members and companion cells that conducts dissolved sugars and other organic compounds from the leaves and stems to the roots and from the roots to the leaves and stems.
Sieve Tube Member
Nonnucleated, cytoplasmic cell of the phloem.
Companion Cell
Nucleated cell that helps the mature sieve tube member function in transporting dissolved substances in the phloem of vascular plants.
Ground Tissue
Plant tissue consisting of parenchyma, collenchyma, and sclerenchyma.
Root Cap
Layer of parenchyma cells that covers the root tip and helps protect root tissues during growth.
Cortex
Layer composed of ground tissues between the epidermis and vascular tissue of a root.
Endodermis
Cell layer at the inner boundary of the cortex; regulates the material that enters the plant’s vascular tissues.
Pericycle
Plant tissue that produces lateral roots.
Petiole
Stalk that connects a plant’s blade to the stem.
Palisade Mesophyll
Leaf-tissue layer that contains many chloroplasts and is the site where most photosynthesis takes place.
Spongy Mesophyll
Loosely packed, irregularly shaped cells with spaces around them located below the palisade mesophyll.
Transpiration
Process in which water evaporates from the inside of leaves to the outside through stomata.
Auxin
Plant hormone that moves in only one direction away from the site where it was produced and can stimulate the elongation of cells.
Gibberellins
Group of plant hormones that are transported in vascular tissue and that can affect seed growth, stimulate cell division, and cause cell elongation.
Ethylene
Gaseous plant hormone that affects the ripening of fruits.
Cytokinin
Plant hormone that promotes cell division by stimulating production of proteins required for mitosis and cytokinesis.
Nastic Response
Reversible, responsive movement of a plant that occurs independent of the direction of the stimulus.
Tropism
Response to an external stimulus in a specific direction.