Biology

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parenchyma

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Botany. the fundamental tissue of plants, composed of thin-walled cells able to divide.

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epidermis

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the outer, nonvascular, nonsensitive layer of the skin, covering the true skin or corium.

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cuticle

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The strip of hardened skin at the base and sides of a fingernail or toenail.

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vascular tissue

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plant tissue consisting of ducts or vessels, that, in the higher plants, forms the system (vascular system) by which sap is conveyed through the plant.

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xylem

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a compound tissue in vascular plants that helps provide support and that conducts water and nutrients upward from the roots, consisting of tracheids, vessels, parenchyma cells, and woody fibers.

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tracheids

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An elongated, water-conducting cell in xylem, one of the two kinds of tracheary elements. Tracheids have pits where the cell wall is modified into a thin membrane, across which water flows from tracheid to tracheid. The cells die when mature, leaving only their lignified cell walls. Tracheids are found in all vascular plants

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phloem

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the part of a vascular bundle consisting of sieve tubes, companion cells, parenchyma, and fibers and forming the food-conducting tissue of a plant.

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primary growth

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Growth in vascular plants resulting from the production of primary tissues by a primary meristem. Elongation of the plant body is usually a consequence of primary growth.

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root cap

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A thimble-shaped mass of cells that covers and protects the root tip

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secondary growth

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Growth in vascular plants from production of secondary tissues by a lateral meristem, usually resulting in wider branches and stems

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vascular cambium

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A cylindrical layer of cambium that runs through the stem of a plant that undergoes secondary growth. The vascular cambium produces vascular tissues, new xylem on its interior side and new phloem on its exterior side. All woody plants and most eudicots have vascular cambium.

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cork cambium

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A lateral ring of meristematic tissue found in woody seed plants, producing cork on the outside of the ring and parenchyma on the inside of the ring

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root

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a part of the body of a plant that develops, typically, from the radicle and grows downward into the soil, anchoring the plant and absorbing nutriment and moisture.

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cortex

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The outer layer of an internal organ or body structure, as of the kidney or adrenal gland.
The outer layer of gray matter that covers the surface of the cerebral hemisphere.
Botany The region of tissue in a root or stem lying between the epidermis and the vascular tissue.

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endodermis

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specialized tissue in the roots and stems of vascular plants, composed of a single layer of modified parenchyma cells forming the inner boundary of the cortex.

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stele

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the central cylinder or cylinders of vascular and related tissue in the stem,

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leaf

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one of the expanded, usually green organs borne by the stem of a plant.
2. any similar or corresponding lateral outgrowth of a stem

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photosynthesis

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the synthesis of complex organic materials, esp. carbohydrates, from carbon dioxide, water, and inorganic salts, using sunlight as the source of energy and with the aid of chlorophyll and associated pigments.

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stoma

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any of various small apertures, esp. one of the minute orifices or slits in the epidermis of leaves, stems, etc., through which gases are exchanged.

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guard cells

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Any fixture or attachment designed to protect or secure against injury, soiling, or defacement, theft or loss

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vascular bundle

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a longitudinal arrangement of strands of xylem and phloem, and sometimes cambium, that forms the fluid-conducting channels of vascular tissue in the rhizomes, stems, and leaf veins of vascular plants, the arrangement varying with the type of plant.

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auxin

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a class of substances that in minute amounts regulate or modify the growth of plants, esp. root formation, bud growth, and fruit and leaf drop.

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gibberellins

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Any of several plant hormones, such as gibberellic acid, used to promote stem elongation.

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cytokinins

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Any of a class of plant hormones that promote cell division and growth and delay the senescence of leaves.

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ethylene

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A colorless, flammable gas that occurs naturally in certain plants and can be obtained from petroleum and natural gas. As a plant hormone, it ripens and colors fruit, and it is manufactured for use in agriculture to speed these processes

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abscisic acid

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a growth-regulating plant hormone, C15H20O4, that promotes dormancy and the aging and abscission of leaves

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sepals

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One of the usually separate, green parts that surround and protect the flower bud and extend from the base of a flower after it has opened

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petals

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One of the often brightly colored parts of a flower immediately surrounding the reproductive organs; a division of the corolla.

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pistil

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the ovule-bearing or seed-bearing female organ of a flower, consisting when complete of ovary, style, and stigma

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carpel

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One of the structural units of a pistil, representing a modified, ovule-bearing leaf.

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double fertilization

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the fertilization process characteristic of flowering plants, in which one sperm cell of a pollen grain fertilizes an egg cell while a second fuses with two polar nuclei to produce a triploid body that gives rise to the endosperm.

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zygote

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the cell produced by the union of two gametes, before it undergoes cleavage.

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endosperm

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nutritive matter in seed-plant ovules, derived from the embryo sac.

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seed

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the fertilized, matured ovule of a flowering plant, containing an embryo or rudimentary plant.

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embryo

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the young of a viviparous animal, esp. of a mammal, in the early stages of development within the womb, in humans up to the end of the second month.

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seed coat

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the outer integument of a seed

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cotyledons

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Botany A leaf of the embryo of a seed plant, which upon germination either remains in the seed or emerges, enlarges, and becomes green. Also called seed leaf.
Anatomy One of the lobules constituting the uterine side of the mammalian placenta, consisting mainly of a rounded mass of villi

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hypocotyl

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the part of a plant embryo directly below the cotyledons, forming a connection with the radicle

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radicle

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a. the lower part of the axis of an embryo; the primary root

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phototrpism

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Growth or movement of a sessile organism toward or away from a source of light

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gravitropism

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oriented growth with respect to the force of gravity

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thigmotropism

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oriented growth of an organism in response to mechanical contact, as a plant tendril coiling around a string support.

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photoperiodism

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the response, as affecting growth or reproduction, of an organism to the length of exposure to light in a 24-hour period.