Ap Biology Chapter 35 Vocabulary

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ABC Model

Back 1

A model of flower formation identifying three classes of organ identity genes that direct formation of the four types of floral organs.

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Adventitious

Back 2

A term describing any plant organ that grows in an atypical location, such as roots growing from stems.

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Annual

Back 3

A flowering plant that completes its entire life cycle in a single year or growing season.

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Apical dominance

Back 4

Concentration of growth at the tip of a plant shoot, where a terminal bud partially inhibits axillary bud growth.

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Apical Meristem

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Embryonic plant tissue in the tips of roots and in the buds of shoots that supply cells for the plant to grow in length.

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Asymmetrical cell division

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In which one daughter cell receives more cytoplasm than the other daughter cell during mitosis. This is fairly common in plant cells and usually signals a key event in development.

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Axillary bud

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A structure that has the potential to form a lateral shoot, or branch. The bud appears in the angle formed between a leaf and a stem.

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Bark

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All tissues external to the vascular cambium, consisting mainly of the secondary phloem and layers of periderm.

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Biennial

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A flowering plant that requires two years to complete its life cycle.

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Blade

Back 10

1.

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2.

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The flattened portion of a typical leaf.

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Bundle sheath

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A protective covering around a leaf vein, consisting of one or more cell layers, usually parenchyma.

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Collenchymas cell

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A flexible plant cell type that occurs in strands or cylinders that support young parts of the plant without restraining growth.

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Companion cell

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A type of plant cell that is connected to a sieve-tube member by many plasmodesmata and whose nucleus and ribosomes may serve one or more adjacent sieve-tube members.

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Cork cambium

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A cylinder of meristematic tissue in woody plants that replaces the epidermis with thicker, tougher cork cells.

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Cortex

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Ground tissue that is between the vascular tissue and dermal tissue in a root or dicot stem.

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Cuticle

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1.

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2.

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The exoskeleton of an arthropod, consisting of layers of protein and chitin that are variously modified for different functions.

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3.

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A tough coat that covers the body of a nematode.

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Derivatives

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New cells that are displaced from an apical meristem and continue to divide until the cells they produce become specialized.

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Dermal tissue system

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The outer protective covering of plants.

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Determinate growth

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A type of growth characteristic of most animals and some plant organs, in which growth stops after a certain size is reached.

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Endodermis

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The innermost layer of the cortex in plant roots; a cylinder one cell think that forms the boundary between the cortex and the vascular cylinder.

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Epidermis

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1.

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2.

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The outer covering of animals.

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Fiber

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A lignified cell type that reinforces the xylem of angiosperms and functions in mechanical support; a slender, tapered sclerenchyma cell that usually occurs in bundles.

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Fibrous root system

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A root system common to monocots consisting of a mat of thin roots spreading out below the soil surface.

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Fusiform initials

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Cells within the vascular cambrium that produce elongated cells such as tracheids, vessel elements, fibers, and sieve-tube members.

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Ground tissue system

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Plant tissues that are neither vascular nor dermal, fulfilling a variety of functions, such as storage, photosynthesis, and support.

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Guard cells

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The two cells that flank the stomatal pore and regulate the opening and closing of the pore.

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Heartwood

Back 31

Older layers of secondary xylem, closer to the center of a stem or root, that no longer transport xylem sap.

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Herbaceous

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Referring to non-woody plants.

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Indeterminate growth

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A type of growth characteristic of plants, in which the organism continues to grow as long as it lives.

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Initials

Back 34

Cells that remain within an apical meristem as sources of new cells.

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Internode

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A segment of a plant stem between the points where leaves are attached.

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Lateral meristem

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A meristem that thickens the roots and shoots of woody plants. The vascular cambium and cork cambium are lateral meristems.

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Lateral root

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A root that arises from the outermost layer of the pericycle of an established root.

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Leaf

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The main photosynthetic organ of vascular plants.

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Leaf primordial

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Fingerlike projections along the flanks of a shoot apical meristem, from which leaves arise.

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Leaf trace

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A small vascular bundle that extends from the vascular tissue of the stem through the petiole and into a leaf.

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Lenticels

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Small raised areas in the bark of stems and roots that enable gas exchange between living cells and the outside air.

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Meristem

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Plant tissue that remains embryonic as long as the plant lives, allowing for indeterminate growth.

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Meristem identity gene

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A plant gene that promotes the switch from vegetative growth to flowering.

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Mesophyll

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The ground tissue of a leaf sandwiched between the upper and lower epidermis and specialized for photosynthesis.

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Morphogenesis

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The development of body shape and organization.

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Morphology

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External form, that varies little among plants within the species.

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Node

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A point along the stem of a plant at which leaves are attached.

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Organ

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A specialized center of body function composed of several different types of tissues.

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Organ identity gene

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Plant homeotic genes that use positional information to determine which emerging leaves develop into which types of floral organs.

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Palisade mesophyll

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One or more layers of elongated photosynthetic cells on the upper part of a leaf; also called palisade parenchyma.

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Parenchyma cell

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A relatively unspecialized plant cell type that carries out most of the metabolism, synthesizes and stores organic products, and develops into a more differentiated cell type.

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Pattern formation

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The ordering of cells into specific three-dimensional structures, an essential part of shaping an organism and its individual parts during development.

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Perennial

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A flowering plant that lives for many years.

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Pericycle

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The outermost layer of the vascular cylinder of a root, where lateral roots originate.

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Periderm

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The protective coat that replaces the epidermis in plants during secondary growth formed of the cork and cork cambium.

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Petiole

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The stalk of a leaf, which joins the leaf to a node of the stem.

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Phase change

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A shift from one developmental phase to another.

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Phloem

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Vascular plant tissue consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the plants.

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Pith

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Ground tissue that is internal to the vascular tissue in a stem; in many monocot roots, parenchyma cells that from the central core of the vascular cylinder.

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Plasticity

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An organism’s ability to alter or “mold” itself in response to local environmental conditions.

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Polarity

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A lack of symmetry. Structural differences in opposite ends of an organism or structure, such as the root end and shoot end of a plant.

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Positional information

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Signals to which genes regulating development respond, indicating a cell’s location relative to other cells in an embryonic structure.

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Preprophase band

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Microtubules in the cortex (outer cytoplasm) of a cell that is concentrated into a ring.

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Primary growth

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Growth produced by apical meristems, lengthening stems and roots.

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Primary plant body

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The tissues produced by apical meristems, which lengthen stems and roots.

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Protoplast

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The contents of a plant cell exclusive of the cell wall.

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Ray initials

Back 67

Cells within the vascular cambrium that produce xylem and phloem rays, radial files that consist mostly of parenchyma cells.

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Root

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An organ in vascular plants that anchors the plant and enables it to absorb water and nutrients from the soil.

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Root cap

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A cone of cells at the tip of a plant root that protects the apical meristem.

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Root hair

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A tiny extension of a root epidermal cell, growing just behind the root tip and increasing surface area for absorption of water and minerals.

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Root system

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All of a plant’s roots that anchor it in the soil, absorb and transport minerals and water, and store food.

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Sapwood

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Outer layers of secondary xylem that still transport xylem sap.

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Sclereid

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A short, irregular sclerenchyma cell in nutshells and seed coats and scattered through the parenchyma of some plants.

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Sclerenchyma cell

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A rigid, supportive plant cell type usually lacking protoplasts and possessing thick secondary walls strengthened by lignin maturity.

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Secondary growth

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Growth produced by lateral meristems, thickening the roots and shoots of woody plants.

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Secondary plant body

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fThe tissues produced by the vascular cambium and cork cambium, which thicken the stems and roots of woody plants.

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Shoot system

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The aerial portion of a plant body, consisting of stems, leaves, and (in angiosperms) flowers.

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Sieve plate

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An end wall in a sieve0tube member, which facilitates the flow of phloem sap in angiosperm sieve tubes.

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Sieve-tube member

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A living cell that conducts sugars and other organic nutrients in the phloem of angiosperms. They form chains called sieve tubes.

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Spongy mesophyll

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Loosely arranged photosynthetic cells located below the palisade mesophyll cells in a leaf.

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Stele

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The vascular tissue of a stem or root.

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Stem

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A vascular plant organ consisting of an alternating system of nodes and internodes that support the leaves and reproductive structures.

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Stoma

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The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.

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Systems biology

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An approach to studying biology that aims to model the dynamic behavior of whole biological systems.

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Taproot system

Back 85

A root system common to eudicots, consisting of one large, vertical root (the taproot) that produces many smaller lateral, or branch, roots.

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Terminal bud

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Embryonic tissue at the tip of a shoot, made up of developing leaves and a compact series of nodes and internodes.

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Tissue

Back 87

An integrated group of cells with a common function, structure, or both.

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Tissue system

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One or more tissues organized into a functional unit connecting the organs of a plant.

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Tracheid

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A long, tapered water-conducting cell that is dead at maturity and is found in the xylem of all vascular plants.

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Vascular bundle

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A strand of vascular tissues (both xylem and phloem) in a stem or leaf.

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Vascular cambium

Back 91

A cylinder of meristematic tissue in woody plants that adds layers of secondary vascular tissue called secondary xylem (wood) and secondary phloem.

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Vascular cylinder

Back 92

The central cylinder of vascular tissue in a root.

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Vascular tissue system

Back 93

A system formed by xylem and phloem throughout a vascular plant, serving as a transport system for water and nutrients, respectively.

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Vein

Back 94

1.

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2.

Back 95

In plants, a vascular bundle in a leaf.

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Vessel element

Back 96

A short, wide, water-conducting cell found in the xylem of most angiosperms and a few nonflowering vascular plants. Dead at maturity, vessel elements are aligned end to end to form micropipes called vessels.

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Vessels

Back 97

Continuous water-conducting micropipes found in most angiosperms and a few nonflowering vascular plants.

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Xylem

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Vascular plant tissue consisting mainly of tubular dead cells that conduct most of the water and minerals upward from roots to the rest of the plant.

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Zone of cell division

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The zone of primary growth in roots consisting of the root apical meristem and its derivatives. New root cells are produced in this region.

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Zone of elongation

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The zone of primary growth in roots where new cells elongate, sometimes up to ten times their original length.

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Zone of maturation

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The zone of primary growth in roots where cells complete their differentiation and become functionally mature.