Basic Difinitions Flashcards
Alternation of generations
The presence of two genetically distinct multicellular stages, one haploid and one diploid, in the plant life cycle. The haploid gametophyte generation begins with meiosis, while the diploid sporo- phyte generation begins with the fusion of sperm and egg.
Gamete
A haploid (1N) reproductive cell
Meiosis
The “reduction division” whereby two successive cell divisions produce four haploid (1N) cells from one diploid (2N) cell. In plants with alterna- tion of generations, spores are produced by meiosis. In animals, which don’t have alternation of generations, gametes are produced by meiosis.
Spores
Reproductive cells formed in plants by meiosis in the sporophyte generation. They give rise by mitotic divisions to the gametophyte generation
Sporophyte
The diploid (2N) mutlicellular structure that produces haploid spores by meiosis
Mitosis
The ordered cellular process by which replicated chromosomes are distributed to daughter cells formed by cytokinesis
Gametophyte
The haploid (1N) multicellular structure that produces haploid gametes by mitosis and differentiation
Pollen
Small structures (microspores) produced by anthers of seed plants. Contain haploid male nuclei that will fertilize the egg in the ovule
Fertilization
The formation of a diploid (2N) zygote from the cellular and nuclear fusion of two haploid (1N) gametes, the egg and the sperm. In angiosperms, fertilization also involves fusion of a second sperm nucleus with the haploid nuclei (usually two) of the central cell to form the endosperm (usu- ally triploid).
Megaspore
The haploid (1N) spore that develops into the female gametophyte
Microspores
The haploid (1N) cell that develops into pollen tube or male gametophyte
Monoecious
Refers to plants in which male and female flowers are found on the same individuals, such as cucumber (Cucumis sativus) and maize (corn; Zea mays).
Dioecious
Refers to plants in which
male and female flowers are found on
different individuals, such as spinach
(Spinacia) and hemp (Cannabis sativa
Double Fertilization
A unique fea- ture of all angiosperms whereby, along with the fusion of a sperm with the egg to create a diploid zygote, a second male gamete fuses with the polar nuclei in the embryo sac to generate the endo- sperm tissue (with a triploid or higher number of chromosomes)
Stem
The typically above ground primary axis of the shoot that bears leaves
and buds. May also occur underground
in the form of rhizomes, corms, and
tubers.
Root
The organ, usually underground, that serves to anchor the plant in the soil, and to absorb water and mineral ions, and conduct them to the shoot. In contrast to shoots, roots lack buds, leaves, or nodes.
Leaves
The main lateral appendages
radiating out from stems and branches.
Green leaves are usually the major photosynthetic organs of the plant.
Node
Position on the stem where leaves are attached
Shoots
That organ, usually above ground, that includes the stem, leaves, buds, and reproductive structures. Function in photosynthesis and reproduction
Primary plant axis
The longitudinal
axis of the plant defined by the positions
of the shoot and root apical meristems
Leaf blade
The broad, expanded area of the leaf; also called the lamina
Plasma membrane
A bilayer of polar lipids and embedded proteins that together form a selectively permeable boundary around a cell
Cytoplasm
The cellular matter enclosed by the plasma membrane exclusive of the nucleus
Cytosol
The aqueous phase of the cytoplasm containing dissolved solutes but excluding supramolecular structures, such as ribosomes and components of the cytoskeleton.
Cell wall
The rigid cell surface structure external to the plasma membrane
that supports, binds, and protects the
cell. Composed of cellulose and other
polysaccharides and proteins
Primary cell walls
The thin (less than 1 μm), unspecialized cell walls that are characteristic of young, growing cells
Secondary cell wall
Cell wall synthe- sized by nongrowing cells. Often multi- layered and containing lignin, it differs in composition and structure from the primary wall.
Middle lamella
A thin layer of pec-
tin-rich material at the junction where
the primary walls of neighboring cells
come into contact
Glucan
A polysaccharide made from
glucose units
Cellulose
A linear chain of (1,4)-
linked β-d-glucose. The repeating unit is
cellobiose
Microfibril
The major fibrillar component of the cell wall compose of layers of cellulose molecules packed tightly together by extensive hydrogen bonding
Hemicelluloses
Heterogeneous group
of polysaccharides that bind to the sur-
face of cellulose, linking cellulose micro-
fibrils together into a network
Pectins
A heterogeneous group of
complex cell wall polysaccharides that
form a gel in which the cellulose–hemi-
cellulose network is embedded
Matrix plysaccharides
Polysaccharides comprising the matrix of plant cell walls. In primary cell walls they consist of pectins, hemicelluloses, and proteins
Lignin
Highly branched phenolic polymer made up of phenylpropanoid alcohols that is deposited in secondary cell walls
Cellulose Synthase
Enzyme that catalyzes the synthesis of individual (1,4)-linked β-d-glucans that make up
cellulose microfibrils
Plasmodesmata
(singular plas- modesma) Microscopic membrane-lined channel connecting adjacent cells through the cell wall and filled with cytoplasm and a central rod derived from the ER called the desmotubule
Symplast
The contunuous system of cell protoplasts interconnected by plasmodesmata
Symplastic transport
The intercellular transport of water and solutes through plasmodesmata
Apoplastic transport
Movement of molecules through the cell wall continuum that is called the apoplast. Molecules may move through the linked cell walls of adjacent cells, and in that way move throughout the plant without crossing a plasma membrane
Size exclusion limit (SEL)
The
restriction on the size of molecules that
can be transported via the symplast. It is
imposed by the width of the cytoplasmic
sleeve that surrounds the desmotubule
in the center of the plasmadesma.
Meristems
Localized regions of ongoing cell division that enable growth during post-embryonic development
Apical meristems
Localized regions made up of undifferentiated cells undergoing cell division without differantiation at the tips of shoots and roots
Primary growth
The phase of plant development that gives rise to new organs and to the basic plant form
Primary plant body
The part of the plant directly derived from the shoot and root apical meristems and primary meristems
Axillary buds
Secoundary meristems that are formed in the axils of leaves
Lateral roots
Arise from the pericycle in mature regions of the root through establishment of secondary mesistems that grow out through the cortex and epidermis, establishing a new growth axis
Pericycle
Meristematic cells forming the outermost layer of the vascular cylinder in the stem or root, interior to the endodermis
Dermal tissue
The tissue system that covers the outside of the plant body;the epidermis of periderm
Epidermis
the outermost layer of plant cells, typically one cell thick
Ground tissue
The internal tissues of the plant, other than vascular tissues
Pith
The ground tissue in the center of the stem or root
Cortex
Ground tissue in the regions of the primary stem or root located between the vascular tissue and the epidermis, mainly consisting of parenchyma
Mesophyll
Leaf tissue found between the upper and lower epidermal layers
Vascular tissue
Plant tissues specialized for the transport of water (xylem) and photosynthetic products (phloem)
