TGP2 glossary Flashcards
acropetal
towards the apex
adventitious
Arising in abnormal position; e.g. roots arising from stem or leaf
cutting, or buds arising from root.
aleurone
The cell layer which surrounds the embryo and endosperm in cereal grains and which secretes amylase that break down the starch in the endosperm.
alpha- (α)
Prefix to designate the chirality at carbon atom no 1 of a sugar residue such as glucose (relative to that at its penultimate carbon atom).
anamorph
asexual form of a fungus
androecium
collective name for all the stamens of an individual flower
angiosperms
The seed plants in which the seed is enclosed in a fruit
annulus
annulus Ring (e.g. of tissue around a mushroom stalk beneath the cap)
anther
‘Head’ of stamen, in which pollen is formed.
antibiotic
a substance produced by one living micro-organism which damages or kills another.
apex
the end of a plant organ furthest from the seed from which that plant grew (adjective: apical); thus, the apex of a shoot is normally the top end, whereas the apex of a downwardly-growing root is the bottom end. In both cases, the apex is the distal end.
apoplast
the part of the plant external to the plasma membrane i.e. the cell walls, intercellular spaces, and dead cells such as xylem. Essentially the non-living part of the plant body. In a large tree much of the wood of the tree trunk, branches, and roots will be part of the apoplast. (see symplast)
appressorium
swelling of a germ tube or hypha which usually functions in attachment to a host plant prior to penetration.
ascogenous
hypha dikaryotic, ascomycete hypha which produces asci.
ascoma or ascocarp
multi-hyphal, sexual reproductive organ of ascomycetes
which is associated with ascospore production.
ascospore
sexual spore of ascomycetes which is produced internally within an ascus.
ascus
cell of ascomycetes within which ascospores are produced immediately following nuclear fusion and meiosis.
autotrophic
mode of nutrition in which all organic requirements are synthesised from CO2 (compare heterotrophic).
avirulence gene
of a pathogen encodes a product that is ‘recognised’ by the product of a plant resistance gene.
axillary bud
A bud situated in the axil of a leaf i.e. in the angle between the upper
side of the leaf and the stem.
base
the end of a plant organ nearest the seed from which that plant grew (adjective: basal); thus, the base of a shoot is normally the lower end, the base of a root is normally the top. In both cases, the base is the proximal end.
basidioma or basidiocarp
multi-hyphal, sexual reproductive organ of basidiomycetes which is associated with basidiospore production.
basidiospore
sexual spore of basidiomycetes which is produced and borne externally on a basidium.
basidium
cell of basidiomycetes which produces basidiospores externally immediately following nuclear fusion and meiosis.
basipetal
Towards the base (see acropetal).
beta- (β)
Prefix to designate the chirality at carbon atom no 1 of a sugar residue such as glucose (relative to that at its penultimate carbon atom). Starch is an αglucan; cellulose is a β-glucan.
bioassay
A test for a substance based on its ability to induce some response in living cells. A bioassay allows you to detect the substance without knowing anything about its chemistry
biotrophy
mode of nutrition in which living host cells are used as a nutrient resource.
bract
A leaf-like structure immediately below a flower or inflorescence.
calyx
collective name for all the sepals of an individual flower.
cambium
A cylinder of meristematic tissue which, by radial growth and anticlinal divisions (parallel to the surface), forms the secondary tissues in woody plants (most of the wood and the inner layers of the bark).
carpel
One of the individual floral organs of the fourth (most distal) floral whorl. Collectively make up the ovary (gynoecium). They produce the female gametes.
caryopsis
simple one-seeded fruit with pericarp firmly united all around the seed coat (e.g. a cereal grain)
cellulose
a highly insoluble, crystalline polysaccharide [β-(1→4)-D-glucan] of the plant cell wall. Occurs in the form of microfibrils.
chitin
a highly insoluble, structural polysaccharide [a β-(1→4)-linked polymer of N- acetyl-D-glucosamine] of many fungal cell walls.
clamp connection
hyphal outgrowth of basidiomycetes associated with dikaryon formation which, during hyphal septation, makes a connection between the resulting two hyphal compartments.
coleoptile
A sheath enclosing the embryonic leaves in grass and cereal seedlings. Its growth is limited to several centimetres. The young leaves then break through its tip as they grow on. The coleoptile is a classical object for the study of the effects of auxin on cell elongation.
collenchyma
A type of cell found in the outer cortex in which the cell walls are unevenly thickened and the intercellular spaces are often absent.
colony
(in mycology) a mycelium, frequently with reproductive structures (filamentous fungi); a group of cells of the same species living together (yeasts).
commensalism
intimate association between two organisms where one partner benefits without affecting the other.
companion cells
Phloem cells which are nucleated and densely protoplasmic, being ‘companions’ to the sieve tubes.
compatible reaction
(in plant pathology) : reaction between a susceptible host and a virulent pathogen.
conidiogenous cell
directly produces conidia.
conidioma
multi-hyphal, asexual reproductive organ which is associated with
conidium production.
conidiophore
hypha which bears conidiogenous cells.
conidium
type of non-motile, asexual spore produced from a conidiogenous cell.
cork
A tissue formed on the outside of woody stems and roots by a special meristem, the cork cambium. Cork cells soon die, but before they do the walls are impregnated with a secretion, suberin, which makes them impermeable to water and gases.
corolla
collective name for all the petals of an individual flower.
cortex
The tissue system between the epidermis and the stele, often mainly of parenchyma but often also containing sclerenchyma. The innermost layer of the cortex is the endodermis, which surrounds the stele.
cotyledon
A seed leaf, specialised for storage of food material and formed in the embryo before the shoot apex is formed. Sometimes the cotyledons become transformed into the first leaves (e.g. tomato). In other plants they emerge from the soil but soon wither (e.g. runner beans); in others they remain below the soil (e.g. peas).
cuticle
A hydrophobic secretion on the outside of the cell wall, especially on the outer (epidermal) surfaces of plants exposed to the air. It is often coated by wax and is relatively impermeable to water and gases.
D-
Prefix to designate the chirality at the penultimate carbon atom of a sugar
residue. Opposite is L-.
determinate
describing growth that stops at a genetically pre-determined size.
Typical of leaves and flowers but not roots.
dicot
dicots) One of the two groups into which the angiosperms are divided and consisting of plants that have two cotyledons in the embryo. Dicotyledons characteristically have broad, net-veined leaves, are often woody, and have floral parts typically in fours or fives. (see also monocotyledons)
dikaryon
cell containing two, usually genetically distinct, haploid nuclei
dimorphic
a fungus able to grow in either a yeast or mycelial form.
distal
Nearer the tip.
elicitor
The term ‘elicitor’ was originally used to refer to molecules and other stimuli that induce phytoalexin synthesis in plant cells, but the term is now used to describe molecules that elicit any of the observed plant defence responses.
endodermis
The innermost layer of the cortex which surrounds the stele and which can act as a barrier to radial movement of solutes. The endodermis of the root has bands of suberin (the Casparian strip) on the radial cell walls.
endoglycanase
Enzyme that can split a polysaccharide molecule by hydrolysing a glycosidic bond in mid-chain.
endosperm
The tissue formed in the developing seed by divisions of the nucleus, in the embryo sac, that results from fusion of one or more embryo sac nuclei with the haploid vegetative nucleus from the pollen tube. The resulting cells, usually triploid, form a nutritive tissue which in cereal grains is the main source of starch for the brewing industry. In many seeds (non- endospermous) the endosperm is digested and the products absorbed by the cotyledons which then become the main food store for the developing seedling (e.g. as in peas).
epidermis
(plural: epidermises) The outermost tissue of the plant, usually consisting of a single layer of cells (although sometimes it proliferates to give several layers) and, in stems and leaves, covered by the cuticle except where there are stomatal apertures.
epigeal
Type of germination in which the cotyledons emerge above the soil and may simply serve as food stores and then wither (e.g. runner bean) or may also become the first photosynthetic organs (e.g. mustard, tomato). (see hypogeal)
etiolation the characteristics of a plant grown in the dark, typically an elongated stem and unexpanded leaves that are yellow or white instead of green.
exoglycanase
Enzyme that can release sugars from a polysaccharide by hydrolysing glycosidic bonds at or near a non-reducing terminus.
fibres
Elongated cells, typically pointed at both ends, with thick, lignified walls and having no protoplast when mature. Sclerenchyma is a tissue composed solely of fibres.
filament
stalk’ of stamen.
flowering
In many plants flowering is promoted by environmental signals. Promotion of flowering by photoperiod (or, strictly, night-length) occurs in three major steps: induction of the leaves by the light stimulus to produce a signal;
The Green Planet 2
evocation (the action of this signal at the shoot apex to commit it to flowering; and realisation (the actual formation of the flowers).
fruit
The tissues which enclose and support the ovules and, later, the seeds. Usually the result of post-fertilisation development of the gynoecium (ovary wall).
galacturonan
Any polysaccharide with a backbone composed mainly of galacturonic acid residues.
gametangium
single-celled sex organ; or cell that contains gametes.
gametophyte
The gamete-producing (haploid or n) generation in plants (which in angiosperms is very much reduced but which is the main part of the plant in mosses).
gel-permeation chromatography
(gel filtration, size exclusion chromatography) Method for fractionating substances on the basis of their Mr values. The largest molecules elute from the column first.
germ tube
hypha which emerged from a germinated spore.
glucan
Any polysaccharide with a backbone composed mainly of glucose
residues.
glucuronoarabinoxylan
A xylan with side-chains containing glucuronate and arabinose residues. [Further polysaccharide names can be constructed on a similar basis.]
glycoprotein
A protein with mono-, oligo- or polysaccharides glycosidically linked to it.
glycosidic bond
Covalent linkage formed between a sugar (usually at carbon atom No. 1) and some other molecule (which may be a sugar), with the loss of 1 molecule of H2O.
guard cell
One of the pair of cells which enclose the pore (aperture) of a stoma and which control the size of the stomatal aperture by their degree of turgidity.
gymnosperms
(Conifers and their relatives) Seed plants in which the seeds are borne naked on scales, in cones, and not enclosed in a fruit. (see Angiosperms)
gynoecium
(gynaeceum) collective name for all the carpels of an individual flower (synonymous with ovary).
haustorium
specialised hyphal branch produced within a host cell and which functions in nutrient absorption.
hemicellulose
one of a group of non-pectic polysaccharides that can be extracted from the plant cell wall with cold concentrated alkali. In vivo, they hydrogen-bond to the cellulosic microfibrils. Examples of hemicelluloses are xyloglucans, xylans, mannans and (only in grasses and cereals) mixed linkage β-(1→3),(1→4)-glucans.
heterokaryon
cell containing two or more genetically distinct nuclei.
heterothallic
condition in which sexual reproduction requires the interaction of two
different individuals of the same species (self-sterile).
