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Home >>Botany Dictionary >> A-Acrostichoi Sorus
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A - A class of flowers having freely exposed nectar.
AB - A flower having partially connected nectar.
Ab - Latin prefix which means`from'.
Abaxial - Not on, pomting away from on facing away from the stem or man axis.
Aberrant - Different from normal.
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Abruptly Pinnate - (of leaves) Pinnate with no smallleafending the stem, opposite odd pinnate.
Abscissa-Phelloid - The unsuberised cells of an abscission layer in the bark.
Abscisic Acid (Abscisin, Dormin) - Growth-inhibiting plant hormone (a sesquiterpene) which is present in a variety of plant organs such as leaves, buds, fruits, seeds and tubers. Promotes senescence and abscission of leaves, induces dormancy in buds and seeds. Antagonizes influences of growthpromoting hormones. Acts by inhibiting nucleic acid and protein synthesis.
Abscission - Any natural process by which two parts become separate as the separating of a spore from a sporophyte.
Abscission Layer - Layer present at base of leaf-stalk in woody dicotyledons and gymnosperms, in which the parenchyma cells get separated from one another through dissolution of the middle lamella before there occurs leaf fall.
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Absolute Transpiration - The rate of water loss from a plant which is determined experimentally.
Absorption Ratio - It is the ratio of the final internal concentration of a particularion in planttissue (i) to the final external concentration of a particular (e), i.e., i/e.
Abstriction - A general term used for the release of a spore from
its stalk, especially by constriction.
Acanaceous - Having sharp points.
Acarpellous - Having no carpels.
Acarpous - Producing no fruit.
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Acantha - A sharp point.Acaulescent - To describe plants which do not have stem or which have an extremely short stem such as tufted or resette plants.
Acaulousion, one - Having no true stem or only a very short one under the earth.
Accessory Bud - A bud which is present additional to the normal axillary bud.
Accessory Cell - A cell which is associated with the guard cell of a stoma, but is differing in structure from it and from the ordinary cells of the epidermis.
Accessory Character - A characteristic of a species which is not essential to its diagnosis, but is sometimes employed to differentiate races.
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Accrescent - Enlarged and persistent. Especially of a calyx which gets enlarged as the fruit ripens.
Accumbent - Touching something specially of cotyledons having edges against radicle.
Acellular (of an organism) - Not divided into separate cells. Many oroganisms made up of one cell are quite complex in structure and in function and, in contrast to the term unicellular, 'acellular' means the biological equivalence of such organisms to the whole of a multicellular organism rather than to one of its cells.
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Accessory Chromosome - Sex Chromosome.
Accessory Fructification - An asexual reproductive structure of lower plants.
Accessory Multiplication - Any asexual reproductive process.
Accessory Pigments - Pigments (e.g., carotones, xanthophylls, chlorophylls b, c and d and the phycobilins) other than chlorophyll a found in photosynthetic cells.
Accessory Spore - An asexual spore.
Accessory Transfusion Tissue - Transfusion tissue which is extending through the mesophyll from the mid-rib to the margins found in certain gymnosperms. e, g., Cycas.
Abrupt - Ending suddenly, as if cut off.
Acentric - A piece of a chromosome or chromatid having no centromere.
Achephalous - Having no head. Said of a style having no welldeveloped stigma.
Acerose, Accrous - Needle-shaped.
Acetvate - Heaped; growth in heaps of groups.
Acervulus - A compact mass of hyphae which bearconidiophores and conidia. Formed by some parasistic ascomycets. The corresponding structure of saprophytic ascomycetes is termed as soprodochium.
Actabuliform - Saucer-like.
Acetaldehyde - CH3CHO, an intermediate in the aerobic andanaerobicrespiration of carbohydrates. Retards or inhibitsgermination and growth of some fungi.
Aceto-orcein - A stain which is used in the preparation of root tip of another squashes for chromosome number.
Acetyl CoA, (Acetyl coenzyme A). A compound having acetyl combined through a sulphur bridge with coenzyme A. The formation of acetyl CoA is an energy-consuming reaction' which involves the conservation of A 1P to AMP and pyrophosphate. His a degradation product of fatty acids, carbohydrates, and some amino acids.
Acetylation - The formation of an acetyl radical from pyruvate during photosynthesis. The enzyme involved is co-enzyme A. The complete reaction may be put as follows:
CH3 CO.COO- + CoA + 2H2O --;
Pyruvate
CH3.COO.CoA + HCO3- + H+
Acetyl CoA
(2) Acetyl CoA + oxalacetate - -; citrate + CoA
N-Acetyl-2-Glucosamine - A glucose derivative, and the unit which gets repeated in the chitin molecule.
Acetyl-S-CoA - An intermediate, which is produced by co-enzyme A when it gets detached carbon dioxide from -keto-acid. during respiration.
Achene - Small, dry, thin-coated one-seeded fruit, not bursting open, e.g., butter cup, sycamore.
Achilary - Having no lip.
Achlamydeae - A division of the archiclamydeae having no petals and no sepals.
Achlamydeoris - Lacking perianth.
Achromatic - Having no colour.
Achromatic Spindle - (See 'Spindle'). In cell-division, a system of apparent fibres which does not get stained by basic dyes. They join the poles of the nucleus, and get diverged towards the centre of the cell.
Achromatin - The nuclear soap, which does not get stained with basic dyes.
Acicular - Refers to the needle shape e.g., leaves of pine (Pinus) trees.
Acid Dyes - Dyes having an acidic organic grouping of atoms (anion) which is the actively staining part, combined with an inorganic cation, e.g., eosin. These dyes stain cytoplasm and collagen.
Acme - The period of maximum vigour of an individual, race, or species.
Aconitrase - An enzyme which takes part in the Citric Acid Cycle (Kreb's Cycle). It dehydrates citrate forming cis-aconitrate which is then converted to D-isocitrate, by the addition of a water molecule.
Acotyledon - A plant without cotyledons (said of the embryo of a higher plant).
Acquired Characteristics - The characters of an individual which get developed due to environmental conditions. According to the theory of acquired characters, these characters can be inherited.
Acquired Variation - A structural anomaly which becomes evident as the individual gets developed.
Acrandrous - Possessing antheridia at the top of the stem, as in some mosses.
Acrocarpous - Fruit borne at the end of a branch.
Acrogame - A division of the Angiospermae in which fertilization occurs through the micropyle (the usual way).
Acrogen - Any plant of the highest series of cryptogams, the archegoniatae.
Acropetal - Development of organs insuccssion towards apex, the oldest at base, youngest at tip, e.g., leaves on a shoot. Also used to indicate the direction of transport of substance with in a plant, i.e., towards the apex. Cf. Basipetal.
Acroscopic - Facing in the direction of apex.
Acrospore - Spore at the end of hypha.
Acrostichoid Sorus - A fem sorus having several fused sori.
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