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Home >> Botany Dictionary >> Archegoniophore-Auxins
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Arthrospore - (1) A spore which is formed by the breaking of the hyphae, especially in the Actinomycetes.
Arillode - Astructure which looks like an aril, but not formed from the placenta.
Aristate - Describing a structure which bears an awn such as glume or lemma. Compare bearded.
Armature - The persistent woody scales which are present at the base of the leaves and stems of Cyatheaceous ferns.
Artefact - A structure which is not usually present in a cell, but produced during investigation, e.g., during staining.
Arthrogenous - (1) Of bacteria where the individual is developed into a spore.
(2) Developed from pieces which are separated from the parent plant.
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Areole - (1) Any area which is outlined clearly on a surface. For example, segments of lamina are demarcated by vein. A surface divided into areoles which is splitted by cracks into areas is known as areolate.
(2) The sunken cushion which is representing a condensed lateral shoot from which spines, branches and flowers are arising. These may occur singly on tubercles or in rows along raised rows
Arginine - amino valoeric acid (NH=C(NH2)-NH. CH2(CH2)2. CH(NH2)COOH). One of the principle amino acids constituting plant protein.
Aril - A fleshy, coloured covering on the seed which arises as an upgrowth of the funicle or base of the ovule and may be a tuft of hairs.
Archegoniophore - An erect reproductive structure in certain liverworts which has a stalk and a disc at the tip of stalk. The disc is having sterile, ray-like structures which are radiating from it. Disc bears archegonia on the lower side. Compare antheridiophore.
Archegonium - The flask-shaped container of the ovum (egg cell) of liverworts, mosses, ferns, and some gynmnosperms. The swollen base (venter) has the egg-cell, and gets surrounded by the neck, with neck canal-cells.
(2) A spore which is formed by the segmentation of, and the separation from the present cell.
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Artificial Classification - A classification which is based at least in part on artificial characters.
Artificial Community - A plant community which is maintained by artificial means, e.g., a garden.
Ascocarp - The fruiting-body of an ascomycete which is usually developed from one fertilized ascogonium. It is made up from asci, paraphysis (sterile hairs) and a denser surrounding periderm.
Ascogenous Hyphae - The hyphae which are growing from the zygote of the Euascomycetes. There are several ascogenous hyphae which develop from each zygote, and each hypha bears several asci.
Ascogonium - The female sex organs of the Euscomycetes, which after fertilization, produce the ascogenous hyphae.
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Ascogonium - The cell, or group of cells of the Ascomycetes which are fertilized by the antheridum.
Asscorbic Acid (Vitaminl C) - A lactone of a sugar acid. It occurs in high concentration in certain fruits and green vegetables. It acts as cofactor in hydroxylation of proline to hydroxyproline.
Ascospore - A haploid spore which is formed in ascus of certain fungi. To nuclei of dikaryotic ascus first fuse and then undergo meiosis to form four haploid nuclei which undergo mitosis forming ascospores in an ascus.
Ascus - A sac like cell in the perfect stage of an Ascomycete, in which the ascospores are produced.
Asepalous - Having no sepals.
Aseptate - Lacking cross-walls.
Asexual - Without sex organs or sex spores.
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Asexual Reproduction - Any method of reproduction which does not involve any fusion of any reproductive units. Structure formed asexually may be a spore or a specialised or unspecialised portion of parent tissue which gets separated from the parent. Compare sexual reqroduction.
Asparagine - One of the amino acids occurring in proteins. COOH.CH2CH(NH2).CONH2. The amide of aspartic acid, and occurs idely in plants.
Assimiatory Quotient, Assimilation Quotient - Describing the ratio of carbon-dioxide intake to oxygen output (CO2/O2). This ratio is usually near 1, which is in agreement with the equation: 6CO2+ 6H2O C6H12O6+ 602.
Association - A large climax community which is named after the dominant types of plant species. Examples are deciduousforest association, health association, etc.
Assortive Mating - Used for non-random breeding among organisms, if breeding occurs between similar phenotypes, it is positive assortive mating leading to inbreeding and if between dissimilar phenotypes, it is negative assortive mating leading to outbreeding. Pollination mechanism is having major influence on the breeding patterns.
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Aster - A star like arrangement formed by fibrils which are radiating from a centriole. Asters become conspicous at poles of spindle as cell division starts in some primitive plant cells.
Astrosclereid (Asteroscleried, Star-sclereid) - A relaltively short sclerenchyma cell (sclereid) having often conspicuously branched shape. They are usually present singly or in small groups and are often found in mesophyll of leaves where they are used for strengthening the structure.
Atactostele - A stele with vascular bundles which are irregularly arranged in the ground tissue, typical in monocotyledonous stems.
Atmometer - An apparatus used for measuring the rate of evaporation from a non living wet surface like a porous clay pot.
Auricle - Small earlike projection from the base of a leaf or a petal. It is seen at the base of a leaf blade in grasaes. See also ligule.
Aurones - Used for one of the two groups of anthochlor flower pigments. They are probably formed by oxidation of chalcones. They are found in many members of Compositae especially genus Coreopsis.
Autapomorphy - Any derived character state which is possessed only by members of one particular taxon. Autapomorphies are used to distinguish related taxa and their numbers.
Autecology - Used for the study of anyone particular population in relation to its particular environmental conditions. It is involving the study of life cycle, effects of all the biotic and abiotic environmental factors at each stage of life cycle with quantitative recording of vartiations within and between populations. Compare snyecology.
Autodiploid - Gamete which has diploid number of chromosomes. Autodiploids may arise either through fault in meiosis or from a tetraploid tissue. These may undergo fusion with another similar gamete to form tetraploid or may develop parthenogenetically. Autodiploid is also used to describe totally homozygous diploid plants which are resulting from doubling of chromosome number of a haploid plant.
Autoecious - Said of the Rusts producing the different spore forms on one host, i.e., completing the life cycle on one host.
Autogamy - (1) Self fertilization.
(2) The fusion of sister cells.
(3) The fusion of nuclei in pairs within one cell of a female organ, without cell fusion having taken place.
Autoicous - Having male and female inflorescences on the same plant.
Automixis - The destruction of cell contents by enzymes produced in the cell. It is due to the disordered metabolism of the cell, and may be caused by substances not normally present in the cell.
Automixis - The minging of chromatin derived from two sex cells which are produced by one individual plant.
Autonomic Movement. Describing the movement of plant or its part in response to some stimulus produced within the plant e.g., beating of cilia and flagella, cyclosis, cyclosis, circumnutation etc.
Autophagy - Describing a process by which certain cells are able to digest superfluous or worn out cell organelles. An autophagic vacoule is formed around the portion of cytoplasm which has one or more such organelles and surrounding cytoplasm secretes hydrolytic enzymes into this, resulting in digestion of organelles and subsequent reabsorption of degradation products. See also autolysis.
Autophyte - A plant synthesising complex food substances from simple compounds, e.g., green plants.
Autopolyploid - A polyploid having identical sets of chromosomes, i.e., derived from the same species.
Autopotamous - Orginating in fresh water.
Autosome - A chromosome (other than a sex chromosome). It is
anormal chromosome, having its normal homologue.
Autospore - An aplanospore of algal cells which is similar in shape and size to the parent cell.
Autosyndesis - Used for the pairing of chromosomes which are coming from the same polyploid parents, or remote polyploid ancestors.
Autotetraploid - A tetraploid having four similar sets of chromosomes.
Autotroph - A plant using carbon dioxide as its sole source of carbon, or more generally a plant manufacturing complex organic compounds from simple inorganic sources. Autotrophic bacteria can employ carbon dioxide.
Autotropism - A tendency to grow in a straight line.
Auxanometer - A piece of apparatus which is used to measure the elongation of plant shoots. It involves a lever to exaggerate the actual growth.
Auxiliary Cell - An accessory cell present in the thallus of some Floridae from which the gonimoblast filaments grow, after the zygore nucleus gets migrated into it from the carpogomium.
Auxins (Plant Growth-Regulators; Plant Growth-Substances; plant hormones.) A substance which is produced inone tissue, and migrated to effect the development of another tissue. The tissues producting the auxin are typically meristematic, and the effect of the auxin is specific. They correlate the growth of the plant. There are certain substances, e.g., gibberillin, produced by one plant which may effect the growth of another plant when applied artificially. The best known is C18H32O5which causes elongation of individual cell in the growing tips of plants.
CONCENTRATION OF IAA, M
The effects of auxin concentration on the growth or different organs.
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