Amitosis - Used for the division of the nucleus by a median construction, without a normal mitosis taking place. The chromosomes to not become visible, and it is unlikely that two identical nuclei result.

Amphithecium - (1) The outer layer of the embryo of the Bryophytes which is derived early by the periclinal division of the cell.

(2) The thalline margin of a lichen apothecium.

Amphitrichous - Having a flagellum at each end of the cell.

Amphitropous - Of an ovule which is bending both wayson the stalk.

Amphivasal Bundle - A vascular bunbdle in which the xylem is surrounding the central strand of phloem.

Amylase - An enzyme which is responsible for the break-down of starch; part of the diastase complex. Amylase attacks the amylase part of the starch molecule, breaking it down to maltose. Amylase attacks the remaining part of the molecule, any amaylase breaking it down to dextrins (5-10 glucose units), which get further attacked by theamylase. Only the 1 :4 linkages in the amylose and amylopectin get attacked by these two enzymes.

Amyloplast - A colourless plastid which is modified for starch storages as in the potato.

Amylose - A long straight-chained polysaccharide, which is made up of about 300 glucose units linked in the 1 : 4 position (see amylopectin). It is a constitutent of starch, and is responsible for the typical blue colour of starches when treated with iodine solution.

Anabolism - Used for the formation of complex molecules from simple ones by living organisms. This process involves the storage of energy.

Anaerobic Respiration - Used for describing the enzymatic breakdown of a substrate releasing energy, without using oxygen. The anaerobic respiration of a given weight of a substrate gives out less energy than the aerobic respiration of the same weight of the same substrate. Facultative anaerobes can use free oxygen, obligate anaerobes do not. See alcoholic fermentation.

Anagenesis - Used for describing the rate or degree of evolution ary divergence.

Analogous - Used for structures which have the same appearance or function, but are not necessarily homologous.

Anandrous - Without stamens.

Anaphysis - A sterigma-like thread in the apothecium of some lichens.

Anatomy - Dealing with the study of structure and distribution of tissues alongwith the study of their component cells inside the body of an organism. Compare morphology.

Anatropous - Used for describing the form of ovule orientation in ovary in which funiculus gets lenghened and ovule is turned 180 on it so that micropyle is folded over and lies near the base of funiculus. It is the most common type of ovule. orientation in plants. Compare orthoropous; campylotropous.

Androdioecius - A plant species which has male and hermaphrodite flowers on separate individuals as in Caltha. Compare andromonoecious, gynodioecious.

Androecium - The whorl in flower which forms male component. It is made up of stamens and sometimes, staminodes, surrounding the innermost female whorl. It is represented in floral formula by letter A.

Androgynophore (Androphore). Used for describing an extension of receptacle of flower between petals and stamens, on which the androecium and gynoecium are borne e.g., in members of Capparaceae.

Androgynous - (1) Having stamens and ovraies present in distinct parts of the same inflorescence.

(2) Having male and female organs on, or in the same branch of the thallus.

Andromonoecious - Of an individual plant or of a species having individuals which bear male and hermaphrodite flowers on the same plant.

Androphere - An elongation of the receptacle of a flower between the corolla and the stamens.

Androsporangium. A sporangium which is producing the an drosporess.

Androspore - A special form of zoospore which is produced by the Oedogoniales. It gets germinated to form the dwarf male filament.

Anemochorous - Used for plants whose fruits or seeds get dispersed by wind; especially plants which retain their seeds or fruit throughout the winter, ready for dispersal in the spring

Anemophilous - Having seeds, pollen spores etc., which are dispersed by wind. I

Anergized Cultures - Used for long-established cultures which become able to synthesize auxins and thus become independent of their exogenous supply.

Aneuploid - A polyploid in which some of the chromosomes of2 one set are missing, so that the chromosome number is not an exact multiple of the haploid number, i.e., an unbalanced polyploid. Sees euploid.

Aneurin - A vitamin which probably promotes root-growth. A growth factor for some fungi and bacteria.

Aneuspory - Said of production of unusual number of spores (usually two) from a spore mother cell in a diploid plant through a modification of meiosis. In megaspore formation in Taraxacum, chromosomes stay in one cell after undergoing first meiotic division so as to form a restitution nucleus. Second meiotic division results in two cells each with unreduced number of chromosomess. One of them develops parthenogentically to yield embryo. Crossing over and hence reassortment of genes may take place during first meiotic division which may result in some of the variation found in apomictic complexes that have arisen by aneuspory.

Angiospermae. A class (sub-division) of the Spermatophyta. It is characterized by the ovules (female gameophytes) completely enclosed in an ovary which forms part of the flower, and swells at maturity to give rise to the fruit. The pollen grains (male gametophy) these are produced in anthers. Typically the xylem is having vessels.

Anisogamy - Used for decribing sexual reproduction involving two gametes which are similar in shape and structure but differ in size and/or motility. Compare isogamy, oogamy.

Annual - A plant which completes its life-cycle in a single season, i.e., a seed germinates and the mature plant so produced dies after having produced seeds, within the season.

Annual Ring - The increment of secondary xylem added to wood of a plant in a single year. In transverse section of wood one or more rings often appears, due to seasonal differences in diameter of tracheary elements. See also growth rings, ring porous wood.

AnnularThickening - The laying down of lignin in separate rings in the walls of xylem vessels and tracheids.

Annulate - (1) Ringed. Made up of ringed segments, or thickened in rings.

(2) Having a membranous ring which is persent on the stipe (of Agarics).

Annulus - (1) The ring of tissue which is found around the inside of the jop of a moss capsule. The cells below it dry out, causing the lid to fall off, and allowing the spores to get dispersed.

(2) An arc of cells which is found around the sporangium of a fern. The outer walls of the cells are not thickened, so that when the cells dry out, tensions are set-up which burst open the sporangium.

(3) The ring-like remains of the veil lift on the stipe after the expansion of the pileus of some Agarics.

(4) A ring of cells present around a bulbil. It takes part in the

vegetative reproduction of some fungi.

Anomocytic - See subsidiary cell.

Anther - The part of the flower of Angiosperms which is producing pollen (microspores), borne at the end of the stamens, and usually having four sporangia.

Anther Culture - Said of the culture of excised anthers on a suitable nutritive medium. Embryoids and subsequently haploid plants can be formed if anthers at a certain stage of development are taken and then cultured under appropriate condition of medium etc.

Antheridial Cell - Occurring in bryophytes and pteridophytes. A cell which is developing into an atheridium.