(n.) A small membranous bladder or tube in which are inclosed the seedlike reproductive particles or sporules of lichens and certain fungi.
Example Sentences:
(1) Fungi of the class Pyrenomycetes (Ascomycotina) form a morphological series ranging from those that shoot ascospores (sexual spores) forcibly from the ascus (spore sac) to fungi that ooze ascospores or have no obvious mechanism for ascospore release.
(2) Our results suggest that once the cells are fully derepressed no mitochondrial genetic information has to be expressed during meiosis and ascus formation.
(3) Although growth of two yeast strains characterized by consistent production of two diploid spores per ascus was inhibited in complex presporulation media containing amitrole, a fraction of the cells produced were able to form asci with more than two spores after transfer to acetate sporulation medium.
(4) Due to the characteristic shape of the ascus and ascospores, T. burgeffiana is to be considered a synonym of M. pulcherrima.
(5) Although the rna mutants do not regulate ribosome synthesis during sporulation, all of these diploid strains fail to complete sporulation at 34 degrees C. The cells are arrested after the second meiotic nuclear division but before ascus formation.
(6) strains develop normally to the stage of ascus formation.
(7) The selected hybrids, which carried the greater part of the parental genetic markers and produced asci containing 2,3 and 4 spores per ascus, were placed on sporulation medium.
(8) 2 x n X2 tests showed that frequencies of individual ascus classes from different perithecia were generally homogeneous, as were second division segregation frequencies.
(9) The proportion of spindle overlap and recombinational asci within the group did not change as shown by ascus dissection.
(10) It was demonstrated that the production of less than four spores per ascus in this yeast is not the result of a lack of meiotic products but of the nonutilization of nuclei from meiosis.
(11) The forespores then elongate, close off, and become separated from the ascus cytoplasm by membranes.
(12) The mechanical force responsible apparently originates from the formation of an ectoplasmic mucilage capable of exerting pressure over all of the ascus contents; when the apex of the peduncle ruptures, the ascospores are violently released.
(13) When partially repressed cells were treated with EthBr, no ascus formation was observed after transfer to sporulation medium.
(14) In fungi that produce an ascus containing four spores, a gene conversion event is manifested as 3:1 or 1:3 (or more rarely 4:0 or 0:4) segregations, in contrast to the normal mendelian 2:2 segregation.
(15) The increase in spore numbers per ascus is attributed either to the induction by amitrole in growth medium of cells with more than one nucleus or to the restoration of normal meioses in the multispored asci.
(16) On the basis of mode of ascus formation and ascospore morphology it is included in the genus Metschnikowia Kamienski as a new species, M. lunata.
(17) Ascus formation occurs after isogamous copulation between sexual protuberances which develop at the ends of arthrospores or between two cells, adjacent mycelial cells, or arthrospores.
(18) Ascus formation in Debaryomyces hansenii includes fusion of two cells, usually mother and daughter while still attached to each other, through short protuberances developed from the cross wall between them.
(19) Metschnikowia australis can be differentiated from other Metschnikowia species and varieties by its inability to form chlamydospores, the formation of two needle-shaped ascospores per ascus, lack of glucose fermentation, and lack of assimilation of both methyl-alpha-D-glucoside and glucono-delta-lactone.
(20) Amitrole treatment causes multispored ascus production by cells of a yeast strain whose asci normally contain two diploid spores.
Basidium
Definition:
(n.) A special oblong or pyriform cell, with slender branches, which bears the spores in that division of fungi called Basidiomycetes, of which the common mushroom is an example.
Example Sentences:
(1) Depending on the stage reached at the time of exposure to the inhibitors, vegetative hyphal tips emerged from the four apical sites for sterigmata, from the tips of sterigmata, from partially formed or abnormal spores, and from the basal regions of the basidium from which paraphyses would be expected to arise.
(2) The number of spores per basidium in the cultivated mushroom Agaricus bisporus can be readily determined using the light microscope.
(3) Microtubules mainly oriented parallel to the longitudinal axis of the basidium are present at prefusion, prophase I and interphase I. Cytoplasmic microtubules are absent when the spindle is present.
(4) The double centrosome in the basidium of Boletus rubinellus has been observed in three planes with the electron microscope at interphase preceding nuclear fusion, at prophase I, and at interphase I.
(5) A golgi apparatus believed to be involved in basidiospore formation has been found in Coprinus lagopus following meiosis in the basidium.
(6) Of a range of compounds tested, only ammonium and glutamine, and some structural analogues, were able to inhibit basidium differentiation.