Number Of Sporangia Research Articles

The influence of cattle excreta on sporulation of {itPhytophthora cinnamomi} Rands

Abstract The number of sporangia on mycelial mats of Phytophthora cinnamomi Rands floated in non-sterile extracts of Auckland soils was increased more than twofold by first amending the soils with aqueous extracts of freshly collected cow's dung or urine 1 week previously. Autoc1aving the extracts or passing them through a 100 mμ millipore filter removed the enhancement factor which appears to be ineffectual unless sporangial initiation factors are already present, as in non-sterile soil extract. The enhancement factor from a dung extract which had been passed through a 0.45 μ filter remained effective in resuspended residue from a 100 μm filter. The factor may have been associated with some of the gut flora which remained in the residue. The enhancement factor is present in naturally amended farmyard soil. It reached comparable levels within 2 weeks in soils below a surface layer of added excreta in an ungrazed area of grassland and was maintained by a further addition of excreta at the end of the second...

Studies on the Development of Asexual Reproductive Structures in Pilobolus

SUMMARYThe formation of trophocysts and sporangiophores in a strain of Pilobolus kleinii which formed trophocysts only after the mycelium had been exposed to light was investigated by altering physical and chemical factors in the environment. A determination of the action spectrum showed that light with wavelengths between 380 and 410 mμ was effective in inducing the formation of trophocysts. Since carotinoids and flavins absorb light in this portion of the visible spectrum, an effort was made to determine which of these classes of compounds was involved by the use of inhibitors. Diphenylamine, which inhibits the formation of certain carotinoids, had no consistent effect on trophocyst formation although pigment formation was suppressed. L-lyxoflavin, which has been reported as a competitive inhibitor of riboflavin, strongly inhibited trophocyst formation. This inhibition of trophocyst formation by lyxoflavin was overcome in part by increasing the duration of exposure of the mycelium to light and was almost completely reversed by addition of riboflavin. The results of trials with inhibitors suggested that it is a flavin rather than a carotinoid in the mycelium of Pilobolus which absorbs light to initiate trophocyst formation. Investigation of the factors affecting sporangiophore initiation by trophocysts showed that (a) few sporangia were produced by trophocysts allowed to develop either in darkness or in continuous light, and (b) when cultures were exposed to light twice, the number of sporangia was proportional to the duration of the second exposure. These results were taken to indicate that light stimulates the initiation of sporangiophores by trophocysts and that the exposure of trophocysts to light is most effective if preceded by a period of darkness.

A Neutral (?) Strain of Mucor sphaerosporus from Missouri

In the caves of the Ranken estate in Missouri, where the atmosphere is moist and the temperature approximately 160 C., was found a segment of a twig matted with a growth of mycelial threads, white in a mass, and hyaline when single. The appearance of the latter was that of many fine root hairs. When transferred to agar substrates, numerous sporangia, sporangioles, oidia, and chlamydospores developed, with no evidence of zygospores. The characteristics and description were similar to those given by Lendner ('08) for Mucor sphaerosporus Hagem 1908. This fungus has been reported chiefly from Europe, and in this country by Waksman ('16) and Gilman and Abbott ('27), as isolations from soil. As far as the author could determine, this is the first report of the above organism from Missouri. A culture sent to Dr. A. F. Blakeslee at the Carnegie Institution of Washington, Department of Genetics, was tested with strains of presumably the same species, one being a minus isolated by Waksman in 1915, and another a plus strain probably from the Centralstelle, of unknown origin. No zygospores were produced. An attempt was made to obtain imperfect hybridization by treating this strain with some of the strong testers in the above laboratory, but no sexual reaction resulted. Growth on various media produced changes in the amount of mycelium, size and number of sporangia, sporangioles, hyphae, oidia and chlamydospores, and in chromogenesis. Thanks are due Dr. Blakeslee and Miss Satina of the Carnegie Institution of Washington for their interest and assistance.