Process Of Spore Germination Research Articles

Reversible inhibition of spore germination by alcohols.

Low levels of alcohols have been found to inhibit the process of spore germination. The extent of germination is dependent upon the concentration of alcohol present in the germinating medium. This inhibition is reversible since removal of the alcohol from the spore environment allows germination to proceed.

Reversible Inhibition of Spore Germination by Alcohols 1

Low levels of alcohols have been found to inhibit the process of spore germination. The extent of germination is dependent upon the concentration of alcohol present in the germinating medium. This inhibition is reversible since removal of the alcohol from the spore environment allows germination to proceed.

Light- and Electron-Microscopic Observations on Spore Germination in Funaria hygrometrica

The process of spore germination in Funaria hygrometrica has been analyzed with light- and electron-microscopic techniques, using laboratory cultures. Dry (ungerminated) spores were successfully fixed, imbedded, and sectioned for both light and electron microscopy. Light is necessary for the germination of spores in inorganic media but unnecessary for germination when glucose is present. Ungerminated spores gave a negative reaction to I2KI, but a positive reaction to Sudan dyes was exhibited by one or two large lipid bodies. The mercuric-bromphenol blue reaction revealed a diffuse network of protein and staining of organelles. The periodic acid-Schiff's (PAS) reaction stained the intine deeply and the cytoplasm faintly. After 24 hr in light, the moistened spores gave a positive starch reaction (particulate bodies), a positive PAS reaction (intine staining and particulate bodies in the cytoplasm staining), and the same lipid and protein reaction as above. After 24 hr in darkness, the moistened spores reacted exactly the same in these tests. Electron microscopy revealed that the effect of darkness and inorganic medium on spore germination was one of temporary retardation of development, especially as regards the internal structure of the chloroplasts. This effect was negated in time so that, after 2 weeks in darkness, the chloroplasts in light- and dark-treated spores appeared identical. The effects of a combination of darkness and organic medium (glucose) were more striking. The chloroplasts in this case were identical in appearance with those in the ungerminated spores, the Golgi bodies were seen to be much more active, and the cell walls were much thicker.

Properties of germinating spores of Dictyostelium discoideum.

The process of spore germination in Dictyostelium discoideum consists of three sequential stages: activation of dormant spores, swelling of activated spores, and emergence of myxamoebae from swollen spores. Dormant and activated spores are resistant to heating, freezing, or drying. Drying and freezing, moreover, may maintain the activated state until the spores are returned to normal conditions. Low temperature incubation after heat shock or the presence of an autoinhibitor will return activated spores to the dormant state. The entire spore germination process is aerobic, being inhibited at any point by oxygen deprivation or respiratory poisons. Each spore of this social organism appears to germinate at its own rate and independent of the other spores in the suspension.

Mutagenic Actions of Cold and X-Rays in Streptomyces

Storage of germinating Streptomyces spores in the cold results in a high frequency of mutation, equivalent under optimum conditions to that caused by X-ray doses of 1000 r or more (1). Further, during the process of spore germination, sensitivity to the mutagenic effect of cold rises sharply, and this rise is at least superficially similar to the increase in sensitivity to X-rayand ultraviolet-induced mutation observed in previous studies (2). Although precise comparisons of the timing of the increases in sensitivity to cold and to radiation had not been carried out, the apparent similarity suggested that an important part of the chains of events leading to mutation might perhaps be common to both kinds of mutagenic agents (3). In view of such a possibility, it was desirable to compare the mutagenic actions of cold and radiation in much greater detail. Parallel observations have therefore been made on the response to cold and to X-rays, comparing in particular (1) the timing of the sensitivity changes, (2) the dose-effect relationships, (3) the effectiveness of combined treatments (as compared with increased exposures to either agent singly), and (4) the relationships between mutation and survival.

OBSERVATIONS ON THE DISEASE OF SEA LYME‐GRASS (ELYMUS ARENARIUS L.) CAUSED BY USTILAGO HYPODYTES (SCHLECHT.) FRIES.

Ustilago Hypodytes was recorded by Berkeley & Broome (1841, 1850) and occurs on Elymus arenarius and Agropyrum species. A knowledge of its life‐history on these plants appeared desirable in view of the possibility of an extension in host range to nearly related cereals, added emphasis being given to this viewpoint by the recent production of perennial Triticum‐Agropyrum hybrids. Elymus arenarius is widely planted to prevent coastal erosion, and no knowledge was available of the effect of the fungus on its suitability for this purpose. The virtual absence of seed production by infected plants is known. In America, Ustilago hypodytes was described by Fischer (1938) as an increasing menace to the cultivation of Agropyrum cristatum (L.) Beauv. and other valuable forage grasses. The disease on Elymus was studied by Bornhövd (1936), who gave a full summary of the literature. She described the process of spore germination and the growth and nuclear behaviour of the fungus on artificial media, but dealt less adequately with the symptoms and spread of the disease and the histology of infection: her inoculation experiments were inconclusive.