Robert M. Page

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 phys...

STUDIES ON PHOTOTROPISM OF YOUNG SPORANGIOPHORES OF PILOBOLUS KLEINII

Abstract— Young sporangiophores of the fungus, Pilobolus kleinii, respond to unilateral illumination by bending or by growing toward light of wavelengths between 312 and 530 mμ, with peaks of sensitivity near 360 and 450 mμ. Young sporangiophores exhibit a negative phototropic response to wavelengths shorter than 300 mμ, with a strong negative response at 280 mμ. Since the action spectrum did not correspond to the absorption spectrum of the pigmented zone as measured in vivo, and since colorless sporangiophores formed on media containing diphenylamine were capable of phototropic response, it is unlikely that the conspicuous orange‐yellow pigment in young sporangiophores is the photoreceptor for phototropism. The results of probing with small beams of light and the behavior of sporangiophores submerged in mineral oil, together with measurements of the refractive index of the tip and base indicate that the photosensitive region is located in the tip of the young sporangiophore.

Sporangium Discharge in Pilobolus: A Photographic Study

Stages in the discharge of sporangia by the fungus, Pilobolus kleinii, were photographed by means of a high-speed electronic flash triggered by a photocell. The photographs confirm that the sporangium is propelled by a jet of cell sap. The jet is deflected from the sporangium and attains a considerable length before it breaks into droplets.

The Effect of Ammonia on Growth and Reproduction of Pilobolus Kleinii

The weight of mycelium and the numbers of trophocysts and zygospores produced by Pilobolus kleinii were greatly increased when certain concentrations of ammonium ion were added to a basal medium wh...

Phototropism in Conidiobolus, Some Preliminary Observations

The action spectrum for phototropism of Conidiobolus conidiophores was determined crudely with glass filters and by projecting a spectrum on cultures of the fungus. The active wavelengths (about 400 to 650 m�) corresponded in general with those absorbed by extracts containing a pigment with an absorption spectrum characteristic of a porphyrin.

Phototropism in Conidiobolus Coronatus

The phototropic responses of Conidiobolus coronatus (Cost.) Batko have been investigated with an emphasis on the responses of the secondary conidiophore. The effects of pH, nutrients, and osmotic p...

The Effect of Temperature and Relative Humidity on the Longevity of the Conidia of Helminthosporium Oryzae

Brown spot of rice caused by Helminthosporium oryzae van Breda de Haan is a disease of importance wherever rice is grown. It causes most damage as a seedling blight, but may lower the yields of more mature stands to some extent by leaf lesions which reduce the effective photosynthetic areas of the leaves. On kernels, brown spot produces lesions which impair the milling quality of rice as well as the yield. Control of the disease consists mainly of seed treatments (Nisikado and Miyake, 1920, Lin, 1936) and field sanitation (Wei, 1936). Secondary spread of the disease is brought about by conidia which are banana-shaped, 5-9 celled reproductive bodies 80-130 p long by 16-22 pt wide. Helminthosporium oryzae has been shown to possess extensive longevity in culture. Nisikado (1922) reported keeping it in culture for 943 days without transfer after which it resumed growth when fresh medium was added. Wei (1936) found that infested portions of rice plants could be stored on trees, on soil and underground for considerable periods without loss of viability by the fungus. In no case, however, has it been clear whether the vegetative mycelium or the conidia were responsible for the persistence, and the conditions of storage were not controlled. Since H. oryzae produces large numbers of conidia on the leaves and heads of infected rice plants during favorable weather conditions, it was of interest to learn something of the longevity of the conidia under various environmental conditions. Therefore ex-