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Biomedical subjects

D L Johnson

Publications and source records attributed to D L Johnson.

At least 343 records · Page 19Linked to original sources
PubMed1972

Phycomyces: growth responses of the sporangium.

During the development of the sporangiophore of the fungus Phycomyces blakesleeanus there occurs a period of several hours when the sporangiophore does not elongate; instead, its "growth" is diverted into the formation of a sporangium at its top. This period of head formation is called stage II. Clearly, growth has not ceased but rather the geometry of the growing area has changed from that of a cylinder to a sphere. The growing sphere is found to have properties similar to the stage IV growing zone in that it functions as a sensory receptor and effector. The growing sporangium responds to both light (light head response) and humidity (wet head response). A model is presented giving a possible mechanism by which the ultimate size of the sporangium is regulated.

Journal Article↗
PubMed1971

The avoidance response in Phycomyces.

Phycomyces sporangiophores grow away from stationary objects, a phenomenon known as the avoidance response. Evidence is presented suggesting that a growth-stimulating gas is emitted from the sporangiophore and is then swept to the leeward side by air currents resulting in higher gas concentration on that side. The presence of a stationary barrier decreases the passive movement of the gas away from the leeward side. It is proposed that an increase of this gas on one side causes that side to grow faster. Indirect evidence suggests that the gas is water vapor.

Dark Adaptation↗
PubMed1969

Honey bee recruitment to food sources: olfaction or language?

Honey bee recruits locate food sources by olfaction and not by use of distance and direction information contained in the recruitment dance. Recruitment efficiency increases as odor of the food source accumulates in the hive, from hour to hour and from day to day. Flight patterns, landing patterns, bee odor, and Nassanoff secretion apparently do not aid in recruitment of bees.

Animal Communication↗