Phycomyces: a change in mechanical properties after a light stimulus.

Tensile tests were conducted on the photoresponsive stage IVb sporangiophore of the fungus Phycomyces before and after a saturating light stimulus. The results demonstrate that an increase in the mechanical extensibility of the cell wall occurs after the light stimulus. This increase in mechanical extensibility occurs in the growing zone of the sporangiophore. The majority of this increase occurs in the region about 300 umeters beneath the sporangium.