Phycomyces: Control of transpiration and the anemotropic reversal

Transpiration rates of single sporangiophores of the fungus Phycomyces blakesleeanus were measured with a microbalance. Sporangiophores transpired at the same rate at both high and low humidities. The transpiration rate was independent of sporangiophore length in the major growth stage, IVb. This finding is consistent with transpiration occurring only in the growing zone, where the cuticular layer is less developed. Sporangiophores in a wind tunnel, which were bending into the applied wind, showed a temporary reversal in their direction of bending in response to a humidity decrease. These results further confirm that water plays a role in the anemotropic and avoidance responses.