Phycomyces: detailed analysis of the anemogeotropic response

Area of Science:

• * Plant Biology
• * Mycology
• * Sensory Biology

Background:

• * Phycomyces sporangiophores display anemotropic (wind-following) and geotropic (gravity-avoiding) growth responses.
• * Understanding these responses is crucial for plant tropism research.
• * Existing models predict an inverse relationship between anemotropism and humidity.

Purpose of the Study:

• * To measure the anemogeotropic equilibrium angle under simultaneous wind and gravity stimuli.
• * To investigate the influence of wind speed and relative humidity on this angle.
• * To test predictions of the mass transfer model for anemotropism.

Main Methods:

• * Developed a procedure to measure the equilibrium bend angle of Phycomyces sporangiophores subjected to simultaneous wind and gravity.
• * Exposed sporangiophores to varying wind speeds and relative humidity levels over extended periods.
• * Measured the resulting anemogeotropic angle relative to the vertical.

Main Results:

• * The anemogeotropic angle increased with both increasing wind speed and increasing relative humidity.
• * This finding contradicts the mass transfer model's prediction of an inverse relationship between anemotropism and relative humidity.
• * Experimental data suggest that self-emitted water vapor is responsible for both anemotropic and avoidance responses.

Conclusions:

• * Phycomyces anemotropism is positively correlated with wind speed and relative humidity.
• * The mass transfer model's prediction regarding humidity is challenged by these findings.
• * Water vapor is implicated as the signaling molecule in Phycomyces anemotropic and avoidance behaviors.