Characterization of thermotropism in primary roots of maize:  dependence on temperature and temperature gradient, and interaction with gravitropism.
Thermotropism in primary roots of Zea mays L. was studied with respect to gradient strength (degrees C cm-1), temperature of exposure within a gradient, pre-treatment temperature, and gravitropic stimulation.  The magnitude of the response decreased with gradient strength.  Maximum thermotropism was independent of gradient strength and pre-treatment temperature.  The range of temperature for positive and negative thermotropism did not change with pre-treatment temperature.  However, the exact range of temperatures for positive and negative thermotropism varied with gradient strengths.  In general, temperatures of exposure lower than 25 degrees C resulted in positive tropic responses while temperatures of exposure of 39 degrees C or more resulted in negative tropic responses.  Thermotropism was shown to modify and reverse the normal gravitropic curvature of a horizontal root when thermal gradients were applied opposite the 1 g vector.  It is concluded that root thermotropism is a consequence of thermal sensing and that the curvature of the primary root results from the interaction of the thermal and gravitational sensing systems.
Fortin M-C
MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing 48824-1312, USA.
Poff
K L
KL
D018522:Gravitropism / Q000502:physiology*; D018517:Plant Roots / Q000254:growth & development* / Q000502:physiology; D013696:Temperature; D018523:Tropism / Q000502:physiology*; D003313:Zea mays / Q000254:growth & development* / Q000502:physiology