THERMOTROPISM OF ROOTS 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 192 



Sophia Eckersox 



(with six figures) 



I. The thermotropic curvatures of certain roots at temperatures 



from io° to 40 C. 



permeability 



from io° to 40 C. 



Introduction 



Our knowledge of thermotropism is in a somewhat confused 

 state. We know little about the thermotropic response of stems. 

 A few scattered observations have been made, indicating that stem 

 tips turn toward the source of heat at low temperatures and away 

 from it at high temperatures. More exact investigations have been 

 made of the thermotropic curvatures of roots, but here there seems 

 to be no uniformity of behavior. Under the influence of unequal 

 temperature on two sides, the roots of different species react differ- 

 ently. Some roots give positive curvatures at low temperatures 

 and negative at high temperatures; others show only positive 

 curvatures, and still others give only negative curvatures. It was 

 with the purpose of clearing up these apparent discrepancies and 

 the hope of finding the physical mechanism of the curvatures that 

 the present investigation was undertaken. 



Thermotropic curvatures of roots 



LITERATURE 



The two important papers on thermotropism of roots are 

 Wortmann's (10) and Klercker's (2). WoRTMANN investi- 



gated four species: 



Mays 



Phaseolus multi floras. He concluded that roots have positive 

 thermotropism at low temperatures and negative at high tempera - 



Botanical Gazette, vol. 58 j 



1*54 



