r 



PERMEABILITY OF CERTAIN PLANT MEMBRANES 



TO WATER 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 230 



F. E. Denny 



(with TWO figures) 

 Introduction 



In the exchange of material between the plant and its environ- 

 ment > 3 groups of substances may be considered important, namely, 

 water, gases, and salts. These enter the plant, pass from one 

 portion to another, and some of this material finally passes out 

 into the environment again. In this process a great many mem- 

 branes must be penetrated. The permeability of these membranes, 

 therefore, is a factor in this material exchange, determining in a 

 measure what substances may enter or leave the plant and at 

 what rate this entrance or exit can take place. For this reason 

 measurements of the permeability of plant membranes become 

 desirable. While much work has been done toward this end from 

 a qualitative standpoint, and while many indirect measurements 

 have been made, direct quantitative measurements in which the 

 results could be referred to known areas of membranes, under a 

 standard set of conditions, have been lacking. 



This paper deals with an attempt to get quantitative data on 

 the permeability of certain plant membranes to water; to determine 

 what laws, if any, hold for the rate of penetration of water as 

 related (i) to temperature, (2) to direction of flow through mem- 

 branes, (3) to concentration of the bathing solutions, and (4) to 

 species of plant under consideration. 



Membranes 



Non-living membranes such as seed coats and the outer scale 

 of the onion bulb were used, as they were suitable for use with the 

 apparatus employed. The importance of non-living membranes 



373I 



(Botanical Gazette, vol. 63 





