Lecture 3 —49— Absorption 



never be satisfactorily approached if experiments were 

 limited to plants growing in so complex and so diffi- 

 cultly controllable a medium as that of the soil. There- 

 fore, experiments on barley plants growing in liquid 

 media — by the so-called water culture method — were 

 initiated and several general relations between the 

 composition of the nutrient media and the absorption 

 of nutrient ions by the plant were observed. 



Even at this earlier period a relatively vast litera- 

 ture existed on the subject of permeability of plant 

 and animal cells and certain concepts of antagonism 

 of ions had been well developed. Most of the methods 

 employed in the study of permeability were indirect 

 and frequently utilized conditions under which the 

 nonnal functioning of the cell could not be expected 

 to continue. Many studies were made on marine or- 

 ganisms living in media of high concentration and so 

 the conclusions were applied to plants growing in soils 

 with reservations. Specifically, we found compara- 

 tively little enlightenment from most of the permea- 

 bility researches with regard to the nature of the 

 processes occurring when plants grow in dilute salt 

 solutions comparable to those of many soil solutions. 

 It did not appear from our results, or from other per- 

 tinent evidence, that the intake of the nutrient ions 

 was merely a diffusion process proceeding to attain- 

 ment of equal concentrations or activities of a solute 

 in internal and external phases, as many texts then, 

 as well as some much more recent texts, taught. 



Studies on Nitella Cells : — In the state of develop- 

 ment of the subject at that time there were more 

 doubts than now concerning the interpretation of evi- 

 dence from experiments on complex plant tissues, 

 especially when the data were obtained by analyzing 

 the whole tissue or the saps expressed from the tissue. 

 Temporarily, therefore, we later turned to the fresh 

 water alga Nitella, which produces multinucleate inter- 

 nodal cells, often several inches in length, from which 



