Annals 
of 
Missouri Botanical Garden 
Vor. 7 FEBRUARY, 1920 No. 1 
HYDROGEN ION CONCENTRATION AND THE COM- 
POSITION OF NUTRIENT SOLUTIONS IN RE- 
LATION TO THE GROWTH OF SEED PLANTS 
B. M. DUGGAR 
Physiologist to the Missouri Botanical Garden, in Charge of Graduate Laboratory, 
Professor of Plant Physiology in the Henry Shaw School of Botany of 
Washington University 
INTRODUCTORY 
By the use of the terms mineral nutrition or salt requirements 
of plants there is connoted a group of physiological processes 
and environmental conditions in which the mineral salts play 
an important róle. Without entering into an elaborate discus- 
sion of these terms it may at least be pointed out that perhaps 
neither one is satisfactorily comprehensive. The last-men- 
tioned is vague, and the other inadequate, due to the fact that 
when plants are grown in a so-called nutrient solution, as is well 
known, it is not merely the nutrient róle the effects of which are 
followed. The concentration of the solute molecules and com- 
ponent ions of the culture solution directly affect the turgor, or 
osmotic surplus; the proportions of the ions—particularly of the 
cations—influence the permeability relations, which, operative 
through the protoplasts, seem to be the fundamental consideration 
in certain ““antagonism ” phenomena; the composition of the salts 
employed determines the acid-alkali equilibrium, that is, the hy- 
drogen ion concentration, the influence of which is apparently 
most complex; and these and other possibilities affect ultimately 
growth, which, in part, of course, involves the incorporation into 
the living framework of the ions of the component salts. 
ANN. Mo. Bor. Garp., Vor. 7, 1920 (1) 
34297 
