The hydrion concentration of plant tissues
In previous articles of this series we have given a general survey of the reaction of stem tissues in a number of families (5), a general survey of the tissue reactions throughout the life-periods of the sunflower (1) and of the bean (6), and also an indication of the possible importance of the carbon dioxide content as a factor governing the hydrion concentration of the cell, especially between pH 6"0 and pH 4"0 which is the usual range in plant tissues (2). In the present article we summarise the data obtained during a general survey of selected herbaceous and woody stems, examined at monthly intervals throughout the year.
ABSORPTION OF NUTRIENTS AND PLANT GROWTH IN RELATION TO HYDROGEN ION CONCENTRATION
The absorption of nutrients depends to a large extent on the reaction of the substrate. At maximal growth the intake of salt is at minimum. Different ions are very differently affected. The intake of water is independent of the absorption of salts.
DIRECT AND INDIRECT DETERMINATIONS OF PERMEABILITY
1. Methods are described for obtaining cell sap from Nitella without contamination. 2. Tests of the cell sap show that in a balanced solution of NaNO3 plus Ca(NO3)2 there is a slow penetration of NO3 and that the cell remains in a normal condition, but in pure NaNO3 there is rapid penetration accompanied by injury. 3. Inasmuch as determinations of electrical conductivity give the same result it may be concluded that this method gives reliable information regarding permeability. 4. While observations on recovery from plasmolysis give similar results, the method is less satisfactory.