Influence of Various Nitrogenous Compounds and Mannitol on Nodule Formation by Clover

The Influence of the Legume in Root‐nodule Symbiosis

“…At low levels of added nitrogen Fred & Wilson (1934) and Orcutt & Wilson (1935) found that some stimulation of infection and nitrogen fixation occurred which was thought to be due to a stimulatory effect on photosynthesis. The influence of added nitrogen was not confined to nitrate, other inorganic and organic forms of nitrogen having similar if less'marked effects (Wilson, 1917;Hopkins & Fred, 1933) and could be largely overcome by encouraging increased photosynthesis with high light and supplementary carbon dioxide (Fred & Wilson, 1934; Weber, 1930;Georgi, 1935;and others) or providing the plant with added carbohydrate in the form of sucrose, dextrose or levulose (Wilson, Fred, 1933), although the sparse nodulation of etiolated peas in the dark was found to be inhibited rather than stimulated bv added sucrose (McGonagle, '949).…”

The Response of Soybeans to Sources of Nitrogen in the Field1

“…Nitrate nitrogen has usually reduced the number of nodules and nitrogen fixation by legumes (6,7,8,II,I2,I3), while small amounts of nitrates and ammonium sulfate have been reported to stimulate nodule production.…”