Influence of Potassium Nitrate on Nodule Formation and Nitrogen Fixation by Clover

The Influence of the Legume in Root‐nodule Symbiosis

“…The nitrogen nutrition of the nodulated legume occupies a special place because of the marked depressing effect of combined nitrogen on infection, nodule size and function, the reduction in nodule number and size and activity being generally proportional to concentration (Wilson, 1917;Hopkins, Wilson & Peterson, 1932; and others) and varying greatly with species of host (Nowotny-Mieczyfiska & Ruszkowska, 1952). 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.…”

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

“…In the normal plants there were a number of the long type of nodules, which are simply large nodules, while the largest number were of the round t-ype, or small nodules. When the nitrogen sources were added, this distribution was changed as was noted for nitrate in a previous publication (9). Even in the lowest concentration (2 mg. of N) of KNO3, (NH4)2S0, urea, and asparagin, the nodules were found, not principally on the tap-root but almost exclusively on the secondary roots.…”

“…The heavy growth of bacteria which occurred on the surface of the agar and along the plant roots of the mannitol-nitrate set apparently exerted a toxic effect upon the plants. The number of nodules is decreased significantly only in the 10-mg. set in series 2. With all of the nitrogen present at the start, it was found in a previous experiment (9) that the number of nodules was irregularly affected. The distribution of the nodules in series 1 is affected as noted previously (9) Thie number of nodules was irregularly affected by the nitrogen treatment.…”

“…METHODS.-The methods and details of planting are given in the previous paper (9). In the tests where mannitol was added, the concentration used was 0.5 per cent.…”

“…In a previous paper (9), the ilifluence of nitrate upon the nunmber and distribution of nodules on red clover plants was considered. It seemned desirable to continue this work, using a nlumber of organic nitrogenous compounds.…”