INFLUENCE OF VARIOUS NITROGENOUS COMPOUNDS AND MANNITOL ON NODULE FORMATION BY CLOVER

Abstract

Red clover plants were grown in bottles of a nutrient solution containing agar and various sources of N[long dash]KN03, (NH4)2SO4, urea, asparagin, clover-seed extract, and yeast extract[long dash]in concentrations of 2, 5, 10, and 20 mgm. of N per bottle. The N sources differed in their effects on number of nodules; and, with increasing concentration of N, results were not entirely consistent. All N sources used decreased the nodule size, and the greater the concentration, the smaller were the nodules. In untreated controls, most of the nodules were on or near the tap-root, a few nodules large or long but mostly of moderate size and round; in presence of N compounds the nodules were principally on the secondary roots and mostly round and small, [long dash]due probably to delayed invasion of the roots. In a 2nd series, 0.5% mannitol, added to the above substrate, abolished the effect of N on position of nodules, but not its effect on size, i.e., the nodules were small, and situated principally on the tap-roots.