The loss of nodules from legume roots and its significance
1942
Wilson, J.K.
Wild white clover was grown under controlled conditions in the greenhouse to a height of about 4 inches and periodically clipped to a height of about 1/2 inch. Such a procedure probably simulates the maturing physiological conditions of many legumes and corresponds to the defoliation which such plants receive under conditions of good grazing management. It also imposes conditions on the root system similar to those which influence adversely the continuity of the nodules on the roots. This imposition reflects itself in the liberation of the nitrogen through the shedding and simultaneous decomposition of the nodules. This has provided a possible mechanism by which a nonlegume growing in association with a legume may obtain at least a portion of its nitrogen from the latter. Knowing that the nodules usually contain a high content of nitrogen, particular attention was given to the effect of defoliation on their disappearance and reappearance with new growth. It was noted that defoliation like shading, drying out of the soil or maturity of the plant, caused some of the nodules to be shed and subsequently to decay. It was noted also that at the initiation of new growth the starch in the nodules largely disappeared. If this withdrawal were sufficiently severe the nodules became waterlogged and usually disintegrated. This might account for the higher content of nitrogen expressed as percentage of the dry weight in the old nodules as compared to that in the new nodules. The disintegration of the nodules, liberating their high content of nitrogen in the soil, may also account for much of the increase of nitrogen in the nonlegume growing in association with the legume.
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