THE DIURNAL FLUCTUATION IN NITROGEN FIXATION IN THE NODULES OF ALNUS GLUTINOSA AND MYRICA GALE

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Abstract
Summary: Maximal rates of nitrogen fixation in the root nodules of first‐year plants of Alnus glutinosa and Myrica gale growing under natural illumination but at nearly constant temperature were found by the acetylene assay to be attained about midday. The nitrogen content of the sap exuding from the stumps of decapitated plants and the level of soluble nitrogen in the nodules were also highest close to midday, the same being true of the rate of respiration in detached nodules.The hypothesis that in view of these findings the midday period must be that of maximum ingress of photosynthates into the nodules is not reflected in analyses of gross carbohydrate levels in the nodules at different times of day.