FREE AMINO ACID POOLS, 15N2 FIXATION AND FIXED N2 ASSIMILATION IN LEUCAENA LEUCOCEPHALA VAR. K‐8

Various organs of Leucaena leucocephala (Lam.) de Wit were analyzed for their levels of total nitrogen and free amino acids as well as for changes in free amino acid pools from the time of germination through nodulation. Also an assessment was made of the sink of fixed N2 (transport product) in the nodules using 15N methodology. L. leucocephala organs showed total nitrogen levels similar to those of other legumes. Asparagine was the most prevalent amino acid in the nodules and roots followed by glutamate and mimosine. Asparagine was the second most common amino acid in the leaves and stems, with mimosine being the most abundant. Strong correlations were found between the total plant levels of aspartate and glutamate, asparagine and NH4+, acetylene reduction and glutamate, and asparagine and plant age. Asparagine amino‐ and amide‐N accounted for over 75% of the fixed 15N2 in nodules. It was concluded that L. leucocephala is an asparagine transporter of fixed N2 in the nodule.