Effects of microbial products on net efflux of amino acids in hydroponic solutions surrounding axenic alfalfa roots. Total efflux +se of 16 amino acids was determined over a 3-h period for plants treated with Z, DAPG, or PHZ. Means identified with *, **, or *** differed significantly from the untreated control by P ≤ 0.05, 0.01, or 0.001, respectively.