Abstract

Protoplasts isolated from calluses of two woody leguminous plants, Leucaena leucocephala and Mucuna gigantea, which contain high levels of the allelochemical amino acids, mimosine and l-DOPA, respectively, were co-cultured to examine their allelopathic activities. The young leaves were first confirmed to have strong inhibitory activity by the sandwich method. Callus cultures were induced and sub-cultured from seeds of L. leucocephala and from leaves of M. gigantea in Murashige and Skoog’s (MS) basal media containing high concentrations of auxin and cytokinins. Protoplasts of both calluses were isolated using the separate well method under strong enzymatic conditions, in high osmotic, 0.8 M mannitol solution. Protoplasts of both species had strong inhibitory effects on the recipient protoplasts of cotyledons of Lactuca sativa (lettuce) co-cultured using 96 multi-well culture plates in the MS basal medium, containing 1 ?M 2,4-dichlorophenoxyacetic acid, 0.1 ?M benzyladenine and 0.8 M mannitol solution. Mimosine was less inhibitory than l-DOPA on the growth of lettuce protoplasts at the stage of colony formation. Amino acid profiles of calluses and protoplasts of the above two species and Mucuna pruriens showed very low contents of mimosine and l-DOPA, respectively. The cause of the high inhibitory allelopathic activities found in Leucaena and Mucuna protoplasts on the growth of lettuce protoplasts was discussed.

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