ALLELOPATHIC EFFECTS OF FOUR <em>EUCALYPTUS</em> SPECIES ON COWPEA (<em>VIGNA</em> <em>UNGUICULATA</em>)

Abstract

Allelopathic investigations into the leachates of bark, fresh leaves and leaf litter of Eucalyptus tereticornis, E. camaldulensis, E. polycarpa and E. microtheca using paper and gas chromatography showed the presence of coumaric, gallic, gentisic, hydroxybenzoic, syringic and vanillic acids, and catechol. The influence of identified phenolics as well as leachates on germination, seedling length, dry matter production, vigour index and nitrogenase activity of cowpea (CO.6) was investigated. Germination was inhibited in all the cases except catechol and coumaric acid at 2 mM concentration. Vigour index was affected by catechol, gallic and syringic acids. Bioassay with leachates revealed inhibition in germination in all the cases, seven days after sowing. Dry matter production and vigour index were reduced by E. tereticornis, E. camaldulensis and E. microtheca. Seedling length was affected in all cases except E. tereticornis, 37 days after sowing. Dry matter production was affected by E. tereticornis and E. camaldulensis. Reduction in vigour index and nitrogenase activity was also noted in all cases, compared with the control.