In vitro bioassay of allelopathy of Arabidopsis thaliana by sandwich method and protoplast co-culture method with digital image analysis.

We examined the allelopathic activities of Arabidopsis thaliana, ecotype Columbia by two in vitro methods. The effect of dried leaves on the growth of recipient lettuce seedlings was examined by the sandwich method. The allelopathic activity on protoplast growth was examined by co-culture with recipient lettuce leaf protoplasts in 50 µl liquid medium using a 96-well culture plate. Non-spherically enlarged or dividing protoplasts of lettuce were counted under an inverted microscope. Inhibition of yellow accumulation during lettuce protoplast growth was quantitated by image analysis of scanned digital images of 96-well culture plates. The results were described as the percentages of control without A. thaliana. The results were compared with those obtained using several plants which had strong allelopathic activities on recipient lettuce using the same methods. The growth of lettuce protoplasts was inhibited at both 4 and 8 days of culture with protoplasts of A. thaliana. The results suggested the usefulness of the protoplast co-culture method for future studies on allelopathy.