Evaluation of Allelochemicals, Abscisic Acid and Coumarin, in Leaf-Origin Suspension Cultured Cells of Prunus yedoensis Using Protoplast Co-Culture Bioassay Method

Allelopathy is a mechanism in which the plant produces allelochemical(s) to survive in nature, by inhibiting the growth of neighboring plants in the field. Dried leaves of Prunus yedoensis and P. lannesiana (50 mg) showed strong inhibitory allelopathic activities. Coumarin in the leaves of P. lannesiana is known and used for its anti-bacterial activity and specific flavor. It is also known as a strong allelochemical in the leaves of a leguminous tree, Gliricidia sepium. However, its role as an allelochemical in Prunus species has not been well investigated. Inhibitory activities of abscisic acid (ABA), a plant hormone, are on the growth of plant protoplasts. The role of ABA on protoplast cultures as an allelochemical in Prunus species has also not been studied.

In this study, the authors first examined the allelopathic activities of young leaves of P. yedoensis and P. lannesiana using the sandwich method; then they reported the effects of both ABA and coumarin on both protoplast cultures of lettuce and P. yedoensis; finally, the content of coumarin in suspension cells of P. yedoensis originating from leaves was investigated. Young leaves and peduncles of Prunus yedoensis and P. lannesiana trees grown in the Yokohama National University were used directly for induction of suspension cultures. Lactuca sativa (lettuce) seeds (Great Lakes) were sterilized with 1.5% NaClO aqueous solution for 15 min, washed with autoclaved water three times and sown on 0.8% agar medium. Contents of abscisic acid in protoplasts were measured using small scale purification and Enzyme Linked Immno Sorbent Assay, and contents of coumarin in leaf-origin susepension cells of P. yedoensis were measured using Gas Chromatography-Mass Spectrometry.

The results indicated that coumarin inhibited the growth of lettuce protoplasts from low concentrations while abscisic acid stimulated. Abscisic acid inhibited the protoplast growth of P. yedoensis from low concentrations while coumarin did not, but inhibited only at a high concentration (1 mM). Coumarin was more likely the allelochemical causing the strong inhibitory allelopathic activities of P. yedoensis in the protoplast co-culture bioassay.

In conclusion, though lettuce seems to be sensitive as a recipient plant, the protoplast co-culture method is applicable to any plant species simulating the neighboring environment before the big-scale field test.

Article by Kouhei Fujise, et al, from Japan.

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