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PHYTOALEXINS, WATER-STRESS AND STOMATA

III. THE EFFECTS OF SOME PHENOLICS, FATTY ACIDS AND SOME OTHER COMPOUNDS ON STOMATAL RESPONSES

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SUMMARY

The effects of several phenolic compounds, some of which accumulate in tissues under the stress of microbial attack, and of some‘water-stress’ compounds (those which accumulate in leaf tissue under water-stress and may cause stomata to close) on stomatal behaviour in epidermal strips of Commelina communis L. were studied.

The phenolics, p-coumaric acid, caffeic acid, chlorogenic acid, salicylic acid and particularly sinapic acid, were strong inhibitors of stomatal opening. The effects on open stomata were less marked but sinapic acid brought about considerable closure while ferulic acid stimulated wider opening.

All the ‘water-stress’ compounds except proline and glutamine, which had no effect on stomatal behaviour, inhibited opening and caused some closure of initially open stomata; ABA, farnesol, undecanoic acid, linoleic acid and a-linolenic acid were all particularly effective.

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