1976. The relationship of tissue chlorogenic acid concentrations and leaching of phenolics from sunflowers grown under varying phosphate nutrient conditions. Can. J. Bot. 54: 593-599. A large increase in the concentration of the isomers of chlorogenic acid was observed in extracts of sunflowers grown under phosphate-deficient conditions when compared with phosphate-sufficient plants. More phenolic compounds were leached from living intact roots, dried roots, and tops of phosphate-deficient plants than from phosphate-sufficient ones. These leachates did not contain any of the isomers of chlorogenic acid or caffeic acid but did contain scopolin. The influence of phosphate deficiency on polyphenol concentrations in plants and their possible role in allelopathic interactions between plants are discussed. KOEPPE, D. E., L. M. SOUTHWICK et J. E. BITTELL. 1976. The relationship of tissue chlorogenic acid concentrations and leaching of phenolics from sunflowers grown under varying phosphate nutrient conditions. Can. J. Bot. 54: 593-599.Les auteurs ont observe une importante augmentation de la concentration des isomeres de I'acide chloroginique dans des extraits de tournesols cultives sous des conditions de deficience en phosphates, comparativement i des plantes cultivkes avec une quantite suffisante de phosphates. Les racines intactes vivantes. ainsi que les racines et les tiges skchies, ont abandonne en solution plus de composes phinoliques chez les plantes dificientes en phosphates que chezcelles qui en avaient suffisamment. Ces lessivats ne contenaient aucun des isomeres de I'acide chlorogenique ou de l'acide cafelque mais contenaient de la scopoline. Les auteurs discutent I'influence de la dkficience en phosphore sur les concentrations en polyphenols des plantesainsi que le r6le possible de ces derniers dans les interactions allelopathiques entre plantes.[Traduit par le journal] IntroductionRecent studies have shown that changes in radiation (13,15,17,41,43), temperature (15, 38), age (7,9,15,23,28,42), and nutrient regime (2,3,5,19,21,32,33,34,35,36) influence the concentrations of the caffeoylquinic acids and scopolin (7-glucoside of 6-methoxy-7-hydroxycoumarin) in plants. These effects of environmental factors on plant phenolic concentration are reviewed in more detail by Rice (25). Although the in vivo physiological effect of changes in the concentrations of phenolic compounds is presently only hypothetical (1, 29), it is well documented that many cinnamic acid derivatives (of which the caffeoylquinic acids and scopolin are examples) affect various enzyme systems in vitro (1 1, 24, 27). In general, phenolic compounds have been implicated in plant-plant allelopathic interactions (30, 38) and have been shown to be