Changes in endogenous phenolic acids during development of Secale cereale caryopses and after dehydration treatment of unripe rye grains

In normal rye caryopses, five phenolic acids were detected: ferulic, sinapi c, vanillic, caffeic and p-coumaric, three of which were found in the free phenolic fraction (p-coumaric, ferulic and sinapic). Total phenolic compoun d and phenolic acid contents were the highest at the initial stage of devel opment and the lowest at the final stage of maturation of rye grains. After the dehydration treatment, total phenolic content decreased relatively sli ghtly in all examined samples of rye caryopses of various I ripeness. The p henolic acid fraction (consisting of both bound and free for-ms) decreased more during dehydration, especially at the initial stage of caryopses devel opment. Cells of unripe rye grains reacted to water stress by lowering the level of total phenolic compounds, and especially the content of phenolic a cids. During the development and ripening of rye caryopses, a gradual incre ase in precocious germination ability of the grain was observed. The enforc ed dehydration stimulated processes of precocious germination of unripe car yopses. The highest stimulation of germination was observed at the initial stage of development of caryopses (22 and 29 DAF). One of the reasons for i nducing faster germination of unripe rye caryopses may be the lowering of t he level of phenolic acids (considered as inhibitors of germination) in car yopses after the dehydration treatment. (C) 2000 Editions scientifiques et medicales Elsevier SAS.