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, sinapic, vanillic, caffeic and p-coumaric, three of which were found in the free phenolic fraction (p-coumaric, ferulic and sinapic). Total phenolic compound and phenolic acid contents were the highest at the initial stage of development and the lowest at the final stage of maturation of rye grains. After the dehydration treatment, total phenolic content decreased relatively slightly in all examined samples of rye caryopses of various ripeness. The phenolic acid fraction (consisting of both bound and free forms) decreased more during dehydration, especially at the initial stage of caryopses development. Cells of unripe rye grains reacted to water stress by lowering the level of total phenolic compounds, and especially the content of phenolic acids. During the development and ripening of rye caryopses, a gradual increase in precocious germination ability of the grain was observed. The enforced dehydration stimulated processes of precocious germination of unripe caryopses. The highest stimulation of germination was observed at the initial stage of development of caryopses (22 and 29 DAF). One of the reasons for inducing faster germination of unripe rye caryopses may be the lowering of the level of phenolic acids (considered as inhibitors of germination) in caryopses after the dehydration treatment.