DEVELOPMENT OF SEED COAT-IMPOSED DORMANCY DURING SEED MATURATION IN CYNOGLOSSUM-OFFICINALE

The relationship between seed phenolics and appearance of seed coat-im posed dormancy during seed development in Cynoglossum officinale L. wa s studied. Up to 24 days after anthesis, seeds failed to germinate upo n imbibition in Petri dishes at 25 degrees C. At 44 days after anthesi s, seeds were fully germinable; removal of seed coats did not improve their germination or 0(2) uptake. At 72 days after anthesis, mature se eds at the base of the cyme did not germinate unless their coats were removed. Removal of seed coat also stimulated 0(2) uptake at this harv est date. The methanol-soluble phenolic content of the seeds increased during the early stages of seed development, in both the seed coat an d the embryo. As seed development continued, the methanol-soluble phen olic content of the embryo stabilized, but that of the seed coat decli ned. This decline was associated with an increase in the thioglycolic acid-soluble phenolics, presumably lignins, in the seed coat. These re sults suggest that polymerization of methanol-soluble phenolics into l ignins in the seed coat during later stages of seed development render s the seed coat of C. officinale impermeable to O-2, and thus keeps th e seed dormant.