Developmental and germinative events can occur concurrently in precociously germinating Chinese cabbage (Brassica rapa ssp Pekinensis) seeds

During germination in the siliquae of developing seeds of a precociously ge rminating (PG) line of Chinese cabbage (Brassica rapa ssp. Pekinensis), the synthesis of cruciferin and oleosins was maintained and the activities of isocitrate lyase and malate synthase increased. Thus, both developmental an d germinative/postgerminative events coexisted within the same PG seeds. Dr ying of the seeds resulted in the developmental events being switched off a nd germinative/post-germinative ones being initiated. Only about 18% of the seeds of the PG line completed germination in the siliquae, so the potenti al for germination of the remaining non-germinating seeds was tested during their development. Isolation of these developing seeds from the siliquae a nd imbibition in water induced PC, but developmental events were terminated and the seeds entered a germinative/post-germinative programme. This termi nation of developmental events in the induced PG seeds was not permanent, h owever, and they could be re-induced by incubating the seeds in ABA on Mura shige and Skoog (Ms) medium. If incubated on MS medium plus a low concentra tion of ABA, both developmental and germinative/post-germinative events cou ld be induced to coexist in the PC seeds up to the time of establishment of the seedlings. Control of the developmental and germinative/postgerminativ e events in the seeds was influenced by the environment in which they were developing, which could be mimicked by manipulating the nutritional status and ABA content in which the seeds were in contact.