ABSCISIC ACID IN SEED DEVELOPMENT AND GERMINATION OF CARIROT 1

ABSTRACT- The leveis of abseisic acid (ABA) iii primary and secondary umbel seeds of carrots (Daucus carola L.) during developmcnt and maturation were determined by gas liquid chromatography and related to seed growth and germination. The leveLof ABA was high during development, reaching a maximum at 2 1-28 DAF, then dedined sharpiy as seeds matured. The high content of endogenous ABA during development did not impair seed growth and germination; however, the germinability of both seed sources was completely blocked by exogenous 10"M ABA. This indicates that ABA might activate two specific mechanisms of action: one promotive during embryogenesis and anothcr one inhibitory during remobilization. Nonetbeless, the data demonstrated, for the first time in ali umbelliferous crop, the endogenous levei of ABA iii developing seeds, and the effect of exogenously applied ABA on seed germination