THE ROLE OF ABSCISIC-ACID IN GERMINATION, STORAGE PROTEIN-SYNTHESIS AND DESICCATION TOLERANCE IN ALFALFA (MEDICAGO-SATIVA L) SEEDS, AS SHOWN BY INHIBITION OF ITS SYNTHESIS BY FLURIDONE DURING DEVELOPMENT

Abscisic acid and osmoticum maintain maturation and protein synthesis of developing alfalfa embryos, individually and in combination, The in situ environment of developing alfalfa zygotic embryos is rich in ABA and low in osmotic potential, When ABA synthesis was inhibited by treating the pods with fluridone at an early stage of development, the seeds which subsequently developed contained low amounts of ABA, but had a similar osmotic potential as untreated control seeds, The reduced ABA in seeds from fluridone-treated pods did not change the morphology except the colour of seeds, nor did it induce viviparous germination or affect storage protein synthesis. However, two non-storage proteins which were synthesized in control seeds during early to mid-development were absent from fluridone-treated seeds, Control seeds containing these two proteins were desiccation-tolerant, whereas the fluridone-treated seeds which lacked them were desiccation-intolerant, at feast until the deposition of storage proteins was nearly complete, Culture of isolated embryos on nutrient medium induced germination and curtailed storage protein synthesis in the embryos. Addition of either ABA or osmoticum to the nutrient medium prevented germination acid maintained storage protein synthesis, When fluridone was added along with osmoticum, germination occurred, but storage protein synthesis was maintained.