PREPARATION AND INITIATION OF GROWTH IN AXIAL ORGANS OF GERMINATING QUIESCENT SEEDS .1. ACCUMULATION OF OSMOTICALLY ACTIVE SUBSTANCES IN AXIAL ORGANS OF BROAD BEAN-SEEDS

The processes responsible for water movement into the axial organs wer e studied in imbibing seeds of broad beans (Vicia faba var. minor L.). Their water content in the range equal to 60 - 72% on a fr wt basis w as considered, including so-called lag phase and subsequent rise in wa ter content up to the radicle protrusion. At 60% water content, the os motic potential of the axial organs comprises only 22% of their water potential. Osmotically active substances are mainly Cl-, NO3-, and Kions, whereas the role of sucrose and fructose is not so important. Fu rther water uptake results from the accumulation of endogenous solutes , K+ and glucose in particular. The osmotic potential contribution to the water potential of the axial organs increases to 61% by the time o f radicle emergence. Subsequently, the small vacuoles enlarge markedly . Therefore, at 60% water content and later, the matric forces ceased to be of primary importance in water uptake by the axial organs. Furth er water absorption occurs mainly due to osmotic forces. The accumulat ion of osmotically active substances and vacuole enlargement provide f or the operation of a physiological mechanism that causes further wate r transport to the cells required for the commencement of their elonga tion.