The effects of mycofloral infection on the viability and ultrastructure ofwet-stored recalcitrant seeds of Avicennia marina (Forssk.) Vierh.

Three questions are considered in the context of the possible effects of se ed-associated mycoflora, typified by Fusarium moniliforme, during hydrated storage of recalcitrant propagules of the tropical species, Avicennia marin a. These pertain to storage lifespan, whether seed susceptibility to fungal attack changes and the possibility of discriminating ultrastructurally bet ween inherent deteriorative changes and those that are fungally-induced. Th e data indicate unequivocally that if fungal activity is curtailed, then th e hydrated storage lifespan of A. marina seeds can be considerably extended . When inoculated immediately with F: moniliforme, newly harvested seeds we re extremely susceptible to the adverse effects of the fungus, while seeds that had been wet-stored for 4 d showed a considerably heightened resilienc e to the effects of the fungus when inoculated at that stage. The enhanced resilience, although declining, persisted in seeds stored hydrated for up t o 10 d prior to inoculation, being lost after 12 d. After 14 d of hydrated storage, seeds became more susceptible to the effects of the fungus than th ose in the newly harvested condition. The resilience of seeds that had been stored in the short-term was associated with ultrastructural changes indic ative of enhanced metabolic activity associated with the onset of germinati on. However, with the sustained stress imposed by wet-storage conditions, t he seeds became increasingly badly affected by the fungus. While it was not possible to discriminate with certainty among deteriorative subcellular ev ents ascribable to inherent deterioration or the effects of the fungus, it is concluded that a comparison of the timing of the onset of degeneration m ay well be diagnostic of its cause.