Fruit Ripeness Effects on Characteristics, Germination and Desiccation Tolerance of Syzygium myrtifolium Walp. Seeds

Abstract

To plant Syzygium myrtifolium Walp. on harsh urban sites, planting materials of seed origin having better developed tap roots are preferred compared to those propagated from stem cuttings. However, fully ripe fruits at 8 weeks after fruit set are heavily lost to birds. In the current study, the unpalatable semi-ripe fruits at 7 weeks were found suitable for propagation. The seeds from the semi-ripe fruits showed mean germination rate of 93% and developed normal seedlings within 1 week, although continued growth with increases in size and fresh weight (FW) in the fruits and seeds was significant towards completion of fruit ripening. Thus, harvesting of fruits within the short period between these two fruit developmental phases is critical in the seed procurement process of this plant species. At the semi-ripe stage, pericarp exhibiting mixture of red and black colour can be a practical guide to indicate the suitable time for harvesting the fruits. Nonetheless, subsequent desiccation trial aimed to determine the storability of the seeds at postharvest found that the seeds obtained from both the semi-ripe and fully ripe fruits had drastic loss of germinability at seed moisture content of approximately 0.3 g H₂O/g FW. Storage of the seeds above this relatively high moisture level for future planting was detrimental because the seeds age rapidly when they remain metabolically active with high respiration rates. Microbial infestation will also be an added problem during seed storage. Therefore, the seeds need to be sown fresh.