The influence of seed maturation on desiccation tolerance in Phalaenopsis amabilis hybrids

The Orchidaceae contains a large number of threatened species that could benefit from seed banking. However, successful seed storage requires a greater understanding of the enigmatic seed biology of orchids. In particular, there is little documentation of the presence or timing of the maturation drying that has been shown to be critical for longevity of agricultural seeds in storage. The aims of this work were to document seed water content, germinability and desiccation tolerance as a function of maturation in developing capsules of hand-pollinated flowers of Phalaenopsis hybrids. Lengthening of capsules was complete by 50 DAP, but capsule diameter continued to increase up to a maximum at 70 DAP. Relative water content rapidly declined from 75% moisture content (fresh weight basis) at 150 DAP to 50% moisture content at 165 DAP where it remained until dehiscence. Seed germinability remained high (75–99.5%) throughout the harvesting period (90–216 DAP), but desiccation tolerance only developed 165 days after pollination. Therefore, if Phalaenopsis seeds are to be stored, we propose that their harvest should be delayed until moisture content drops below 50%.

Research highlights▶ Phalaenopsis seeds become germinable after histodifferentiation (90 DAP). ▶ Maturation drying begins in Phalaenopsis seeds at 150 DAP. ▶ Phalaenopsis seeds become desiccation tolerant after 160 DAP when seeds have dried to less than 55% (fresh weight basis). ▶ Phalaenopsis capsules can be collected prior to dehiscence and yield desiccation tolerant seed.