Above: The underside of fern fragments reveals hundreds of spores protected by extremely fine hair-like growths.
By Emily Sezate, Fern Lab Technician
Although they’re often overlooked and underappreciated, Hawaiʻi’s rare native ferns play a critical role in healthy forest ecosystems. Among these ferns is palai lāʻau (Adenophorus periens), an endemic species once found on all the main Hawaiian islands. In recent years, however, this small, epiphytic fern has steadily declined and by 2016 it was believed to be extinct, but in 2021, thanks to the efforts of botanists and advances in drone technology, a population of palai lāʻau was rediscovered on the island of Kauaʻi.
Assessed as Critically Endangered on the IUCN Red List of Threatened Species and a target plant for the University of Hawaiʻi’s Plant Extinction Prevention Program (PEPP), botanists have been closely watching this rare fern since its rediscovery, waiting for the opportunity to collect fertile material.
When scientists observed spores maturing on multiple plants, the time to collect had come. After our conservation partners at PEPP contacted NTBG, we agreed that our fern lab was well suited to care for the prized spores. We knew that gathering plant material from multiple plants would increase the odds of a successful germination.
Left: Weedy ferns, mosses, and other contaminants are routinely monitored in order to prevent competition for resources. Ferns in NTBG’s fern lab are kept under 24 hour red and blue lights to promote photosynthesis and help form strong roots. Right: A tiny fragment of a native Hawaiian fern.
Immediately after collecting spores from the forest, PEPP botanists delivered fern samples to the NTBG lab. Prior to their arrival, I sterilized trays and filled them with the appropriate growing medium so I could sow the spores right away. Most fern spores remain dormant until favorable conditions arise and they can be dried and potentially stored for years. Palai lāʻau, however, has what are called “green spores” meaning that they are active immediately and begin using their resources without a dormant phase.
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Green spores stored in a cool, dark space will survive about a week. Knowing this gave me a greater sense of urgency. Typically, fern spores would be dried for several weeks during which time they would fall from plant material and can be collected. But without this drying period, I knew I had to work under a microscope using a tool the size of a sewing needle, slowly, gently gathering spores one by one and then transferring them onto the growing medium. The process took several days and resulted in four trays of what are called gametophytes, the earliest stage of sexual differentiation in a fern’s life cycle.
Left: Because spores are barely visible to the naked eye, a microscope must be used when laying them out in culture trays for favorable growing conditions until they are large enough to be planted in small pots. Right: Microscopic fern reproductive structures called sporangia are meticulously placed on growing media using a needle-like tool.
Spores in every tray germinated quickly since their resource cells were immediately active, but germination has been an incredibly slow process. More than two months later, the ferns are only five to seven cells tall and impossible to see with the naked eye. Eventually they will fertilize each other and have the potential to develop into sporophyte — what most people think of as a fern.
Once the ferns are mature enough to be taken from the lab, they will be returned to the forest in areas similar to where they were first collected. As conservationists, our goal is to first grow enough of this rare species to produce a healthy population that can be monitored in the wild. Those ferns will allow us to repeat the cycle of collecting and propagating until this species is no longer under threat.
Working with partner organizations across the state, we have the potential to realize this goal. Meanwhile, we continue to document growth patterns of these tiny “baby ferns” knowing that this data will aid in establishing the best protocols for saving this rare Hawaiian fern and other species found only in Hawaiʻi.