The UN’s Global Strategy for Plant Conservation program has set a 2020 deadline for conserving 75% of the world’s threatened plant species outside of their natural habitat. But, based on the results of a new study, the prospects of meeting that target aren’t very good. According to a paper published earlier this month in Nature Plants, 36% of “critically endangered” species produce recalcitrant seeds, meaning that they can’t survive being dried out. And that means that they aren't candidates for the traditional seed banking process, Phys.org reports. The study, performed by scientists affiliated with the Royal Botanic Gardens, Kew, also found that 35% of “vulnerable” species and 27% of “endangered” species generate seeds that cannot be banked using the common method of freezing them at about -4 degrees Fahrenheit.
Among them are trees such as oak, avocado, cacao, and mango. “As successful as seed banking is for some species, it is not suitable for all seed plants and we need to invest in other ways to safeguard recalcitrant seeds,” says study co-author John Dickie, per Earth.com. One of those other ways to preserve recalcitrant seeds may be cryopreservation, which involves removing the embryo from a seed and freezing it at about -320 degrees Fahrenheit using liquid nitrogen. Per Phys.org, Kew has been using cryopreservation at its Millennium Seed Bank for years and is planning to develop a protocol to “kick-start large-scale use” of the method. (Animal species aren't doing so well, either.)