Plantbanking our rainforests
Global seedbanking efforts have conserved a huge proportion of the worlds dryland species and Senior Principal Research Scientist Dr Cathy Offord says it's now time to focus on those plant species that can’t be seedbanked.
"These species produce seed that will not survive drying or freezing, or they just don’t produce seeds at all," Dr Offord says.
"The highest proportion of such plants are found in rainforests and other wet habitats and for many of these species, we need to consider a process we call 'plantbanking'," says Dr Offord.
Contrast dryland Acacias with Castanospermum australe, an Australian coastal rainforest species (Black Bean or Moreton Bay Chestnut). Both are from the same taxonomic family, Fabaceae, the pea family, yet their seed storage potentials are completely different.
Black Bean seeds are typical of many rainforest trees in that they are large, with a thin seed coat. When mature, the seed is lime green and ready to germinate straightaway.
"Unfortunately, the seed of this species dies when it is dried and cannot be frozen for long-term conservation in a seed bank," says Dr Offord.
On the other hand, other rainforest species may be able to tolerate drying, but not freezing.
"Many seeds from rainforest species therefore cannot be conserved in a seed bank using traditional methods and they are generally termed ‘recalcitrant’," Dr Offord says.
The conservation of recalcitrant rainforest species is complex, which is why it’s received relatively little attention. Traditionally, rainforest species have been conserved ex situ by growing them in a garden or plantation.
"This provides a source of material to propagate from, but the genetic diversity is generally low compared to seed bank collections that can hold thousands of individuals," says Dr Offord.
Other techniques are available, such as tissue culture, which is labour intensive compared to seed banking and many fewer individuals can be conserved.
Cryostorage of shoots or embryos in liquid nitrogen at ultra-low temperature (less than -180 degrees Celsius) is another alternative and is similar to the storage of mammalian sperm, eggs and embryos.
"The technique shows great promise for recalcitrant plants, but its success varies from species to species and requires concerted research for rainforest species," says Dr Offord.
Plantbanking our rainforest species requires a mixture of these techniques to get effective conservation outcomes.