Wakehurst landscape by RBG KewRoyal Botanic Gardens, Kew
Trees are anchors of life
Deforestation in Sabah (2005-09-03) by Andrew McRobbRoyal Botanic Gardens, Kew
35% of the world's tree species, threatened with extinction
The main threats to tree species are human activities, such as forest clearance and other forms of habitat loss, direct exploitation for timber and other products, and the spread of invasive pests and diseases. Climate change is also having a clearly measurable impact.
Seed banks are champions in tree conservation
In conventional seed banks, like Kew’s Millennium Seed Bank, seeds are dried to low moisture contents and stored at sub-zero temperatures (typically at -20°C in a freezer) for the long term. Seeds can be retrieved and used to restore threatened or extinct populations and species.
Seeds that need cryopreservation by RBG KewRoyal Botanic Gardens, Kew
However, seeds of many tree species cannot be banked
Seeds of many tree species, such as oaks or chestnuts, do not tolerate the drying needed for their storage in conventional seed banks. The seeds that are sensitive to drying are known in the seed jargon as ‘recalcitrant’ seeds.
Kew's heritage trees by RBG KewRoyal Botanic Gardens, Kew
Recalcitrant seeded trees are found in temperate forests
For example, iconic trees that are dominant in temperate forests such as horse chestnuts (Aesculus sp.) and oaks (Quercus sp.) produce recalcitrant seeds.
Njuma River in Ebo Forest, Cameroon by RBG KewRoyal Botanic Gardens, Kew
Recalcitrant seeded trees are also usual in tropical forests
Alarmingly, recalcitrant seeded tree species are very common in tropical evergreen rain forests, one of the most threatened ecosystems globally. Kew scientists predicted that near 50% of trees and shrubs in tropical evergreen rain forests produce recalcitrant seeds.
Cryopreservation is needed to preserve many tree seeds
Cryopreservation is one method suggested for the long-term conservation of the genetic resources of recalcitrant seeded species. Cryopreservation is the preservation of cells and tissues at the ultra low temperatures of liquid nitrogen (-196°C), which are almost 10 times lower than the temperature reached in a home freezer (-20°C).
Tissue culture is needed to regrow cryopreserved trees
Cryopreservation is often used to conserve isolated tree tissues such as seed embryos or meristems, or cell lines. Tissue culture is the cultivation of these cells/tissues on specially formulated nutrient media. Under the right conditions, an entire plant can be regenerated .
Science for conserving threatened trees
At Kew, scientists are working to understand the fundamental basis of low temperature stress tolerance and enable the development of innovative and global cryopreservation solutions for trees. So far, we have developed succesful approaches for several oaks and horse chestnuts.
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