Quercus species are often considered ‘foundation’ components of several temperate and/or subtropical forest ecosystems. Xia et al. study water relations and survival of excised axes in response to water loss and cryo-exposure for four Quercus species from subtropical China (Q. franchetii, Q. schottkyana) and temperate USA (Q. gambelii, Q. rubra) and find that species adapted to arid and semi-humid climates still produce recalcitrant seeds. They conclude that the ability to avoid freezing rather than drought may be a more important selection factor to increase desiccation tolerance, and that cryopreservation of recalcitrant germplasm from temperate species is currently feasible, whilst additional protective treatments are needed for ex situ conservation of Quercus from tropical and subtropical areas.
A study finds that four Quercus species adapted to arid and semi-humid climates still produce recalcitrant seeds.