5% MC and −20 °C). These seeds will be available to research organisations, for restoring trees to the UK countryside and for increasing tree cover. The Forestry Commission is a key partner, providing advice on target species and help with collection. A priority list of 50 trees and shrubs has been targeted for collection, including: Juniperus communis (common juniper), and the subspecies Juniperus ssp. hemisphaerica, designated selleck chemicals as critically endangered on the IUCN Red List; Cotoneaster cambricus (wild cotoneaster), a rare species with just a handful of wild trees; and Pyrus cordata (Plymouth pear), designated as vulnerable on the IUCN Red List and one of Britain’s

rarest trees. Information on the seed biology (storage and germination) of tree species is sparse beyond the main species of interest to commercial Baf-A1 datasheet forestry (Young and Young, 1992 and Vozzo, 2002). Consequently, the prospects for ex situ seed banking is unclear for the vast majority of the estimated 60,000–100,000

tree species in the world ( Oldfield et al., 1998). Such shortcomings can be addressed, in time, through screening seeds of representative tree species for storage physiology (i.e., desiccation tolerance and longevity) and through the development of predictive models for physiological responses. In all countries it is the case that not all tree species produce seeds that can be stored in conventional seed banks (dry and cold) due to sensitivity of the seeds to desiccation; the so-called recalcitrant response. For example, in Central Amazonia (Brazil) indications are that c. 60% of tree species produce recalcitrant seeds. Over the last 20 years considerable progress has been made in: (i) understanding the mechanisms of desiccation-induced viability loss on drying; (ii) estimating the proportion of the world’s flora that produce such seeds (i.e., diagnosis); and (iii) developing methods that can help conserve such species in ex situ cryo-banks

(i.e., storage biotechnology). In contrast to desiccation tolerant (orthodox) seed, recalcitrant seeds lack the ability to “switch-off” metabolically late in development or to undergo intracellular dedifferentiation (Berjak and Pammenter, 2013), such that these seeds must be stored under moist conditions, Farnesyltransferase where longevity is often curtailed by germination and the proliferation of seed-associated fungi. Reactive oxygen species and programmed cell death have been implicated in desiccation stress in recalcitrant seeds, for example, for Q. robur (English oak) ( Kranner et al., 2006), and during accelerated ageing of orthodox seeds, for example, for Ulmus pumila (Siberian elm) ( Hu et al., 2012), which has led to increased interest in manipulating the gaseous environment during seed storage, including through the use of nitrous oxide ( Iakovoglou et al., 2010). Studies on the mechanistic basis of seed desiccation (in)tolerance are ongoing.