Investigations on ex situ conservation of selected Australian palms

Abstract

Of the approximately 2500 species of Arecaceae, only a very small number has been studied extensively due to their global economic significance. This includes date palm, oil palm and coconut. Other palm species are generally under-studied since they are not well known outside of their natural distribution despite the likelihood of contributing considerably to the local economy. While the western culture generally regards palms as ornamentals, palm and palm products are an integral part of life in the tropics and sub-tropics. Over-exploitation and other land-use pressures in these regions have resulted in the disappearance of many species from wild stands; while climate change coupled with stresses like weeds is forecasted to exacerbate the rate of loss. Consequently, Arecaceae has been increasingly recognised as a susceptible family with 65% of the species recorded by International Union for Conservation of Nature (IUCN) under the LSQUOthreatenedRSQUO category, hence the need for conservation and propagation. A major hurdle for in situ conservation of palms is germination, which can take up to years, while the absence of lateral buds impedes conventional vegetative propagation. This study focuses on the development of ex situ conservation methods for selected Australian palms in the genera Livistona and Archontophoenix. This includes investigations on seed storage behaviour and in vitro germination of zygotic embryos as a precursor to developing cryopreservation techniques. The results of this investigation indicate that A. cunninghamiana seeds are desiccation-sensitive whilst L. decora and L. nitida seeds are desiccation-tolerant. This suggests that seeds of these Livistona spp. may be stored using standard seed storage methods and will allow for collection and long-term seed storage of these species. This is currently being tested. For A. cunninghamiana, which is desiccation sensitive, further investigations for viability at a range of moisture contents and temperatures, including liquid nitrogen storage to try to develop a reliable seed storage protocol are currently being done. As an alternative to seed storage, in vitro germination of zygotic embryos has been investigated as a precursor to a possible cryopreservation of zygotic embryos. The results indicate that germination of zygotic embryos is both rapid and effective and this method will now be used in the development of A. cunninghamiana embryos.