Seed Storage Physiology of Lophomyrtus and Neomyrtus , Two Threatened Myrtaceae Genera Endemic to New Zealand.

There is no published information on the seed germination or seed storage physiology of Lophomyrtus bullata , Lophomyrtus obcordata , and Neomyrtus pedunculata. This lack of information is hampering conservation efforts of these critically endangered species. This study investigated the seed morphology, seed germination requirements, and long-term seed storage methods for all three species. The impact of desiccation, desiccation and freezing, as well as desiccation plus storage at 5 °C, -18 °C, and -196 °C on seed viability (germination) and seedling vigour was assessed. Fatty acid profiles were compared between L. obcordata and L. bullata . Variability in storage behaviour between the three species was investigated through differential scanning calorimetry (DSC) by comparing thermal properties of lipids. L. obcordata seed were desiccation-tolerant and viability was retained when desiccated seed was stored for 24 months at 5 °C. L. bullata seed was both desiccation- and freezing-sensitive, while N. pedunculata was desiccation-sensitive. DSC analysis revealed that lipid crystallisation in L. bullata occurred between -18 °C and -49 °C and between -23 °C and -52 °C in L. obcordata and N. pedunculata . It is postulated that the metastable lipid phase, which coincides with the conventional seed banking temperature (i.e., storing seeds at -20 ± 4 °C and 15 ± 3% RH), could cause the seeds to age more rapidly through lipid peroxidation. Seeds of L. bullata , L. obcordata and N. pedunculata are best stored outside of their lipid metastable temperature ranges.