Seed biology can inform conservation actions: a case study on Geijera parviflora

Knowledge of seed biology is imperative for effective curation and utilisation of seeds.

We studied the seed biology and reproduction of Geijera parviflora, a species suitable for ecological restoration and ornamental horticulture that has largely been overlooked because of issues with unreliable germination and viability.

Germination in response to dormancy-breaking treatments and soil seed burial, and variation in germination at an inter-population level were assessed for G. parviflora. Seed storability in a conventional seedbank was tested. Floral phenology was assessed.

Germination of untreated and seed coat removed seeds were 0 ± 0.0% and 67 ± 5.5% respectively. Seed germination varied between 21.9 ± 1.8 and 66.6 ± 5.5% at an inter-population level. Seeds buried in soil for 6 months showed 11.7 ± 0.8% germination without any treatment. All seeds buried for 12 months were non-viable. Drying seeds from 11.4 ± 0.19% to 5.79 ± 0.17% moisture content resulted in 40% less germination. Visual observation of floral attributes confirmed the presence of orange-coloured pollen grains for 3.5 ± 0.48 days from floral opening. The stigmatic surface became shiny 3.5 ± 0.21 days after floral opening.

Seeds of G. parviflora demonstrate physiological dormancy; treatments that remove seed coat resistance against embryo growth enable germination. Local environmental conditions may explain the inter-population variation in germination. Seeds are short-lived in soil and ex situ seedbank conditions. In soil, seeds release dormancy at the end of first winter, so seeds are available to germinate the following spring/summer with high rainfall. Floral phenology assessment indicated protandrous sequential hermaphroditism, which may reduce the probability of self-pollination in G. parviflora.

This knowledge supports use of G. parviflora in ecological restoration and horticulture.