Just as Persoonia seeds take a long time to germinate in the wild, they also very time-consuming and slow to germinate in a laboratory. This is because we need to remove the fleshy outer layers and the endocarp. Currently, we remove the endocarp one fruit at a time.
Our current methodology at the Australian PlantBank has been simplified and can be replicated outside of a laboratory (with some modifications), and fruits can be batch processed or done individually.
Persoonia seed processing
1. Fruits should be separated from any significant detritus, placed in sealed plastic bags and left at room temperature to ferment for 2-3 weeks.
2. Soak fruits in sterile water for 15 minutes to soften the outer exocarp and fleshy mesocarp layers.
3. Remove fruits from the water and physically macerate fruits to separate the pyrene (endocarp + seed) from the fleshy layers. If working with small numbers of fruits:
a. Squeeze the pyrene from the outer layers using forceps; or,
b. Peel away the fleshy layers from the pyrene using forceps.
4. Wash and clean pyrenes in sterile water with a weak bleach solution (~1-2%).
5. Rinse and pat dry pyrenes and place in a drying room (15°C and 15% relative humidity) for at least one week.
The pyrenes (endocarp + seed) can then be vacuum-sealed and stored as an ex situ conservation collection or used for propagation work. There are also several issues that can occur when germinating Persoonia seeds in the lab, including prolific microbial contamination, very low seed fill and damage when cracking the endocarp. Surface-sterilising seeds can help reduce microbial contamination.
We find there is little if any increase in germination success when seeds are pre-treated with gibberellic acid (GA3) or smoke. When germinating Persoonia seeds, we often achieve greatest success mimicking spring temperatures.