Inside a fleshy Persoonia fruit is a hard, woody endocarp that protects the seed. The endocarp must break down in the soil before germination can occur. This makes Persoonia difficult to germinate in the lab.
Persoonia have two dormancy types:
Mechanical dormancy (genus wide) is created by a woody endocarp that protects the seed and restricts germination. We know that at least 50% of the endocarp must be removed for germination to occur. When dispersed from the plant, the endocarp is strong enough to withstand up to 40-50kg of force before cracking!
Physiological dormancy (species-specific) occurs as the seeds themselves may require a chemical stimulant such as gibberellic acid or smoke to increase germination success. Germination may only occur under specific temperatures as well.
Current practice in our lab is as follows:
- Leave collected Persoonia fruits to ferment at room temperature for a minimum of 2 weeks.
- Physically macerate fruits to separate endocarp from fleshy layers. Wash and clean in weak bleach solution and dry in drying room for minimum 1 week.
- Soak endocarps in sterile water overnight.
- Crack endocarps using a vice.
- Extract seeds and soak in weak bleach solution for 10 minutes.
- Sow on water agar (± chemical stimulant) and incubate at the optimal germination temperature
There are also several issues that we may face when germinating Persoonia seeds in the lab, including prolific microbial contamination, very low seed fill and damage when cracking the endocarp.
Emery, N. (2016) Crime seed investigation: the perplexities of Persoonia. Wildlife Australia 53(2), 15-17.
Emery, N., Catelotti, K. & Offord, C. (2016). Research on eastern Australian Persoonia. Australian Plants 28, 210-217.