Woollsia pungens: Germination and Seedling Growth – Publication

Extract from a publication reporting research funded in part by the Australian Flora Foundation

From: Palmer J. and Ashford A. (2004) Woollsia pungens:: germination and seedling growth. Australian Plants 22:243-252

John Palmer and Anne Ashford
School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, 2052

Woollsia pungens (Cay.) F. Muell. is commonly found in dry sclerophyll forest and heathland on nutrient poor sandstone and coastal dunes throughout eastern Australia (Powell, 1992). The highly perfumed flowers are normally white but pale pink forms have been reported and plants with deep crimson flowers occur on the Beecroft Peninsula at Jervis Bay in NSW (Fairley and Moore, 2000). The plant may have horticultural potential for its slender flowering shoots and floral perfume. Described here are procedures we have developed to grow Woollsia plants under glasshouse conditions, as part of a program to inoculate the hair roots of seedlings growing in non-soil sterile containers with mycorrhizal cultures. We have also examined germination and seedling growth.

Our trials show that W. pungens seed is comparatively fertile and there are no special requirements for germination. A feature of germination is a 3-4 week delay before root emergence. Since the embryo in the mature seed is well developed and occupies the full length of the seed, this delay is not due to the time taken by the root apex to reach the seed’s surface. Possibly it’s the result of a growth inhibitor within the seed taking time to break down and allow embryo growth to commence. If this is the case, then the inhibitor appears to be unaffected by chemicals such as gibberellic acid or ethylene. Of particular interest is the lack of response to heat and smoke, or smoked water, since other epacrids require exposure to heat and/or smoke for germination (Gilmour et al., 2000). Seed from individual plants, collected in 2001, showed that plants at some localities produced more fertile seed than others. The reason for this variability is not yet known.

Although the germination trials indicated that soil assists the successful establishment of Woollsia seedlings, the technique that we used of germinating surface sterilised seed on paper, gave good germination rates and may be useful for other species as a means to improve germination and accurately record percentage germination.

Maintenance of high humidity was found to be essential for successful seedling establishment and subsequent growth under glasshouse conditions. It is possible that a deficiency exists in the seedling’s water transport system (Allaway and Ashford 1996), or that adaptation of stomata to a reduction in atmospheric humidity occurs only slowly. We are attempting to acclimatise seedlings to fluctuating humidity by partially opening the box lids to allow a reduction in humidity in daylight hours. Early results indicate that this hardening process is most successful when carried out at low temperature in winter, and with young seedlings less than 6 months old.

This investigation has revealed that post-germination, W. pungens enters a juvenile state which is unaffected by day length, season and light intensity and which lasts for 18 months to 2 years in our trials. The occurrence of this condition has not previously been reported for Woollsia. Possibly it occurs in other epacrids.