Sexual reproductionSexual reproduction

Sexual reproduction

The Wollemi Pine is a gymnosperm with its reproductive organs borne on modified leaves called sporophylls, which are arranged in cone or cone-like structures called strobili (Harden 1990). Male cones appear in early to mid-summer and mature in spring when pollen is shed (Zimmer et al. 2015a). Female cones can first be observed in mid to late summer, and they are pollinated in the following spring. Fertilisation occurs approximately one year after pollination. Several months later, in late summer and early autumn, seed cones mature and female cones disintegrate, shedding their seed and individual bract-scales (Offord et al. 1999; Zimmer et al. 2015a; Prakash et al. unpubl. data).

Embryo development follows a similar pattern to Agathis australis (Owens et al. 1997), extending over almost 2 years from pollination to seed maturity. Interestingly, in Wollemia many ovules are destroyed by active pollen tubes (Prakash & Clarke unpubl. data). This may contribute to the relatively low rates of seed viability observed in Wollemi Pine—generally, less than 10% of the c. 250 ovules in female cones develop into viable seeds (Offord et al. 1999).

The Wollemi Pine is a monecious species (male and female cones occur on the same tree). Some level of self-pollination is likely to be occurring and may explain the production of seeds reported from single cultivated individuals. This may be contributing to inbreeding and the low diversity found in individuals stands (Stevenson et al. 2023 preprint). Seeds may also be produced by apomixis (asexual reproduction via seeds), although this is not known to occur in this family. The production of seeds follows a similar pattern to other members of the family, taking 18-24 months from the first emergence of female cones to seed maturity and cone dehiscence. Controlled studies on the breeding system of the Wollemi Pine are in progress at BMBGMT (Offord & Phelan, unpubl. data).