Effect of scarification and soaking on seed germination and viability of Podocarpus henkelii and P. latifolius (Podocarpaceae)

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Abstract Seed dormancy defines the environmental conditions in which a seed can germinate. Germination is timed to avoid unfavourable environmental conditions for plant establishment and growth. Podocarpaceae have an underdeveloped embryo which may delay germination. We aimed to establish if Podocarpus henkelii and P. latifolius produce underdeveloped embryos and examine the kind of dormancy the seeds have. The seed characteristics of P. henkelii and P. latifolius were observed, and we tested for seed germination after pretreating the seeds in water, hydrochloric acid and mechanical scarification and then tested for viability and the presence of the embryo. Embryos in fresh seeds of P. henkelii and P. latifolius had an embryo length/seed length ratio < 0.5 which suggested that the embryos were small and underdeveloped. Both podocarps produced fleshy seeds, P. latifolius had the smallest seed (mass: 0.19 g; length: 10.54 mm) and P. henkelii the largest (mass: 2.44 g; length: 23.69 mm). After exposing the seeds to the pretreatments, the seeds of both species did not germinate after ~6 months. However, viability testing showed that >90% of the seeds were viable with >95% of the seeds having embryos. Considering that the pretreatments did not facilitate seed germination in both species and that both podocarps have underdeveloped embryos that were viable P. henkelii and P. latifolius may have morphological or morphophysiological dormancy.

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