Seed germination of five species from the subalpine shrubland of a mountainous oceanic island with high conservation value (Reunion Island)

Little is known about the seed ecology of native plants from subalpine and alpine vegetation zones on oceanic islands, although their biodiversity is unique and vulnerable (e.g. facing fires and biological invasions). This study of seed germination focuses on five species, which are representative of the subalpine shrubland of Reunion Island. The main objectives are to identify the presence of dormancy and light requirements, and to evaluate whether GA3 or a smoke-infused water could substitute for the light requirement for seed germination. Over one month, germination tests were performed under different conditions at three temperatures (15, 20 and 25 degrees C), in light (12-hours light/12-hours dark) and in dark. Seeds were also treated using a single spraying of gibberellic acid (GA3 at 1000 ppm) and a smoke-infused water (named Smoke Water in the study). No dormancy was detected for Stoebe passerinoides. For Erica reunionensis, Agarista buxifolia, Hubertia tomentosa and Hypericum lanceolatum subsp. angustifolium, a potential non-deep physiological dormancy (with a conditional dormancy state) was detected. Moreover, for Agarista buxifolia and Erica reunionensis (Ericaceae), light is required for seed germination. Gibberellic acid (GA3 at 1000 ppm) substitutes for light, except at 25 degrees C for E. reunionensis. Smoke Water does not improve seed germination, except at 15 degrees in dark for E. reunionensis. A better understanding of seed germination for species from subalpine and alpine vegetation zones will mean better threat management and restoration actions.

Automated summary

This study investigates the seed germination of five species from the subalpine shrubland of Reunion Island. It reveals the presence of dormancy in some plants and the potential of gibberellic acid as a substitute for light in promoting seed germination. The study also finds limited improvement in seed germination with smoke-infused water.