Seed dormancy in Stachytarpheta species (Verbenaceae) from high-altitude sites in south-eastern Brazil

- Dry storage and exogenous gibberellin (GA3) may lead to increase in germinablity.
- Non-deep physiological dormancy is present in most of the species studied.
- Differences in germination may be related to habitats and geographic distributions.

The genus Stachytarpheta (Verbenaceae) comprises numerous endemic species and taxa threatened with extinction and its main diversity center is the Espinhaço mountain chain in central-eastern Brazil. Although cases of seed dormancy are known from other genera of the family, there have been no reports of dormancy in Stachytarpheta. We investigated the viability and germination of recently harvested seeds of 12 species of Stachytarpheta evaluating the effects of light, alternating temperature, gibberellin and dry storage on germination. Seed sizes were measured and they were tested for viability (tetrazolium test) and germination at constant and alternating temperatures under 12-h photoperiod. Ten species were evaluated for the effects of GA3 on germination, and four species were dry stored for 12 months and their germination then evaluated. Results showed differences in germination among species that appeared to be related to their natural habitats and geographic distributions. Stachytarpheta seeds are small and most species showed low germination as well as light requirements for germination Incubating seeds under alternating temperatures resulted in germination increase of 30% of the species studied in relation to exposure to constant temperatures. Both dry storage (after-ripening) and application of GA3 resulted in significantly increases of germination of most of the investigated species. The responses to the treatments were not homogeneous among all of the species, indicating differences in their dormancy levels. Although no uniform pattern was identified for the genus, our results indicate that most of the taxa studied have non-deep physiological dormancy, which is commonly seen in species with restricted distributions.