Dormancy Breaking and the Influence of Temperature, Substrate and Light on Germination of Colubrina glandulosa Seeds

Abstract

The subjugation of global ecosystems by human beings has increased the rates of extinction, threatening not just the well-being of people, but also affecting the natural ecosystems services (Johnson et al., 2017). In Brazil, several forest ecosystems are degraded as a result from the anthropic activities. For this reason, restoring and expanding these environments turned into an important task, which is beneficial for biodiversity, climate, water quality, as well as for providing other ecosystem services (Bright et al., 2017; Houghton & Nassikas, 2018). Due to the forest restoration expansion and the increasing demand for seedlings production, studies focused on the ecophysiology of seed germination in native forest species are on the rise due to their environmental and economic potential use. Moreover, it contributes to the rational exploitation and use of these species (Rodrigues Filho et al., 2019; Santos et al., 2019; Oliveira et al., 2020a). Among the species that may be used on forest restoration is Colubrina glandulosa Perkins (Rhamnaceae). This native species is a pioneer that occurs from the eastern coast of Brazil to Paraguay and Peru. It grows quickly, facilitating the establishment of other species that require shading areas, thus being important for the ecological succession. In addition, it has a huge using potential in carbon compensation projects and its seeds present physical dormancy, which allows them to remain inactive in the seed bank, an important strategy for the population dynamics (Silva et al., 2015; Marcos Filho, 2015; Camara et al., 2017; Morais Júnior et al., 2018; Melo Júnior et al., 2018). However, there is no methodology available in the Rules for Seed Analysis (Brasil, 2009) that determines procedures to be applied for germination tests in this species (Melo Júnior et al., 2018). Abstract This study aimed to define a methodology that, when combined with temperature, can overcome the dormancy and also to determine the adequate substrate and light conditions for germination of Colubrina glandulosa Perkins, contributing to seed analysis and restoration projects. In the experiment of dormancy and temperature, seeds were immersed in sulfuric acid for 30, 60, 90, 120 and 150 minutes and set to germinate at temperatures of 20-30 °C, 25 °C and 30 °C. The used substrates were sand, vermiculite, Tropstrato® substrate, coconut powder, blotting paper and paper towel. As for the light supplied, the seeds were subjected to four luminosity regimes: white light, far-red light, red light and light absence. Temperatures of 20-30 °C and 30 °C achieved better results, with exposure in sulfuric acid for 120 and 150 minutes. The substrates sand and vermiculite were the most suitable. The species germinated in all light regimes treatments used.