Germination patterns in the Succulent Karoo Biome, South Africa

Abstract

The timing of germination and seedling establishment is critical for the existence and survival of plants in arid environments. The dormancy mechanisms that play a major role in regulating the timing of germination in the plant species that were investigated from the Succulent Karoo included physiological dormancy (after-ripening) and physical dormancy (hard-seededness). A leaching treatment improved the germination in only approximately 10% of the investigated species. Environmental factors, such as light and temperature also influence the breaking of dormancy and timing of germination. In general, annual species germinated better in the light, whereas perennial species germinated better in the absence of light. Most of the species are adapted to germinate during autumn or winter with an optimum temperature for germination for most of the investigated species from 15°C to 20°C, but many species germinated optimally at even lower temperatures (<15°C). In general, the optimum temperatures were slightly higher when the seeds germinated in the light when compared with seeds germinated in darkness. On the whole, the species investigated from the Succulent Karoo exhibited a spectrum of germination patterns, from those that risk a few seeds in many rainfall events, to those that germinate only after large rainfall events but then risk the bulk of the seed crop.