Species-specific responses of “Critically Endangered” and “Least Concern” Aloe seed germination to environmental conditions in Tanzania

Abstract

The majority of Aloe species are threatened by anthropogenic activities, trade, and the effects of climate change, but little is known on seed biology and appropriate conservation measures. Hence, understanding the germination behaviour of Aloe species will help in mitigating the negative effect of changing environmental conditions. “Critically Endangered” (A. boscawenii and A. pembana) and “Least Concern” (A. lateritia, A. volkensii and A. secundiflora) Aloe species’ seed germination was tested under various environmental parameters which are said to be crucial for Aloe species seed germination and included treatments of possible climate change scenarios. We varied temperature, light, scarification, KNO3 addition and salinity and compared the response of the “Critically Endangered” versus the “Least Concern” Aloe species. “Least Concern” Aloe species were used as a control because they have adapted to a wide range of environmental conditions in contrast to “Critically Endangered” Aloe species, which often have a restricted range and specific environmental needs. All Aloe species germinated best at moderate temperatures (25 °C–30 °C) and low KNO3 levels (0.01 mg/l). Dark conditions triggered higher germination percentages for all Aloe species except for A. boscawenii. Saline water suppressed the germination of all Aloe species compared to Aloe species grown in distilled water medium only. Aloe seeds grown in filter paper distilled water medium germinated better than Aloe seeds grown on a soil medium. The “Least concern” (IUCN Red List) A. lateritia germinated better than other species, followed by “Critically endangered” A. pembana and A. secundiflora. Generally, Aloe seed germination is nurtured by moderate temperatures and low concentrations of KNO3. Hence, the effect of global warming will affect the survival of most Aloe species. The better germination performance under shade highlights the importance of parent plants, or at least a healthy canopy cover, in the Aloe species habitat. Aloe seeds showed species-specific responses to various environmental conditions (except for A. pembana), which reflects their Red List status.