The role of reprodutive and vegetative functional traits on abiotic stress responses in species from campo rupestre and restinga

Abstract

Plants are constantly subjected to stressful conditions, requiring them to develop resistance mechanisms to a wide range of stressors. Vegetative and seed traits provide insights into how species have adapted to diverse environmental conditions. Understanding how plant characteristics respond to the environment offers crucial knowledge for biodiversity conservation, which can inform decisions on preservation, conservation of species, populations, or communities, and ecological restoration programs. In the current climate scenario, plant populations are prone to events of water seasonality and rising temperatures. Given this climatic context, this study focused on two ecosystems: the Campo rupestre and the Restinga. These environments are significant for the ecosystem services they provide and the constant threats they have faced over the years. To this end, four studies were conducted: i) the effect of hydration and dehydration (HD) cycles on Campo rupestre seeds; ii) extreme high temperatures and HD cycles on the germination of three Vellozia species; iii) the relationship between vegetative and seed traits in species from a Restinga in southeastern Brazil; and iv) the combined stress of high temperatures and discontinuous hydration on a characteristic Restinga species. It was observed that there is a relationship between biometric and germination traits in seeds of four Campo rupestre species, which can be used to select and add species for the restoration of disturbed environments. However, their progression may be detrimental to seed germination, leading to mortality and consequently impacting the regeneration and maintenance of natural populations. HD cycles improve germination parameters and confer fire stress tolerance in Vellozia sp. seeds. The fire tolerance generated by Vellozia seeds undergoing HD cycles is an exaptation process, inducing greater accumulation of proline and abscisic acid. The Restinga vegetation exhibits a stress-tolerant ecological strategy, with diverse light and temperature requirements for seed germination. A correlation study showed a positive relationship between leaf dry matter content and seed biometric and germination traits. When the species Canavalia rosea was subjected to HD events and high temperatures, its seeds showed greater susceptibility to combined stresses than to isolated ones, reducing germination and viability. Understanding the response dynamics of Campo rupestre and Restinga species to abiotic stresses, such as water and thermal stress, is essential for ensuring the maintenance of these two ecosystems and the ecosystem services they provide. Focusing efforts, resources, and research on seed ecophysiology is increasingly necessary, as seeds are responsible for the maintenance of natural populations, the colonization of new environments, and seedling recruitment.