From ashes to sprouts: priming and fire-induced seed germination of campo rupestre species

Abstract

Fire is a natural disturbance that integrates the landscapes of open ecosystems such as the Campo Rupestre (CR), where species have adapted and thrived in post-fire conditions over time. Although fire is present in this environment, its physiological effects on vegetation dynamics are still poorly understood. Still, it is known that it plays an important role in the recruitment of seedlings from seeds found in the soil seed bank, which can experience cycles of hydration and dehydration by absorbing chemical molecules derived from burning vegetation. Here, we investigated the technique of priming seeds with smoke compounds in seeds of Vellozia compacta and Vellozia caruncularis in a simulation of the passage of fire through the seed bank. The experiment was composed of primed or non-primed seeds with smoked water, which were buried in three different soil seed bank simulations: (1) control, (2) ashes from burned vegetation of campo rupestre, and (3) fire passage on vegetation of campo rupestre. After the treatments, two days of being umifified, the seeds were exhumed for physiological analysis. Germination parameters were analyzed (germination percentage, and germination speed index - GSI), and biochemical markers (total soluble sugars, total amino acids, and malondialdehyde - MDA) were quantified in the seedlings. Priming with “smoked water” showed better germination parameters in both species in the fire simulation conditions (3). In contrast, for the biochemical parameters in the seedlings, the amount of total soluble sugars and total amino acids was higher in the control conditions and under fire simulation with the ashes. This response was more stimulated with the application of priming. The priming was important for reducing the MDA levels, a compound formed by lipid peroxidation. This study suggests that the physiological and biochemical effects of priming with chemical components from smoke in seeds of Velloziaceae species of CR can generate a memory in plants in the initial growth phase. However, this response is complex, and further studies are needed to understand the role of fire in germination and seedling recruitment.