Interactive effects of water deficit and smoke on seed regeneration in ground-layer Cerrado species

In savanna ecosystems, water availability and fire are interconnected, shaping plant structure and diversity. In Cerrado, factors such as water seasonality and fire-related cues (e.g., smoke) interact to influence recruitment. This study investigated the germinative and post-germinative responses of Cerrado ground-layer species to a gradient of water potential reduction, both independently and in combination with smoke water (SW). It assessed the effects of smoke and water deficit on treatment (WDT) and post-water deficit recovery (WDR), exploring the potential protective role of smoke under these conditions.

Different concentrations of polyethylene glycol 6000, both alone and in combination with 10 and 25 mL L-1 of SW, were used to assess the germination and seedling growth responses of 15 Cerrado ground-layer species at 25°C. After WDT, species were subjected to the WDR (using only deionized water) to evaluate recovery capacity. Effect sizes were used to evaluate species' responses to the treatments and whether these responses were associated with growth forms (i.e., shrubs and herbs).

Reduced water potential was the primary factor negatively impacting germination and post-germination responses. While species-specific, SW had a protective effect on germination and seedling growth under moderate water deficit. Tolerance to water deficit was more evident in shrub species, whereas positive responses to SW were more common in herbaceous species. During WDR, most species either recovered from WDT and germinated or maintained seed viability. Herbaceous species showed a stronger recovery, with germination reaching control levels.

Both water potential reduction and SW influence the germination and seedlings' growth of Cerrado ground-layer species and growth forms. Smoke can alleviate stress induced by water deficit, with species showing tolerance without loss of seed viability, suspending germination under stress but retaining their ability to recover.