Effects of Temperature Peaks and Water Stress on Tropical Seed Germination: Experimental Trials With Species From Brazil's Northeastern Coastal Zone

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ABSTRACT Understanding the effects of high temperatures and water deficit on germination provides valuable insights into seed stress tolerance, guiding the use of native seeds in ecological restoration. This study aimed to evaluate the effects of (1) temperature peaks and (2) water stress treatments and post‐stress recovery on the germination of some selected animal‐dispersed species typically found in the northeastern coastal zone of Brazil. Temperature peaks were simulated in a germination chamber, varying daily from 25°C to 40°C for 15 days, compared to a constant‐temperature control (Experiment 1). Water deficit was simulated using PEG 6000 (treatments: Ψ = 0, −0.4, −0.8, −1.2 MPa) over 30 days. After this period, stress was alleviated, and seeds were monitored for an additional 30 days (Experiment 2). In Experiment 1, seeds of Miconia ciliata and Myrcia guianensis had a significant decrease in germination percentage following the temperature peaks, while Eschweilera ovata germinated faster. Myrciaria floribunda and Schinus terebinthifolia showed low germination in both treatments. Seeds reached 47%–57% germination in the 30‐day controls in Experiment 2 (except M. floribunda , with 26%), but germination did not occur under water deficit treatments. Following stress relief, germination gradually increased until 60 days, recovering up to 40%, depending on the species. Although a proportion of the seeds recovered germinability after stress alleviation, their overall sensitivity to water deficit resulted in delayed and partial germination. This may represent a bottleneck for seedling recruitment in coastal zones, posing challenges for direct seeding and germination timing in restoration projects.

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