Sensitivity of seed germination to water stress in high-altitude populations of a threatened palm species

• Divergence in seed germination patterns among populations of the same species is important for understanding plant responses to environmental gradients and potential plant sensitivity to climate change. In order to test responses to flooding and decreasing water potentials, over 3 years we germinated and grew seeds from three habitats of Euterpe edulis Mart. occurring along an altitudinal gradient.
• Seed germination and root growth were evaluated under different water availability treatments: control, flood, −0.4 MPa, −0.8 MPa, in the years 2012, 2013 and 2014, and in the final year of the experiment (2014) at −1.0 MPa and −1.5 MPa.
• Seeds from the montane habitat did not germinate in the flooding treatment. Seed germination of all three habitats decreased in the −1.5 MPa treatment and the montane habitat had lowest germination in this treatment. Time required for half of the seeds to germinate increased up to −0.8 MPa. Seeds from montane habitats germinated more slowly in all treatments. The only difference in seed germination synchrony was an increase in the submontane population under the flooding treatment. However, synchrony decreased at the lowest water potentials. Roots of the montane population were more vigorous in most treatments, except at −0.8 MPa.
• The unusual ability of these seeds to germinate at low water potentials might be related to early seed germination at the onset of the rainy season, which potentially decreases seed predation pressure. Seeds of the montane population were more sensitive to both types of water stress. A predicted increase in the frequency and intensity of extreme high rainfall or drought events may predispose early stages of this population to adverse factors that might negatively affect population viability with elevational in future climate change scenarios.