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

Abstract

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 the responses to flooding and decreasing water potentials we germinated and grew seeds of three habitats of Euterpe edulis Mart. occurring along an altitudinal gradient, over a period of three years. Seed germination and root growth were evaluated under different water availability treatments: control, flood, -0.4MPa, -0.8MPa, for 2012, 2013 and 2014 years, and in the last year of the experiment (2014), -1.0MPa and -1.5MPa. Seeds of the montane habitat did not germinate in the flood treatment. Seed germination of all three habitats decreased in the -1.5MPa treatment. Montane habitat had the lowest seed germination at -1.5MPa. Time required for half of the seeds to germinate increased up to -0.8MPa. Seeds of montane habitats germinated slower in all the treatments. The only difference observed in seed germination synchrony was an increase in submontane population in flooding treatment. However, synchrony decreased at the lowest water potential treatments. Roots of montane population were more vigorous in most treatments, except in -0.8 MPa. The unusual ability of seeds to germinate at low water potentials might be related to early seed germination at the onset of the rainy season, potentially decreasing 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, which might negatively affect population viability along elevational in future climate change scenarios.