Germination response to water availability in populations of Festuca pallescens along a Patagonian rainfall gradient based on hydrotime model parameters

Abstract

Sensitivity to water availability is a key physiological trait for grassland species located in arid and semiarid environments, where successful germination is closely related to rainfall dynamics. Festuca pallescens inhabits diverse environments along a steep precipitation gradient in North Patagonia, thus offering a suitable model for the study of germination behavior in response to water availability. By analyzing germination in nine populations using a hydrotime model approach, we aimed to find within-species variation. Seed population behavior was analyzed under different hydric conditions using hydrotime model parameters (hydrotime, mean base water potential and its standard deviation). We estimated the mean base water potential for F. pallescens (ψb(50) = − 2.79 ± 0.45 MPa), which did not differ significantly between populations. However, the hydrotime parameter (θH) varied markedly, suggesting physiological adaptation to local environments. Higher values of θH were found in populations located at the extremes of the distribution gradient, indicating that germination may be prevented or delayed in conditions that are suboptimal for the species. Since the variation in hydrotime model parameters did not follow a cline, micro-environmental cues may have the greatest influence on the physiological behavior of the species, rather than the macroscale rainfall gradient.

Seed Germination Ecology of Semiparasitic Weed Pedicularis kansuensis in Alpine Grasslands

“…In the field, seed germination, which may take several days or weeks, will probably encounter periods of drought. Crucial aspects in the germination process are the soil water potential and the length of the hydration period [33,34]. When the soil water potential is suitable (<15% PEG) for P. kansuensis, the seeds begin to germinate after absorbing enough water.…”

Effect of Water Deficit on Germination, Growth and Biochemical Responses of Four Potentially Invasive Ornamental Grass Species

“…One of the germination parameters most used in the literature is the base water potential for a 50% inhibition of the maximum germination (Ψb 50 ). When comparing the studied species with non-invasive plants, the obtained Ψb 50 values are generally lower [ 72 , 74 ], confirming their higher ability to germinate in a wide range of osmotic potentials. These data reveal the hydrotime model as a valuable tool for evaluating the invasive capacity of alien species.…”

“…The hydrotime model describes the germination response to osmotic stress and its relationship with the adaptive responses of species to their habitats [ 74 ]. θH is related to the period between the start of imbibition and the start of radicle emergence and, consequently, the time required for germination, whereas Ψb measures the range of water potentials in which seeds can germinate [ 74 ]. The studied species showed hydrotime values from 2.3 to 1.8 MPa·days.…”

“…The studied species showed hydrotime values from 2.3 to 1.8 MPa·days. These values are low if compared to different populations of the Poaceae Festuca pallescens from Patagonia, with values ranging from 30.9 to 13.6 MPa·days [ 74 ], or different Stipa species of cool and warm habitats, with values between 31 and 173 MPa·days [ 75 ]. Compared to other species of the same family, the four grasses examined in this study require shorter time for seed germination, which gives them a competitive advantage over native species.…”

The Influence of Induced Drought Stress on Germination of Cenchrus ciliaris L. and Cenchrus setigerus Vahl.: Implications for Rangeland Restoration in the Arid Desert Environment of Kuwait

“…The seed germination responses of both Cenchrus species were adversely affected by increased water stress. It is probable that water stress dehydrated the seeds and affected the germination percentage including varying patterns of seed response to water availability among various osmotic potential treatments [22] . The percentage of seed germination in both Cenchrus species strongly decreased at lower water potentials from -1.5 MPa to 2.0 MPa, suggesting the negative effect of water absorption by the seeds.…”