Germination of grass caryopses at increasing water deficit under simulated current and future temperature regimes
Description
Our proposal was to study the impacts of increasing water stress and temperature on the survival and germination of caryopses of neotropical grass species occurring in dry- and wet grasslands of the Cerrado biome (Brazil). The Cerrado is the second largest biome of the South America, largely covered by savanna and other vegetation types subjected to periodic fires, as the grasslands. Considering that dry grasslands are subjected to higher soil temperatures and water deficit than wet grasslands, our expectation was that caryopses from dry grassland species would be more tolerant to both increasing water stress and higher temperatures (predicted for the future) than caryopses from wet grassland species. We found that more intense water stress reduced the survival of caryopses for both dry and wet grassland species. Temperature regime predicted for the future reduced the viability of wet grassland species and affected the germination strategy of dry grassland species. These results indicate that increasing water stress and temperature predicted for the future may compromise the recruitment potential of dry and wet grassland species, thus directly impacting the dynamics and resilience of these ecosystems in a future scenario. This study was recently accepted for publication at the American Journal of Botany (2022). The table here provided brings data on the germinability (%), median germination time (T50, in hours) and viability (%) of neotropical grass caryopses from dry and wet grasslands subjected to increasing water stress treatments under simulated current and future temperature regimes. We have organized the data to facilitate its analysis in R. It is quite self-explanatory, but one can find a tab (metadata) which details each variable. The R script used in the present study is also provided.
Files
Steps to reproduce
Caryopses were collected from six dry grassland and four wet grassland species (Poaceae) in different months of 2015, 2017 and 2018. The collections were non-systematic, with a minimum of 30 mother plants for each species, considering the availability of dispersed caryopses and their representativeness in dry and wet grasslands. The caryopses collected from each mother plant were mixed to constitute one single and representative sample of caryopses per grass species. The plants were monitored regularly, and the collections were performed manually. We simulated current and predicted future temperature regimes in germination chambers with a 12h photoperiod of white light. For the current scenario, an alternating temperature regime of 17/27°C was programmed in the night-day cycle, respectively, experimentally representing the average minimum and maximum temperatures of the rain season. To simulate the temperature regimes predicted for the future, the chambers were regulated for an alternating temperature regime of 23/33°C, a scenario which represents the average of six global IPCC climate models (2014) under a pessimistic scenario (A2) forecast for the period 2071-2100 for the central region of Brazil. The effects of water deficit on caryopses survival and germination were tested for the present and future scenarios using solutions of polyethylene glycol 6000 (PEG 6000) to simulate negative osmotic potentials. Solutions of PEG 6000 were prepared to generate osmotic potentials from -0.2 to -1.0 MPa, representative of soil water potentials registered in Cerrado soils. The experiments were monitored every 48h for 30 days, using radicle emergence and its geotropic curvature as germination criterion.