Environmental stress, future climate, and germination of Myracrodruon urundeuva seeds 1

Abstract

Myracrodruon urundeuva, a native species from the Brazilian Caatinga, is widely distributed across its endemic region, where it also plays an essential socioeconomic role. The objective of this study was to evaluate the influence of environmental stress on the germination of M. urundeuva seeds harvested in different years (2010 to 2013). Seeds were germinated at constant temperatures between 10 to 40 °C, osmotic potentials from 0 to -0.8 MPa (in polyethylene glycol 6000 solutions), and from 0 to -0.5 MPa (in NaCl solutions). The experiment was conducted according to a completely randomized design, with three replicates of 50 seeds, in a factorial scheme (harvest year x stress intensity) for each environmental stress. Germination data were then analysed using thermal, hydro and halo time models, and future germination responses projected according to climate change scenarios. The germination thermal thresholds ranged from 7.4 to 53.3 oC. The germination base osmotic threshold (using polyethylene glycol) was -0.6 MPa and the base osmotic threshold in NaCl was -0.43MPa. Seeds from different harvest years showed distinct tolerance to environmental stresses. The thermal, hydro and halo-time models were efficient to describe the germinative response of seeds, and the climate models allowed to identify the germination responses of M. urundeuva in future climate. According to the models for future climate (RCP 8.5), the reduction of rainfall by 2100 will directly affect seed germination and seedling recruitment of M. urundeuva.

Hydropriming changes temperature thresholds for seed germination of tree species from the Caatinga, a Brazilian tropical dry forest

“…In this study, the temperature thresholds, as well as the sub and supra-optimum thermal times of the species, showed that they can germinate in a wider temperature range after ondergoing HD cycles, obtaining with T b below 10 °C and T c above 40 °C. Agreeing to our results, studies on seeds native to the Caatinga reported that different species and all seed lots (from different harvests and provenances) germinated in a wide thermal range, with T b below 10 °C and/or T c above 40 °C (Gomes et al, 2019;Oliveira et al, 2019;Dantas et al, 2020).…”

“…Seeds GR has been studied on different species subjected to several factors, such as storage time, water deficit and different temperatures, in order to obtain the germination thresholds (Oliveira et al, 2019;Gomes et al, 2019;Daibes and Cardoso, 2020). In this study, the temperature thresholds, as well as the sub and supra-optimum thermal times of the species, showed that they can germinate in a wider temperature range after ondergoing HD cycles, obtaining with T b below 10 °C and T c above 40 °C.…”

“…A linear regression analysis was performed to calculate the interception on the x-axis of both sub and supra-optimum temperatures, providing estimates of base and ceiling temperatures (T b and T c ) for germination, respectively, below and above which seeds fail to germinate (Covell et al, 1986). The interception of linear regression lines was used to estimate optimum temperature (T o ; Hardegree, 2006;Oliveira et al, 2019;Dantas et al, 2020).…”

Effect of reduced water potential on seed germination of a forest tree: a hydrotime approach

“…Temperature and water potential show important interactions to describe germination parameters under laboratory conditions (Alvarado and Bradford, 2002). However, few studies were accounted for such interactions (hydrothermal time) in Brazilian species (Simão et al, 2010;Oliveira et al, 2019). Seedling emergence from soil seedbanks should also be examined, in order to validate such models under field conditions (Forcella et al, 2000).…”

“…Concerning native species, few studies in current literature investigated such threshold models regarding water relations and seed germination of tropical trees (Daws et al, 2008). Some studies evaluated the role of Ψ on seed germination of Brazilian species (Botelho and Perez, 2001;Fonseca and Perez, 2003;Rego et al, 2007), but rarely explaining whether germination would fit the presupposes of hydrotime models (Cardoso and Pereira, 2008;Oliveira et al, 2019). Most attention regards to the role of temperature, rather than water potential, as described by thermal time models in neotropical species (Cardoso and Pereira, 2009;Pires et al, 2009;Daibes and Cardoso, 2018;Duarte et al, 2018).…”