Salinity Adaptation and the Contribution of Parental Environmental Effects in Medicago truncatula

Abstract

High soil salinity negatively influences plant growth and yield. Some taxa have evolved mechanisms for avoiding or tolerating elevated soil salinity, which can be modulated by the environment experienced by parents or offspring. We tested the contribution of the parental and offspring environments on salinity adaptation and their potential underlying mechanisms. In a two-generation greenhouse experiment, we factorially manipulated salinity concentrations for genotypes of Medicago truncatula that were originally collected from natural populations that differed in soil salinity. To compare population level adaptation to soil salinity and to test the potential mechanisms involved we measured two aspects of plant performance, reproduction and vegetative biomass, and phenological and physiological traits associated with salinity avoidance and tolerance. Saline-origin populations had greater biomass and reproduction under saline conditions than non-saline populations, consistent with local adaptation to saline soils. Additionally, parental environmental exposure to salt increased this difference in performance. In terms of environmental effects on mechanisms of salinity adaptation, parental exposure to salt spurred phenological differences that facilitated salt avoidance, while offspring exposure to salt resulted in traits associated with greater salt tolerance. Non-saline origin populations expressed traits associated with greater growth in the absence of salt while, for saline adapted populations, the ability to maintain greater performance in saline environments was also associated with lower growth potential in the absence of salt. Plastic responses induced by parental and offspring environments in phenology, leaf traits, and gas exchange contribute to salinity adaptation in M. truncatula. The ability of plants to tolerate environmental stress, such as high soil salinity, is likely modulated by a combination of parental effects and within-generation phenotypic plasticity, which are likely to vary in populations from contrasting environments.

Adjusting phenotypes via within‐ and across‐generational plasticity

“…One pattern is that progeny plasticity can be masked when maternal plants experience stressful, resource‐limited or ‘extreme’ environments. For example, germination responses to shade, warmer temperatures and increased salinity in the offspring environment were only observed when maternal plants were not grown in these environments (Zhang et al ., ; Vu et al ., ; Leverett et al ., ; Moriuchi et al ., ). This masking can occur when the maternal treatment alone maximized germination or induced such intense dormancy that progeny cues were not able to overcome it.…”

“…temperatures and increased salinity in the offspring environment were only observed when maternal plants were not grown in these environments (Zhang et al, 2012;Vu et al, 2015;Leverett et al, 2016;Moriuchi et al, 2016). This masking can occur when the maternal treatment alone maximized germination or induced such intense dormancy that progeny cues were not able to overcome it.…”

“…Within-generation plasticity can also mask maternal effects on progeny traits. For instance, effects of high maternal salinity on progeny germination time, flowering time and growth were only expressed in offspring grown in low salinity (Vu et al, 2015;Groot et al, 2016;Moriuchi et al, 2016). Within-and trans-generation plasticity may also operate in the same direction.…”

Tolerancia a la salinidad de <i>Passiflora tarminiana</i> Coppens & Barney

“…These events take place simultaneously and quickly in order to mobilize all the metabolic apparatus for adaptation and survival of the plants. The adaptation of plants to NaCl involves metabolic events such as synthesis of organic solutes and ion partitioning (Moriuchi et al, 2016). However, responses to salinity include changes in leaf properties such as thickness, surface micromorphology and cuticular wax.…”

“…In most cultivated plants, sensitivity to salinity and drought conditions are associated with the inability to prevent and/or tolerate high concentrations of salts. In light of this, the capacity for salt exclusion is an important mechanism of tolerance (Moriuchi et al, 2016).…”