Direct and indirect selection on flowering time, water‐use efficiency (WUE, δ¹³C), and WUE plasticity to drought in Arabidopsis thaliana

Abstract

Flowering time and water-use efficiency (WUE) are two ecological traits that are important for plant drought response. To understand the evolutionary significance of natural genetic variation in flowering time, WUE, and WUE plasticity to drought in Arabidopsis thaliana, we addressed the following questions: (1) How are ecophysiological traits genetically correlated within and between different soil moisture environments? (2) Does terminal drought select for early flowering and drought escape? (3) Is WUE plasticity to drought adaptive and/or costly? We measured a suite of ecophysiological and reproductive traits on 234 spring flowering accessions of A. thaliana grown in well-watered and season-ending soil drying treatments, and quantified patterns of genetic variation, correlation, and selection within each treatment. WUE and flowering time were consistently positively genetically correlated. WUE was correlated with WUE plasticity, but the direction changed between treatments. Selection generally favored early flowering and low WUE, with drought favoring earlier flowering significantly more than well-watered conditions. Selection for lower WUE was marginally stronger under drought. There were no net fitness costs of WUE plasticity. WUE plasticity (per se) was globally neutral, but locally favored under drought. Strong genetic correlation between WUE and flowering time may facilitate the evolution of drought escape, or constrain independent evolution of these traits. Terminal drought favored drought escape in these spring flowering accessions of A. thaliana. WUE plasticity may be favored over completely fixed development in environments with periodic drought.

Leveraging abscisic acid receptors for efficient water use in Arabidopsis

“…The underlying mechanisms, however, are not fully elucidated. Gains in WUE have been found to be associated with trade-offs in growth potential (8)(9)(10). WUE is controlled by genes regulating stomatal density and size (11)(12)(13).…”

Rice Root Architectural Plasticity Traits and Genetic Regions for Adaptability to Variable Cultivation and Stress Conditions

“…In addition to root architectural plasticity, plasticity in traits such as root anatomy, WUE, and phenology has been reported to be related to more stable plant performance across varying environments in various species (Sadras et al, 2009;Niones et al, 2012Niones et al, , 2013Kenney et al, 2014). In the case of rice, phenological plasticity in response to drought may be difficult to assess because rice shows delayed flowering under drought, and this delay can be reduced by plasticity in root architectural traits that improve water uptake (i.e.…”

Variation in and adaptive plasticity of flower size and drought-coping traits

“…Physiologically, plants may exhibit plasticity in stomatal conductance, whereby they close their stomata to limit water loss under drought, increasing instantaneous water-use efficiency (WUE), which is the ratio of carbon gained via photosynthesis to water lost via transpiration (Heschel et al 2004;Caruso et al 2006;Sherrard and Maherali 2006;Nicotra et al 2007;Maherali et al 2010;Lázaro-Nogal et al 2015). Plasticity in integrative WUE has been observed using stable carbon isotopes (d 13 C; Aspelmeier and Leuschner 2004;Franks 2011;Edwards et al 2012;Kenney et al 2014), which are often more reliable than instantaneous measures, because d 13 C reflects WUE integrated over longer periods of time. Finally, plasticity in development rate is an important mechanism for some plant species, such as annuals, to cope with drought by enabling them to reproduce and senesce before the onset of drought undermines their fitness (Gianoli 2004;Heschel and Rignios 2005;Sherrard and Maherali 2006;Maherali et al 2010;Franks 2011;Kenney et al 2014;Gugger et al 2015).…”

“…Plasticity in integrative WUE has been observed using stable carbon isotopes (d 13 C; Aspelmeier and Leuschner 2004;Franks 2011;Edwards et al 2012;Kenney et al 2014), which are often more reliable than instantaneous measures, because d 13 C reflects WUE integrated over longer periods of time. Finally, plasticity in development rate is an important mechanism for some plant species, such as annuals, to cope with drought by enabling them to reproduce and senesce before the onset of drought undermines their fitness (Gianoli 2004;Heschel and Rignios 2005;Sherrard and Maherali 2006;Maherali et al 2010;Franks 2011;Kenney et al 2014;Gugger et al 2015).…”