At the

coarse level, we can ask if variation in intrinsic WUE is primarily due to variation in A or g s. For example, threefold variation in g s and twofold variation in leaf N concentration among natural accessions of Arabidopsis suggest substantial variation in g s and A may separately or in concert be responsible for the observed variation in δ13C (Christman et al. 2008; Des Marais et al. 2012). Des Marais et al. (2012) found large differences in physiology between life history classes in Arabidopsis. Although, the Des Marais study focused on variation in gene expression, they also reported constitutive variation in leaf structural traits between life history classes. Winter SRT1720 annual types had higher intrinsic WUE. This is consistent with coordinated selection on WUE, A, and g s and life history observed in other species (Geber and Dawson 1997). Higher WUE was associated with lower leaf water content (LWC) and specific leaf area (SLA) (Des Marais et al. 2012). Taken together, these results YM155 supplier suggest that increased leaf density is associated with higher photosynthetic capacity (Terashima et al. 2011), but may come at the cost of lower stomatal and mesophyll conductance to CO2 (Parkhurst and Mott 1990; Evans et al. 1994; Syvertsen et al. 1995; Volasertib nmr Kogami et al. 2001). Studies in Arabidopsis have identified extensive natural variation in plant–water

relations and gas exchange physiology (Juenger et al. 2005, 2010; Masle et al. 2005; Bouchabke et al. 2008; Christman et al. 2008; McKay et al. 2008; Monda et al. 2011; Des Marais et al. 2012; Pons 2012). The present study was undertaken to examine natural variation in leaf physiological traits that are the likely cause of the observed variation in δ13C and associated WUE parameters in natural accessions of Arabidopsis, and to determine

if these traits vary independently or co-vary in a coordinated Edoxaban and predictable manner. First, we tested if the expected relationship between transpiration efficiency (shoot dry mass/transpiration; TE) and leaf δ13C was present in 96 natural accessions of Arabidopsis. In a smaller set of 18 natural accessions spanning the range of variation in δ13C, we measured rosette A, g s, and intercellular CO2 concentration (C i) and examined the relationship of C i and δ13C. To further characterize natural variation in A, we examined maximal carboxylation rate (V cmax) and photosynthetic electron transport rate (Jmax) in three accessions using photosynthetic carbon dioxide response curves (Sharkey et al. 2007). Additionally, we used gas exchange measurements coupled with online isotopic measurements to determine instantaneous carbon isotope discrimination using tunable diode laser spectroscopy (TDL) (Flexas et al. 2006; Barbour et al. 2007; Heckwolf et al. 2011) to estimate g m in stomatal regulation mutants to investigate the relationship of these mechanistically related traits (Warren et al.