Gravimetric phenotyping of whole plant transpiration responses to atmospheric vapour pressure deficit identifies genotypic variation in water use efficiency

Abstract

There is increasing interest in rapidly identifying genotypes with improved water use efficiency, exemplified by the development of whole plant phenotyping platforms that automatically measure plant growth and water use. Transpirational responses to atmospheric vapour pressure deficit (VPD) and whole plant water use efficiency (WUE, defined as the accumulation of above ground biomass per unit of water used) were measured in 100 maize (Zea mays L.) genotypes. Using a glasshouse based phenotyping platform with naturally varying VPD (1.5-3.8kPa), a 2-fold variation in WUE was identified in well-watered plants. Regression analysis of transpiration versus VPD under these conditions, and subsequent whole plant gas exchange at imposed VPDs (0.8-3.4kPa) showed identical responses in specific genotypes. Genotype response of transpiration versus VPD fell into two categories: 1) a linear increase in transpiration rate with VPD with low (high WUE) or high (low WUE) transpiration rate at all VPDs, 2) a non-linear response with a pronounced change point at low VPD (high WUE) or high VPD (low WUE). In the latter group, high WUE genotypes required a significantly lower VPD before transpiration was restricted, and had a significantly lower rate of transpiration in response to VPD after this point, when compared to low WUE genotypes. Change point values were significantly positively correlated with stomatal sensitivity to VPD. A change point in stomatal response to VPD may explain why some genotypes show contradictory WUE rankings according to whether they are measured under glasshouse or field conditions. Furthermore, this novel use of a high throughput phenotyping platform successfully reproduced the gas exchange responses of individuals measured in whole plant chambers, accelerating the identification of plants with high WUE.

The disadvantages of being a hybrid during drought: A combined analysis of plant morphology, physiology and leaf proteome in maize

“…The type of the response to declining water availability ( e . g ., whether the respective genotypes have or do not have a change point in their transpiration response to a changing atmospheric vapour pressure deficit) is evidently also important [69]. In our previous study performed with the same drought-susceptible and -resistant inbred lines of maize, the drought-resistant line CE704 not only maintained open stomata under conditions of mild (6 days without water) drought but even increased its g S .…”

Trait components of whole plant water use efficiency are defined by unique, environmentally responsive genetic signatures in the model C4grassSetaria

“…This complex trait is determined by many factors including photosynthetic carbon assimilated per unit of water transpired (Condon et al, 2002; Farquhar et al, 1989; Morison et al, 2008; Penman and Schofield, 1951; Seibt et al, 2008), leaf architecture (Brodribb et al, 2007; Sack and Holbrook, 2006), stomata characteristics (Franks and Farquhar, 2006; Lawson and Blatt, 2014), epidermal wax content (Premachandra et al, 1994), canopy and root architecture (White and Snow, 2012; Martre et al, 2001), stomatal dynamics (Blatt, 2000; Hetherington and Woodward, 2003; Lawson et al, 2010; Flood et al, 2011; Lawson et al, 2012), hydraulic transport (Edwards et al, 2012; Holloway-Phillips and Brodribb, 2011), portion of carbon lost from respiration (Escalona et al, 2012; Tomás et al, 2014) and partitioning of photo-assimilate (Carmo-Silva et al, 2009; Chaves, 1991). Given that plant species (Stewart et al, 1995; Winter et al, 2005; Zegada-Lizarazu and Iijima, 2005; Zhou et al, 2012) and ecotypes within species (Kenney et al, 2014; Lopez et al, 2015; Nakhforoosh et al, 2016; Pater et al, 2017; Ryan et al, 2016; Xu et al, 2009) exhibit variation in WUE it is likely that the characteristics which determine this trait are under genetic control and have evolved in response to different environmental conditions such as water availability (Assouline and Or, 2013; Brodribb et al, 2009; Huxman et al, 2004). Therefore, WUE is likely influenced by both genetically encoded developmental programs and changes in growth environments throughout the plant lifecycle (Fleury et al, 2010).…”

Role of leaf photosynthesis and stomatal conductance in determining the genotypic variation in whole-plant Transpiration Efficiency (TE) in Sorghum

“…Genotypic variation in TE has been reported in various crops, including wheat (Condon et al, 1990), rice (Impa et al, 2005), peanut (Wright et al, 1994), sunflower (Lambrides et al, 2004), maize (Pilbeam et al, 1995;Ryan et al, 2016a) and sorghum (Hammer et al, 1997;Mortlock and Hammer, 1999;Vadez et al, 2011;Xin et al, 2008). This genetic variation is suggestive of greater scope for further development of more drought-tolerant and water-efficient sorghum varieties (Borrell et al, 2006).…”

“…Genotypic differences in the response of T/GLA to VPD have been reported in several crops, including soybean Sinclair, 2009), pearl millet (Kholová et al, 2010b), maize Gholipoor et al, 2013) and sorghum (Gholipoor et al, 2010), and can be associated with differences in the response, both, below and above the breakpoint. This genotypic variation in transpiration rate has been linked to differences in stomatal response to high VPD (Jackson et al, 2016;Medina and Gilbert, 2015;Ryan et al, 2016b;Vadez et al, 2014;Vadez and Ratnakumar, 2016;Yang et al, 2012) and is reportedly linked to crop TE (Mortlock and Hammer, 1999;Sinclair et al, 2005;Vadez and Ratnakumar, 2016). Limited transpiration can enable soil water conservation for later growth stages, particularly during post-anthesis and grain filling stages.…”

“…At the plant level, TE is the amount of plant biomass produced (g) per unit of water captured for transpiration (kg) (Hammer et al, 1997), typically measured over a few months. At the leaf level, what is termed intrinsic TE is the ratio of instantaneous rates of CO2 assimilation (photosynthesis) and leaf conductance to water (Condon et al, 2002; Tuberosa, 2012), which is measured over a few seconds to a few minutes.Genotypic variation in TE has been reported in various crops, including wheat (Condon et al, 1990), rice (Impa et al, 2005), peanut (Wright et al, 1994), sunflower (Lambrides et al, 2004), maize (Pilbeam et al, 1995;Ryan et al, 2016a) and sorghum (Hammer et al, 1997;Mortlock and Hammer, 1999;Vadez et al, 2011;Xin et al, 2008). This genetic variation is suggestive of greater scope for further development of more drought-tolerant and water-efficient sorghum varieties (Borrell et al, 2006).…”