Intraspecific variation in embolism resistance and stem anatomy across four sunflower (Helianthus annuus L.) accessions

Abstract

Drought-induced xylem embolism is a key process closely related to plant mortality during extreme drought events. However, this process has been poorly investigated in crop species to date, despite the observed decline of crop productivity under extreme drought conditions. Interspecific variation in hydraulic traits has frequently been reported, but less is known about intraspecific variation in crops. We assessed the intraspecific variability of embolism resistance in four sunflower (Helianthus annuus L.) accessions grown in well-watered conditions. Vulnerability to embolism was determined by the in situ flow-centrifuge method (cavitron), and possible trade-offs between xylem safety, xylem efficiency and growth were assessed. The relationship between stem anatomy and hydraulic traits was also investigated. Mean P was -3 MPa, but significant variation was observed between accessions, with values ranging between -2.67 and -3.22 MPa. Embolism resistance was negatively related to growth and positively related to xylem-specific hydraulic conductivity. There is, therefore, a trade-off between hydraulic safety and growth but not between hydraulic safety and efficiency. Finally, we found that a few anatomical traits, such as vessel density and the area of the vessel lumen relative to that of the secondary xylem, were related to embolism resistance, whereas stem tissue lignification was not. Further investigations are now required to investigate the link between the observed variability of embolism resistance and yield, to facilitate the identification of breeding strategies to improve yields in an increasingly arid world.

Coordinated plasticity maintains hydraulic safety in sunflower leaves

“…Given that leaves have a shorter lifespan and are usually exposed to greater variations in water potential, it seems likely that they may exhibit a higher degree of plasticity in vulnerability when compared to stems. When considered in the context of relatively low plasticity of stem vulnerability in sunflower (Stiller & Sperry, 2002;Ahmad et al, 2018), this seems to be the case for this species. Additionally, it is notable that sunflower appears to exhibit a higher degree of vulnerability segmentation than other herbs such as tomato (Skelton et al, 2017).…”

Over‐accumulation of abscisic acid in transgenic tomato plants increases the risk of hydraulic failure

“…Analyses in this regard have produced mixed results to date. At the intraspecific level, Corcuera, Cochard, Gil‐Pelegrin, and Notivol () found a correlation between greater hydraulic conductivity and lower embolism resistance in maritime pine, whereas Ahmad et al () showed that sunflower accessions that were more resistant to xylem embolism also transported water more efficiently. The lack of trade‐off between xylem safety and efficiency was further evidenced in Scots pine (Martínez‐Vilalta et al, ) and European beech (Schuldt et al, ), as well as at the interspecific level across a large pool of woody species distributed worldwide (Gleason et al, ).…”

“…Some herbaceous grasses have been found to be more resistant to embolism than previously thought: the xylem pressure inducing a 50% loss of hydraulic conductivity (Ψ 50 ) ranged from −0.5 MPa in reed canary grass (Phallaris arundinacea) to −7.5 MPa in European feather grass (Stipa pennata; Lens et al, 2016). The few estimates of crop Ψ 50 available so far range from −1.6 MPa in rice (Stiller, Lafitte, & Sperry, 2003) to −3 MPa in sunflower (Ahmad et al, 2017), but embolism resistance can vary significantly between different varieties within a crop species (Ahmad et al, 2017). The limited number of studies investigating crop hydraulics were carried out on maize (Cochard, 2002a;Li, Sperry, & Shao, 2009;Ryu, Hwang, Kim, & Lee, 2016;Tyree, Fiscus, Wullschleger, & Dixon, 1986), sugarcane (Neufeld et al, 1992), sunflower (Ahmad et al, 2017;Cardoso, Brodribb, Lucani, DaMatta, & McAdam, 2018;Stiller & Sperry, 2002), and rice (Stiller et al, 2003;Stiller, Sperry, & Lafitte, 2005).…”

Signal coordination before, during and after stomatal closure in response to drought stress

“…Several studies have shown that this methodology is not prone to the open vessel artifact (Jacobsen & Pratt, 2012;Sperry et al, 2012;Hacke et al, 2014). Therefore, this technique was chosen because maximum vessel length of sunflower stems (23 cm; Ahmad et al, 2018) exceeded the sample length that was examined in this study. Fourteen-cm-long stem segments of well-watered sunflowers were cut under water and fixed in a custom-made centrifuge rotor (Sorvall RC-5C; Thermo Fisher Scientific, Waltman, MA, USA).…”