Embolized Stems Recover Overnight in Zea mays: The Role of Soil Water, Root Pressure, and Nighttime Transpiration

Abstract

It is not currently well-understood how much xylem conductance is lost in maize plants during the day, if conductance is recovered during the night, or what soil water conditions are required for recovery to take place. To answer these questions we designed a greenhouse experiment whereby two genetically dissimilar maize genotypes were subjected to a level of water stress commonly experienced in the field (Ψxylem ∼-2 MPa). We then measured the loss of stem-specific conductivity associated with this level of stress, as well as the overnight recovery following three re-watering treatments: Ψsoil ∼ 0 MPa, Ψsoil ∼-0.40 MPa, and Ψsoil ∼-1.70 MPa. Mid-day leaf water potentials of -1.98 MPa resulted in stem-specific conductivity (KS) values that were 31.5% of maximal (i.e., 68% loss). Returning soils to field capacity (Ψsoil ∼ 0 MPa) overnight allowed for the significant recovery of KS (76% of maximal), whereas partial watering (Ψsoil ∼-0.40 MPa) resulted KS values that were 51.7% of maximal values, whereas not watering resulted in no recovery (35.4% of maximal; Ψsoil ∼-1.7 MPa). Recovery of KS was facilitated by the generation of root pressure and low rates of nighttime transpiration.

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

“…Root pressure has been considered as a potential mechanism involved in both repair of embolized vessels and water supply to shoots in the absence of transpiration (Cao, Yang, Zhang, & Brodribb, 2012;Charrier et al, 2016;Ewers, Cochard, & Tyree, 1997;Knipfer, Eustis, Brodersen, Walker, & McElrone, 2015;Steudle, 2001). However, whereas root pressure has been reported to occur in a variety of crop species such as barley (Knipfer & Fricke, 2010), maize (Gleason et al, 2017), rice (Stiller et al, 2003), sugarcane (Meinzer, Grantz, & Smit, 1991) and tomato (De Swaef, Hanssens, Cornelis, & Steppe, 2013), xylem repair in herbaceous and woody species has been seldom observed (Choat et al, 2019;Lens et al, 2016;Sperry, 2013).…”

Wheat leaves embolized by water stress do not recover function upon rewatering

“…It is also possible that root pressure induces refilling in the field, possibly only under high soil moisture conditions, or that refilling may have occurred in this study if plants were monitored for a longer period of time after rewatering. Some research has suggested that daily losses of xylem conductance are repaired overnight in rice leaves (Stiller & Lafitte, ), while others have visualized refilling in the stems of maize (Gleason et al, ). It should be noted that these studies used methods that involved excised plant material, unlike the non‐invasive in vivo method that was used in this study as it minimizes the risk of exogenous embolism.…”

“…Grasses represent a significant technical challenge for measuring cavitation due to their small size, fragility, and vascular arrangement (Bramley et al, ; Cochard et al, ; Jansen, Schuldt, & Choat, ). In addition, it is generally assumed that cavitation in grasses may not be as catastrophic as it is in woody plants due to the presence of sufficient root pressure to repair embolism in grasses such as wheat and bamboo (Cao, Yang, Zhang, & Brodribb, ; Gleason et al, ; Ryu, Hwang, & Lee, ; Trillo & Fernandez, ).…”

“…Maintaining a continuous supply of water to the leaves for photosynthesis is vital for plant survival and presents a significant challenge in a drying climate (Brodribb, 2006;Gleason et al, 2017;Larter et al, 2017;Pfautsch et al, 2016;Stocker, 2014). Water is transported through the xylem under negative pressure (tension), driven by water loss from open stomata at the leaves (Dixon, 1914;Dixon & Joly, 1895;Tyree & Zimmermann, 2002).…”

Vessel scaling in evergreen angiosperm leaves conforms with Murray's law and area‐filling assumptions: implications for plant size, leaf size and cold tolerance

“…Although we recognize that species may diverge from this optimal solution if fitness in a particular environment places a premium on other traits, such as height or mechanical safety, in general we might expect limited leaf size and plant size when the hydraulic radii or conduit number is constrained at the base of the plant. However, we do note that the occurrence of emboli (from freezing–thawing or low water potential) do not necessarily represent insurmountable impediments to water transport in either gymnosperm or angiosperm species (McCulloh et al ., ; Secchi & Zwieniecki, ; Trifilò et al ., ; McCulloh & Meinzer, ; Gleason et al ., ).…”