Abstract
Plants have evolved multiple strategies to survive and adapt when confronting the changing climate, including elevated CO2 concentration (e[CO2]) and intensified drought stress. To explore the role of abscisic acid (ABA) in modulating the response of plant water relation characteristics to progressive drought under ambient (a[CO2], 400 ppm) and e[CO2] (800 ppm) growth environments, two tomato (Solanum lycopersicum) genotypes, Ailsa Craig (AC) and its ABA-deficient mutant (flacca), were grown in pots, treated with or without exogenous ABA, and exposed to progressive soil drying until all plant available water in the pot was depleted. The results showed that exogenous ABA application improved leaf water potential, osmotic potential, and leaf turgor and increased leaf ABA concentrations ([ABA]leaf) in AC and flacca. In both genotypes, exogenous ABA application decreased stomatal pore aperture and stomatal conductance (gs), though these effects were less pronounced in e[CO2]-grown AC and gs of ABA-treated flacca was gradually increased until a soil water threshold after which gs started to decline. In addition, ABA-treated flacca showed a partly restored stomatal drought response even when the accumulation of [ABA]leaf was vanished, implying [ABA]leaf might be not directly responsible for the decreased gs. During soil drying, [ABA]leaf remained higher in e[CO2]-grown plants compared with those under a[CO2], and a high xylem sap ABA concentration was also noticed in the ABA-treated flacca especially under e[CO2], suggesting that e[CO2] might exert an effect on ABA degradation and/or redistribution. Collectively, a fine-tune ABA homeostasis under combined e[CO2] and drought stress allowed plants to optimize leaf gas exchange and plant water relations, yet more detailed research regarding ABA metabolism is still needed to fully explore the role of ABA in mediating plant physiological response to future drier and CO2-enriched climate.
Highlights
Elevated atmospheric carbon dioxide concentrations (e[CO2]), a major component of climate change, causes an increase in global mean surface temperature (Jia et al, 2019)
Avila et al (2020) found that coffee plants grown at e[CO2] could better maintain leaf water potential and hydraulic conductance than their ambient [CO2]-counterparts under drought stress, thereby improving plant fitness
Plant Growth and Soil Water Depletion In Ailsa Craig (AC), exogenous abscisic acid (ABA) application did not have a significant influence on Leaf dry weight (LDW) and stem dry weight (SDW), while e[CO2] increased both LDW and SDW
Summary
Elevated atmospheric carbon dioxide concentrations (e[CO2]), a major component of climate change, causes an increase in global mean surface temperature (Jia et al, 2019). Avila et al (2020) found that coffee plants grown at e[CO2] could better maintain leaf water potential ( leaf) and hydraulic conductance than their ambient [CO2]-counterparts under drought stress, thereby improving plant fitness. Early studies have reported that e[CO2]-induced stomatal closure could reduce plant water consumption hereby increasing the availability of water in the soil during drought (Field et al, 1995), recent studies revealed that plant grown at e[CO2] might depleted soil water faster due to enlarged leaf area (Temme et al, 2018; Liu et al, 2019). Haworth et al (2016) indicated that the reduced effectiveness of stomatal closure at e[CO2] could impair crops’ tolerance to severe drought despite of an improved water use efficiency Early studies have reported that e[CO2]-induced stomatal closure could reduce plant water consumption hereby increasing the availability of water in the soil during drought (Field et al, 1995), recent studies revealed that plant grown at e[CO2] might depleted soil water faster due to enlarged leaf area (Temme et al, 2018; Liu et al, 2019). Haworth et al (2016) indicated that the reduced effectiveness of stomatal closure at e[CO2] could impair crops’ tolerance to severe drought despite of an improved water use efficiency
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