A novel root‐to‐shoot stomatal response to very high CO₂ levels in the soil: electrical, hydraulic and biochemical signalling

Abstract

Investigations were undertaken in the context of the potential environmental impact of carbon capture and storage (CCS) transportation in the form of a hypothetical leak of extreme levels of CO2 into the soil environment and subsequent effects on plant physiology. Laboratory studies using purpose built soil chambers, separating and isolating the soil and aerial environments, were used to introduce high levels of CO2 gas exclusively into the rhizosphere. CO2 concentrations greater than 32% in the isolated soil environment revealed a previously unknown whole plant stomatal response. Time course measurements of stomatal conductance (gs), leaf temperature and leaf abscisic acid (ABA) show strong coupling between all three variables over a specific period (3 h following CO2 gassing) occurring as a result of CO2‐specific detection by roots. The coupling of gs and ABA subsequently breaks down resulting in a rapid and complete loss of turgor in the shoot. Root access to water is severely restricted as evidenced by the inability to counter turgor loss, however, the plant regains some turgor over time. Recovery of full turgor is not achieved over the longer term. Results suggest an immediate perception and whole plant response as changes in measured parameters (leaf temperature, gs and ABA) occur in the shoot, but the response is solely due to detection of very high CO2 concentration at the root/soil interface which results in loss of stomatal regulation and disruption to control over water uptake.

Plant responses to simulated carbon capture and storage (CCS) CO2 pipeline leakage: the effect of soil type

“…This response was investigated in more detail and found to be a whole plant response affecting the water status of the plant. 27 The majority of the findings of this short-term study (a reduction in above and below ground biomass when CO 2 treatments are compared to controls) reflect those conducted on more long-term field trials such as work at the Zero Emission Research and Technology (ZERT) Center, Montana, USA 2 and the ASGARD facility. [23][24][25]…”

“…The reduction in root biomass provides a mechanism for the inability of plants to access sufficient nutrients and water. This response was investigated in more detail and found to be a whole plant response affecting the water status of the plant …”

Suggestions for plant parameters to monitor potential CO2 leakage from carbon capture and storage (CCS) sites

“…The content of leaf water and root TP in the ‘CO 2 ’ treatment condition was significantly decreased by 3% and 27% compared to the control, respectively (Table ). These results indicated that root absorption of soil water and nutrients was lower in the ‘CO 2 ’ treatment condition, which might lead to changes in the rhizospheric conditions . Meanwhile, the roots in the ‘CO 2 treatment condition’ had 73% and 7% higher starch and TC content compared to the control, respectively (Table ).…”

“…Standard errors are shown as perpendicular lines (n = 6) and asterisks represent significant differences between the 'CON' and 'CO 2 ' treatments according to ANOVA as follows: ***, P < 0.01; **, P < 0.05; and *, P < 0.10. the rhizospheric conditions. 20,22,30 Meanwhile, the roots in the 'CO 2 treatment condition' had 73% and 7% higher starch and TC content compared to the control, respectively ( Table 3). As storage organs, roots can store photosynthate in the form of starch.…”

“…The rhizosphere can be a promising zone for root-level monitoring of soil CO 2 leakage, because the roots are affected first by leaked CO 2 from CCS facilities. 7,22 Moreover, damaged root growth could cause reduced uptake of water and nutrients, which can change the rhizospheric environment as a secondary effect of high soil CO 2 levels. Kim et al 20 reported that N 2 O emissions dramatically increased within 3 days of CO 2 injection.…”