Root O₂ consumption, CO₂ production and tissue concentration profiles in chickpea, as influenced by environmental hypoxia

TY - JOUR

T1 - Root O2 consumption, CO2 production and tissue concentration profiles in chickpea, as influenced by environmental hypoxia

AU - Colmer, Timothy David

AU - Winkel, Anders

AU - Kotula, Lukasz

AU - Armstrong, William

AU - Revsbech, Niels Peter

AU - Pedersen, Ole

N1 - © 2019 The Authors New Phytologist © 2019 New Phytologist Trust.

PY - 2020/4/1

Y1 - 2020/4/1

N2 - Roots in flooded soils experience hypoxia, with the least O2 in the vascular cylinder. Gradients in CO2 across roots had not previously been measured. The respiratory quotient (RQ; CO2 produced : O2 consumed) is expected to increase as O2 availability declines. A new CO2 microsensor and an O2 microsensor were used to measure profiles across roots of chickpea seedlings in aerated or hypoxic conditions. Simultaneous, nondestructive flux measurements of O2 consumption, CO2 production, and thus RQ, were taken for roots with declining O2. Radial profiling revealed severe hypoxia and c. 0.8 kPa CO2 within the root vascular cylinder. The distance penetrated by O2 into the roots was shorter at lower O2. The gradient in CO2 was in the opposite direction to that of O2, across the roots and diffusive boundary layer. RQ increased as external O2 was lowered. For chickpea roots in solution at air equilibrium, O2 was very low and CO2 was elevated within the vascular cylinder; the extent of the severely hypoxic core increased as external O2 was reduced. The increased RQ in roots in response to declining external O2 highlighted the shift from respiration to ethanolic fermentation as the severely hypoxic/anoxic core became a progressively greater proportion of the root tissues.

AB - Roots in flooded soils experience hypoxia, with the least O2 in the vascular cylinder. Gradients in CO2 across roots had not previously been measured. The respiratory quotient (RQ; CO2 produced : O2 consumed) is expected to increase as O2 availability declines. A new CO2 microsensor and an O2 microsensor were used to measure profiles across roots of chickpea seedlings in aerated or hypoxic conditions. Simultaneous, nondestructive flux measurements of O2 consumption, CO2 production, and thus RQ, were taken for roots with declining O2. Radial profiling revealed severe hypoxia and c. 0.8 kPa CO2 within the root vascular cylinder. The distance penetrated by O2 into the roots was shorter at lower O2. The gradient in CO2 was in the opposite direction to that of O2, across the roots and diffusive boundary layer. RQ increased as external O2 was lowered. For chickpea roots in solution at air equilibrium, O2 was very low and CO2 was elevated within the vascular cylinder; the extent of the severely hypoxic core increased as external O2 was reduced. The increased RQ in roots in response to declining external O2 highlighted the shift from respiration to ethanolic fermentation as the severely hypoxic/anoxic core became a progressively greater proportion of the root tissues.

U2 - 10.1111/nph.16368

DO - 10.1111/nph.16368

M3 - Journal article

C2 - 31838743

SN - 0028-646X

JO - New Phytologist

JF - New Phytologist

ER -