Sap fluxes from different parts of the rootzone modulate xylem ABA concentration during partial rootzone drying and re-wetting.
Previous studies with partial rootzone drying (PRD) irrigation demonstrated that alternating the wet and dry parts of the rootzone (PRD-Alternated) increased leaf xylem ABA concentration ([X-ABA]leaf) compared with maintaining the same wet and dry parts of the rootzone (PRD-Fixed). To determine the relative contributions of different parts of the rootzone to this ABA signal, [X-ABA]leaf of potted, split-root tomato (Solanum lycopersicum) plants was modelled by quantifying the proportional water uptake from different soil compartments, and [X-ABA]leaf responses to the entire pot soil-water content (θpot). Continuously measuring soil-moisture depletion by, or sap fluxes from, different parts of the root system revealed that water uptake rapidly declined (within hours) after withholding water from part of the rootzone, but was rapidly restored (within minutes) upon re-watering. Two hours after re-watering part of the rootzone, [X-ABA]leaf was equally well predicted according to θpot alone and by accounting for the proportional water uptake from different parts of the rootzone. Six hours after re-watering part of the rootzone, water uptake by roots in drying soil was minimal and, instead, occurred mainly from the newly irrigated part of the rootzone, thus [X-ABA]leaf was best predicted by accounting for the proportional water uptake from different parts of the rootzone. Contrary to previous results, alternating the wet and dry parts of the rootzone did not enhance [X-ABA]leaf compared with PRD-Fixed irrigation. Further work is required to establish whether altered root-to-shoot ABA signalling contributes to the improved yields of crops grown with alternate, rather than fixed, PRD.
Department of Citriculture, IMIDA, 30150 La Alberca, Murcia, Spain.
J G
JG
Pérez-Pérez
Centre for Sustainable Agriculture, Lancaster Environment Centre, University of Lancaster, Lancaster LA1 4YQ, Uk i.dodd@lancaster.ac.uk.
I C
IC
Dodd
D000040:Abscisic Acid / Q000378:metabolism*; D018481:Convection; D003890:Desiccation; D018551:Solanum lycopersicum / Q000502:physiology; D053147:Plant Exudates / Q000378:metabolism*; D018515:Plant Leaves / Q000502:physiology; D018517:Plant Roots / Q000378:metabolism*; D012987:Soil / Q000737:chemistry; D014867:Water / Q000737:chemistry*; D052584:Xylem / Q000378:metabolism*
D053147:Plant Exudates; D012987:Soil; D014867:Water; D000040:Abscisic Acid
ABA; irrigation scheduling; partial rootzone drying; root-to-shoot signalling; soil moisture heterogeneity.; soil moisture sensors