Root hydraulic conductivity and adjustments in stomatal conductance: hydraulic strategy in response to salt stress in a halotolerant species

Abstract

Recent advances at the molecular level are introducing a new scenariothat needs to be integrated into the analysis of plant hydraulicproperties. Although it is not yet clear to what extent this scenarioalters the current proposal for the hydraulic circuit models, itintroduces new insights when studying plants that are able to easilyovercome water restrictions. In this context, our aim was to explorewater adjustments in a halotolerant model (Beta vulgaris) by studyingthe coordination between the root in terms of root hydraulicconductivity (L-pr) and the shoot as reflected in the stomatalconductance (g(s)). The root water pathways were also analysed in termsof root suberization (apoplastic barrier) and aquaporin transcriptlevels (cell-to-cell pathway). Beta vulgaris showed the ability torapidly lose (4 h) and gain (24 h) turgor when submitted to salt stress(200 mM). The reduction profile observed in L-pr and g(s) was consistentwith a coupled process. The tuning of the root water flow involved smallvariations in the studied aquaporin's transcripts before anatomicalmodifications occurred. Exploring L-pr enhancement after halting thestress contributed to show not only a different profile in restoringL-pr but also the capacity to uncouple L-pr from g(s). Beta vulgarisroot plays a key role and can anticipate water loss before the aerialwater status is affected.