CONICET | Buscador de Institutos y Recursos Humanos

Water flow through plants has been described as a passive mechanism (diffusion and bulk flow) based on the analogy with Ohm's law. A hydraulic circuit with resistances (R, m-3 s MPa) at the root, shoot and canopy levels is proposed to describe water movements as a continuum known as SPAC (soil-plant-atmosphere). Given a water potential gradient (ΔΨ, MPa), an increase or decrease in the water flow (J, m-3 s-1) modifies the hydraulic conductance (Lo¸ m3 s-1 MPa-1) along the plant?s hydraulic circuit. In this model, the daytime transpiration water loss of the aerial part in the plant -modulated by stomatal conductance (gs, mmol m-2 s-1)- is the main contributor to the driving force that ensures water entry through the roots. At the root level, the root hydraulic conductivity (Lpr) is one of the parameters that better reflects the efficiency to promote water absorption as well as to prevent water loss. Indeed, a reduction on Lpr is the most conserved strategy to cope with soil water deficit. In our work we characterize the adjustment capacity of Lpr in Beta vulgaris and Sorghum bicolor plants submitted to different salt stress treatments, ranging from 0 to 200 mM NaCl (50 mM step). An integral characterization of water status was performed to look into each species hydraulic circuit. The different strategies to cope with salt stress allow also exploring Lpr management. Interestingly, the Lpr reduction profile shows a threshold of 80% in the reduction as the maximum adjustment capacity. The profile of reduction was different to the leaf water management (by means of analyzing stomatal conductance) reflecting that the aerial part is not necessarily coupled to the root water management. The contribution of water pathways involved in root water movement is discussed in terms of the root working as a rheostat.Supported by Prestamo BID PICT11 2239, PIP-CONICET & UBACyT1417, all grants to GA.