16 research outputs found
Stomatal and hydraulic conductance in growing sugarcane: stomatal adjustment to water transport capacity*
How do leaf hydraulics limit stomatal conductance at high water vapour pressure deficits?
Below-ground hydraulic conductance is a function of environmental conditions and tree size in Scots pine
During measurements of root hydraulics with pressure probes, the contribution of unstirred layers is minimized in the pressure relaxation mode: comparison with pressure clamp and high-pressure flowmeter
Low temperature and mechanical stresses differently gate aquaporins of root cortical cells of chilling-sensitive cucumber and -resistant figleaf gourd
Relationships between sap flow and water potential in woody or perennial plants on islands of the Great Barrier Reef.
The influence of the light environment and photosynthesis on oxidative signalling responses in plant-biotrophic pathogen interactions
Comparison between gradient-dependent hydraulic conductivities of roots using the root pressure probe: the role of pressure propagations and implications for the relative roles of parallel radial pathways
The definitive version is available at www.blackwell-synergy.comHydrostatic pressure relaxations with the root pressure probe are commonly used for measuring the hydraulic conductivity (Lpr) of roots. We compared the Lpr of roots from species with different root hydraulic properties (Lupinus angustifolius L. ‘Merrit’, Lupinus luteus L. ‘Wodjil’, Triticum aestivum L. ‘Kulin’ and Zea mays L. ‘Pacific DK 477’) using pressure relaxations, a pressure clamp and osmotic gradients to induce water flow across the root. Only the pressure clamp measures water flow under steady-state conditions. Lpr determined by pressure relaxations was two- to threefold greater than Lpr from pressure clamps and was independent of the direction of water flow. Lpr (pressure clamp) was two- to fourfold higher than for Lpr (osmotic) for all species except Triticum aestivum where Lpr (pressure clamp) and Lpr (osmotic) were not significantly different. A novel technique was developed to measure the propagation of pressure through roots to investigate the cause of the differences in Lpr. Root segments were connected between two pressure probes so that when root pressure (Pr) was manipulated by one probe, the other probe recorded changes in Pr. Pressure relaxations did not induce the expected kinetics in pressure in the probe at the other end of the root when axial hydraulic conductance, and probe and root capacitances were accounted for. An electric circuit model of the root was constructed that included an additional capacitance in the root loaded by a series of resistances. This accounted for the double exponential kinetics for intact roots in pressure relaxation experiments as well as the reduced response observed with the double probe experiments. Although there were potential errors with all the techniques, we considered that the measurement of Lpr using the pressure clamp was the most unambiguous for small pressure changes, and provided that sufficient time was allowed for pressure propagation through the root. The differences in Lpr from different methods of measurement have implications for the models describing water transport through roots and the potential role of aquaporins.Helen Bramley, Neil C. Turner, David W. Turner and Stephen D. Tyerma