Water relations and hydraulic architecture of two Patagonian steppe shrubs:

IOGNA P.A.; BUCCI SJ; SCHOLZ FG; GOLDSTEIN G

JOURNAL OF ARID ENVIRONMENTS

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Año: 2011 vol. 75 p. 763 - 772

0140-1963

On a local scale, topography influences microclimate, vegetation structure and the morpho-physiological attributes of plants. We studied the effects of microclimatic differences between NE and SW-facing slopes on the water relations and hydraulic properties of two dominant shrubs of the Patagonian steppe in Argentina (Retanilla patagonica and Colliguaja integerrima). The NE-facing slope had higher irradiance and air saturation deficits and lower soil water availability and wind speed than the SW-facing slope. Predawn and midday YL and osmotic potentials were significantly lower in shrubs on the NE-facing slope. Osmotic adjustment and more elastic cell walls helped the plants to cope with a more xeric environment on NE-facing slope. Higher water deficits on NE-facing slope were partially compensated by a higher leaf and stem water storage. While stem hydraulic efficiency did not vary between slopes, leaf hydraulic conductance was between 40% and 300% higher on the NE-facing slope. Changes observed in leaf size and in SLA were consistent with responses to mechanical forces of wind (smaller and scleromorphic leaves on SW-facing slope). Morpho-physiological adjustments observed at a short spatial scale allow maintenance of midday YL above the turgor loss point and demonstrate that leaves are more responsive to microclimatic selective pressures than stems.