The stem xylem of Patagonian shrubs operates far from the point of catastrophic dysfunction and is additionally protected from drought-induced embolism by leaves and roots

BUCCI, SANDRA J.; SCHOLZ, FABIÁN G.; PESCHIUTTA, MARÍA LAURA; ARIAS, NADIA; MEINZER FREDERICK C. ; GOLDSTEIN, GUILLERMO

PLANT, CELL AND ENVIRONMENT (PRINT)

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2013 vol. 33 p. 2163 - 2174

0140-7791

Hydraulic architecture was studied in shrub species differingin rooting depth in a cold desert in Southern Argentina. Allspecies exhibited strong hydraulic segmentation betweenleaves, stems and roots with leaves being the most vulnerablepart of the hydraulic pathway. Two types of safety marginsdescribing the degree of conservation of the hydraulic integritywere used: the difference between minimum stem or leafwater potential (Y) and the Y at which stem or leaf hydraulicfunction was reduced by 50% (Y ? Y50), and the differencebetween leaf and stem Y50. Leaf Y50 ? stem Y50 increased withdecreasing rooting depth. Large diurnal decreases in rootspecifichydraulic conductivity suggested high root vulnerabilityto embolism across all species. Although stem Y50became more negative with decreasing species-specific Ysoiland minimum stem Y, leaf Y50 was independent of Y andminimum leaf Y. Species with embolism-resistant stems alsohad higher maximum stem hydraulic conductivity. Safetymargins for stems were >2.1 MPa, whereas those for leaveswere negative or only slightly positive. Leaves acted as safetyvalves to protect the integrity of the upstream hydraulicpathway, whereas embolism in lateral roots may help todecouple portions of the plant from the impact of drier soillayers.