Genotypic, Developmental and Drought-Induced Differences in Root Hydraulic Conductance of Contrasting Sugarcane Cultivars

Hydraulic properties of entire root systems and isolated rootsof three contrasting sugarcane clones were evaluated using transpiration-induceddifferences in hydrostatic pressure across intact root systems,root pressure-generated xylem sap exudation, and pressure-fluxrelationships. Regardless of the measurement technique employed,the clones were ranked in the same order on the basis of theirleaf area–specific total root system hydraulic conductance(C_root). All methods employed detected large developmental changesin G_rootroot with maximum values occurring in plants with approximately02 m₂ total leaf area. Genotypic ranking according to G_root,was reflected as a similar ranking according to root length-specifichydraulic conductance (L) of individual excised roots. Genotypicdifferences in G_root and L were consistent with anatomical characteristicsobserved in individual roots. Patterns of G_root, during soildrying and following re-irrigation suggested that the declinein G_root, observed during soil drying occurred within the rootsrather than at the soil–root interface and may have beencaused in part by xylem cavitation in the roots. Key words: Root hydraulic conductance, Saccharum spp, transpiration, root pressure, pressure-flux