ESTIMATION OF ROOT HYDRAULIC CONDUCTIVITY ON INTACT PEACH AND CITRUS ROOTSTOCKS

Estimates of root hydraulic conductivity (Lp) were obtained on intact peach (Prunus persica x P. davidiana 'Nemaguard') and sour orange (Citrus aurantium L.) rootstocks over a broad range of transpiration rates. Within a species, Lp was lower when estimated using the Ohm's law analog than the reciprocal of the slope of the linear regresssion between transpiration (E) and stem xylem water potential (psi). Nonzero y-intercepts in linear regressions of psi vs. E resulted in the lack of agreement between Lp estimates. Removal of the root system caused xylem psi to rapidly approach zero in both species when E almost-equal-to 0, suggesting that factors responsible for nonzero y intercepts resided within roots. Lp was 2.2 and 3.5 times lower for sour orange than peach when calculated by the Ohm's law and regression methods, respectively.