SOME PHYSIOLOGICAL AND MORPHOLOGICAL-CHARACTERISTICS OF CITRUS PLANTS FOR DROUGHT RESISTANCE

Tolerance and avoidance mechanisms to drought stress were studied in 6-month-old plants of Newhall orange (Citrus sinensis (L.) Osbeck) and Ellendale tangor (orange x mandarin hybrid) (Citrus sinensis (L) Osbeck x Citrus reticulata Blanco) during a drought/rewatering cycle under controlled conditions, Drought stress did not promote osmotic adjustment, while elastic adjustment (tissue elasticity increase) was noted in stressed orange and tangor plants. Both citrus plants showed a parallel decrease in leaf conductance (g(1)) and leaf water potential (Psi(1)) under water stress. Tangor plants had a more efficient water conservative strategy than orange, based on the characteristics of canopy architecture (lower canopy area and a more closed canopy with leaves nearly vertically oriented) together with a significant decrease in cuticular transpiration rates (TRc) under stress.