SOME PHYSIOLOGICAL AND MORPHOLOGICAL-CHARACTERISTICS OF CITRUS PLANTSFOR 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) Osbec k x Citrus reticulata Blanco) during a drought/rewatering cycle under controlled conditions, Drought stress did not promote osmotic adjustme nt, while elastic adjustment (tissue elasticity increase) was noted in stressed orange and tangor plants. Both citrus plants showed a parall el decrease in leaf conductance (g(1)) and leaf water potential (Psi(1 )) under water stress. Tangor plants had a more efficient water conser vative strategy than orange, based on the characteristics of canopy ar chitecture (lower canopy area and a more closed canopy with leaves nea rly vertically oriented) together with a significant decrease in cutic ular transpiration rates (TRc) under stress.