02088naa a2200253 a 450000100080000000500110000800800410001902200140006010000200007424501100009426000090020452013620021365000110157565000230158665000170160965300140162665300160164070000210165670000230167770000220170070000170172270000190173977300760175816530642005-11-03       2005    bl uuuu     u00u1 u    #d  a0103-90161 aSILVA, C. R. da  aWater relations and photosynthesis as criteria for adequate irrigation management in 'Tahiti' lime trees.  c2005  aIrrigation scheduling based on soil moisture status is one of the most useful methods because of its practicality and low cost. The effects of available soil water depletion on evapotranspiration (ETc), transpiration (E), leaf water potential at predawn (Yp) and midday (Ym), stomatal conductance (gs) and net CO2 assimilation (A) in lime 'Tahiti' trees (Citrus latifolia) were evaluated to improve irrigation schedule and minimize water use without causing water stress. The trees were spaced 7 x 4 m and drip-irrigated by four drippers with the available soil water content (AWC) depleted by suspension of irrigation (40 days). Leaf water potential was measured on a pressure chamber (Yp and Ym) and leaf gas exchange was measured by infrared gas analyzer (E, gs and A). Evapotranspiration was determined with the aid of weighing lysimeter. Water soil  content and potential (Ys) were monitored with TDR probes and tensiometers, respectively, installed at 0.3, 0.6 and 0.9 m depths. Meteorological variables were monitored with an  automatic weather station in the experimental area. The threshold AWC level for the onset of ETc decline was 43%, and 60% for gs, A, E and Yp. Also, Yp was more sensitive to AWC than  Ym, and is therefore a better tool for irrigation. When AWC was around 60%, values of Yp and Ys were -0.62 MPa and -48.8 kPa, respectively.  aCitrus  aevapotranspiration  agas exchange  alysimeter  atensiometer1 aFOLEGATTI, M. V.1 aSILVA, T. J. A. da1 aALVES JÚNIOR, J.1 aSOUZA, C. F.1 aRIBEIRO, R. V.  tScientia Agricola, Piracicabagv. 62, n. 5, p. 415-422, set./out. 2005.