The effects of a high temperature on leaf photosynthetic response of Lupinus albus, a species native from the Mediterranean zone, were studied under varying tissue water status and irradiance (/). At leaf temperatures optimal (25 °C) or near-optimal (15 ®C) for carbon assimilation in lupins, photosynthetic capacity (P^) was decreased at leď relative water content (RWC) around 60 %. The temperature above the optimum (e g. 35 oC) decreased at high RWC (80 %). Irrespective of the leaf water status the optimum leaf temperature for in lupins was around 25 "C. The inhibition of P^ by lupin leaf discs at 35 °C was greatly enhanced at high I. Leaf disc treatment at 35 in the dark did not change quantum yield or Pn. When in addition to 35 the leaves were subjected to high I (TS + IS) or to high I and dehydration (TS + IS + WS), then a substantial decrease was observed in the quantum yield (66 and 77 % of the values in Controls, respectively) and in (31 and 56 %, respectively).