This study was aimed at evaluating the effects of five levels of drip irrigation in three castor bean cultivars (IAC Guarani, Mirante 10 and BRS Paraguaçu) by measuring the dry mass production by the different plant parts (leaf blade, petiole and plant stem) as well as by measuring the gas exchange processes (photosynthesis, stomatal conductance and transpiration). The experiment was conducted in the field, at the Fazenda Experimental, Vale do Curu, Pentecoste, Ceará (Br). The experiment was conducted in a randomized blocks in a 5x3 factorial scheme, in split plots with three repetitions. The treatments were five irrigation levels (25, 50, 75, 100 and 125% of the class "A" pan evaporation (CAE) applied to the three cultivars. The different irrigation levels influenced the variables: petiole dry mass, stomatal conductance and photosynthesis, and maximum values for these variables were obtained with irrigation level corresponding to 125% of the Class A pan evaporation. There was a different response in biomass production and gas exchanges from each of the three cultivars, in all variables, except in petiole dry mass.
Ricinus communis; biomass; photosynthesis
