In this study,individuals of setariagrass (Setaria anceps Stapf.), limpograss (Hemarthriaaltissima [Poir] Stapf. & Hubbard), nilograss (Acroceras macrumStapf.) and angola grass (Brachiaria purpurascens [Raddi] Henr.) weresubmitted to moderate drought. The characteristics of chlorophyll a fluorescence(inicial fluorescence, Fo; maximum fluorescence, Fm; photochemistry efficiency,Fv/Fm; photochemical quenching, qP; non-photochemical quenching, qN andrelative electron transport rate, ETR) were investigated in an experiment carriedout in greenhouse, using plastic pots. The experimental treatments were allocatedin a randomized complete blocks design, with three replications. The valuesof Fo and Fm decreased in all species after 10 days of drought, this effectbeing more evident in nilograss and setariagrass. The Fv/Fm values for nilograssand setariagrass decreased dramatically while that one for hemarthriagrass didnot differ from the control. This results suggest a lower photochemical efficiencyof photosynthesis in nilograss and setariagrass under water stress comparedto hemarthriagrass and to the hea,lthy plants. The highest values of qN wereobserved for hemarthriagraas and angolagrass. This showed that the increasedcapacity to dissipate the excessive energy to drive photosynthesis was satisfactoryto maintain a low reduction state of the primary electron acceptor of the photosystemII (measured as qP). In general, ETR curves in response to increasing photosyntheticphoton flux differed from control to stressed plants, especially for nilograss.In this species, a serious damage caused by water stress provoked a significantreduction to the efficiency of the electron transporters of PSII.
