Transpiratory rate of eucalypt seedlings in response to water levels in the soil and to association with Brachiaria

The effects of Brachiaria brizantha Stapf on the transpiratory rate of Euca lyptus citriodora Hook and E.grandis W Hill ex Maiden seedlings cultivated in soils with three levels of water under greenhouse conditions were evalua ted. Treatments were arranged in a factorial design, with four repetitions (2x3x4): two species (E. citriodora and E. grandis), three levels of water (20%, 23% and 26%), and four populations of B. brizantha (0, 1, 2 and 3 pla nts per vase). Water level in the vases was maintained constant until the l ast experiment evaluation, at 70 days after seedlings transplant. Measureme nts were done with an infrared gas analyzer (IRGA). Independently of water level in the soil, Brachiaria brizantha demonstrated its competitiveness fo r E. citriodora and E. grandis initial growing, by transpiratory rate reduc tion. E citriodora or E grandis seedlings upper third leaves presented high er transpiratory rate than mean and lower third leaves, independently of B. brizantha population and water level in the soil.