PHYSIOLOGICAL RESPONSE OF MAIZE AND WEEDS IN COEXISTENCE

This study aimed at evaluating the physiology of maize and weeds when living under different densities. The randomized block design with 4 replications was used. The factorial scheme 5 x 2 + 1 and 5 x 3 was adopted, for maize and weeds respectively, corresponding to weed species (Bidens pilosa, Commelina benghalensis, Urochloa brizantha, Sorghum arundinaceum and Ipomoea triloba) and infestation density (control, 15 and 30 plants m(-2)). Weeds were kept in coexistence with the maize hybrid DKB 390 PRO 2, with an additional treatment for maize plants absent of competition. It was kept in coexistence with maize hybrid DKB 390 PRO 2 besides an additional treatment with maize plants absent of competition. On day 45 and 60 after maize planting (DAP) physiological reviews were performed within the culture, and 38 days after weed transplanting (DAT), an infrared gas analyzer (IRGA) was used. There were physiological changes in maize due to the coexistence with weeds. On day 45 DAP, the competition, regardless of the weed species, caused less photosynthetic rate in maize coexisting with 15 plants m(-2); the stomatal conductance was lower in both densities. On day 60 DAP, maize in competition with 15 and 30 plants m(-2) showed lower transpiration rate. U. brizantha and S. arundinaceum showed reduction in photosynthesis and transpiration, due to increased density and coexistence with maize.