The objective of this study is to evaluate the interference of reduced spacing in the physiological and characteristics production components of maize hybrids (Zea mays L.). Four line spacings (95, 80, 60 and 40 cm) were tested using three commercial hybrids (H1, H2 and H3) in Senador Guiomard, Acre, Brazil. The experimental design of randomized complete blocks was used in subdivided plots. The experiment lasted four months, where the parameters measured were CO2 assimilation and gas exchange, water use and carboxylation efficiencies and productivity. Reduction in spacing did not influence the photosynthesis, with slightly differences at stomatal conductance and transpiration. However, it was observed that the H3 presented higher efficiency of water use and carboxylation at the larger spacings. Moreover, there was an increase in the number of ears and grain yield per hectare in reduced spacing, with H3 plants presenting a superior mass of 100 grains among the cultivars. It is concluded that H3 (P4285YHR) presents essential physiological characteristics favouring yields at reduced spacings compared to crops requiring larger spacing. In addition, reduced spacing lines for the maize crop do not reduce atmospheric CO2 assimilation, resulting in larger productivity per cultivated area among the three tested hybrids. Key words: Production, photosynthesis, Zea mays.
