Abstract Temperature and flood depths influence the growth and development of irrigated rice. The objective of this study was to evaluate the initial response of two rice genotypes on oxidative stress, growth and nitrogen accumulation of rice seedlings under different temperatures and flood depths in a water seeded system. The study was conducted in 2012 using a phytotron chamber. Treatments were a combination of two air temperatures regimes (17 and 20°C), two rice genotypes (IRGA 425 and Epagri114) and three flood dephs (1, 5 and 9 cm). The results showed that temperature affected seedling performance, with greater dry mass for roots and shoots, as well as greater nitrogen accumulation at 20°C at a flood depth of 1 cm for both genotypes. The H 2 O 2 concentration in the root increased with increasing flood depth, with a significantly greater increase for the 114 Epagri genotype. The activity of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) varied depending on the genotype, with SOD being the most expressive, increasing its activity with increasing flood depth. Chlorophyll and carotenoid contents decreased significantly with increasing flood depth, with less interference for IRGA 425. Temperature and flood depth affected nitrogen absorption, dry matter accumulation and oxidative stress in rice seedlings in the system tested. The lowest stresses were observed in rice plants subjected to the flood depth of 1 cm at 20 °C, and cultivar IRGA 425 was more tolerant to increased depth of water when compared to cultivar Epagri 114
