Abstract Iron is essential to plant development. However, its excess can provoke an increase in reactive oxygen species and oxidative stress in plants. The objective of this work was to verify the effects of high concentrations of iron on the oxidative stress of seeds and young plants of Cecropia hololeuca and Carica papaya. The species were submitted to concentrations of 0.045, 4 and 8mM of iron in the form of ferrous sulfate and FeEDTA. The experiments of germination and initial growth took place in a growth chamber, with temperature of 25ºC and 12h photoperiod. We performed the lipid peroxidation test by extraction and quantification of malonaldehyde and hydrogen peroxide. The application of iron did not cause a significant elevation in the contents of malonaldehyde and hydrogen peroxide in the germination of C. hololeuca and C. papaya. In the young plants, the hydrogen peroxide did not change in any of the treatments. However, it was possible to observe an expressive increase in malonaldehyde concentration in both species when exposed to FeEDTA 4 to 8mM. The results indicate a sensibility of C. hololeuca and C. papaya to high iron levels, amplifying the oxidative stress process that can harm their growth and initial development.

ABSTRACT Senna pendula seeds dormancy is caused by impermeability of the seed coat to water. In order to determine the best methodology to overcome dormancy and to perform a morphological characterization, two batches of seeds were submitted to the following treatments: a) mechanical scarification of the seed coat; b) immersion in hot water at 70 °C for 5, 10, 15 and 20 minutes; c) immersion in hot water at 90 °C for 5, 10, 15 and 20 minutes; d) sulfuric acid concentrate for 5, 10, 15 and 20 minutes; e) no treatment. The experiment was conducted in laboratory using a completely randomized design, with four replications of 25 seeds each, with daily verification for 7 days. The results showed that the use of water does not overcome the dormancy, however mechanical and chemical scarifications were the most effective treatments, with germination percentage of up to 94%.