SILÍCIO E ÓXIDO NÍTRICO COMO ATENUADORES DO ESTRESSE SALINO EM ALFACE E FEIJOEIRO

Abstract

This thesis, composed of two chapters, aimed to evaluate the deleterious effects of salinity on bean and lettuce plants, as well as the possible beneficial effects of Si and NO in relieving the stress caused by NaCl. Both studies were conducted in a greenhouse. In the experiment with bean plants, saline stress was induced with the addition of 60 mmol L-1 of NaCl in the nutrient solution and for the resistance induction treatments, five doses of silicon (Si) were used (0; 1; 2; 3; 4 mmol L-1 of Si). In general, salinity reduced the levels of photosynthetic pigments, the levels of nitrogen and the accumulation of dry mass. With the increase of the doses of Si, there was an increase in the levels of photosynthetic pigments, in the production of dry matter and in the levels of N. In the experiment with lettuce plants, the treatment with Si was carried out with the addition of 1.5 mmol L-1 of Si, saline stress was induced with the addition of 100 mmol L-1 of NaCl in the nutrient solution and the treatment with NO was carried out by spraying 50 mL of sodium nitroprossiate at a dose of 100 μmol L-1 of NO . In general, salinity reduced leaf transpiration and photosynthesis, increased lipid peroxidation and the activity of SOD and POX enzymes. The isolated application of Si increased the activity of the NR enzyme and reduced the activity of the SOD and POX enzymes. On the other hand, the joint application of Si + NO increased leaf transpiration, reduced maximum fluorescence and also reduced sodium content in plants under saline stress.