Nitric Oxide as an Attenuator of Ecophysiological Changes in Corn (Zea mays L.) Plants Submitted to Copper Toxicity

The aim of this work was to evaluate the attenuating effect of the nitric oxide donor (sodium nitroprusside-NPS) on the ecophysiological responses of corn plants (Zea mays L.) submitted to copper toxicity. The corn seeds of the K9606 VIP3 variety were soaked for 48 hours in Germitest with solution containing treatment with sodium nitroprusside Na2 [Fe (CN) 5 NO] 2H2O (0, 200 and 300µM), sodium ferrocyanide Na4Fe (CN) 6 ( 300, 100 and 0 µM) respectively and deionized water (control), sown in buckets with 15 kg of soil incubated for 50 days containing copper concentrations CuSO4.5H2O (0, 60 and 200 mg kg-1). The design consisted of randomized blocks with 12 treatments and 4 repetitions, making a total of 48 plants. in ecophysiological variables: height, leaf area and number of leaves, stem diameter increased by 32, 66% and 11.29% in the treatments with 60 mg kg-1 of copper and 200 mg kg-1 of copper, respectively. There was no effect of treatments on the chlorophyll content measured by the SPAD index and gas exchange. The chlorophyll a fluorescence variables indicate that the concentration of 200 mg kg-1 of copper caused damage to the structure of the PS II reaction center complexes and indicate a slightly protective effect of nitric oxide-NO present in sodium nitroprusside and cyanide present in sodium ferrocyanide, reflecting a smooth functioning of the maximum activity of photosystem II and the electron transport chain.