Óxido nítrico como agente mitigador do estresse salino em Physalis angulata l.

Abstract

Saline stress can involve several actions in plant, mainly responses that induce stress tolerance, acting in a coordinated way, such as controlling water loss, osmotic adjustments, ionic homeostasis and antioxidant defense. However, for such responses, the stress perception by plant is necessary and thus, be transmitted to the protective inducing machinerythrough the action of the signaling agents. Nitric oxide (NO), due to its particular properties, is considered an important signaling molecule in face of stress conditions, playing an important role in the plants defense. Thus, the aim of this work was to evaluate the main biochemical and physiological responses of P. angulata plants under saline stress, as well as the role of the NO mitigating potential. The salt stress conditions were simulated in two experiments in a greenhouse with floating hydroponic system, containing five electrical conductivity levels of the nutrient solution - EC (EC0: 0.00; EC1: 1.80; EC2: 3.60; EC3: 5.40 and EC4: 7.2 dS m-1) in experiment I and sodium nitroprusside concentrations (SNP, 0, 25, 50, 75 and 100 μM), an exogenous NO donor, in experiment II. Water relations, gas exchange, sugars accumulation, proteins, amino acids, nitrate reductase activity in leaves and growth parameters were evaluated. Water relations (water potential and osmoprotectors) were affected mainly in plants under severe salt stress (7.2 dS m-1), as well as gas exchange, where the decrease in stomatal conductance at the highest levels of stress caused reductions in the photosynthetic rate, which consequently affected the growth of plants. It was observed that P. angulata plants adjusted osmotically, which accumulated sugars as a mechanism of acclimatization to salinity. The application of SNP mitigated the effects of salt stress on photosynthesis and nitrate reductase. Plants exposed to the stressor in the presence of SNP showed greater water potential and the damage caused by salt was reversed. NO reversed and/or attenuated the symptoms of salinity on plant growth, especially in the accumulation of dry matter and leaf area. Low concentrations of SNP are indicated to mitigate the negative effects of salt stress, promoting the improvement in photosynthetic rates, minimizing the decrease in leaf water potential and growth and pre-acclimatization with 65 μM is recommended for the cultivation of this species under saline environment.