Uso do peróxido de hidrogênio na aclimatação do manjericão ao estresse salino

Abstract

Salinity is one of the major problems faced by agriculture, one of the effects being the accumulation of reactive oxygen species, responsible for oxidative stress. However, H2O2 at low concentrations may increase tolerance of plants against salinity. The basil has aroused great economic interest, being cultivated for the commerce in natura and mainly for industrial production of essential oils. This study was carried out with the objective to verify the effects of H2O2 application on oil production and tolerance of basil variety Gennaro de menta ao estresse plants to saline stress. The experiment was conducted in a greenhouse of the Programa de Pós-graduação em Engenharia Agrícola (PPGEA) [graduate program in agricultural engineering] and analysis were carried out at the Biochemistry Laboratory, both of the Universidade Federal do Recôncavo da Bahia (UFRB) in Cruz das Almas, Bahia. Two preliminary experiments were conducted to identify the concentration and time of exposure to H2O2 capable of promoting higher plant growth under salinity conditions. In all experiments the seeds were germinated in disposable cups containing coconut fiber and irrigated with nutrient solution. Preliminary results indicated that the previous application of 1,0 μM H2O2 for 48 h and 1000 μM H2O2 for 24 h were the treatments that produced the highest dry mass of leaves. In the final experiment, the seedlings were submitted to six treatments: T1-0 mM NaCl and 0 μM H2O2; T2-80 mM NaCl and 0 μM H2O2; T3-80 mM NaCl and 1000 μM H2O2/24 h in the pre-salt stress seedling stage; T4-80 mM NaCl and 1 μM H2O2/48 h in the pre-salt stress seedling stage; T5-80 mM NaCl and 1000 μM H2O2/24 h in the pre-salt stress seedling stage and at 15 days of salt stress; T6-80 mM NaCl and 1 μM H2O2/48 h in the pre-salt stress seedling stage and at 15 days of salt stress. The plants were collected after 15 and 25 days of stress and were analyzed for biomass production, relative water content, inorganic and organic solutes, pigment and essential oil production. The application of 1 μM H2O2 / 48 h and its reapplication, at 15 days of salt stress, increased leaf dry mass production in comparison to other saline treatments. A reduction was also observed in the relative water content and increase of the succulence and the sclerophilic index with the salinity. The increase of succulence was more pronounced with the application of H2O2. Salinity increased the pigment contents only in the absence of H2O2. The levels of Cl-, Na+ and organic solutes increased with the salinity, being this effect more pronounced in the treatments that received H2O2. It was also observed that the oil content, yield and productivity were induced by salinity and H2O2. The results indicate that the application of H2O2 increases the tolerance in basil to salinity and that its hydroponic cultivation with brackish water is a new technology for the production of oil.