Métodos de aplicação de H2O2 como atenuantes do estresse salino na produção de mudas de gravioleira.

Abstract

The soursop culture represents great socioeconomic importance for the Northeast Brazilian region. However, in this region, the concentrations of salts present in the waters added to the water deficit during several months of the year, affect the growth and development of the plants.Therefore, the objective of this research was to evaluate the growth, physiology and quality of soursop seedlings under salt stress and different methods of applying hydrogen peroxide as a mitigation of the deleterious effect of irrigation water salinity during the formation phase of seedlings. The study was conducted in plastic bags under the condition of a greenhouse belonging to the academic unit of agricultural engineering at the Federal University of Campina Grande, using a sand-textured Entisol, from the municipality of Lagoa Seca, PB, during the period from April to September 2019. The treatments resulted from the combination of five levels of electrical conductivity of irrigation water (0.6, 1.2, 1.8, 2.4 and 3.0 dS m-1) and four methods of application of hydrogen peroxide (M1 - without application, M2 - application by imbibition, M3 - application by foliar spraying and M4 - application by imbibition and spraying), in the 5 x 4 factorial arrangement, which were distributed in the completely randomized design, with four replications and two plants per plot, making a total of 160 plants. The application method via leaf spraying minimizes the effect of salt stress on gas exchange. The method of application via seed soaking was efficient in attenuating salt stress on the variables of soursop growth at 85 days after sowing (DAS), fresh and dry root phytomass, leaf succulence, specific leaf area, leaf area and seedling quality at 145 days after sowing (DAS) and resulted in increased levels of total and total chlorophyll and maximum and variable fluorescence of soursop seedlings. The use of saline waters, with electrical conductivity up to 3.0 dS m-1 allowed the production of quality seedlings, especially when using a hydrogen peroxide application method via seed soaking, since the Dickson Quality Index was higher than the minimum acceptable.