Salinity is one of the modern agriculture major obstacles, causing several physiological disturbances in plants, adversely affecting its growth and development. Therefore, some techniques are required in order to alleviate the negative effects of salinity stress on plants, as for example an adequate nitrogen fertilization. The aim of this study was to assess the ecophysiological responses of sugar apple plants (Annona squamosa L.) submitted to different salinity levels and nitrogen fertilization doses. The experimental design was a randomized block in an incomplete factorial scheme, with five electrical conductivities of the irrigation water (ECw: 0.5, 1.01, 2.25, 3.49 and 4.0 dS m-1) and five nitrogen doses (0, 101, 350, 598.2 and 700 mg dm-3), with four replicates, generated from the Box Central Composite experimental design matrix. Through a daily course, it was observed variations in gas exchange, chlorophyll content and fluorescence parameters. The gas exchange, chlorophyll content and fluorescence parameters were measured on photosynthetically active leaves. There was significant interaction between the salinity levels (ECw) and nitrogen doses for the chlorophyll indexes. The electrical conductivity of the irrigation water caused significant negative effects on chlorophyll fluorescence. Therefore, it can be stated that the sugar apple plants ecophysiology varies through the day and that salinity affects its chlorophyll content and fluorescence.

The salinity of irrigation water and soil create considerable challenges in agriculture, as they harm the physiological processes and growth of plants. The exogenous application of antioxidant compounds, such as salicylic acid, can reduce the damage caused by salt stress. Thus, this study aimed to evaluate the attenuation of salt stress induced by salicylic acid in Ocimum basilicum “Cinnamon”. The experiment was performed in randomized blocks with five irrigation water salinity levels (0.5, 1.3, 3.25, 5.2 and 6.0 dS m-1) and five salicylic acid concentrations (0, 0.29, 1.0, 1.71 and 2.0 mM), with five repetitions and two plants per plot. Growth, gas exchange, and chlorophyll indices and fluorescence were evaluated 30 days after the salt treatment was applied. An increase in the salinity of irrigation water decreased the plant height, stem diameter, number of leaves, stomatal conductance, instantaneous water use efficiency, and initial fluorescence of basil “Cinnamon”. Salicylic acid was revealed to attenuate the harmful effects of irrigation water salinity on gas exchange, total chlorophyll, and initial and maximum fluorescence of basil plants.

A salinidade da água de irrigação é um dos grandes entraves da agricultura moderna, podendo causar danos ao metabolismo e, consequentemente, ao desenvolvimento das plantas. Atualmente há uma grande demanda por substâncias que possam atenuar tais efeitos, dentre elas destaca-se o ácido salicílico. Com isso, objetivou-se avaliar os efeitos da aplicação de ácido salicílico na cultura da melancia (Citrullus lanatus L.) sob estresse salino. O delineamento experimental foi em blocos casualizados, em esquema fatorial incompleto, com quatro repetições e duas plantas por repetição. Os tratamentos resultaram da combinação de cinco concentrações de ácido salicílico (0,00; 0,15; 0,50; 0,85 e 1,00 mM) e cinco condutividades elétricas da água de irrigação (0,50; 1,01; 2,25; 3,49 e 4,00 dS m^-1). Aos 30 dias após transplantio foram avaliados o desenvolvimento, trocas gasosas, índices e fluorescências de clorofila. Os dados foram submetidos a análise de variância e em seguida foram produzidas bandas de confiança (confbands) e correlação de Pearson. A aplicação de ácido salicílico (até 0,85 mM) apresenta efeitos benéficos para a morfofisiologia da melancia, enquanto o aumento da condutividade elétrica da água de irrigação pode apresentar efeitos deletérios.