Desempenho de cultivares de manjericão em sistema semi-hidropônico utilizando soluções nutritivas salinizadas

Abstract

Basil (Ocimum basilicum L.) is a medicinal species also used in cooking, being an important alternative of income for small vegetable producers, but there are still few studies with this species, especially on its tolerance to salt stress. Thus, alternatives have been tested in order to achieve good yields despite using saline waters, and hydroponics is one of the main techniques. Given the above, this study aimed to evaluate the performance of basil cultivars in response to nutrient solution salinity in semi-hydroponic cultivation. The experiment was conducted in a greenhouse at the Department of Agronomic and Forestry Sciences of the Federal Rural University of the Semi-Arid Region, in Mossoró-RN, Brazil. The experimental design used was randomized blocks, in 5 x 3 factorial scheme, with three replicates, and the experimental plot was represented by pots containing 3 dm3 of coconut fiber and one plant each, totaling 135 plants. Treatments resulted from the combination of five basil cultivars (‘Grecco a Palla’, ‘Alfavaca Basilicão’, ‘Alfavaca Verde’, ‘Lemoncino’ and ‘Roxo’) with three nutrient solutions (S1- standard nutrient solution, NS (2.0 dS m-1); S2 - NS + NaCl (3.5 dS m-1); S3 – NS + NaCl (5.0 dS m-1). Planting was carried out using seedlings and irrigation was applied by a drip system. Plants were evaluated at full flowering stage for physiological variables (initial fluorescence, maximum fluorescence, variable fluorescence, maximum quantum efficiency of photosystem II, effective quantum efficiency of photosystem II, non-photochemical dissipation, non-regulated photochemical dissipation, electron transport rate) and development (number of leaves, height, stem diameter, number and length of inflorescences, number of branches, fresh mass of leaves, branches, and inflorescences, dry mass of leaves, branches, inflorescences and total, leaf area, specific leaf area, leaf area ratio and leaf succulence). The obtained data were subjected to analysis of variance, and the factors were further analyzed when there was significant response to the interaction between them. Treatment effects were analyzed by a test of means comparison. Salinity effect on basil growth and chlorophyll fluorescence varied among the cultivars. The cultivars ‘Alfavaca Basilicão’, ‘Alfavaca Verde’ and ‘Roxo’ were tolerant to all salinity levels tested, whereas ‘Grecco a Palla’ and ‘Lemoncino’ were tolerant to salinity of up to 3.5 dS m-1. Fertigation using high-salinity water causes major changes in the chlorophyll a fluorescence of the sensitive basil cultivars. The cultivars ‘Grecco a Palla’ and ‘Alfavaca verde’ were little affected by the increase in salinity, being the most tolerant to salt stress. In the cultivars ‘Alfavaca basilicão’, ‘Lemoncino’ and ‘Roxo’, chlorophyll fluorescence was strongly affected by salinity. The tolerance ranking based on chlorophyll fluorescence is: ‘Grecco a Palla’ = ‘Alfavaca verde’ > ‘Alfavaca basilicão’ > ‘Lemoncino’ > ‘Roxo’