Aplicação de ácido húmico na qualidade de raízes de beterraba cultivada sob estresse salino

Abstract

Beetroot (Beta vulgaris) is an edible root plant characterized by its sweet and earthy flavor, although there are other colors, the most commonly found color is red – intense purplish. It can be consumed cooked, used in juices, and even raw in salads. Beetroot is one of the most consumed vegetables worldwide, it is abundant in mineral nutrients, such as potassium, sodium, phosphorus, calcium, zinc, iron and vitamins such as provitamin A, vitamins B1, B2, B3, B6 and C. Some vegetables are more sensitive to abiotic factors, such as salinity, which causes oxidative stress in plants, thus negatively affecting their production and quality. In order to mitigate these negative effects that salinity causes, the use of attenuators is being investigated as a strategy to increase production and also enable the use of saline waters in semi-arid regions. The use of humic acid can reduce the effects of damage caused by irrigation with saline water and can also improve the chemical, physical and biological conditions of the soil. Thus, the objective of the present work was to evaluate the post-harvest quality of beetroot cultivated under irrigation with saline water and application of humic acids. The experiment was carried out with a completely randomized experimental design in a 3 × 2 factorial scheme (three concentrations of HA: 0, 38 and 76 mg L-1 ; two salinity conditions: 80 mM NaCl and water). Colorimetry, firmness, soluble solids content, determination of total sugars, total phenolics and betacyanins and betaxanthins were carried out. Salinity reduced firmness and betaxanthin content, but increased the content of soluble solids, sugars and betacyanins in beet roots. Humic acid reduced the levels of total sugars, betacyanins and betaxanthins in beet roots. Regarding colorimetry, the stressed plants showed color closer to the red tone, also with greater color saturation (higher chroma), while HA did not affect the color of beetroot roots. Thus, it is concluded that salinity increased the quality of the roots, as evidenced by the higher sugar and betalain content and redder color. In contrast, the application of HA reduced or did not increase root quality, and is not recommended for beet production.