Melatonin mitigates salt stress effects on the growth and production aspects of radish

ABSTRACT High concentration of salts in the soil impacts the availability of water and nutrients essential for plant growth and physiology. Therefore, management strategies that can mitigate the negative effects of salt stress are necessary, such as the use of plant hormones. Thus, this study aimed to evaluate the effect of salt stress and the application of melatonin on the growth and production aspects of radish plants. The experiment was carried out in a randomized block design, in a 3 × 3 factorial scheme, with four replications, considering one plant per experimental plot. The treatments consisted of three electrical conductivities of irrigation water - ECw (0.5, 2.75, and 5.0 dS m-1) and three concentrations of melatonin (0, 0.5, and 1.0 mM). Growth variables were evaluated, namely plant height, stem diameter, number of leaves, leaf area, dry mass of leaves, petioles and roots, specific leaf area, leaf area ratio, and leaf weight ratio. In addition, production aspects were analyzed, namely bulb length, bulb diameter, and bulb fresh weight. Exogenous application of melatonin reduces the deleterious effects of salt stress on the growth and production aspects of radish plants. Application of melatonin at a dose of 0.5 mM is the most recommended to mitigate the effects of salt stress up to the level of 2.75 dS m-1. The use of melatonin opens new perspectives for the development of management strategies aimed at optimizing growth and protecting the radish crop under saline conditions. RESUMO A alta concentração de sais no solo provoca impacto na disponibilidade de água e nutrientes essenciais para o crescimento e fisiologia das plantas. Assim, são necessárias estratégias de manejo que possam mitigar os efeitos negativos do estresse salino, como por exemplo o uso de hormônios vegetais. Assim, este estudo teve como objetivo avaliar o efeito do estresse salino e aplicação de melatonina sobre crescimento e aspectos produtivos de plantas de rabanete. O experimento foi realizado em delineamento em blocos casualizados, em esquema fatorial 3 × 3, com quatro repetições, sendo considerada uma planta por parcela experimental. Os tratamentos foram compostos por três condutividades elétricas da água de irrigação - CEa (0,5; 2,75 e 5,0 dS m-1) e três concentrações de melatonina (0; 0,5 e 1,0 mM). Foram avaliadas a altura de plantas, diâmetro do caule, número de folhas, área foliar, massa seca de folhas, pecíolos e raízes, área foliar específica, razão de área foliar e