Aplicação foliar de iodo na mitigação dos efeitos do déficit hídrico em plantas de soja

Abstract

Soybean (Glycine max (L.) Merrill) is one of the world's most important agricultural crops, widely used for human and animal nutrition and biofuel production. In Brazil, the main challenge to increasing its productivity is water deficit, which compromises essential physiological and biochemical processes, including photosynthesis, cell growth, and redox balance. Iodine is a non essential yet beneficial element for plants, possessing antioxidant and regulatory potential; thus, its application to cultivated plants can certainly offer advantages. Given this context, the objective of this study was to evaluate the capacity of iodine to mitigate the effects of water deficit in soybean plants. For the experiment, a completely randomized design was used. Two water regimes (80% of field capacity [control] and 50% of field capacity [water deficit]) and two iodine sources—potassium iodide (KI) and potassium iodate (KIO₃)—were employed, with two application rates (5 and 10 mM) for each source. Two experiments were conducted in which the iodine sources were tested separately, combining the application rates and water regimes. Physiological and morphological parameters were analyzed during the water deficit period and after recovery. Morphophysiological, seed yield, gas exchange, and biochemical parameters, as well as leaf water potential (midday and predawn), were measured throughout the crop cycle. The results indicate that foliar application of potassium iodide (KI) yielded less consistent responses regarding soybean plant tolerance to and recovery from water deficit. Conversely, the application of potassium iodate (KIO₃) produced more pronounced effects—particularly at the 10 mM concentration—favoring the maintenance of crop growth and yield, as well as better physiological recovery following rehydration.