Positive modulation of selenium on photosynthetic performance in soybean under iron depletion

Although iron (Fe) is abundant in most agricultural soils, its bioavailability to plants is limited. The Fe deficiency can cause significant changes in plant metabolites, impacting the plant’s life cycle. In this context, selenium (Se) has been shown promising effects against Fe deficiency. However, there are few studies addressing the role of Se against the deleterious effects of Fe deficiency, mainly with the soybean crop. Hence, this study aimed to evaluate the effects of Se on dry mass, Fe concentration in the roots and shoots, as well as the photosynthetic performance and primary metabolism in soybean plants subjected to Fe deficiency. The experimental design used was completely randomized with 4 treatments: 1) absence of Fe without Se; 2) absence of Fe with Se; 3) sufficiency of Fe without Se (control); and 4) sufficiency of Fe with Se. Our results demonstrated that Fe deficiency combined with the absence of Se significantly reduced shoot and root dry mass, as well as Fe concentration in plants. Additionally, Fe deficiency had a detrimental impact on photosynthetic traits, whereas Se-treated plants exhibited a higher net CO₂ assimilation rate and improved carboxylation efficiency and photochemical characteristics. Moreover, Fe deficiency negatively influenced primary metabolism, leading to the altered accumulation of sucrose and amino acids, and reduced protein concentration and ammonia. In contrast, Se-treated plants showed lower accumulation of sucrose and maintenance of protein concentration. These findings highlight the potential of Se as a valuable intervention to mitigate Fe deficiency in soybean crops.