Sulfur-selenium interaction on biofortification of rocket and lettuce plants

Abstract

Selenium (Se) is essential to the humans and animals health. However, yet a great fraction of the world’s population suffers from Se deficiency. In this sense, agronomic biofortification with Se has been shown to be an efficient approach to increase Se intake. Although not essential to plant metabolism, Se can confer benefits on crop development and yield. However, plants have different accumulative capacities and responses to Se. In addition, as a sulfur (S) analogue, Se shares uptake, translocation and assimilation pathways with S, which can affects Se concentration in plants. Thus, two experiment were performed under greenhouse conditions aimed to: (i ) evaluate the effect of S x Se interactions on growth, photosynthesis, antioxidant system and nutritional quality of rocket plants grown under different S and Se treatments applied via soil and foliar; and ( ii ) compare the effect of Se and S treatments on growth and biochemical responses between Se accumulative (rocket) versus nonaccumulative (lettuce) plants. The results of the first experiment showed that Se foliar application was the most efficient method to increase Se concentration in rocket p lants. Although the regulatory effect that S imposes on the Se uptake has reduced shoot Se concentration, S fertilization showed to be essential for maintaining yield and nutritional quality, as well as to improve antioxidant defenses and photosynthetic activity of rocket plants enriched with Se. This fact evidence the importance of maintaining adequate S and Se levels in biofortified plants. The results of the second experiment indicate that the greater tolerance that rocket presented to Se treatment when compared with lettuce, might be due to higher redox capacity, demonstrated by the greater ascorbate peroxidase (APX) activity and higher glutathione (GSH) and non-protein thiols (NPT) contents. In addition, much higher levels of Se in proteins were observed in rocket than lettuce, indicating that Se accumulators might have higher tolerance to selenoamino acids in proteins, which presumably affect the normal function of enzymes and proteins.