Alteration of nutrient uptake and secondary metabolism connection by foliar application of citrus flavonoids to broccoli plants

Abstract The nutritional value of broccoli is largely attributed to its abundant secondary metabolites such as phenolic compounds and glucosinolates (GSLs). However, the dynamic relationship between these compounds, including potential synergistic or antagonistic interactions that influence plant physiology and metabolism, remains unclear. In this study, we aimed to elucidate the intricate interplay between phenolic compounds and GSLs in broccoli plants and their consequent effects on primary metabolism and regulatory mechanisms governing water and nutrient uptake. To investigate this, we externally supplied citric phenolic compounds to broccoli plants, and then measured the levels of GSLs and phenolic compounds, along with assessing physiological parameters such as biomass, gas exchange, and nutrient content. Additionally, the expression of genes related to GSLs and phenolics biosynthesis, as well as genes involved in water transport were measured. Our results revealed a complex interrelation between phenolic compounds and GSLs, with phenolic compounds significantly modulating the response of GSLs and influencing the expression of aquaporin genes. This modulation had notable effects on nutrient regulation mechanisms in broccoli plants. Overall, our findings shed light on the regulatory mechanisms underlying the interaction between phenolic compounds, GSLs and growth, providing insights into their roles in plant physiology and metabolism.