Application of high performance liquid chromatography in the characterization of iron stress response

When Fe‐efficient plants become Fe deficient, physiological responses occur which may increase the availability of Fe in the root environment. Iron‐stress responses of the sunflower (Helianthus annus L.) include a lowering of the medium pH, an increase in the reducing capacity of the root, and a release of riboflavin into the root medium. In this investigation, compounds released into the root medium during Fe‐stress were characterized using high performance liquid chrbmatography (HPLC). Samples of nutrient solution from hydroponically grown sunflowers (cultivar Large Russian) were analyzed by HPLC using an acetonitrile : water gradient.. Absorbance at 254 nm was recorded as compounds were separated. Negligible concentrations of compounds absorbing at 254 nm were found to be released by non‐stressed sunflower plants; however, nutrient solutions from Fe‐stressed plants contained riboflavin and at least two other compounds not present in control nutrient solutions. The concentration of these compounds increased as Fe‐stress became more severe and decreased during recovery from Fe‐stress. Analysis of nutrient solutions from Fe‐stressed and control tomato (Lycopersicon esculentum Mill.) of the Fe‐efficient cultivar Floradel demonstrated increases in compounds absorbing at 254 nm under conditions of Fe‐stress. Iron inefficient tomato (13820) and Fe‐efficient (WF9) and inefficient (Ys1/ys1) cultivars of corn (Zea Mays L.) did not release compounds absorbing at 254 nm into the nutrient solution under conditions of Fe‐stress. High performance liquid chromatography is a promising method for the characterization of chemical modification of the root environment during the Fe‐stress response.