Effects of some mineral nutrients on gibberellic acid levels in maize plants (Zea mays L.)

The effects of different concentrations of various macroelements on growth and endogenous GAs levels in root, stem, and leaf tissue of maize plants (Zea mays L.) were studied. Plants were cultivated in sand and supplied twice a week with a nutrient solution containing optimum, excessive, or deficient concentrations of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and iron. Plants were harvested from three different periods: vegetation (4–5 leaves), flowering, and fruiting. The levels of gibberellic acid-like substances (GA₃ equivalents ng g^-1 FW) were determined by using high-performance liquid chromatography (HPLC). In the first period (vegetative; 4–5 leaves), the levels of GAs in root, stem, and leaf of maize plants treated with excessive concentration of N, P, and Mg were increased between 6% and 27%. In the second period (flowering), significant increase was not observed in the levels of GAs, whereas a decrease was determined between 8% and 35%. In the third period (fruiting), the levels of GAs were lower (between 11% and 76%) than control plants in all applications.