Effects of Different Mineral Nutrients on Abscisic Acid in Maize (Zea Mays)

Abstract

The effects of different concentrations of various macroelements on growth and endogenous ABA (absisic acid) levels in root, stem, leaf and flower tissue of maize (Zea mays) were studied. Plants were cultivated in sand and supplied twice a week with a nutrient solution containing optimum, excessive or deficient concentrations of nitro(Yen. phosphorus, potassium, calcium, magnesium, sulphur and iron. Plants were harvested at three different stages: vegetative (4-5 leaves), flowering, and fruiting. Fresh weight, leaf and stem size, leaf number and ABA concentrations differed remarkably between plants cultured in abnormal concentrations of macroelements compared to the controls. In general, deprivation of macroelements caused an increase in ABA levels. Deficiency of N, P, K, S and Fe in the nutrient solution resulted in marked increases in the levels of ABA extracted from root, leaf, stem and flower at the three developmental stages. Excessive concentrations of these macroelements resulted in a decrease in ABA levels in all parts of plants at all three stages as compared with their respective controls. ABA levels in roots, stems, and leaves were elevated from 3% to 159% in N, P, K, and S limited plants whereas the levels of ABA in these same organs were reduced from 1% to 98% in the presence of excessive levels of N, K, P and S.