Abstract
The influence of different concentrations of some bioregulators by foliar application {methyl jasmonate (MJ) and Prohexadione- Ca (Pro-Ca)} on growth, pigment content and volatile oil composition and radical scavenging activity of onion plant were accomplished during two consecutive seasons. The obtained results indicated that foliar application of MJ (at 150mg/l) or Pro-Ca at (30 ppm), significantly promoted onion growth and quality as height, branches number and leaves weights for new and dry onion leaves, crisp and dry loads of branches and yield (g/plant). On the other hand, MJ application led to noteworthy decrease in the plant height at all the used treatments. A significant increase in mineral ions content of the produced onion seeds by foliar application of MJ and Pro-Ca at all the used levels. All the usages of bioregulators produced positive modifications in the photosynthetic pigments as well as yield and oil content of onion plants. Based on the finding, it is recommended the use of MJ and Pro-Ca twice, at the rate of 100 and 20 ppm, respectively for higher onion yield /acre (AC). Moreover, GC/MS analysis shown that the chief identified constituents of volatile oil of onion treated with MJ and Pro-Ca were 4-Mercaptononan-2-ol, 3-Mercaptononyl acetate, Diallyl thiosulfinate, 4-Mercaptononan-2-one, Diallyl trisulphide, 2-Heptyl thiophene, Methyl propyl trisulphide, 1,3-Propanedithiol, 3,5-Diethyl-1,2,4 trithiolane and 3,5-Methyl ethyl-1,2,4,trithiolane. MJ and Pro-Ca usages caused qualitative alterations in these components of onion volatile oil. In addition, the bioregulators used caused significant variation in the free radical scavenging effect measured by DPPH and B- carotene assays of onion volatile oil compared to TBHQ.