Abstract

This study was conducted at the Experimental Farm of the Faculty of Agriculture, in May during the two seasons of 2008 and 2009 on roselle plants (Hibiscus sabdariffaL.). The objective was to improve the vegetative growth, yield characters and antioxidant activity of plants growing under different organic and inorganic media conditions in response to the spray of amino acids, humic acids and micro elements. The results showed great similarity which had been noticed with the majority of the studied characters in both seasons. The highest values of plant height, number of branches per plant, stem diameter, fresh and dry weights of leaves and branches per plant, number of days to flowering, number of fruits per plant, fresh and dry weights of sepals per plant and seed yield per plant were obtained when the plants were grew in a soil mixed with compost or magnetic iron and sprayed by humic acid in comparison with the rest of the treatments. Comparing the values of the previous characters when compost plus humic acid was used to that of magnetic iron plus humic acid, it could be stated that these values were greater with the first treatment than that of the second one in both seasons. The lowest values of the characters were noticed always with the mixture of compost or magnetic iron with amino acids or with micro elements, although these values were still higher than that of the compost or a single magnetic iron, or that of the control treatments in both seasons. The best scavenging activity against DPPH radical was observed with plants treated with compost plus humic acid and this correlated with the total anthocyanin content.

Key words: Roselle plants, antioxidant activity, compost, amino acid, magnetic iron, micro elements.