Growth of embryogenic sweet orange callus on media varying in the ratio of nitrate to ammonium nitrogen

Embryogenic callus from Citrus sinensis (L.) Osbeck cv. Hamlin was cultured for 28 days on 20 media arranged in a 5×2×2 factorial varying in the ratio of nitrate to ammonium nitrogen, total inorganic nitrogen, and benzyladenine. Fresh weight increase of callus and final medium pH were significantly affected by total inorganic nitrogen and the ratio of nitrate to ammonium. The nitrate to ammonium ratio accounted for 55% of the variation in the fresh weight increase of the callus and 93% of the variation in the final medium pH. Varying the NO₃ ^-:NH₄ ^- ratio provided adequate pH control.Abbreviation BA benzyladenine