Elfeky et al. Page 102 RESEARCH PAPER OPEN ACCESS Physiological impact of sodium azide on Helianthus annus seedlings S. Elfeky * , S. Abo-Hamad, K. M. Saad-Allah Botany Department, Faculty of Science, Tanta University, Tanta, Egypt Article published on May 26, 2014 Key words: Sodium Azide, Carotenoides, Anti-oxidant Enzymes, Electrophoresis, Lipid Peroxidation. Abstract The present study was carried out to demonstrate the effect of sodium azide on Helianthus annuus var.“Giza 53” at the green house of Botany Department, Faculty of Science, Tanta University, Egypt. Seeds were soaked in different concentrations of sodium azide (0.5, 1.0 and 2.0 mM) for different time intervals (30, 60, 90, 120 and 150 minutes). Control was maintained by soaking the seeds in distilled water only. The increased concentrations of sodium azide and time of soaking had a negative effect on the percentage of germination, shoot height, chla, chlb, lipid peroxidation and catalase activity. Increasing the concentrations and time of soaking of sodium azide stimulated the antioxidant defense of Helianthus annuus by increasing carotenoids, peroxidase activity and protein content. Pattern of protein was changed with increasing concentration and time of soaking. * Corresponding Author: S. Elfeky sd_elfeky@yahoo.com International Journal of Agronomy and Agricultural Research (IJAAR) ISSN: 2223-7054 (Print) 2225-3610 (Online) http://www.innspub.net Vol. 4, No. 5, p. 102-109, 2014