Leila Zeinali Yadegari , Reza Heidari , Jirair Carapetian , Chilling Pretreatment Causes Some Changes in Respiration, Membrane Permeability and Some Other Factors in Soybean Seedlings, Research Journal of Biological Sciences, Volume 3,Issue 9, 2008, Pages 1054-1059, ISSN 1815-8846, rjbsci.2008.1054.1059, (https://makhillpublications.co/view-article.php?doi=rjbsci.2008.1054.1059) Abstract: When plants with tropical and subtropical origins, like soybean, expose to low temperatures, suffer some injuries that some times are lethal for them. Cold temperature damage is a common problem for soybean in temperate regions. So it can be a good strategy that exposes these plants to low temperatures slightly above freezing temperature, to increase their chilling tolerance. Physiological responses to chilling, including antioxidative enzyme activity, respiration, membrane permeability were investigated in soybean to identify mechanisms of chilling tolerance. Plants were exposed to 15°C (cold-acclimated) or 25°C (nonacclimated) for 24 h, under 250 µmol m-2s-1 Photosynthetically Active Radiations (PAR). Then all plants were exposed to 4°C (chilling temperature) for 24 h and allowed to recover at 25°C for 24h. We analyzed the activity of Ascorbate Peroxidase (APX) and Guaiacol Peroxidase (GPX) in leaves. It revealed that the activity of APX and GPX induced in leaves. The respiration and membrane permeability of nonacclimated leaves were higher than the cold acclimated ones in chilling stress. Keywords: Acclimation;antioxidant;ascorbate peroxidase;chilling;guaiacol;peroxidase;permeability;respiration