References Akça, Y., Murat Asma, B., and Ayhan, C. 2000. Studies on the effect of NPK fertilization on frost tolerance in the Hacihalilodlu apricot (Prunus armeniaca L.) cultivars. Acta Horticulturae 525: 413-420. Anonymous 2013. http://www.maj.ir/portal/Home/Default.aspx? Category ID=20ad 5e49- c727-4bc9-9254-de648a5f4d52. Barranco, D., Ruiz, N., and Gómez-del-Campo, M. 2005. Frost tolerance of eight olive cultivars. HortScience 40 (3): 558-560. Bartolozzi, F., and Fontanazza, G. 1999. Assessment of frost tolerance in olive (Olea europaea L.). Scientia Horticulturae 81: 309 - 319. Bartolini, G., Di Monte, G., Rea, E., and Toponi, M. A. 1999. Protein patterns in response to cold stress on clones of Olea europaea L. cv. Leccino. Acta Horticulturae 474: 481- 484. Cakmak, I. 2005. The role of potassium in alleviating detrimental effects of abiotic stresses in plants. Journal of Plant Nutrition and Soil Science 168 (4): 521-530. D’Angeli, S., and Altamura, M. M. 2007. Osmotin induces cold protection in olive trees by affecting programmed cell death and cytoskeleton organization. Planta 225: 1147- 1163. Emami, A. 1997. Plant Analysis Methods (Volume I). Soil and Water Research Institute, Tehran, Iran. Publication No. 982 (in Persian). Eris, A., Gulen, H., Barut, E., and Cansev, A. 2007. Annual patterns of total soluble sugars and proteins related to cold-hardiness in olive (Olea europaea L. ‘Gemlik’). Journal of Horticultural Science and Biotechnology 82: 597-604. Fernández-Escobar, R., Navarro, S., and Melgar J.C. 2011. Effect of nitrogen status on frost tolerance of olive trees. Acta Horticulturae 924: 41-45. Fiorino, P., and Mancuso, S. 2000. Differential thermal analysis, supercooling and cell viability in organs of (Olea europaea L.) at subzero temperatures. Advanced Horticultural Science 14: 23-27. Ghaemmaghami, S. 2010. Study of cold stress resistance factors in different cultivars of olive. MSc. Thesis, Faculty of Sciences, University of Tehran, Tehran, Iran. Gómez-del-Campo, M., and Barranco, D. 2005. Field evaluation of frost tolerance in 10 olive cultivars. Plant Genetic Resources 3 (3): 385 - 390. Kasraei, R. 1994. Review on Plant Nutrition Science. Tabriz University Press, Tabriz. Iran (in Persian). La Porta, N., Zacchini, M., Bartolini, S., Viti, R., and Roselli, G. 1994. The frost hardiness of some clones of cv. Leccino. Journal of Horticultural Science 69 (3): 433-435. Mancuso, S. 2000. Electrical resistance changes during exposure to low temperature measure chilling in freezing tolerance in olive tree (Olea europaea L.) plants. Plant, Cell and Environment 23: 291- 299. Palliotti, A., and Bongi, G. 1996. Freezing injury in the olive leaf and effects of mefluidide treatment. Journal of American Society for Horticultural Sciences 71: 57-63. Pellett, H. M., and Carter, J. V. 1981. Effect of nutritional factors on cold hardiness of plants. Horticulture Review 3: 144-171. Roselli, G., Benelli, G., and Morelli, D. 1989. Relationship between stomatal density and winter hardiness in olive (Olea europaea L.). Journal of Horticultural Science 64 (2): 199 - 203. Roselli, G., and Venora, G. 1990. Relationship between stomatal size and winter hardiness in the olive. Acta Horticulturae 286: 89 - 92. Simkeshzadeh, N., Mobli, M., Etemadi, N., and Bani Nasab, B. 2011. Evaluation of cold tolerance in some olive cultivars by measuring chlorophyll fluorescence and morphological injuries. Journal of Horticultural Science 24 (2): 163-169 (in Persian). Soleimani, A., Lessani, H., Talaie, A. R., and Tabaeiaghdaei, M. 2008. A survey of cold hardiness in some olive (Olea europaea L.) cltivars. Acta Horticulturae 791: 519-522. Zeinanloo, A. A., Golmohamadi, M., Azimi, M., Naeini M. R., Feridoni, H., and Asgari, H. 2010. Investigation on frost damage and selection of tolerance olive cultivars. Seed and Plant Improvement Institute, Karaj, Iran. Working paper, 65pp. (in Persian).