بررسی تأثیر محلول‌پاشی اپی‌براسینولید بر فعالیت برخی آنزیم‌های آنتی‌اکسیدان، نیترات ردوکتاز و رنگدانه‌های فتوسنتزی لوبیا تحت تنش خشکی

نوع مقاله : مقالات پژوهشی

نویسندگان

1 دانشجوی دکتری فیزیولوژی گیاهان زراعی دانشکده کشاورزی، دانشگاه زنجان، زنجان، ایران

2 دانشیار گروه زراعت و اصلاح نباتات دانشکده کشاورزی، دانشگاه زنجان، زنجان، ایران

3 استادیار گروه زراعت و اصلاح نباتات دانشکده کشاورزی، دانشگاه زنجان، زنجان، ایران

چکیده

به­منظور بررسی واکنش برخی پارامترهای فیزیولوژیکی لوبیا و امکان افزایش عملکرد دانه این گیاه با کاربرد اپی‌براسینولید تحت تنش خشکی، پژوهشی به‌صورت اسپلیت فاکتوریل در قالب طرح بلوک‏های کامل تصادفی در سه تکرار در مزرعه‌ تحقیقاتی دانشکده‌ کشاورزی دانشگاه زنجان در سال زراعی 1395-1394 اجرا شد. در این پژوهش، شرایط آبیاری در دو سطح شامل آبیاری مطلوب و اعمال تنش خشکی به عنوان عامل اصلی و دو ژنوتیپ‌ لوبیا شامل رقم کوشا و ژنوتیپ COS16 و چهار غلظت براسینواستروئید شامل عدم مصرف (شاهد)، دو، چهار و شش میکرومولار به‌صورت فاکتوریل در کرت­های فرعی قرار گرفتند. در مرحله‌ گلدهی، تنش خشکی اعمال شد و همزمان با اعمال تنش خشکی، بوته­های لوبیا با براسینواستروئید (اپی­براسینولید) محلول‌پاشی شد. نتایج نشان داد که فعالیت آنزیم‌های آنتی اکسیدان تحت تنش خشکی به طور معنی‌داری در مقایسه با شرایط آبیاری مطلوب افزایش پیدا کرد، به‌طوری‎که اعمال تنش خشکی به ترتیب باعث افزایش 89/38، 09/84، 46/40 و 37/27 درصد در فعالیت کاتالاز، گایاکول پراکسیداز، آسکوربات پراکسیداز و سوپراکسید دیسمیوتاز نسبت به آبیاری مطلوب شد. همچنین بالاترین فعالیت آنزیم‌های کاتالاز، گایاکول پراکسیداز، آسکوربات پراکسیداز و سوپراکسید دیسمیوتاز با کاربرد غلظت‌های مختلف اپی‌براسینولید در شرایط اعمال تنش خشکی حاصل شد. کاربرد اپی‌براسینولید با افزایش فعالیت آنزیم‌ نیترات ردوکتاز و محتوای کلروفیل و کاروتنوئیدها باعث افزایش عملکرد دانه ژنوتیپ‌های لوبیا در هر دو شرایط آبیاری مطلوب و تنش خشکی شد. بالاترین عملکرد دانه با کاربرد غلظت 2 میکرومولار اپی­براسینولید با میانگین‌ 2/2068 کیلوگرم بر هکتار به­دست آمد. در بین ژنوتیپ‌های مورد مطالعه نیز رقم کوشا در شرایط آبیاری مطلوب با میانگین 45/3025 کیلوگرم بر هکتار بیشترین عملکرد دانه و ژنوتیپ COS16 در شرایط تنش خشکی با میانگین 89/980 کیلوگرم بر هکتار کمترین عملکرد دانه را نشان دادند. بنابراین کاربرد اپی‌براسینولید را به‏عنوان راهکاری جهت افزایش مقاومت به تنش خشکی و افزایش عملکرد دانه لوبیا در شرایط آبیاری مطلوب و تنش خشکی می‌توان پیشنهاد نمود.

کلیدواژه‌ها


عنوان مقاله [English]

Study the effect of Epibrassinolide application on the activity of some antioxidant enzymes, nitrate reductase, and photosynthetic pigments of common bean under drought stress

نویسندگان [English]

  • Mahsa Mohammadi 1
  • Majid Pouryousef 2
  • Afshin Tavakoli 2
  • Ehsan Mohseni Fard 3
1 PhD. Student in Plant Physiology, Faculty of Agriculture, University of Zanjan, Zanjan, Iran
2 Associate Professor, Department of Agronomy and Plant breeding, Faculty of Agriculture, University of Zanjan, Zanjan, Iran
3 Assistant Professor, Department of Agronomy and Plant Breeding, Faculty of Agriculture, University of Zanjan, Zanjan, Iran
چکیده [English]

Introduction
Drought is one of the most important environmental stresses and is one of the most common causes of plant growth retardation and yields, and usually decreases the productivity of plants along with other environmental stresses, including salinity and heat. One of the reasons that environmental stresses such as drought, reduces growth and plant photosynthesis ability, is a disturbance in the balance between the production of free oxygen radicals and the protective mechanisms that remedy these radicals which results in the accumulation of reactive oxygen species (ROS), induction of oxidative stress, damage to proteins, membrane lipids, and other cellular components. Under adverse environmental conditions, the role of antioxidant defense system in protecting cellular membranes and other growing organs against oxidative damage seems to be very important. Brassinosteroids (BRs) comprise a group of steroidal hormones that have been implicated in a wide range of physiological responses in plants, including stem elongation, growth of pollen tubes, ethylene biosynthesis, proton pump activation, the regulation of gene expression, activation of enzymes, response to different stresses, nucleic acid and protein synthesis, and photosynthesis. In addition, BRs can protect against damage from stresses such as drought, salinity, and high temperature by activating various mechanisms in plants and increasing the activity of enzymatic antioxidants such as catalase, superoxide dismutase, peroxidase, and glutathione reductase. The purpose of this study was to investigate the possibility of increasing the activity of some antioxidant enzymes, nitrate reductase, photosynthetic pigments, and finally, the seed yield of common beans with the use of Epibrassinolide under drought stress conditions.
 
Materials & Methods
A split factorial experiment was conducted based on randomized complete block design with three replications at the research farm of Faculty of Agriculture, the University of Zanjan during the 2016-2017 cropping season. In this experiment, two irrigation conditions included optimal irrigation and drought stress were applied to main plots and two common bean genotypes including Kusha cultivar and COS16 genotype, and four levels of brassinosteroid including of no-application (control), two, four, and six μM were allocated to subplots as factorial. Drought stress was applied at the flowering stage, and common bean plants were sprayed with brassinosteroid (Epibrassinolide) simultaneously with drought stress. In this study, the activity of catalase, guaiacol peroxidase, ascorbate peroxidase, and superoxide dismutase, nitrate reductase, chlorophyll and carotenoid contents, and seed yield were studied.
 
Results & Discussion
The results showed that drought stress increased the activity of catalase, guaiacol peroxidase, ascorbate peroxidase, and superoxide dismutase by 38.89%, 84.09%, 40.46%, and 27.37% in contrast with the optimal irrigation, respectively. The highest activity of catalase, guaiacol peroxidase, ascorbate peroxidase, and superoxide dismutase were obtained using different concentrations of Epibrassinolide under drought stress conditions. The application of 2, 4, and 6 μM of Epibrassinolide in drought stress conditions increased by 73.33%, 86.67%, and 113.33% in the catalase activity, increased by 56.36%, 71.82%, and 62.73% in the guaiacol peroxidase activity, increased by 12.82%, 46.15%, and 13.46% in the ascorbate peroxidase activity, and increased by 29.15%, 41.49%, and 47.11% in the superoxide dismutase activity in comparison with non-application of this hormone. It has been reported that the use of BRs significantly improves plant drought tolerance and reduces the accumulation of reactive oxygen species by increasing the activity of antioxidant enzymes. It has been reported that the application of BRs increased the antioxidant enzymes activity in maize, tomato, mustard, soybean, and barley. Also, nitrate reductase activity increased by using of Epibrassinolide, which can enhance plant tolerance to environmental stress. The highest activity of nitrate reductase was obtained by application of 4 μM of Epibrassinolide, which did not show any significant difference with other concentrations. Improvement in the activity of nitrate reductase can be attributed to the effect of BRs on translation or transcription of nitrate reductase, or nitrate absorption at the membrane surface. In optimal irrigation conditions, the use of different concentrations of Epibrassinolide has a slight increase in the contents of chlorophyll a, b, and total, and the use of 4 μM of this hormone resulted in the highest increase in the above traits compared to non-application of the hormone. However, under drought stress conditions, this increase was significant, and the use of 2 μM of this hormone resulted in the highest increase in the above traits compared to non-application of the hormone. In other words, the use of Epibrassinolide in drought stress conditions caused a higher increase in chlorophyll a, b, and total contents relative to optimal irrigation conditions. Application of Epibrassinolide increased the seed yield in both common bean genotypes by increasing the activity of antioxidant enzymes, nitrate reductase, and chlorophyll and carotenoid contents. The highest seed yield was obtained by application of 2 μM of Epibrassinolide with an average of 2068.2 kg/ha. Among the studied genotypes, the Kusha cultivar in optimal irrigation conditions (with an average of 3025.45 kg/ha) had the highest seed yield and the COS16 genotype in drought stress conditions (with an average of 980.89 kg/ha) had the lowest seed yield.
 
Conclusion
In general, the use of Epibrassinolide can be suggested as a solution to increase drought stress tolerance and enhance the growth and seed yield of common beans under optimal irrigation and drought stress conditions. In addition, the achievement of comprehensive information on the positive effects of Epibrassinolide requires a study of this hormone in different weather conditions and with other different bean genotypes.

کلیدواژه‌ها [English]

  • Ascorbate peroxidase
  • Chlorophyll and carotenoid contents
  • Irrigation
  • Seed yield
  • Superoxide dismutase
  1. Abedi, T., and Pakniyat, H. 2010. Antioxidant enzyme changes in response to drought stress in ten cultivars of Oilseed Rape (Brassica napus L.). Czech Journal of Genetics and Plant Breeding 46(1): 27-34.
  2. Ahammed, G.J., Zhou, Y.H., Xia, X.J., Mao, W.H., Shi, K., and Yu, J.Q. 2013. Brassinosteroid regulates secondary metabolism in tomato towards enhanced tolerance to phenanthrene. Biologia Plantarum 57(1): 154-158.
  3. Ahmadizadeh, M., Valizadeh, M., Zaefizadeh, M., and Shahbazi, H. 2011. Antioxidative protection and electrolyte leakage in durum wheat under drought stress condition. Journal of Applied Sciences Research 7(3): 236-246.
  4. Ahmed, F.E., and Suliman, A.S.H. 2010. Effect of water stress applied at different stages of growth on seed yield and water use efficiency of cowpea. Agriculture and Biology Journal of North America 1(4): 534-540.
  5. AL-Ghamdi, A.A. 2009. Evaluation of oxidative stress tolerance in two wheat (Triticum aestivum) cultivars in response to drought. International Journal of Agriculture and Biology 11: 7-12.
  6. Ali, B., Hasan, S.A., and Hayat, S. 2008. A role for brassinosteroids in the amelioration of aluminium stress through antioxidant system in mung bean (Vigna radiata L. Wilczek). Environmental and Experimental Botany 62(2): 153-159.
  7. Alonso, R., Elvira, S., Castillo, F.J., and Gimeno, B.S. 2001. Interactive effects of ozone and drought stress on pigments and activities of antioxidative enzymes in Pinus halepensis. Plant Cell and Environment 24(4): 905-916.
  8. Amjad, H., Noreen, B., Javed, A., and Nayyer, I. 2011. Differential changes in antioxidants, proteases, and lipid peroxidation in flag leaves of wheat genotypes under different levels of water deficit conditions. Plant Physiology and Biochemistry 49(2): 178-185.
  9. Anjum, S.A., Wang, L.C., Farooq, M., Hussain, M., Xue, L.L., and Zou, C.M. 2011. Brassinolide application improves the drought tolerance in maize through modulation of enzymatic antioxidants and leaf gas exchange. Journal of Agronomy and Crop Science 197(3): 177-185.
  10. Armand, N., Amiri, H., and Ismaili, A. 2016. Interaction of methanol spray and water-deficit stress on photosynthesis and biochemical characteristics of Phaseolus vulgaris L. cv. Sadry. Photochemistry and Photobiology 92: 102-110.
  11. Arnon, D.I. 1949. Copper enzymes in isolated chloroplasts polyphenol oxidase in Beta vulgaris. Plant Physiology 24(1): 1-15.
  12. Arora, P., Bhardwaj, R., and Kanwar, M.K. 2010. 24-epibrassinolide induced antioxidative defense system of Brassica juncea L. under Zn metal stress. Physiology and Molecular Biology of Plants 16(3): 285-293.
  13. Asghari, M., and Zahedipour, P. 2016. 24-Epibrassinolide acts as a growth-promoting and resistance-mediating factor in strawberry plants. Journal of Plant Growth Regulation 35(3): 722-729.
  14. Bajguz, A. 2000. Effect of brassinosteroids on nucleic acids and protein content in cultured cell of Chlorella vulgaris. Plant Physiology and Biochemistry 38(3):209-215.
  15. Bajguz, A., and Hayat, S. 2009. Effects of brassinosteroids on the plant responses to environmental stresses. Plant Physiology and Biochemistry 47(1):1-8.
  16. Bastos, E.A., Nascimento, S.P., Silva, E.M., Filho, F.R.F., and Gomide, R.L. 2011. Identification of cowpea genotypes for drought tolerance. Revista Ciencia Agronomica 42(1): 100-107.
  17. Beauchamp, C., and Fridovich, I. 1971. Superoxide dismutase: improved assays and an assay applicable to acrylamide gels. Analytical Biochemistry 44(1): 276-287.
  18. Behnamnia, M., Kalantari, Kh.M., and Rezanejad, F. 2009. Exogenous application of brassinosteroid alleviates drought-induced oxidative stress in Lycopersicon esculentum L. General and Applied Plant Physiology 35(1-2): 22-34.
  19. Bera, A.K., Pramanik, K., and Mandal, B. 2014. Response of biofertilizers and homobrassinolide on growth, yield and oil content of sunflower (Helianthus annuus L.). African Journal of Agricultural Research 9(48): 3494-3503.
  20. Bhardwaj, R., Arora, N., Sharma, P., and Arora, H.K. 2007. Effects of 28-homobrassinolide on seedling growth, lipid peroxidation and antioxidative enzyme activities under nickel stress in seedlings of Zea mays L. Asian Journal of Plant Sciences 6(5): 765-772.
  21. Bradford, M.M. 1976. A rapid and sensitive method for the quantization of microgram quantities of protein utilizing the principle of protein-dye binding. Analytical Biochemistry 72(1-2): 248-254.
  22. Casadebaig, P., Debaeke, P., and Lecoeur, J. 2008. Thresholds for leaf expansion and transpiration response to soil water deficit in a range of sunflower genotypes. European Journal of Agronomy 28(4): 646-654.
  23. Chance, B., and Maehly, A.C. 1955. Assay of catalases and peroxidase. Methods Enzymol 2: 764-775.
  24. Contour-Ansel, D., Torres-Franklin, M.L., Zuily-Fodil, Y., and Cruz de Carvalho, M.H. 2010. An aspartic acid protease from common bean is expressed 'on call' during water stress and early recovery. Journal of Plant Physiology 167(18): 1606-1612.
  25. Ding, H.D., Zhu, X.H., Zhu, Z.W., Yang, S.J., Zha, D.S., and Wu, X.X. 2012. Amelioration of salt-induced oxidative stress in eggplant by application of 24-epibrassinolide. Biologia Plantarum 56(4): 767-770.
  26. Fariduddin, Q., Khanam, S., Hasan, S.A., Ali, B., Hayat, S., and Ahmad, A. 2009. Effect of 28-homobrassinolide on the drought stress-induced changes in photosynthesis and antioxidant system of Brassica juncea L. Acta Physiologiae Plantarum 31(5): 889-897.
  27. Gaber, M.A. 2010. Insights into the significance of antioxidative defense under salt stress. Plant Signaling & Behavior 5(4): 369-374.
  28. Gupta, K.J., Stoimenova, M., and Kaiser, W.M. 2005. In higher plants, only root mitochondria, but not leaf mitochondria reduce nitrite to NO, in vitro and in situ. Journal of Experimental Botany 56: 2601-2609.
  29. Habibi, G. 2013. Effect of drought stress and selenium spraying on photosynthesis and antioxidant activity of spring barley. Acta Agriculturae Slovenica 101(1): 31-39.
  30. Hasanuzzaman, M., Nahar, K., Alam, M.M., and Fujita, M. 2012. Exogenous nitric oxide alleviates high temperature induced oxidative stress in wheat (Triticum aestivum L.) seedlings by modulating the antioxidant defense and glyoxalase system. Australian Journal of Crop Science 6(8): 1314-1323.
  31. Hojati, M., Modarres-Sanavy, S.A.M., Karimi, M., and Ghanati, F. 2011. Responses of growth and antioxidant systems in Carthamus tinctorius L. under water deficit stress. Acta Physiologia Plantarum 33(1): 105-112.
  32. Hosseinzadeh, S.R., Amiri, H., and Ismaili, A. 2015. Effect of vermincompost fertilizer on photosynthetic characteristics of chickpea (Cicer arietinum L.) under drought stress. Photosynthetica 54(1): 87-92.
  33. Jiang, M., and Zhang, J. 2001. Effect of abscisic acid on active oxygen species, antioxidative defense system and oxidative damage in leaves of maize seedlings. Plant and Cell Physiology 42(11): 1265-1273.
  34. Kang, Y.Y., and Guo, S.R. 2011. Role of brassinosteroids on horticultural crops. In: S. Hayat and A. Ahmad (Eds). Brassinosteroids: A Class of Plant Hormone. Springer, Dordrech, pp 269-288.
  35. Kartal, G., Temel, A., Arican, E., and Gozukirmizi, N. 2009. Effects of brassinosteroids on barley root growth, antioxidant system and cell division. Plant Growth Regulation 58(3): 261-267.
  36. Khan, M.H., and Panda, S.K. 2008. Alternations in root lipid peroxidation and antioxidative responses in two rice cultivars under NaCl-salinity stress. Acta Physiologia Plantarum 30: 81-89.
  37. Khripach, V.A., Zhabinskii, V.N., and De Groot, A.E. 1999. Brassinosteroids: A New Class of Plant Hormones. Academic Press, San Diego.
  38. Kosova, K., Vítamvas, P., Urban, M.O., and Prasil, I.T. 2013. Plant proteome responses to salinity stress-comparison of glycophytes and halophytes. Functional Plant Biology 40(9): 775-786.
  39. Koussevitzky, S., Suzuki, N., Huntington, S., Armijo, L., Sha, W., Cortes, D., Shulaev, V., and Mittler, R. 2008. Ascorbate peroxidase 1 plays a key role in the response of Arabidopsis thaliana to stress combination. Journal of Biological Chemistry 283: 34197-34203.
  40. Li, Y.H., Liu, Y.J., Xu, X.L., Jin, M., An, L.Z., and Zhang, H. 2012. Effect of 24-epibrassinolide on drought stress-induced changes in Chorispora bungeana. Biologia Plantarum 56(1): 192-196.
  41. Liu, H.C., Tian, D.Q., Liu, J.X., Ma, G.Y., Zou, Q.C., and Zhu, Z.J. 2013. Cloning and functional analysis of a novel ascorbate peroxidase (APX) gene from Anthurium andraeanum. Journal of Zhejiang University Science 14(12): 1110-1120.
  42. Mackintosh, C., Douglas, P., and Lillo, C. 1995. Identification of a protein that inhibits the phosphorylated form of nitrate reductase from spinach (Spinacia oleracea) leaves. Plant Physiology 107: 451-457.
  43. Mai, Y.Y., Lin, J.M., Zeng, X.L., and Pan, R.J. 1989. Effect of homobrassinolide on the activity of nitrate reductase in rice seedlings. Plant Physiol Commun 2: 50-52.
  44. Malik, A.A., Li, W.G., Lou, L.N., Weng, J.H., and Chen, J.F. 2010. Biochemical/physiological characterization and evaluation of in vitro salt tolerance in cucumber. African Journal of Biotechnology 9(22): 3284-3292.
  45. Mishra, A., and Jha, B. 2011. Antioxidant response of the microalga Dunaliella salina under salt stress. Botanica Marina 54(2): 195-199.
  46. Mittler, R. 2002. Oxidative stress, antioxidants and stress tolerance. Trends in Plant Science 7(9): 405-410.
  47. Munoz-Perea, C.G., Teran, H., Allen, R.G., Wright, J.L., Westermann, D.T., and Singh, S.P. 2006. Selection for drought resistance in dry bean landraces and cultivars. Crop Science 46: 2111-2120.
  48. Nakano, Y., and Asada, K. 1981. Hydrogen peroxide is scavenged by ascorbate-specific peroxidase in spinach chloroplasts. Plant and Cell Physiology 22(5): 867-880.
  49. Nazari, M., Maali Amiri, R., Mehraban, F.H., and Khaneghah, H.Z. 2012. Change in antioxidant responses against oxidative damage in black chickpea following cold acclimation. Russian Journal of Plant Physiology 59(2): 183-189.
  50. Sairam, R.K. 1994. Effects of homobrassinolide application on plant metabolism and grain yield under irrigated and moisture-stress conditions of two wheat varieties. Plant Growth Regulation 14: 173-181.
  51. Sengupta, K., Mitra, S., and Ray, M. 2009. Effect of brassinolide on growth and yield of summer greengram crop. Indian Agriculturist 53(3/4): 155-157.
  52. Sharma, P., Bhardwaj, R., Arora, N., and Arora, H.K. 2007. Effect of 28-homobrassinolide on growth, zinc metal uptake and antioxidative enzyme activities in Brassica juncea L. seedlings. Brazilian Journal of Plant Physiology 19(3): 203-210.
  53. Sharma, P., Jha, A.B., Dubey, R.S., and Pessarakli, M. 2012. Reactive oxygen species, oxidative damage, and antioxidative defense mechanism in plants under stressful conditions. Journal of Botany 14: 1-26.
  54. Singh-Gill, S., and Tuteja, N. 2010. Reactive oxygen species and antioxidant machinery in abiotic stress tolerance in crop plants. Plant Physiology and Biochemistry 48(12): 909-930.
  55. Sirhindi, G., Kumar, S., Bhardwaj, R., and Kumar, M. 2009. Effects of 24-epibrassinolide and 28-homobrassinolide on the growth and antioxidant enzyme activities in the seedlings of Brassica juncea L. Physiology and Molecular Biology of Plants 15(4): 335-341.
  56. Talaat, N.B., and Shawky, B.T. 2012. 24-Epibrassinolide ameliorates the saline stress and improves the productivity of wheat (Triticum aestivum L.). Environmental and Experimental Botany 82: 80-88.
  57. Talaat, N.B., Shawky, B.T., and Ibrahim, A.S. 2015. Alleviation of drought-induced oxidative stress in maize (Zea mays L.) plants by dual application of 24-epibrassinolide and spermine. Environmental and Experimental Botany 113: 47-58.
  58. Talaat, N.B., and Shawky, B.T. 2016. Dual application of 24-Epibrassinolide and Spermine confers drought stress tolerance in maize (Zea mays L.) by modulating polyamine and protein metabolism. Journal of Plant Growth Regulation 35(2): 518-533.
  59. Thussagunpanit, J., Jutamanee, K., Sonjaroon, W., Kaveeta, L., Chai-Arree, W., Pankean, P., and Suksamrarn, A. 2015. Effects of brassinosteroid and brassinosteroid mimic on photosynthetic efficiency and rice yield under heat stress. Photosynthetica 53(2): 312-320.
  60. Upreti, K.K., and Murti, G.S.R. 2004. Effects of brassinosteroids on growth, nodulation, phytohormone content and nitrogenase activity in French bean under water stress. Biologia Plantarum 48(3): 407-411.
  61. Vardhini, B.V., and Anjum, N.A. 2015. Brassinosteroids make plant life easier under abiotic stresses mainly by modulating major components of antioxidant defense system. Frontiers in Environmental Science DOI: 10.3389/fenvs.2014.00067.
  62. Verma, A., Malik, C.P., and Gupta, V.K. 2012. In vitro effects of brassinosteroids on the growth and antioxidant enzyme activities in groundnut. International Scholarly Research Network Doi:10.5402/2012/356485.
  63. Wang, C., Yang, C.P., and Wang, Y.C. 2009. Cloning and expression analysis of an APX gene from Betula platyphylla. Journal of Northeast Forestry University 37(3): 79-81.
  64. Xu, P.L., Guo, Y.K., Bai, J.G., Shang, L., and Wang, X.J. 2008. Effects of long-term chilling on ultrastructure and antioxidant activity in leaves of two cucumber cultivars under low light. Physiologia Plantarum 132(4): 467-478.
  65. Yong, Z., Hao-Ru, T., and Ya, L. 2008. Variation in antioxidant enzyme activities of two strawberry cultivars with short-term low temperature stress. Journal of Agricultural Sciences 4: 456-462.
  66. Yuan, G.F., Jia, C.G., Li, Z., Sun, B., Zhang, L.P., Liu, N., and Wang, Q.M. 2010. Effect of brassinosteroids on drought resistance and abscisic acid concentration in tomato under water stress. Scientia Horticulturae 126(2): 103-108.
  67. Zeid, I.M., and Shedeed, Z.A. 2006. Response of alfalfa to putrescine treatment under drought stress. Biologia Plantarum 50(4): 635-640.
  68. Zhang, M., Zhai, Z., Tian, X., Duan, L., and Li, Z. 2008. Brassinolide alleviated the adverse effect of water deficits on photosynthesis and the antioxidant of soybean (Glycine max L.). Plant Growth Regulation 56(3): 257-264.