ارزیابی پاسخ‌های مورفوفیزیولوژیکی ارقام گیاه آفتابگردان (Helianthus annuus L.)تحت رژیم های مختلف آبیاری
محورهای موضوعی : ژنتیک
محمد امینی
1
(گروه زراعت و اصلاح نباتات، واحد علوم و تحقیقات گرگان، دانشگاه آزاد اسلامی، گرگان، ایران)
حسین عجم نوروزی
2
(گروه زراعت، دانشکده کشاورزی، دانشگاه آزاد اسلامی، گرگان، ایران)
ابوالفضل فرجی
3
(گروه زراعی و باغی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان گلستان، سازمان تحقیقات، آموزش و ترویج کشاورزی، گرگان، ایران.)
بهرام مجد نصیری
4
(گروه زراعی و باغی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان اصفهان، سازمان تحقیقات، آموزش و ترویج کشاورزی، اصفهان، ایران.)
کلید واژه: تنش خشکی, رنگدانه‌های فتوسنتزی, فتوسنتز خالص, ارقام متحمل,
چکیده مقاله :
برای تعیین نیاز آبی ارقام گیاه آفتابگردان آزمایشی در سال 1394 و 1395 با استفاده از طرح اسپیلیت‌پلات در قالب طرح بلوک‌های کامل تصادفی با 4 تکرار در ایستگاه زراعی اردستان اصفهان اجرا گردید. تیمارهای مورد بررسی عبارت بودند از: 3 رژیم آبیاری D1، D2 و D3 به‌ترتیب آبیاری پس از 60، 120 و 180 میلی‌متر تبخیر از تشتک تبخیر کلاس A و پنج رقم ارقام آفتابگردان آذرگل، پروگرس، گابور،هایسان 25 و‌هایسان 36. نتایج نشان داد که در شرایط بدون تنش و تنش ملایم، ارقام آذرگل و پروگرس دارای بیشترین میزان دوره پرشدن دانه، وزن هزار دانه، قطر ساقه و قطر طبق بودند. در شرایط تنش کمبود آب شدید ارقام پروگرس و گابور برتری محسوسی داشتند به طوری که رقم پروگرس بیشترین میزان دوره پرشدن دانه، وزن هزار دانه، قطر ساقه و رقم گابور بیشترین میزان غنچه دهی، گلدهی و قطر ساقه را داشتند. در بررسی خصوصیات فیزیولوژیک در شرایط بدون تنش و تنش ملایم مشاهده شد که در ارقام پروگرس و گابور میزان کلروفیل a، b، کاروتنوئیدها، کلروفیل کل و فتوسنتز خالص در مقایسه با سایر ارقام افزایش معنی داری داشت. در شرایط تنش شدید نیز ارقام پروگرس و گابور در محتوای کلروفیل a، b و کلروفیل کل بر دیگر ارقام مورد بررسی برتری داشتند. در بررسی محتوای پرولین برگی نتایج نشـان داد که با افزایش شدت تنش محتوای پرولین برگی به‌صورت معنی داری افزایش یافت. در بین ارقام مورد بررسی در شرایط تنش شدید، محتوای پرولین برگی در ارقام پروگرس و گابور نسبت به سایر ارقام افزایش معنی‌داری داشت. نتایج این پژوهش نشان داد که ارقام آذرگل، گابور و پروگرس تحمل بیشتری نسبت به تنش کم آبی در مقایسه با ارقام‌هایسان 25 و‌هایسان 36 دارد.
In order to determine the water requirement of sunflower cultivars, an experiment was conducted during 2015-2016 at Ardestan Station, Isfahan. The experiment was carried out in a factorial randomized complete block design with four replications. Treatments included 3 irrigation regimes (D1: irrigation after 60 mm, D2: irrigation after 120 mm, D3: irrigation after 180 mm evaporation from small tub evaporation) and 5 sunflower cultivars (Azargol, Prograss, Gabur, Hysan 25, and Hysan 36). Results showed that under non-stress and moderate stress, Azargol and Prograss cultivars had the highest rate, in terms of seed filling period, the weight of 1000 grains, stem diameter, and head diameter. Under severe stress, Prograss and Gabur cultivars were remarkable, so that Prograss cultivar had the highest seed filling period, weight of 1000 grains, stem diameter, and Gabur cultivar had the highest number of budding, number of flowering, and stem diameter. In the study of physiological characteristics, results showed that under non-stress and moderate stress chlorophyll a, b, total chlorophyll, and net-photosynthesis in cultivars Progerass and Gabor were significantly increased compared to other cultivars. In severe stress conditions, the Progress and Gabor cultivars in chlorophyll a, b and total chlorophyll content were superior to other cultivars. The results of proline analysis indicated that proline leaf content increased significantly with water stress. Among the cultivars under severe stress conditions, proline leaf content in Progerass and Gabor cultivars was significantly higher than other cultivars. The results of this study showed that Azargol, Gabor, and Progerass cultivars are more tolerant than Hysan 25 and Hysan 36.
Ahmadpour, R., Hosseinzadeh, S.R. and Chashiani, S. (2016). Study of root morpho-physiological and biochemical characteristics of lentil (Lens culinaris Medik.) in response to moisture stress. Journal of Iranian Plant Echophysiological Resarch. 2(2): 123-135.
Ahmadpour, R., Hosseinzadeh, S.R., Armand, N., Chashiani, S. (2017). Evaluation of growth features, photosynthetic pigments and antioxidant enzymes activity of lentils cultivars in response to water stress. Nova Biologica Reperta. 4(3): 226-235.
Amiri, H., Dousty, B. and Hosseinzadeh, S.R. (2018). Water Stress-induced Changes of Morphological, Physiological and Essential Oil Compounds in Thymus eriocalyx from Iran. Journal of Essential Oil Bearing Plants. 21(5): 1210-1223.
Amiri, H., Ismaili, A. and Hosseinzadeh, S.R. (2017). Influence of vermicompost fertilizer and water deficit stress on morpho-physiological features of chickpea (Cicer arietinum L. cv. karaj). Compost Science and Utilization. 25(3): 152–165.
Baloglu, M.C., Kavas, M., Aydin, G., Öktem, H.A. and Yücel, A.M. (2012). Antioxidative and Physiological Responses of Two Sunflower (Helianthus annuus) Cultivars under PEG-Mediated Drought Stress, Turkish Journal of Botany. 36(6): 707-714.
Barens, D.L. and Wooley, D.G. (2009). Effects of moisture stress at different stages of growth, Camparison of a single – eared and two – eared corn hybrid. Agronomy Journal. 61: 788–790.
Bayoumi, T.Y., Eid, M. and Metwali, E.M. (2008). Application of physiological and biochemical indices as a screening technique for drought tolerance in wheat genotypes. African Journal of Biotechnology. 7: 2341-2352.
Beck, E., Fettig, S., Knake, C., Hartig, K. and Bhattarai, T. (2007).Specific and unspecific responses of plants to cold and drought stress. Journal of Bioscience. 32: 501-510.
Bian, Sh. and Jiang Y. (2008).Reactive oxygen species, antioxidant enzyme activities and gene expression patterns in leaves and roots of Kentucky bluegrass in response to drought stress and recovery. Scientia Horticulturae. 120: 264-270.
Chimenti, C.A., Pearson, J. and Hall, A.J. (2002). Osmotic adjustment and yield maintenance under drought in sunflower. Field Crop Research. 75: 235-246.
Cox, W.J. and Jolliff, G.D. (2000). Growth and yield of sunflower and soybean under soil water deficits. Agronomy Journal. 78:226-230.
Galle, A., Csiszar, J., Tari, I. and Erdei, L. (2002). Changes in water and chlorophyll fluorescence parameters under osmotic stress in wheat cultivars. Acta Biologica Szegedieniensis. 46: 85-86.
Gamze, O., Mehmet Demir, K.A. and Mehmet A.T. (2005). Effects of salt and drought stresses on germination and seedling growth of pea (Pisum sativum L.). Turkish Journal of Agriculture and Foresty. 29: 237-242.
Ghaffari, M., Toorchi, M., Valizadeh, M. and Shakiba, M.R. (2012). Morpho-Physiological Screening of Sunflower Inbred Lines under Drought Stress Condition. Turkish Journal of Field Crops.17(2):185-190.
Goksoy, A.T., Demir, A.O., Turan, Z.M. and Dagusta, N. (2004). Responses of sunflower (Helianthus annuus L.) to full and limited irrigation at different growth stages. Field Crops Research. 87: 167-178.
Guerfel, M., Baccouri, O., Boujnah, D., Cha, W. and Zarrouk, M. (2008). Impacts of water stress on gas exchange, water elations, chlorophyll content and leaf structure in the two main Tunisian olive (Olea europaea L.) cultivars. Scientia Horticulturae. 1: 1-7.
Gunes, A., Cicek, N., Inal, A., Alpaslan, M., Eraslan, F., Guneri, E. and Guzelordu, T. (2006). Genotypic response of chickpea (Cicer arietinum L.) cultivars to drought stress implemented at pre-and post an thesis stages and its relations with nutrient uptake and efficiency. Plant Soil Environment. 52: 868-876.
Hashemi Dezfoli, A., Kocheki, A. and Banayan Aval, M. (1995). Increasing the yield of crops. Publications by University of Mashhad. 183pp.
Hassanpour, H., Khavari-Nejad, R.A., Niknam, V., Najafi, F. and Razavi, K. (2012). Effects of penconazole and water deficit stress on physiological and antioxidative responses in pennyroyal (Mentha pulegium L.). Acta Physiolgia Plantarum. 34(4): 1537-1549.
Helal, R.M. and Samir, M.A. (2008).Comprative response of drought tolorant and drought sensitive maize genotypes to water stress. Austeralian Journal of crop science. 1: 31-36.
Hosseinzadeh, S.R., Amiri, H. and Ismaili, A. (2016). Effect of vermicompost fertilizer on photosynthetic characteristics of chickpea (Cicer arietinum L.) under drought stress. Photosynthetica. 54(1): 87-92.
Hosseinzadeh, S.R., Amiri, H.and Ismaili, A. (2017). Nutrition and biochemical responses of chickpea (Cicer arietinum L.) to vermicompost fertilizer and water deficit stress. Journal of Plant Nutrition 40(16): 2259–2268.
Javaid, T., Bibi, A., Sadaqat, H.A. and Javed, S. (2015). Screening of Sunflower (Helianthus annuus L.) Hybrids for Drought Tolerance at Seedling Stage. International Journal of Plant Science and Ecology. 1(1): 6-16.
Karimi, M.M. and Siddique, K.H.M. (1991).Crop growth rates of old and modern wheat cultivars. Australian Journal of Agricultural Research. 42:13-20.
Karimzaded-Asl, KH., Mazaheri, D., Peghambari. S.A.(2003). Efect of four irrigation intervals on the seed yield and quantitative characteristics of three sunflower cultivar. Iranian Journal Agriculture Science. 34 (2). 293-301.
Khamari, S., Ghasemi, K., Alyari, H. and Zehtab Salmasi, S. (2007). The effect of irrigation on phenology and yield of three sunflower cultivars in Tabriz. Journal of Agricultural Sciences and Natural Resources. 14(6): 72-80.
Khavari-Nejad, R.A. (1988). Effects of Ca/Na interaction on carbon dioxide exchange and growth of NaCl-stressed sunflower plants. Photosynthetica. 22(4): 562- 566.
Nadeem,T.M.H.,Imran,M. and Kamil Husain,M.(2002). Evaluation of sunflowers in bred lines for drought tolerance. International Journal of Agriculture and Biology. 10: 398-400.
Naderi Darbaaghshahi, M., Normohammadi, Gh., Majidi, A., Darwish, F., Rad, A. and Madani, H. (2005). Investigating the response of summer safflower to different drought stress in Isfahan region. Journal of Agricultural Sciences. 7(3): 225-212.
Nagarathna, T.K., Shadakshari, Y.G., Ramakrishna, P.V.R., Jagadish, K.S. and Puttarangaswamy, K.T. (2012). Examination of root characters, isotope discrimination, physiological and morphological traits and their relationship used to identify the drought tolerant sunflower (Helianthus annuus L.) genotypes. Helia. 35(56): 1-8.
NeSmith, D.S.(1992). Estimating summer squash leaf area nondestructively. Horticulture Science. 27(1): 77-86.
Pagter, M., Bragato, C. and Brix, H. (2005).Tolerance and physiological responses of Phragmites australis to water deficit. Aquatic Botany. 81: 285-299.
Rahbarian, R., Khavari-nejad, R., Ganjeali, A., Bagheri, A.R. and Najafi, F. (2011). Drought stress effects on photosynthesis, chlorophyll fluorescence and water. Acta Biologica Cracoviensia-Series Botanica. 53: 47-56.
Rasti Sani, M., Lahouti, M. and Ganjeali, A. (2014). Effect of drought stress on some morphophysiological traits and chlorophyll fluorescence of red bean seedlings (Phaseolus vulgaris L.). Iranian Journal of Pulses Resarch. 5(1):103-116.
Razi, H. and Asaad. T.(1998). Evaluation the change of important agronomic traits and drought stress tolerance related criteria in sunflower cultivars. Journal of Agricultural Sciences and Natural Resources. 2(1): 31-43.
Roche, J., Hewezi, T., Bouniols, A. and Gentzbittel, L. (2009). Real-time PCR monitoring of signal transduction related genes involved in water stress tolerance mechanism of sunflower. Plant Physiology and Biochemistry. 47: 139-145.
Roshdi, M., Heydari Sharifabad, H., Karimi, M., Nourmohammadi, GH.and Darvish, F. (2006). A Syrvey on the impact of water deficiency over the yield of sunflower seed cultivar and its components. Journal Agriculture Science. 12(1): 109-121.
Sikder, S., Foulkes, J. and West, H. (2015). Evaluation of photosynthetic potential of wheat genotypes under drought condition. Photosynthetica. 53: 47-54.
Soleymanifard, A., Pourdad, S.S., Naseri, R.and Mirzaei, A. (2011). Effect of planting pattern on phonological characteristics and growth indices of safflower (Carthamus tinctorius L.) in rainfed conditions. Iranian Journal of Crop Sciences. 13(2): 282-298.
Vorasoot, N., Songsri, P., Akkasaeng, C., Jogloy, S. and Patanothi, A. (2003). Effect of water strees on yield and agronomic characters of peanut (Arachis hypogaea L.). Songklanakarin Journal of Science and Technology. 25: 283-288.
Wang, W., Vinocur, B. and Altman, M.A. (2003). Plant responses to drought towards genetic engineering for stress tolerance. Planta 218: 1-14.
Xu, Z., Zhou, G. and Shimizu, H. (2009). Are plant growth and photosynthesis limited by predrought following rewatering in grass? Journal of Experimental Botany. 60: 3737–3749.
Yordanov, I., Velikova, V. and Tsonev, T. (2003). Plant responses to drought and stress tolerance. Bulgharestan Journal of Plant Physiology. 2: 187-206.
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Ahmadpour, R., Hosseinzadeh, S.R. and Chashiani, S. (2016). Study of root morpho-physiological and biochemical characteristics of lentil (Lens culinaris Medik.) in response to moisture stress. Journal of Iranian Plant Echophysiological Resarch. 2(2): 123-135.
Ahmadpour, R., Hosseinzadeh, S.R., Armand, N., Chashiani, S. (2017). Evaluation of growth features, photosynthetic pigments and antioxidant enzymes activity of lentils cultivars in response to water stress. Nova Biologica Reperta. 4(3): 226-235.
Amiri, H., Dousty, B. and Hosseinzadeh, S.R. (2018). Water Stress-induced Changes of Morphological, Physiological and Essential Oil Compounds in Thymus eriocalyx from Iran. Journal of Essential Oil Bearing Plants. 21(5): 1210-1223.
Amiri, H., Ismaili, A. and Hosseinzadeh, S.R. (2017). Influence of vermicompost fertilizer and water deficit stress on morpho-physiological features of chickpea (Cicer arietinum L. cv. karaj). Compost Science and Utilization. 25(3): 152–165.
Baloglu, M.C., Kavas, M., Aydin, G., Öktem, H.A. and Yücel, A.M. (2012). Antioxidative and Physiological Responses of Two Sunflower (Helianthus annuus) Cultivars under PEG-Mediated Drought Stress, Turkish Journal of Botany. 36(6): 707-714.
Barens, D.L. and Wooley, D.G. (2009). Effects of moisture stress at different stages of growth, Camparison of a single – eared and two – eared corn hybrid. Agronomy Journal. 61: 788–790.
Bayoumi, T.Y., Eid, M. and Metwali, E.M. (2008). Application of physiological and biochemical indices as a screening technique for drought tolerance in wheat genotypes. African Journal of Biotechnology. 7: 2341-2352.
Beck, E., Fettig, S., Knake, C., Hartig, K. and Bhattarai, T. (2007).Specific and unspecific responses of plants to cold and drought stress. Journal of Bioscience. 32: 501-510.
Bian, Sh. and Jiang Y. (2008).Reactive oxygen species, antioxidant enzyme activities and gene expression patterns in leaves and roots of Kentucky bluegrass in response to drought stress and recovery. Scientia Horticulturae. 120: 264-270.
Chimenti, C.A., Pearson, J. and Hall, A.J. (2002). Osmotic adjustment and yield maintenance under drought in sunflower. Field Crop Research. 75: 235-246.
Cox, W.J. and Jolliff, G.D. (2000). Growth and yield of sunflower and soybean under soil water deficits. Agronomy Journal. 78:226-230.
Galle, A., Csiszar, J., Tari, I. and Erdei, L. (2002). Changes in water and chlorophyll fluorescence parameters under osmotic stress in wheat cultivars. Acta Biologica Szegedieniensis. 46: 85-86.
Gamze, O., Mehmet Demir, K.A. and Mehmet A.T. (2005). Effects of salt and drought stresses on germination and seedling growth of pea (Pisum sativum L.). Turkish Journal of Agriculture and Foresty. 29: 237-242.
Ghaffari, M., Toorchi, M., Valizadeh, M. and Shakiba, M.R. (2012). Morpho-Physiological Screening of Sunflower Inbred Lines under Drought Stress Condition. Turkish Journal of Field Crops.17(2):185-190.
Goksoy, A.T., Demir, A.O., Turan, Z.M. and Dagusta, N. (2004). Responses of sunflower (Helianthus annuus L.) to full and limited irrigation at different growth stages. Field Crops Research. 87: 167-178.
Guerfel, M., Baccouri, O., Boujnah, D., Cha, W. and Zarrouk, M. (2008). Impacts of water stress on gas exchange, water elations, chlorophyll content and leaf structure in the two main Tunisian olive (Olea europaea L.) cultivars. Scientia Horticulturae. 1: 1-7.
Gunes, A., Cicek, N., Inal, A., Alpaslan, M., Eraslan, F., Guneri, E. and Guzelordu, T. (2006). Genotypic response of chickpea (Cicer arietinum L.) cultivars to drought stress implemented at pre-and post an thesis stages and its relations with nutrient uptake and efficiency. Plant Soil Environment. 52: 868-876.
Hashemi Dezfoli, A., Kocheki, A. and Banayan Aval, M. (1995). Increasing the yield of crops. Publications by University of Mashhad. 183pp.
Hassanpour, H., Khavari-Nejad, R.A., Niknam, V., Najafi, F. and Razavi, K. (2012). Effects of penconazole and water deficit stress on physiological and antioxidative responses in pennyroyal (Mentha pulegium L.). Acta Physiolgia Plantarum. 34(4): 1537-1549.
Helal, R.M. and Samir, M.A. (2008).Comprative response of drought tolorant and drought sensitive maize genotypes to water stress. Austeralian Journal of crop science. 1: 31-36.
Hosseinzadeh, S.R., Amiri, H. and Ismaili, A. (2016). Effect of vermicompost fertilizer on photosynthetic characteristics of chickpea (Cicer arietinum L.) under drought stress. Photosynthetica. 54(1): 87-92.
Hosseinzadeh, S.R., Amiri, H.and Ismaili, A. (2017). Nutrition and biochemical responses of chickpea (Cicer arietinum L.) to vermicompost fertilizer and water deficit stress. Journal of Plant Nutrition 40(16): 2259–2268.
Javaid, T., Bibi, A., Sadaqat, H.A. and Javed, S. (2015). Screening of Sunflower (Helianthus annuus L.) Hybrids for Drought Tolerance at Seedling Stage. International Journal of Plant Science and Ecology. 1(1): 6-16.
Karimi, M.M. and Siddique, K.H.M. (1991).Crop growth rates of old and modern wheat cultivars. Australian Journal of Agricultural Research. 42:13-20.
Karimzaded-Asl, KH., Mazaheri, D., Peghambari. S.A.(2003). Efect of four irrigation intervals on the seed yield and quantitative characteristics of three sunflower cultivar. Iranian Journal Agriculture Science. 34 (2). 293-301.
Khamari, S., Ghasemi, K., Alyari, H. and Zehtab Salmasi, S. (2007). The effect of irrigation on phenology and yield of three sunflower cultivars in Tabriz. Journal of Agricultural Sciences and Natural Resources. 14(6): 72-80.
Khavari-Nejad, R.A. (1988). Effects of Ca/Na interaction on carbon dioxide exchange and growth of NaCl-stressed sunflower plants. Photosynthetica. 22(4): 562- 566.
Nadeem,T.M.H.,Imran,M. and Kamil Husain,M.(2002). Evaluation of sunflowers in bred lines for drought tolerance. International Journal of Agriculture and Biology. 10: 398-400.
Naderi Darbaaghshahi, M., Normohammadi, Gh., Majidi, A., Darwish, F., Rad, A. and Madani, H. (2005). Investigating the response of summer safflower to different drought stress in Isfahan region. Journal of Agricultural Sciences. 7(3): 225-212.
Nagarathna, T.K., Shadakshari, Y.G., Ramakrishna, P.V.R., Jagadish, K.S. and Puttarangaswamy, K.T. (2012). Examination of root characters, isotope discrimination, physiological and morphological traits and their relationship used to identify the drought tolerant sunflower (Helianthus annuus L.) genotypes. Helia. 35(56): 1-8.
NeSmith, D.S.(1992). Estimating summer squash leaf area nondestructively. Horticulture Science. 27(1): 77-86.
Pagter, M., Bragato, C. and Brix, H. (2005).Tolerance and physiological responses of Phragmites australis to water deficit. Aquatic Botany. 81: 285-299.
Rahbarian, R., Khavari-nejad, R., Ganjeali, A., Bagheri, A.R. and Najafi, F. (2011). Drought stress effects on photosynthesis, chlorophyll fluorescence and water. Acta Biologica Cracoviensia-Series Botanica. 53: 47-56.
Rasti Sani, M., Lahouti, M. and Ganjeali, A. (2014). Effect of drought stress on some morphophysiological traits and chlorophyll fluorescence of red bean seedlings (Phaseolus vulgaris L.). Iranian Journal of Pulses Resarch. 5(1):103-116.
Razi, H. and Asaad. T.(1998). Evaluation the change of important agronomic traits and drought stress tolerance related criteria in sunflower cultivars. Journal of Agricultural Sciences and Natural Resources. 2(1): 31-43.
Roche, J., Hewezi, T., Bouniols, A. and Gentzbittel, L. (2009). Real-time PCR monitoring of signal transduction related genes involved in water stress tolerance mechanism of sunflower. Plant Physiology and Biochemistry. 47: 139-145.
Roshdi, M., Heydari Sharifabad, H., Karimi, M., Nourmohammadi, GH.and Darvish, F. (2006). A Syrvey on the impact of water deficiency over the yield of sunflower seed cultivar and its components. Journal Agriculture Science. 12(1): 109-121.
Sikder, S., Foulkes, J. and West, H. (2015). Evaluation of photosynthetic potential of wheat genotypes under drought condition. Photosynthetica. 53: 47-54.
Soleymanifard, A., Pourdad, S.S., Naseri, R.and Mirzaei, A. (2011). Effect of planting pattern on phonological characteristics and growth indices of safflower (Carthamus tinctorius L.) in rainfed conditions. Iranian Journal of Crop Sciences. 13(2): 282-298.
Vorasoot, N., Songsri, P., Akkasaeng, C., Jogloy, S. and Patanothi, A. (2003). Effect of water strees on yield and agronomic characters of peanut (Arachis hypogaea L.). Songklanakarin Journal of Science and Technology. 25: 283-288.
Wang, W., Vinocur, B. and Altman, M.A. (2003). Plant responses to drought towards genetic engineering for stress tolerance. Planta 218: 1-14.
Xu, Z., Zhou, G. and Shimizu, H. (2009). Are plant growth and photosynthesis limited by predrought following rewatering in grass? Journal of Experimental Botany. 60: 3737–3749.
Yordanov, I., Velikova, V. and Tsonev, T. (2003). Plant responses to drought and stress tolerance. Bulgharestan Journal of Plant Physiology. 2: 187-206.