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The Effect of Epibrassinolide on Senescence in Wheat Leaves

The Effect of Epibrassinolide on Senescence in Wheat Leaves ARTICLES B&E S. Sağlam-Çağ Istanbul University, Faculty of Science, Department of Botany, Istanbul, Turkey Correspondece to: Serap Sağlam-Çağ Email: [email protected] ABSTRACT Brassinosteroids (BRs) are new groups of plant hormones with signifi cant growth-promoting activity. Brassinolide (BL) is the most biologically active BR. BRs are considered as hormones, as they infl uence varied developmental processes like growth, germination of seeds, rhizogenesis, fl owering and senescence. Senescence is regulated by phytohormones. This research shows that epibrassinolide (eBL) accelerates or delays senescence in wheat leaf segments. For this aim, epibrassinolide was applied exogenously into the excised wheat leaf segments. An increase in peroxidase activity and decrease in protease activity, chlorophyll content (at 10 and 0.1 μM. eBL) were detected. However, protein content decreased only at 10 μM. eBL . Finally, it was observed that eBR accelerated senescence specially at high concentration. Keywords: Epibrassinolide, senescence, wheat leaf segment, Wheat (Triticum aestivum L.) seeds were planted in sawdust chlorophyll, protein, peroxidase, protease and they were grown in plant growth chamber (12 h light, 12 h dark photoperiod and 25±2 C). Six fi rst leaf segments (3cm. Introduction each) from 10 days old wheat seedlings were placed in 5 cm Brassinosteroids (BRs) are steroid hormones that regulate the diameter petri dishes already containing 3 ml of experimental solution. Epibrassinolide was used at different concentrations growth and development of plants (2, 10, 20,). In plants, many (0.001μM, 0.1μM and 10 μM) as an experimental solutions. steroids have been identifi ed, but only one class of steroids called collectively brassinosteroids have wide distribution Distilled water was used for control treatments. throughout the plant kingdom and unique growth-promoting Measurement of total chlorophyll content activity when applied exogenously (12). Brassinosteroids Total chlorophyll content was determined according to the have various physiological and morphological effects on Arnon (1949) in wheat leaf segments which were incubated plants, including cell and stem elongation, inhibition of root for 3, 5, 7 and 10 days after harvested (1). Leaf segments were formation, leaf bending, proton pump activation, ethylene homogenized in 80 % acetone. The samples were centrifugated production, tracheary element differentiation and activation of at 4 000 g for 5 min. and the optical density of the supernatant stress responses (4, 15, 16, 17, 25). Brassinolide was the fi rst was read at 663 and 645 nm using a spectrophotometer. Initial plant steroid with hormonal activities (21). values of each analysis were measured in leaf segments at the Brassinosteroids increase chlorophyll breakdown (23) but start of each experiment. inhibit anthocyanin biosynthesis (6). On the other hand, BRs accelerate senescence (9, 19, 24, 26) but the studies about this Measurement of soluble protein content topic are not enough. Soluble protein contents were estimated as in Bradford (1976) The senescence of leaves and cotyledons involves in using bovine serum albumin as standart (5). The experimental changes their photosynthetic apparatus. Because yellowing materials were homogenized in 0.1 M phosphate buffer is so conspicuous, chlorophyll breakdown has served as the pH (7.0) with the proportion of 100 mg fresh weigt/ml, and major parameter for the measurement of leaf senescence. then the extracts were centrifugated for 45 minutes at 13 Brassinosteroids are effective in accelerating this breakdown 000 rpm. 0.1 ml. of supernatants was added to 5 ml of ¼ indicates that this hormon is somehow involved in inconstanting diluted Coomassie Brillant Blue G-250 (Merc) (Bio-Rad) and the photosynthetic apparatus of plant organs. vigorously mixed. After keeping it in the dark for 15 minutes, the absorption of the protein in the extract against blank at 595 The objective of this study is to compare the effect of different nm was spectrophotometrically measured and calculated as μg epibrassinolide (eBL) concentrations such as 0.001μM, 0.1μM protein/ml. and 10μM on senescence in wheat leaf segments. Determination of peroxidase activity Materials and Methods Peroxidase activity (POD) was determined by employing the Plant material method of Birecka et al. (3). With this method, by experimental Epibrassinolide (Sigma-E 1641) [(22R,23R)-2α,3α,22,23- materials were homogenized in 0.1 M pH 5.8 K-phosphate Tetrahydroxy-7-oxa-B-homo-5α-ergostan-6-one] 78821-43- buffer, using the proportion of 100 mg fresh weight/ml, and 9; 72962-43-7 (it is solved in ethanol) was used in this study. then the extracts were centrifugated for 45 minutes at 13 BIOTECHNOL. & BIOTECHNOL. EQ. 21/2007/1 63 000 rpm. Supernatants were treated with 15 mM guaiacol and fi nal control (Fig. 2). There are several reports show that (Merc) and 5 mM H O POD activity increases during the senescence of excised leaves (Merc) in 0.1 M phosphate buffer. The 2 2 (7, 8, 18). POD activity unimportantly increased 9% in fi nal absorbance of the coloured product in the extract was recorded spectrophotometer control leaf segments compared to initial control. POD activity every 10 seconds for 2 minutes at 470 nm in (Shimadzu UV 160), and the peroxidase activity was gradually increased in all of the eBL treated leaf segments th quantitatively provided as ∆A/g fresh weight/minutes with the compared to fi nal control condition on 7 day of incubation. spectral method (3). These results showed that there was not a correlation between chlorophyll contents and POD activity. Parish (18) suggested Determination of protease activity that the increase in the activity of POD is one of the most reliable Protease activity on 7th day of incubation was determined indicators of maturity and senescence. It seems possible that according to Kaur-Sawhney et al. (11). POD has functional signifi cance during the senescence process Statistical analysis: Each treatment was analysed with at least of leaf segments of wheat. seven replicate tissue samples bulked at least six leaf segments. The data presented here are the mean values ± SE of seven independent experiments. Results and Discussion In this study, have been selected only incubated leaf segments for 7 day. Because, there was gradually increase in the th chlorophyll content on 7 day compaired to the other days th th th (3 , 5 and 10 days) with treatment of decreasing eBL concentration in wheat leaf segments. Exogenous application of 0,1 and 10 μM eBL solutions to leaf segments was effective in accelerating chlorophyll breakdown. Total chlorophyll Fig. 2. Effects of different concentrations of epibrassinolide on peroxidase content showed a 1.12 and 1.21 fold decrease in 0.1 and 10 activity in wheat leaf segments which were incubated for 7 day after μM eBL treatments comparing with the control leaves on 7th harvested day of incubation (Fig. 1) and the chlorophyll content was In this resarch, the soluble protein contents decreased at the highest in 0.001 μM eBL. But it was similar with initial 10μM eBL. On the other hand, 0.001 and 0.1μM eBL did not control. Many researchers have reported that exogenously exhibite signifi cant differences according to the 10 μM (Fig. 3). applied brassinosteroids accelerated the loss of photosynthetic pigments of leaves and cotyledons during the senescence (13, 26). Although 10 and 0.1μM eBL effects in this study showed the parallel results with literature, the effect of 0.001μM eBL was not the same as this concentration inhibated the chlorophyll loss. When the chlorophyll contents were compared between th initial and fi nal control leaf segments, 30 and 56% loss on 7 th and 10 day were found respectively. Decreasing chlorophyll loss at 0.001 μM eBL is attract attention. Fig. 3. Effects of different concentrations of epibrassinolide on protein content in wheat leaf segments which were incubated for 7 day after harvested It has been known that the synthesis of the proteolytic enzymes proceeds the senescence period (8, 14). However, Thayer et al., (22) have revealed the necessity of protein synthesis to occur senescence signal and also the requirement of the synthesis of proteases for breakdown of proteins during the senescence. Protease activities were very low at initial compared to fi nal Fig. 1. Effects of different concentrations of epibrassinolide on total chlorophyll content in wheat leaf segments which were incubated for 3, 5, 7 and 10 days control leaf segments which were already senescenced, in this after harvested study. The inhibition in protease activities was stimulated when POD activity showed the greatest effect when 0.1μM eBL leaves fl oated on eBL solutions, compared to the fi nal control was used. POD activity increased 2.4, 2.9 and 2.4 fold in (Fig. 4). Various concentrations of eBL had inhibitory effect on 0.001, 0.1 and 10 μM, respectively when compared with initial acid and neutral protease activities, specially neutral protease 64 BIOTECHNOL. & BIOTECHNOL. EQ. 21/2007/1 activity inhibited gradually with the decreasing concentration of 5. Bradford M. (1976) Anal. Biochem., 72, 248-254. eBL. The acid protease activity was stimulated gradually with 6. Brosa C. (1999) Crit. Rev. Biochem. Mol. Bio., 34, 339- the decreasing concentration of eBL. It is noteworthy that the neutral protease activity in fi nal control, treated segments and 7. Chang C.J., Kao C.H. (1998) Plant Growth Regulation, initial control displayed a high level volume when compared 25, 11-15. with the acid protease activity. The results of treatment at 8. Çağ S., Cevahir G., Ünal M., Kaplan E., Çıngıl Ç., 10μM eBL showed a degradation of excised segment proteins Kösesakal T. (2004) Fresenius Environmental Bulletin, during yellowing. Besides, it is possible to induce that the 13(8), 733-739. low level of the activity in treated segments may not cause the 9. He YJ., Xu RJ., Zhao YJ. (1996) Acta Phytophysiol, 22, accelerating of senescence. 58-62. 10. Joo S., Seo Y.S., Kim S.M., Hong D., Park K.Y., Kim W.K. (2006) Physiol. Plant., 126(4), 592 11. Kaur-Sawhney R., Shih LM., Cegielska T., Galston AW. (1982) FEBS Letters, 145, 345-349. 12. Mandava NB. (1988) Annual. Plant Physiol. Plant Mol. Bio., 39, 23-52. 13. Mandava NB., Sasse, JM., Yopp JH. (1981) Physiol. Plant., 53, 453-461. 14. Martin, C., Thimann, KV. (1972) Plant Physiol., 49, 64- 15. Müssig, C., Altmann, T. (1999) Plant Physiol. Biochem., 37(5), 363-372 . Fig. 4. Effects of different concentrations of epibrassinolide on protease activity 16. Nakamura A., Nakajima N., Goda H., Shimada Y., in wheat leaf segments which were incubated for 7 day after harvested Hayashi, I., Nozaki H., Asami T. Yoshida S., Fujioka S. The ability of brassinosreroids to promote senescence (2006) The Plant Journal, 45, 193. in detached cotyledons (26) and leaves (9) was reported. In 17. Oh M.H. (2003) J. Plant Biotechnol., 5(1), 63-67. conclusion, eBL is also active in acceleration of senescence of 18. Parish, R.W. (1968) Planta, 82, 1-13. excised wheat leaves. The results of this research are exhibited 19. Rao S.S.R., Vardhini B.V., Sujatha E., Anuradha S. eBL as a promising plant growth regulator in physiological (2002) Current Sci., 82,1239-1245. studies. 20. Schaller H. (2003) Progress in Lipid Research 42, 163- Acknowledgements 175. Author is grateful to the Research Fund of Istanbul University, 21. Srivastava, L.M (2002) Academic Press, Elsevier Science, Istanbul, Turkey, for fi nancial support (project No. UDP- 0-12-660570 p.205. 296/12052004) 22. Thayer S.S, Choe H.T, Tang A., Huffaker, R.C. (1987) The American Society of Plant Physiologist, 71-80. 23. Vardhini B.V., Rao S.S.R. (2002) Phytochemistry, 16, REFERENCES 843-847. 1. Arnon, D.I. (1949) Plant. Physiol., 24, 1-15. 24. Yin Y, Wang Z.Y, Mora-Garcia S, Li J, Yoshida S, Asami 2. Bajguz, A. and Tretyn, A. (2003) Phytochemistry 62, T., Chory J. (2002) Cell, 109,181-191. 1027-1046. 25. Yokota T. (1997) Trends Plant Sci., 2, 137-143. 3. Birecka, H., Briber, A. and Catalfamo, JL. (1973). Plant 26. Zhao Y.J., Xu R.J., Luo W.H. (1990) Chin. Sci. Bull., 35, Physiol., 52, 43-49. 928-931. 4. Bishop GJ., Yokota T. (2001) Plant Cell Physiol., 49, 114- BIOTECHNOL. & BIOTECHNOL. EQ. 21/2007/1 65 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Biotechnology & Biotechnological Equipment Taylor & Francis

The Effect of Epibrassinolide on Senescence in Wheat Leaves

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Taylor & Francis
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© 2007 Taylor and Francis Group, LLC
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1314-3530
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DOI
10.1080/13102818.2007.10817415
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Abstract

ARTICLES B&E S. Sağlam-Çağ Istanbul University, Faculty of Science, Department of Botany, Istanbul, Turkey Correspondece to: Serap Sağlam-Çağ Email: [email protected] ABSTRACT Brassinosteroids (BRs) are new groups of plant hormones with signifi cant growth-promoting activity. Brassinolide (BL) is the most biologically active BR. BRs are considered as hormones, as they infl uence varied developmental processes like growth, germination of seeds, rhizogenesis, fl owering and senescence. Senescence is regulated by phytohormones. This research shows that epibrassinolide (eBL) accelerates or delays senescence in wheat leaf segments. For this aim, epibrassinolide was applied exogenously into the excised wheat leaf segments. An increase in peroxidase activity and decrease in protease activity, chlorophyll content (at 10 and 0.1 μM. eBL) were detected. However, protein content decreased only at 10 μM. eBL . Finally, it was observed that eBR accelerated senescence specially at high concentration. Keywords: Epibrassinolide, senescence, wheat leaf segment, Wheat (Triticum aestivum L.) seeds were planted in sawdust chlorophyll, protein, peroxidase, protease and they were grown in plant growth chamber (12 h light, 12 h dark photoperiod and 25±2 C). Six fi rst leaf segments (3cm. Introduction each) from 10 days old wheat seedlings were placed in 5 cm Brassinosteroids (BRs) are steroid hormones that regulate the diameter petri dishes already containing 3 ml of experimental solution. Epibrassinolide was used at different concentrations growth and development of plants (2, 10, 20,). In plants, many (0.001μM, 0.1μM and 10 μM) as an experimental solutions. steroids have been identifi ed, but only one class of steroids called collectively brassinosteroids have wide distribution Distilled water was used for control treatments. throughout the plant kingdom and unique growth-promoting Measurement of total chlorophyll content activity when applied exogenously (12). Brassinosteroids Total chlorophyll content was determined according to the have various physiological and morphological effects on Arnon (1949) in wheat leaf segments which were incubated plants, including cell and stem elongation, inhibition of root for 3, 5, 7 and 10 days after harvested (1). Leaf segments were formation, leaf bending, proton pump activation, ethylene homogenized in 80 % acetone. The samples were centrifugated production, tracheary element differentiation and activation of at 4 000 g for 5 min. and the optical density of the supernatant stress responses (4, 15, 16, 17, 25). Brassinolide was the fi rst was read at 663 and 645 nm using a spectrophotometer. Initial plant steroid with hormonal activities (21). values of each analysis were measured in leaf segments at the Brassinosteroids increase chlorophyll breakdown (23) but start of each experiment. inhibit anthocyanin biosynthesis (6). On the other hand, BRs accelerate senescence (9, 19, 24, 26) but the studies about this Measurement of soluble protein content topic are not enough. Soluble protein contents were estimated as in Bradford (1976) The senescence of leaves and cotyledons involves in using bovine serum albumin as standart (5). The experimental changes their photosynthetic apparatus. Because yellowing materials were homogenized in 0.1 M phosphate buffer is so conspicuous, chlorophyll breakdown has served as the pH (7.0) with the proportion of 100 mg fresh weigt/ml, and major parameter for the measurement of leaf senescence. then the extracts were centrifugated for 45 minutes at 13 Brassinosteroids are effective in accelerating this breakdown 000 rpm. 0.1 ml. of supernatants was added to 5 ml of ¼ indicates that this hormon is somehow involved in inconstanting diluted Coomassie Brillant Blue G-250 (Merc) (Bio-Rad) and the photosynthetic apparatus of plant organs. vigorously mixed. After keeping it in the dark for 15 minutes, the absorption of the protein in the extract against blank at 595 The objective of this study is to compare the effect of different nm was spectrophotometrically measured and calculated as μg epibrassinolide (eBL) concentrations such as 0.001μM, 0.1μM protein/ml. and 10μM on senescence in wheat leaf segments. Determination of peroxidase activity Materials and Methods Peroxidase activity (POD) was determined by employing the Plant material method of Birecka et al. (3). With this method, by experimental Epibrassinolide (Sigma-E 1641) [(22R,23R)-2α,3α,22,23- materials were homogenized in 0.1 M pH 5.8 K-phosphate Tetrahydroxy-7-oxa-B-homo-5α-ergostan-6-one] 78821-43- buffer, using the proportion of 100 mg fresh weight/ml, and 9; 72962-43-7 (it is solved in ethanol) was used in this study. then the extracts were centrifugated for 45 minutes at 13 BIOTECHNOL. & BIOTECHNOL. EQ. 21/2007/1 63 000 rpm. Supernatants were treated with 15 mM guaiacol and fi nal control (Fig. 2). There are several reports show that (Merc) and 5 mM H O POD activity increases during the senescence of excised leaves (Merc) in 0.1 M phosphate buffer. The 2 2 (7, 8, 18). POD activity unimportantly increased 9% in fi nal absorbance of the coloured product in the extract was recorded spectrophotometer control leaf segments compared to initial control. POD activity every 10 seconds for 2 minutes at 470 nm in (Shimadzu UV 160), and the peroxidase activity was gradually increased in all of the eBL treated leaf segments th quantitatively provided as ∆A/g fresh weight/minutes with the compared to fi nal control condition on 7 day of incubation. spectral method (3). These results showed that there was not a correlation between chlorophyll contents and POD activity. Parish (18) suggested Determination of protease activity that the increase in the activity of POD is one of the most reliable Protease activity on 7th day of incubation was determined indicators of maturity and senescence. It seems possible that according to Kaur-Sawhney et al. (11). POD has functional signifi cance during the senescence process Statistical analysis: Each treatment was analysed with at least of leaf segments of wheat. seven replicate tissue samples bulked at least six leaf segments. The data presented here are the mean values ± SE of seven independent experiments. Results and Discussion In this study, have been selected only incubated leaf segments for 7 day. Because, there was gradually increase in the th chlorophyll content on 7 day compaired to the other days th th th (3 , 5 and 10 days) with treatment of decreasing eBL concentration in wheat leaf segments. Exogenous application of 0,1 and 10 μM eBL solutions to leaf segments was effective in accelerating chlorophyll breakdown. Total chlorophyll Fig. 2. Effects of different concentrations of epibrassinolide on peroxidase content showed a 1.12 and 1.21 fold decrease in 0.1 and 10 activity in wheat leaf segments which were incubated for 7 day after μM eBL treatments comparing with the control leaves on 7th harvested day of incubation (Fig. 1) and the chlorophyll content was In this resarch, the soluble protein contents decreased at the highest in 0.001 μM eBL. But it was similar with initial 10μM eBL. On the other hand, 0.001 and 0.1μM eBL did not control. Many researchers have reported that exogenously exhibite signifi cant differences according to the 10 μM (Fig. 3). applied brassinosteroids accelerated the loss of photosynthetic pigments of leaves and cotyledons during the senescence (13, 26). Although 10 and 0.1μM eBL effects in this study showed the parallel results with literature, the effect of 0.001μM eBL was not the same as this concentration inhibated the chlorophyll loss. When the chlorophyll contents were compared between th initial and fi nal control leaf segments, 30 and 56% loss on 7 th and 10 day were found respectively. Decreasing chlorophyll loss at 0.001 μM eBL is attract attention. Fig. 3. Effects of different concentrations of epibrassinolide on protein content in wheat leaf segments which were incubated for 7 day after harvested It has been known that the synthesis of the proteolytic enzymes proceeds the senescence period (8, 14). However, Thayer et al., (22) have revealed the necessity of protein synthesis to occur senescence signal and also the requirement of the synthesis of proteases for breakdown of proteins during the senescence. Protease activities were very low at initial compared to fi nal Fig. 1. Effects of different concentrations of epibrassinolide on total chlorophyll content in wheat leaf segments which were incubated for 3, 5, 7 and 10 days control leaf segments which were already senescenced, in this after harvested study. The inhibition in protease activities was stimulated when POD activity showed the greatest effect when 0.1μM eBL leaves fl oated on eBL solutions, compared to the fi nal control was used. POD activity increased 2.4, 2.9 and 2.4 fold in (Fig. 4). Various concentrations of eBL had inhibitory effect on 0.001, 0.1 and 10 μM, respectively when compared with initial acid and neutral protease activities, specially neutral protease 64 BIOTECHNOL. & BIOTECHNOL. EQ. 21/2007/1 activity inhibited gradually with the decreasing concentration of 5. Bradford M. (1976) Anal. Biochem., 72, 248-254. eBL. The acid protease activity was stimulated gradually with 6. Brosa C. (1999) Crit. Rev. Biochem. Mol. Bio., 34, 339- the decreasing concentration of eBL. It is noteworthy that the neutral protease activity in fi nal control, treated segments and 7. Chang C.J., Kao C.H. (1998) Plant Growth Regulation, initial control displayed a high level volume when compared 25, 11-15. with the acid protease activity. The results of treatment at 8. Çağ S., Cevahir G., Ünal M., Kaplan E., Çıngıl Ç., 10μM eBL showed a degradation of excised segment proteins Kösesakal T. (2004) Fresenius Environmental Bulletin, during yellowing. Besides, it is possible to induce that the 13(8), 733-739. low level of the activity in treated segments may not cause the 9. He YJ., Xu RJ., Zhao YJ. (1996) Acta Phytophysiol, 22, accelerating of senescence. 58-62. 10. Joo S., Seo Y.S., Kim S.M., Hong D., Park K.Y., Kim W.K. (2006) Physiol. Plant., 126(4), 592 11. Kaur-Sawhney R., Shih LM., Cegielska T., Galston AW. (1982) FEBS Letters, 145, 345-349. 12. Mandava NB. (1988) Annual. Plant Physiol. Plant Mol. Bio., 39, 23-52. 13. Mandava NB., Sasse, JM., Yopp JH. (1981) Physiol. Plant., 53, 453-461. 14. Martin, C., Thimann, KV. (1972) Plant Physiol., 49, 64- 15. Müssig, C., Altmann, T. (1999) Plant Physiol. Biochem., 37(5), 363-372 . Fig. 4. Effects of different concentrations of epibrassinolide on protease activity 16. Nakamura A., Nakajima N., Goda H., Shimada Y., in wheat leaf segments which were incubated for 7 day after harvested Hayashi, I., Nozaki H., Asami T. Yoshida S., Fujioka S. The ability of brassinosreroids to promote senescence (2006) The Plant Journal, 45, 193. in detached cotyledons (26) and leaves (9) was reported. In 17. Oh M.H. (2003) J. Plant Biotechnol., 5(1), 63-67. conclusion, eBL is also active in acceleration of senescence of 18. Parish, R.W. (1968) Planta, 82, 1-13. excised wheat leaves. The results of this research are exhibited 19. Rao S.S.R., Vardhini B.V., Sujatha E., Anuradha S. eBL as a promising plant growth regulator in physiological (2002) Current Sci., 82,1239-1245. studies. 20. Schaller H. (2003) Progress in Lipid Research 42, 163- Acknowledgements 175. Author is grateful to the Research Fund of Istanbul University, 21. Srivastava, L.M (2002) Academic Press, Elsevier Science, Istanbul, Turkey, for fi nancial support (project No. UDP- 0-12-660570 p.205. 296/12052004) 22. Thayer S.S, Choe H.T, Tang A., Huffaker, R.C. (1987) The American Society of Plant Physiologist, 71-80. 23. Vardhini B.V., Rao S.S.R. (2002) Phytochemistry, 16, REFERENCES 843-847. 1. Arnon, D.I. (1949) Plant. Physiol., 24, 1-15. 24. Yin Y, Wang Z.Y, Mora-Garcia S, Li J, Yoshida S, Asami 2. Bajguz, A. and Tretyn, A. (2003) Phytochemistry 62, T., Chory J. (2002) Cell, 109,181-191. 1027-1046. 25. Yokota T. (1997) Trends Plant Sci., 2, 137-143. 3. Birecka, H., Briber, A. and Catalfamo, JL. (1973). Plant 26. Zhao Y.J., Xu R.J., Luo W.H. (1990) Chin. Sci. Bull., 35, Physiol., 52, 43-49. 928-931. 4. Bishop GJ., Yokota T. (2001) Plant Cell Physiol., 49, 114- BIOTECHNOL. & BIOTECHNOL. EQ. 21/2007/1 65

Journal

Biotechnology & Biotechnological Equipment – Taylor & Francis

Published: Jan 1, 2007

Keywords: Epibrassinolide; senescence; wheat leaf segment; chlorophyll; protein; peroxidase; protease

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