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|Title:||Effect of exogenous H<sub>2</sub>O<sub>2</sub> on antioxidant enzymes of <i>Brassica juncea</i> L. seedlings in relation to 24-epibrassinolide under chilling stress|
<i>Brassica juncea </i>L.
|Abstract:||Hydrogen peroxide is most stable molecule among reactive oxygen species, which play a vital role in growth and development of plant as signaling molecule at low concentration in response to various abiotic and biotic stresses. Exogenous application of H<sub>2</sub>O<sub>2</sub> is known to induce chilling tolerance in plants. Brassinosteroids are plant steroid hormones known for their anti-stress properties. In this study, effect of exogenous H<sub>2</sub>O<sub>2</sub> on antioxidant defense system of <i>Brassica juncea</i> L. seedlings was investigated in 24-epibrassinolide (24-EBL) treated and untreated seedlings under chilling stress. The surface sterilized seeds of <i>B. juncea</i> L. were germinated in petriplates containing different concentrations of H<sub>2</sub>O<sub>2</sub> alone and in combination with 10<sup>-8 </sup>M 24-EBL. Chilling treatment (4 ºC) was given to 10-days old seedlings grown in different treatments for 6 h daily up to 3 days. 24 h recovery period was given to chilling treated seedlings by placing at 25ºC ± 2ºC and harvested for antioxidant enzymes on 14<sup>th</sup> day after sowing (DAS). Treatment of 24-EBL in combination with H<sub>2</sub>O<sub>2</sub> (15 and 20 mM) helped in reducing the toxicity of seed and seedlings due to H<sub>2</sub>O<sub>2</sub> exposure on their germination rate, shoot and root length respectively. 24-EBL treatment at seed and seedling stage helped in alleviating the toxic effect of H<sub>2</sub>O<sub>2</sub> through antioxidant defense system by increasing the activities of various enzymes involved in antioxidant defense system such as catalase (CAT, E.C. 184.108.40.206), ascorbate peroxidase (APOX, E.C. 220.127.116.11), and superoxide dismutase (SOD, E.C. 18.104.22.168). In conclusion, exogenous pretreatment of H<sub>2</sub>O<sub>2</sub> to seeds of <i>B. juncea </i>L. adapted the seedlings to tolerate chilling stress, which was further ameliorated in combination of H<sub>2</sub>O<sub>2</sub> with 24-EBL.|
|ISSN:||0975-0959 (Online); 0301-1208 (Print)|
|Appears in Collections:||IJBB Vol.47(6) [December 2010]|
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