Kavina.J et al. / Journal of Pharmacy Research 2011,4(8), Available online through

Transcription

1 Research Article ISSN: Kavina.J et al. / Journal of Pharmacy Research 2011,4(8), Available online through Influence of Growth Regulators and Fungicides on Antioxidant Potential of Mentha Piperita Linn Kavina.J*, R.Gopi and R.Panneerselvam Department of Botany, Stress physiology lab, Annamalai University, Annamalai nagar , Tamil Nadu, India Received on: ; Revised on: ; Accepted on: ABSTRACT The changes in antioxidant potentials were studied in Mentha piperita Linn. Plants under treatments with Gibberilic acid (GA), Abscisic acid (ABA) and Difenoconozole (DIZ). The treatments were given as soil drenching methods on 30, 45, 60 and 75 days after planting (DAP). The plants were uprooted on45,60,75 and 90 DAP and separated into root, stem and leaf used for analyses. The antioxidant potentials potentials was studied in terms of non enzymatic antioxidant molecules like ascorbic acid (AA), total phenol and reduced glutathione (GSH) and activities of antioxidant enzyme, viz., Peroxidase(POX), Superoxide dismutase (SOD), Ascorbate peroxidase(apx), Polyphenol oxidase (PPO) and Catalase (CAT). The GA ABA & DIZ treatments increased the AA, total phenol, GSH, APX, SOD, PPO, CAT. These preliminary results suggest that,the application of GA,ABA &DIZ may be a useful tool to increase the antioxidant production in medicinal plants like M.Piperita. Key words: Antioxidant enzymes, Non-antioxidant enzymes, Mentha piperita. INTRODUCTION Application of plant growth hormones is a promising benefit to enhance yields of vegetative parts, which produce secondary metabolites. Gibberellins are involved in several plant development processes and promote a number of desirable effects including stem elongation, uniform flowering, reduced time to flowering, increased flower number and size ( Khassawneh et.,al 2006). Abscisic acid are involved in regulating processes such as embryo maturation, seed development and germination, cell division and elongation, stomatal opening, root development, floral transition and tolerance to abiotic and biotic stresses like drought, salinity and low temperature (Giraudat et al., 1994; Mahovachi et al., 2005). Likewise trizole compounds induce many morphological changes like shoot inhibition, stimulation of root elongation, increasing chlorophyll content, altered carbohydrate status and increase in the level of enzyme activity in Catharanthus (Jaleel et al., 2007a). The most common methods of application of growth regulators are foliar sprays and soil drenches. In practical application of plant hormones, the best practices in stable production of secondary metabolite contents in medicinal plants, is through soil drenching (Jaleel et al., 2006) Mentha piperita is one of the highly exploited and studied medicinal plants beling to the family Lamiaceae. Mentha leaves and flowering tops are the functional parts that are used as herbs and for oil extraction. Main chemical compounds present in Mentha sps., Menthol, Menthone, Tannin and Terpenic derivatives. Both fresh and dried leaves are used for producing medicinal products. Herb properties are stomachic, anti-spasmodic, anti-tussive, insectifuge, as tonic. Leaves and flowers as fresh and dried oil are used in the form of infusion, fluid extract, syrup powder, essence and juice. MATERIALS AND METHODS Medicinally important plant species, Mentha piperita, were selected for the present investigation. Them stem cutting (suckers) were obtained from the Horticulture Department, Faculty of Agriculture, Annamalai University Tamilnadu. The plant growth regulators Gibberellic acid (GA 3 ) and Abscisic acid (ABA) were purchased from sigma chemicals Bangalore, Difenoconazole (DIZ) a triazolic group of fungicide having PGR properties is obtained from syngenta, India Ltd., Mumbai (India).used for the study. The experimental part of this work was carried out in Botanical garden and Stress physiology lab, Department of Botany, Annamalai University, Tamilnadu. During this study the average temperature was ± 32/26 C and relative humidity (RH) varied between per cent. *Corresponding author. J.Kavina, Ph.D Research scholar, Department of Botany, Stress Physiology Lab, Annamalai University, Annamalai Nagar, Chidhambaram Non-Antioxidant enzyme extractions and assays Estimation of AA content AA content was assayed as described by Omay et al The extract was prepared by grinding 1 g of fresh material with 5mlof 10% TCA, centrifuged at 3500 rpm for 20 min, re extracted twice and supernatant made up to 10 ml and used for assay. To 0.5 ml of extract, 1ml of DTC reagent (2,4-dinitro phenylhydrazine-thiourea CuSO4 reagent) was added, incubated at37 0 C for 3 h and 0.75 ml of ice-cold 65% H2SO4 was added, allowed to stand at 30 0 C for 30 min, resulting colour was read at 520 nm in spectrophotometer (U2001- Hitachi). The AA content was determined using a standard curve prepared with AA and the results were expressed in milligram per gram dry weight(dw). Estimation of Total phenol content Total phenols was assayed as described by Malick and Singh (1980).500 mg of fresh plant tissue was ground in a pestle and mortar with 10 ml of 80 per cent ethanol. The homogenate was centrifuged at 10,000 rpm for 20 min. The supernatant was evaporated to dryness. The residue was dissolved with 5ml of distilled water and used as extract. To 2 ml of the extract, 0.5 ml of Folin Ciocalteare reagent was added. After 3 min, 2 ml of 20% Na 2 CO 3 solution was mixed throughoutly. The mixture was kept in boiling water for exactly one min, and after cooling the absorbance was read at 650 nm. The total phenol was determined using a standard curve prepared with different concentration of gallic acid and expressed in mg g -1 dry weight. Estimation of GSH content The GSH content was assayed as described by Griffith and Meister (1999). Two hundred milligrams of fresh material was ground with 2ml of 2% metaphosphoric acid and centrifuged at 17,000 rpm for 10 min. Adding 0.6 ml 10% sodium citrate neutralized the supernatant. One milliliter of assay mixture was prepared by adding 100 µl extract, 100µl distilled water, 100µl 5,5-dithio-bis- (2-nitrobenzoic acid) and 700 _l NADPH. The mixture was stabilized at 25 0 C for 3 4 min. Then 10µl of glutathione reductase was added, read the absorbance at 412 nm in spectrophotometer and the GSH contents were expressed in microgram per gram fresh weight (FW). Antioxidant enzyme extractions and assays. Assay of SOD activity The activity of SOD was assayed as described by Beauchamp and Fridovich ( 2000) The reaction mixture contained Mriboflavin,0.1M methionine, M KCN and M nitroblue tetrazolium (NBT) salt dissolved in 3ml of 0.05M sodium phosphate buffer (ph 7.8).Three milliliters of the reaction medium was added to 1ml of enzyme extract. The mixtures were illuminated in glass test tubes by two sets of Philips 40W fluorescent tubes in a single row. Illumination was started to initiate the reaction at 30 0 C for 1h. Identical solutions that were kept under dark served as blanks. The absorbance was read at 560 nm in the spectrophotometer against the blank. SOD activity is expressed in Umg -1 protein (U = change in 0.1 absorbance h -1 mg -1 protein).

2 Kavina.J et al. / Journal of Pharmacy Research 2011,4(8), Assay of APX activity The activity of APX was determined by the method of Asada and Takahashi (198). The reaction mixture (1 ml) contained50mm potassium phosphate buffer (ph 7.0), 0.5mM ascorbic acid, 0.1mM H2O2 and 200µl of enzyme extract.the absorbance was read as decrease at 290 nm against the blank, correction was done for the low, non-enzymatic oxidation of ascorbic acid by H O (extinction coefficient2.9mm -1 cm -1 ). The enzyme activity was expressed in 2 U 2 mg -1 protein (U = change in 0.1 absorbance min -1 mg -1 protein). Assay of CAT activity The activity of CAT was measured according the method of Chandlee and Scandalios (1984) with small modification. The assay mixture contained 2.6 ml of 50mM potassium phosphate buffer (ph 7.0), 0.4 ml of 15mM H 2 and 0.04 ml of enzyme extract. The decomposition of H 2 was followed by the decline in absorbance at 240 nm. The enzyme activity was expressed in Umg- 1 protein (U=1mMof H 2 reduction min -1 mg -1 protein). For all the enzymatic calculations protein was determined by the method of Bradford,using bovine serum albumin (BSA, Sigma, USA) as the standard. Assay of PPO activity The assay of PPO was carried out by the method of Kumar and Khan (1982). Assay mixture for PPO contained 2ml of 0.1M phospate buffer (ph 6.0), 1ml of 0.1M catechol and 0.5ml of enzyme extract. This was incubated for 5 min at 25 C, after which adding 1ml of 2.5N H2SO4 stopped the reaction. The absorbancy of the purpurogallin formed was read at 495 nm. To the blank 2.5 N H 2 SO 4 was added of the zero time of same assay mixture. PPO activity is expressed in U mg -1 protein (U=Change in 0.1 absorbance min -1 mg -1 protein). For all the enzymatic calculations protein was determined by the method of Bradford (1976), using bovine serum albumin (BSA, Sigma, USA) as the standard. Assay of POX activity Peroxidase was assayed by the method of Kumar and Khan (1982). Assay mixture of peroxidase contained 2ml of 0.1M phoshate buffer (ph 6.8), 1ml of 0.01M pyrogallol, 1ml of 0.005M H 2 and 0.5 ml of enzyme extract. The solution was incubated for 5min at 25 C after which the reaction was terminated by adding 1ml of 2.5N H 2 SO 4. The amount of purpurogallin formed was determined by measuring the absorbance at 420nm against a blank prepared by adding the extract after the addition of 2.5N H 2 SO 4 at zero time. The activity was expressed in unit mg -1 protein. One unit is defined as the change in the absorbance by 0.1 min -1 mg -1 protein. RESULTS: EFFECT OF GA, ABA and DIZ ON NON-ANTIOXIDANT ENZYME AC- TIVITY: Effect of GA, ABA and DIZ on Total phenol content: (Fig 1) The total phenol content in all parts of the plant increased with the age in control and treatments. The increase was higher in ABA treatments, accumulation of total phenol content in root and stem tissue was observed on 90 DAP and it was and percent over control respectively. But in the leaf tissue the increase was noted percent over control. Fig-1 Effect of difenoconozole, abscisic acid and gibberellic acid on total phenols content of Mentha piperita Effect of GA, ABA and DIZ on AA content: (Fig 2) The AA contents show variations in different treatment when compared to control. A maximum of increase was noted on 90 DAP in DIZ and GA treatment in both and stem tissues it was and 130 percent over control. But in leaf the increase was significant in all treatment, the maximum increase was noted on 90 DAP in DIZ treatment and it was percent over control. Fig 2 Effect of difenoconozole, abscisic acid and gibberellic acid on ascorbic acid of Mentha piperita Effect of GA, ABA and DIZ on GSH content: (Fig 3) The reduced glutathione content of the plants increased with the age in control and treated M.Piperita plant tissues. All the treatment increased the GSH content when compared to control. DIZ treatments increased the GSH in root on 90 DAP, it was percent over control. But in stem and leaf the maximum increase was noted in 90 DAP in GA treatments and it was and percent over control.

3 Kavina.J et al. / Journal of Pharmacy Research 2011,4(8), Fig 4 Effect of difenoconozole, abscisic acid and gibberellic acid on peroxidase of Mentha piperita Effect of GA, ABA and DIZ on APX activity: (Fig 5) The APX activity of Mentha piperita plant increased with the age in control and treated plant tissue (root.,leaf ).All the treatment showed increase when compared to control. But ABA treatments show more increase in root and leaf tissue, when compare to other treatments and it was percent and percent over control. In stem DIZ treatments increases the APX activity and it was percent over control. Fig 3.Effect of difenoconozole, abscisic acid and gibberellic acid on reduced glutathione content of Mentha piperita EFFECT OF GA,ABA AND DIZ ON ANTIOXIDANT ENZYME ACTIVITY: Effect of GA, ABA and DIZ on POX activity (Fig 4) The root, stem and leaf the POX activity under increased with the age in control and treatments. There was highly increase in POX activity under GA, ABA and DIZ treatments when compared to control. A maximum of increase was noted on 90 DAP in GA treatments in root and it was nearly percent over control. In stem and leaf tissue the maximum of increase was noted on 90 DAP in DIZ treatment and it was percent and percent over control. Fig 5- Effect of difenoconozole, abscisic acid and gibberellic acid on ascorbate peroxidase of Mentha piperita Effect of GA, ABA and DIZ on SOD activity: (Fig 6) The SOD activity of plant increased with the age in control and treated plant tissue. The SOD activity increased under GA, ABA and DIZ when compared to

4 Kavina.J et al. / Journal of Pharmacy Research 2011,4(8), control. The high activity was noted on 90 DAP in DIZ treatment in all parts like root, stem and leaf, it was percent in root, in stem and percent in leaf when compared with control plants. Fig 7. Effect of difenoconozole, abscisic acid and gibberellic acid on polyphenol oxidase of Mentha piperita Effect of GA, ABA and DIZ on CAT activity: (Fig 8) In Mentha plants the activity of catalase increased with the age in control and treated plants. The increase was higher in GA, ABA and DIZ treatments when compared to control. A high activity in root was noted on 90 DAP in ABA treatment; it was percent over control. But in stem and leaf the CAT activity of higher in 90 DAPS in GA treatments. It was percent in leaf when compared with control plants. Fig 6-Effect of difenoconozole, abscisic acid and gibberellic acid on SOD activity of Mentha piperita Effect of GA, ABA and DIZ on PPO activity: (Fig 7) The PPO activity increases with age in control and treated plants. There was slightly increase with ABA when compared to control. In root, stem and leaf a maximum of increase was noted on 90 DAP in DIZ treatment and it was percent, percent and percent respectively when compared with control plants.

5 Kavina.J et al. / Journal of Pharmacy Research 2011,4(8), (Manivannan et al., 2007). Treatment with GA 3 increased the APX activity in M.Piperita. Similar results were previously reported in C.roseus plants in both soil drench and foliar application of GA 3 (Jaleel et al., 2007b). Superoxide dismutase (SOD) The treatments DIZ, ABA and GA 3 significantly increased the SOD activity in the leaves, stem and roots of M.piperita. Treatment with GA 3 increased the SOD activity in Catharanthus plants in both soil drench and foliar applications (Jaleel et al., 2007b). An increase in SOD activity was reported in tridimefon treatment in banana (Biyan et al., 1995). Similar results were observed in uniconazole treatment in wheat (Sgherri et al., 2000) and cassia seedlings (Sheela and Pandey, 2003). The antioxidant enzymes SOD activity increased under GA 3 treatment. The SOD activity remains low, the addition of GA 3 enhanced the SOD activity and it was highly marked over control plants. The different parts of the plant showed varied acticity SOD catalase the dismulation of - to H 2 and (Foyer et al., 1994; Jaleel et al., 2007) Fig 8. Effect of difenoconozole, abscissic acid and gibberellic acid on catalase activity of Mentha piperita DISCUSSION NON-ENZYMATIC ANTIOXIDANTS Total phenols In the present study, the total phenol content significantly increased with DIZ, ABA and GA 3 treatments in M.piperita at all stages of growth. Total phenol content in the leaves of mango seedlings increased as a result of PBZ treatment, the increase being more marked at higher dosage of PBZ (Murti and Upreti, 2003). It has been suggested that peroxidase could act as efficient H 2 scavenging system in plant vacuoles in the presence of phenolics and reduced ascorbate (Zancani and Nagy, 2000). Sgherri et al., 2003 hypothesized a cycle where H 2 is scavenged by phenolic compound. Phenolics are oxidized to phenoxyl radicals. This phenoxyl radical reduces the ascorbic acid into monodehydro ascorbate. Increased phenol content was previously reported in coleus under hexaconazole treatments (Lakshmanan et al., 2007). Ascorbic acid The ascorbic acid content was increased with age in DIZ and GA 3 treated plants of M.piperita. ABA decreased the ascorbic acid content in roots at all stages of growth. A decrease in ascorbic acid was reported in ABA treatment in plants (Zhang et al., 2006). Ascorbic acid has been proposed to have roles on regulation of photosynthesis (Foyer, 1993; Noctor and Foyer, 1998). Ascorbic acid is readily oxidized to monodehydro ascorbic acid as part of its antioxidant function (Smirnoff, 1995) in Nicotiana plumbaginifolia (Kampfenkel et al., 1995). The ascorbic acid content increased in Catharanthus roseus with GA 3 treatment (Jaleel et al., 2007). Uniconazole increased the level of the antioxidants like, ascorbic acid in tomato seedlings and protect membrane by preventing or reducing oxidative damage (Sensaratna et al., 1998). Singh 1996 reported an increase in ascorbic acid content in the fruit juice of paclobutrazole treated Mangifera indica.l. Similar results were observed in citrus (Jain et al., 2002). Reduced glutathione The treatments increased in reduced glutathione content in M.Piperita. Triazoles increased the reduced glutathione content in carrot (Gopi et al., 2007). Triadimefon and paclobutrazol increased the reduced glutathione content in C.roseus (Jaleel et al., 2006, 2007a). GA 3 treatments increased the reduced glutathione content in M.Piperita, which was previously tested in soil drench and foliar application (Jaleel et al., 2007b). ANTIOXIDANT ENZYMES Peroxidase (POX) Treatment with DIZ, ABA and GA 3 increased the POX activity in all the parts of M.Piperita when compared to control. DIZ treatment shows more increase in POX activity when compared to other treatments. Radix astragali plants under water deficit stress showed an enhancement in POX activity (Tan et al., 2006). Water deficit stress increased the POX activity in soybean (Zhang et al., 2006) and which is further increased by uniconazole treatment. Increased peroxidase activity is a common response to oxidative and abiotic stresses. Therefore peroxidase could be part of the enzymatic system connected with the increase in ethylene formation in plants like spinach (Ozturk and Demir, 2003). Ascorbate peroxidase (APX) The ascorbate peroxidase activity increased under different treatments in M.Piperita. Triazoles increased the level of APX activity in Solenostemon rotundifolius (Kishorekumar et al., 2008). Paclobutrazol increased the APX activity in peanut plants under drought stress (Sankar et al., 2007); Similar results were observed in vigna plants under propiconazole treatments Polyphenol oxidase (PPO) The PPO activity of the plants increased with the age in control and treated in Mentha piperita plants. PPO activity was increased in roots of ABA when compared to other two treatments. An increased in PPO activity was found in grape vines under paclobutrazol treatment. (Hunter and Procter, 1992). Tomato plants showed higher PPO activity when subjected to salt stress in combination with paclobutrazol treatments (Sankar et al., 2006). Catalase (CAT) The activity of catalase increased with DIZ, ABA and GA 3 treatments in M. piperita. An increase in catalase activity was noted in barley leaves and there by effective scavenging of H 2 to provide antioxidant defense mechanism (Vanacker et al., 1998). The H 2 scavenging system represented by APX and CAT are more important in imparting tolerance that SOD as reported in oxidative stress in wheat (Asada, 1994; Willekens et al., 1997) (Sairam et al., 1998). An increase in catalase activity was noted in triazole treatment in Catharanthus (Jaleel et al., 2006b, 2007a). REFERENCES 1. Asada, K Production and action of active oxygen species in photosynthetic tissues. In: Foyer, C.H. Mullineaux P.M. (ed.). Causes of photooxidative stress and amelioration of defense systems in plants. Boca. Raton, USA, CRC Press, Inc., pp Asada, K.,M. Takahashi Production and Scavenging of active oxygen in photosynthesis. In Kyleee DJ, Osmond. B, and Arntzen CJ (Eds), photo inhibition, Amsterdam: Elsevier, pp Beaudoin, N., C.Serizet, F.Gosti, J.Giraudat, Interactions between abscisic acid and ethylene signaling cascade: Plant cell 12 : Biyan, Z., L. Lifeng, H. Huibai and W. Zehuai Effects of low temperature and paclobutrazol on superoxide dismutase and abscisic acid of banana (Musa sp.). Acta Hort. Sinica. 24: Chandlee, J.M., J.G. Scandalios Analysis of variants affecting the catalase development program in maize sctellum. Theor. Appl. Genet.69: Foyer CH., J. Harbinson, oxygen metabolism and the regulation of photosynthetic electron transport. In CH. Foyer, PM. Mullineaux, (ed), causes of photooxidative stress and amelioration of defense systems in plants. CRC Press, Boca Raton, FL, pp Foyer, C., P. Descourvieres and K.J. Kunert Protection against oxygen radicals : an important defence mechanism studied in transgenic plant. Plant Cell Environ., 17: Foyer, C.H., Ascorbic acid. In: R.G. Aischer and J.L. Hess (Eds), Antioxidants in higher plants. CRC press, Inc, Florida Giraudat, J, F. Parcy, N. Bertauche, F. Gosti and J. Leung Current advances in abscissic acid action and signaling. Plant Mol. Biol. 26: Gopi. R, C.A.jaleel, R.Sairam, G.M.A.lakshmanan, M.Gomathinayagam, R.Pannerselvam differential effects of hexaconazole and paclobutrazol on biomass, electrolyte leakage, lipid peroxidation and antioxidant potential of Daucus carota L. Collids Surf. B: Biointerfaces 60 : Griffith, O.W., A.Meister potent and specific inhibition of glutathione synthesis by buthionine sulfoximine (S-N-butylhomocysteine sulfoximine). J.Biol.chem.. 254: Hunter, D.M. and J.K.A. Proctor Paclobutrazol affects growth and fruit composition of potted grapevines. Hort. Sci., 27 : Jain, S.K., R. Sing and K.K. Misra Effect of paclobutrazol on growth, yield and fruit quality of lemon (citrus limon). Indian J. Agric. Sci., 72(8): Jaleel C.A., R. Gopi, G.M. Alagu Lakshmanan, R. Panneerselvam. 2006a. Triadimefon induced changes in the antioxidant metabolism and ajmalicine production in Catharanthus roseus (L.) G. Don. Plant Sci. 171: Jaleel C.A., R. Gopi, P. Manivannan, R. Panneerselvam. 2007b. Responses of antioxidant defense system of Catharanthus roseus (L.) G. Don. to paclobutrazol treatment under salinity, Acta Physiol. Plant. 29: Jaleel, C.A., R. Gopi, P. Manivannan, A. Kishorekumar, M. Gomathinayagam and R. Panneerselvam, 2007a. Changes in biochemical constituents and induction of early sprouting by triadimefon treatment in white yam (Dioscorea rotundata Poir.) tubers during storage. J. Zhejiang Univ. Sci. B, 8 (4): Kampfenkal, K.M. Van Montague and D. Inze Effects of iron excess on Nicotiana plumbaginifolin Plant Physiol, 107:

6 Kavina.J et al. / Journal of Pharmacy Research 2011,4(8), 18. Kumar, K.B., P.A.Khan Peroxidase and polyphenol oxidase in excised Ragi (Elusine coracana CV. PR 202) leaves during senescence. India J. Exp, Bot. 20: Lakshmanan, G.M.A., C.A.Jaleel, M.Gomathinayagam, R.Panneerselvam, Changes in antioxidant potential and sink organ dry matter with pigment accumulation induced by hexaconazole in Plectranthus forskholic Briq. C.R. Biologies 330: Mahouachi, J.A. Gromez Cadenas, E.Primo Millo, M. Talon Antagonistic changes between abscisic acid and gibberellins in citrus fruits subjected to a serious of different water conditions. J. Plant growth Regul. 24 : Malick, C.P., M.B. Singh Plant enzymology and histo enzymology. Kalyani Publishers, New Delhi, P Manivannan P., C.A. Jaleel, B. Sankar, A. Kishorekumar, R. Somasundaram, G.M. Alagu Lakshmanan and R. Panneerselvam Growth, biochemical modifications and proline metabolism in Helianthus annuus L. as induced by drought stress. Colloids Surf. B: Biointerfaces, 59: Murti, G.S.R., K.K. Upreti Endogenous hormones and phenols in rootstocks seedlings of mango cultivars and their relationship with seedlings vigour. European J.Hort.Sci.68 : N.M. Al-Khassawneh, N.S. Karam, R.A. Shibli, Growth and flowering of black iris (Iris nigricans Dinsm.) following treatment with plant growth regulators, Sci. Hortic. 107 (2006) Noctor, G., C.H. Foyar Ascorbate and Glutathione: Keeping active oxygen under control. Annu. Rev. Plant Physiol. Plant Mil. Biol. 49: Omay, S.T., J.D. Turnbull, H.E. Sauberilich Selected methods for the determination of ascorbic acid in animal cells, tissues and fluids. Methods Enzymol. 11: Ozturk, L., and Y. Demir Effect of putrescine and ethephon on some oxidative stress enzyme activities and proline content in salt stressed spinach leaves. Plant Growth Regul., 40: Sairam, R.K., P.S. Deshmukh and D.C. Saxena, Role of antioxidant systems in wheat genotypes tolerance to water stress. Biol. Plantarum, 41: Sankar B., C.A. Jaleel, P. Manivannan, A. Kishorekumar, R. Somasundaram and R. Panneerselvam Drought induced biochemical modifications and praline metabolism in Abelmoschus esculentus (L.) Moench. Acta Bot. Croatica, 66: Sankar B., C.A. Jaleel, R. Somasundaram, P. Manivannan, A. Kishorekumar, R. Sridharan and R. Panneerselvam2006. Influence of triadimefon on the carbohydrate metabolism of salt stressed Abelmoschus esculentus (L.) Moench. seedlings. J. Theor. Exp. Biol., 2 (3 & 4): Senaratna, T., C.E. Mackay, B.D. McKersie and R.A. Fletcher Uniconazole induced chilling tolerance in tomato and its relationship to antioxidant content. J. Plant Physiol., 133: Sgherri, C., E. Cosi, F. Navari Izzo, Phenols and anti- oxidative status of Raphanus sativus grown in cropper excess Physiol. Plant 118 : Sgherri, C.L., M. Michada and M.I. Flavia Antioxidative enzymes in wheat subjected to increasing water deficit and reatering. J. Plant Physiol., 157: Sheela, A. and V. Pandey Stimulation of stress-related Antioxidative enzymes in combating oxidative stress in cassia seedlings. Indian J. Plant Physiol., 8(3): Singh, D.K., Effect of paclobutrazol on growth and bearing of mango cultivars. Ph.D. Thesis, Govind Ballabh Plant University of Agriculture and Technology, Pantnagar, Uttar Pradesh (Unpublished). 36. Smirnoff, N Antioxidant systems and plant response to the environment. In: N. Smirnoff (Ed.), Environment and plant metabolism flexibility and acclimation Bio-scientific publishers, Oxford, U.K., pp Tan Y., L. Zongsuo, S. Hongbo, D. Feng, Effect of water deficits on the activity of anti-oxidative enzymes and osmoregulation among three different genotypes of Radix astragali at seeding stage, Coll. Surf. B. Biointerfaces 49: Vanacker, H., T.L.W. Carver and C.H. Foyer Pathogen-induced changes in the antioxidant status of the apoplast in barley leaves. Plant Physiol., 117: Willekens, H., D. Inze, M. Van Montagu and W. Van camp Catalase in plants. Molecular Breeding. 1: Zancain, M.G. Nagy Phonol dependent H2O2 breakdown by soybean root plasma membrane bound peroxides is regulated by ascorbate and thiols. J Plant Physiol. 156 : Zhang J., W. Jia, J. Yang, A. M. Ismail Role of ABA in integrating plant responses to drought and salt stresses. Field Crops Research 97: Zhang J., W.Jia, J. Yang, A.M. Ismail Role of ABA in integrating plant responses to drought and salt stresses, Field crops Res. 97 : Source of support: Nil, Conflict of interest: None Declared