Zinc Toxicity in Tomato Plants

Transcription

1 World Applied Sciences Journal 24 (5): , 203 ISSN IDOSI Publications, 203 DOI: /idosi.wasj Zinc Toxicity in Tomato Plants P.Vijayarengan and G.Mahalakshmi Department of Botany, Annamalai university, Annamalainagar , Tamilnadu, India Submitted: Jul 5, 203; Accepted: Aug 2, 203; Published: Aug 29, 203 Abstract: Tomato (cultivar PKM ) plants were raised in pots containing e soil amended wi various levels of zinc (control, 50, 00, 50, 200 and 250 mg kg soil). Five replicates were maintained for each level. Morphological parameters like root and shoot leng, total leaf area and dry weight of root and shoot of tomato plants were recorded at an interval of 5 days (5, 30, 45, 60, 75, 90 and 05 day). Zinc treatment at all levels tested (except 50 and 00 mg kg ) decreased e various grow and yield parameters such as leng of e root and shoot, area of leaves and dry weight of root and shoot of tomato plants. However e 50 and 00 mg kg zinc level in e soil showed a positive effect on e overall grow and dry matter yield of tomato plants. Key words: Zinc Tomato Grow Dry matter yield INTRODUCTION Tomato (Lycopersicon esculentum Mill.) belonging to e family Solanaceae (2n = 24) is The term heavy metal commonly refers to metals originated from Sou America. It occupies a 3 eier wi a specific weight higher an 5 g/cm or an outstanding place among important vegetables of atomic number above 20. These properties are not e world. In India it is cultivated under ha of relevant for biological effects, yet e heavy metals land wi production of 7.9 lakh metric tonnes. Keeping enclose essential nutrients, beneficial elements and ese points in view e present investigation has been elements which, at e present stage of knowledge, are made to study e extent of zinc toxicity on grow and not considered to have a function in organisms. All of dry matter yield of tomato (Lycopersicon esculentum em become toxic at relatively low concentrations. But Mill.) cultivar PKM-. toxicity is not an exclusive characteristic of elements classed as heavy metals. So e heavy metals are a very MATERIALS AND METHODS heterogenous group of elements which greatly differ in eir chemical properties and biological functions. For Seed Materials: The experimental plant, e tomato is reason e term heavy metal is discredited [] and belongs to e family Solanaceae, and it is one of e e terms trace elements or trace metals are preferred important vegetables of e world. Certified seeds of by numerous auors [2]. In studies on metal toxicity tomato cultivar PKM- were obtained from e market. mechanisms a classification based on complex formation Seeds wi uniform size and weight were chosen for is considered e most appropriate [3]. But as Tiller [4] experimental purpose. pointed out heavy metal may be a useful umbrella term for metals classed as environmental pollutants. The term Pot Culture Experiments: Tomato (Lycopersicon heavy metal is also used for metals like aluminium which esculentum Mill.) cultivar PKM- plants were grown alough it is not heavy, plays an important role as toxic in pots in untreated soil (control) and in soil to which metal in acidic environments [5]. Among e myriad of zinc had been applied (50, 00, 50, 200 and 250 mg kg heavy metals zinc occupies e prominent position, since soil). The inner surface of pots were lined wi a it plays a vital role in e grow and development of polyene sheet. Each pot contained 6 kg of air dried soil. plants. Zinc is one of e essential nutrients of plants for The zinc as finely powdered (ZnSO 47H2O) was applied to normal grow and development. e surface soil and oroughly mixed wi e soil. Corresponding Auor: P. Vijayarengan, Department of Botany, Annamalai university, Annamalainagar , Tamilnadu, India. 649

2 World Appl. Sci. J., 24 (5): , 203 Fifteen seeds were sown in each pot. All pots were Shoot Leng (Cm Plant ): Shoot leng of tomato at watered to field capacity daily. Plants were inned to a different stages of grow under zinc stress is represented maximum of seven per pot, after a week of germination. in Table 2. Maximum shoot leng was recorded on 05 Each treatment including e control was replicated seven day at 50 mg kg (50.38) plants of tomato. 250 mg kg times. concentration plants of tomato showed e minimum leng of shoot (4.97) on 5 day. F-test values for e Sample Collection: The plant samples were collected at difference between zinc levels and sampling days were fifteen days intervals viz., 5, 30, 45, 60, 75, 90, 05 day for significant at %. e measurement of various morphomatrical grow parameters. Seven plants from each replicate of a pot was 2 Total Leaf Area (Cm Plant ): Total leaf areas of tomato analyzed for its various parameters and e average was under zinc stress recorded at different stages of grow calculated. These mean values were used for statistical are represented in Table 3. Total leaf area of tomato plants analysis. of 5 day were found to be.73, 2.92, 2.82,.5,.50 and.26 at control, 50, 00, 50, 200 and 250 mg kg soil Morphological Parameters: The various respectively. It increased in e subsequent sampling morphological parameters such as root leng, periods and decreased at high levels ( mg kg ) shoot leng, total leaf area and dry weight of root of zinc in e soil. ANOVA values were significant at % and shoot per plant were determined for every sample. for zinc levels and non significant for samplings days. The total leaf area was measured by LICOR Photoelectric area meter. Dry Matter Production (G Plant ) Root: The root dry weight of tomato plants raised in RESULTS various levels of zinc at different stages of grow is furnished in Table 4. When compared to e control zinc Morphological Parameters at 50 mg kg and 00 mg kg level in e soil increased Root Leng (Cm Plant ): The root leng of e dry weight of root and decreased e root dry weight tomato plants at different stages of grow under zinc at high levels ( mg kg ) in all e sampling days. stress is represented in Table. Root leng of Statistical analysis revealed significant (%) F-test values tomato increased at 50mg kg (6.28) and 00mg kg for zinc levels in e soil and sampling days. (4.28) on 05 day and decreased furer wi an increase of zinc level in e soil. The root Shoot: The results showed in Table 5, indicated at e leng of tomato increased in various sampling maximum shoot dry weight value occurred at 50 mg kg days and decreased wi an increase in e of tomato (.720) on 05 day. Minimum dry weight of concentration of zinc in e soil. F-test values were shoot was observed on 5 day at 250 mg kg (0.048). non significant for zinc levels and significant at % for F-test values calculated for e zinc levels and sampling sampling days. days were significant at %. Table : Effect of zinc on root leng (cm plant ) of Lycopersicon esculentum Mill. Zinc added in e soil (mg kg ) Control (+0.94) 4.60 (+33.72) 5.27 (+23.4) 8.78 (+4.39) 2.98 (+3.77) 4.27 (+22.48) 6.28 (+20.23) (+3.77) 3.57 (+3.77) 4.55 (+6.55) 8.50 (+.07) 0.02 (+.72) 2.4 (+6.52) 4.28 (+5.46) (-6.4) 3.42 (-0.58) 3.30 (-22.7) 6.74 (-9.85) 7.62 (-22.63) 9.67 (-6.99) 0.58 (-2.86) (-23.0) 3. (-9.59) 2.84 (-33.48) 6.5 (-22.59) 6. (-37.96) 8.95 (-23.7) 0.0 (-25.40) (-25.28) 2.90 (-5.69) 2.60 (-39.) 5.44 (-35.3) 5.27 (-46.49) 8.35 (-28.32) 9.02 (-33.38) Zinc levels.38 NS 6.62** ** Significant at per cent level NS- Non significant Per cent over control values are given in pareneses. 650

3 Table 2: Effect of zinc on shoot leng (cm plant World Appl. Sci. J., 24 (5): , 203 ) of Lycopersicon esculentum Mill. Zinc added in e soil (mg kg ) Control (+4.69) 4.75 (+29.95) 4.5 (+7.93) 23.8 (+.87) (+35.27) (+5.58) (+48.00) (+.73).74 (+3.43) 3.88 (+5.87) 2.92 (+5.79) (+2.0) (+9.05) (+7.45) (-3.3).34 (-0.08).62 (-.36) 8.25 (-.92) 2.87 (-.74) 28.7 (-9.85) 3.50 (-7.46) (-2.86).27 (-0.70) 8.45 (-35.54) 6.57 (-20.02) 9.3 (-22.) 22.4 (-30.48) (-26.73) (-3.56).02 (-2.90) 7.72 (-4.) 5.24 (-26.44) 8. (-26.95) (-34.56) (-3.72) Zinc levels 4.37** 4.48** ** Significant at per cent level Per cent over control values are given in pareneses. Table 3: Effect of zinc on leaf area (cm plant 2 ) of Lycopersicon esculentum Mill. Zinc added in e soil (mg kg ) Control (+68.78) (+88.30) 48.4 (+5.38) (+93.32) (+65.0) (+3.76) (+.4) (+63.00) (+60.52) (+2.65) 77.8 (+39.34) 3.90 (+20.99) (+.98) (+0.27) 50.5 (-2.7) 2.20 (-32.07) (-28.93) (-38.05) (-22.9) (-56.86) (-29.53) (-3.29) 9.89 (-44.93) (-45.06) (-47.8) (-44.05) (-60.35) (-45.79) (-27.6) 8.9 (-50.38) 2.04 (-7.4) (-54.29) (-57.58) (-65.65) (-48.02) Zinc levels 8.7**.20 NS ** Significant at per cent level NS-Non significant Per cent over control values are given in pareneses. Table 4: Effect of zinc on root dry weight (g plant ) of Lycopersicon esculentum Mill. Zinc added in e soil (mg kg ) Control (+58.97) (+35.29) (+45.90) (+72.90) (+86.97) (+57.64) (+67.6) (+35.89) (+7.84) (+36.06) (+30.6) (+47.59) 0.38 (+2.24) (+44.88) (-30.76) (-23.52) (-29.50) (-26.53) (-9.22) 0.27 (-5.58) (-27.46) (-38.46) (-39.2) (-42.62) (-38.54) (-25.73) (-27.6) (-37.20) (-56.4) (-58.82) (-45.90) (-58.37) (-4.70) (-45.38) (-54.37) Zinc levels 4.72** 8.39** ** Significant at per cent level Per cent over control values are given in pareneses. 65

4 Table 5: Effect of zinc on shoot dry weight (g plant World Appl. Sci. J., 24 (5): , 203 ) of Lycopersicon esculentum Mill. Zinc added in e soil (mg kg ) Control (+34.46) (+8.00) (+38.96) (+2.98) (+3.3).480 (+78.89).720 (+76.87) (+7.02) (-3.2) (+26.5) (+.43) (+6.87) (+8.68).242 (+28.23) (-4.46) (-22.82) (-23.97) (-9.50) 0.66 (-6.64) (-7.53) (-6.78) (-24.25) (-33.44) (-28.06) (-38.47) 0.0 (-36.39) (-26.38) (-32.9) (-37.02) (-3.50) (-37.60) (-53.65) (-38.82) (-38.00) (-4.86) Zinc levels 5.72** 4.90** ** Significant at per cent level Per cent over control values are given in pareneses. DISCUSSION The reduction in dry matter yield of plants at higher concentrations of heavy metals was also observed by Morphological Parameters Kalyanaraman and Sivagurunaan (cadmium, copper and Root and Shoot Leng: Root and shoot leng of tomato zinc) [7], Murugesan (copper) [8] and Vijayarengan plants decreased wi an increase in zinc level in e soil. (zinc) [8]. Root and shoot leng of tomato were found to be higher Zinc treatment at 50 and 00 mg kg soil level at 50 and 00 mg kg. Similar decrease in plant height was proved to be favourable for e overall grow of tomato observed by Sharma and Sharma (chromium)[6], plants. Under lower zinc application, improved root Moustakas et al. (lead) [7] and Vijayarengan (zinc) [8]. system helped e plant in better absorption of water and Zinc at high levels may inhibit e root grow directly by oer nutrients dissolved in it and consequently improved inhibition of cell division or cell elongation or e grow of different organs and e entire plant [9]. combination of bo, resulting in e limited exploration of The improvement in e grow efficiency of plant orgarn e soil volume for uptake and translocation of nutrients might also be due to beneficial effects of zinc treatments and water and induced mineral deficiency [9]. The results on e physiological activities and oer enzyme reaction of e present study also confirmed ese views. in e transformation of carbohydrates and activities of hexokinase of plants which were responsible in improving Leaf Area: Leaf area of tomato decreased wi increase in e grow of plant and its component organs ultimately e zinc content of e soil. However it increased at 50 and influencing e relative development of plant parts and 00 mg kg soil level. Similar reduction in total leaf area eir grow efficiency. Similar improvement in grow and due to chromium [6], cadmium and manganese [0], lead yield due to zinc application has been reported by [] and nickel [2] was observed. The decrease in leaf Sivasankar et al. [20]. The overall decrease in grow and area at higher concentration of zinc can be attributed to dry matter yield of tomato plants was due to e toxic eier a reduction in e number of cells as judged by effects of higher concentrations of zinc. It might also be Nieman [3] in e leaves of Phaseolus vulgaris or due to due to e reason at e stressed plants spent more reduction in cell size [4]. The metals might be inhibiting energy for eir survival in e hostile environment, which mitotic activity or producing cytological abnormalities, oerwise would be available for eir overall grow mutagenic activities and degradation of DNA [5]. processes. This led to e decrease in e overall grow of e stressed plants. Dry Matter Production: Dry matter yield in various parts of tomato varied according to zinc level. Dry matter of CONCLUSION root, stem, leaf and shoot was e highest at 50 and 00 mg kg zinc level, but it showed a gradual decline from From e present investigation it was concluded at 50 mg kg level onwards. There are large numbers of e 50 and 00 mg kg level of zinc in e soil was reports at e heavy metals increased e dry matter beneficial for e grow of tomato plants. The level of yield of various plant parts at lower levels [8, 6]. zinc in e soil above 50 mg kg proved to be toxic. 652

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