IJCRR - Vol 08 Issue 05, March
Date of Publication: 13-Mar-2016
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IMPACT OF CADMIUM ON GERMINATION AND EARLY SEEDLING GROWTH OF CAJANUS CAJAN L.
Author: Swapna B.
Abstract:Cadmium is a highly toxic heavy metal that contaminates soil and adversely affects the plant growth which results in the decrease of crop production. The objective of this study was to find the effect of cadmium on germination and early seedling growth of Cajanus cajan. Seeds placed on sterilized filter papers were exposed to varying concentrations of cadmium solutions (20, 60, 100, 200 and 400 ppm) made using anhydrous Cadmium chloride under laboratory conditions. Increasing concentrations of cadmium chloride significantly reduced the germination percentage, root length, shoot length, fresh weight, dry weight when compared to control.
Keywords: Cadmium, germination, Cajanus cajan, Proline
INTRODUCTION Heavy metals are the natural components of the earth crust and are present insoil, water and living matter. Elevated levels of heavy metals due to anthropogenic activities such as extended use of superphosphate fertilizers, sewage discharge, industrial effluents and smelters dust spreading cause heavy metal pollution. The uptake and accumulation of heavy metals by plants is hazardous, since plants are part of the food chain. Contamination of food supplies by heavy metals may lead to risk for human and animal health (1). Cadmium, one of the toxic heavy metals has no essential function in plants. It has high mobility in the soil- plant system. Plants exhibit numerous toxic effects as a result of cadmium exposure. The impact of cadmium on various crop plants and their morphological, physiological and molecular responses during stress has been well elucidated by many authors. Genotypic differences in response to cadmium exposure have been reported in various species including wheat (2), cotton (3), pea (4) and rice (5). This is may be due to high mobility of cadmium and its hyperaccumulation leading to leaf chlorosis (6). Such symptoms determine the severity of stress, and therefore may be useful in detecting stress effects and developing appropriate strategies to increase stress tolerance (7, 8). Pigeonpea (Cajanus cajan L.) is an important legume crop (Family-Fabaceae) in the semiarid tropics. It has high commercial and nutritive value. It is an ideal source of protein. The symptoms of cadmium toxicity and seedling survival have close association with each other and determine the final plant stand. Despite scattered information existing (1,9), the present study is carried out to explore the effect of cadmium on germination and early seedling growth of Pigeonpea (cvPushpa).
MATERIAL AND METHODS Seeds of Pigeon pea (Cajanus cajan (L.) Millspaugh) cv. Pushpa obtained from commercial vendors in the local market were surface sterilized using 0.1% HgCl2 and washed repeatedly with sterile distilled water to remove the remnants of adsorbed sterilants. The seeds were then transferred to the germination boxes lined with sterile filter papers for germination and subjected to varying concentrations of cadmium solutions (20, 60, 100, 200 and 400 ppm) made using anhydrous CdCl2 . Distilled water was used in place of cadmium solution to maintain the control. The experiment was conducted with three replications of fifteen seeds each.
For growth analysis, samples were collected on 7th day after sowing and growth parameters like % seed germination, root length, shoot length, fresh and dry weights were measured. Emergence of the radicle was taken as an index for the purpose of identifying seed germination. A cotton thread and cm ruler was used to measure the root length of the seedlings to the nearest mm. Fresh weight of the seedlings was recorded to the nearest mg using an electronic balance. The seedlings were oven dried at 800 C in a hot air oven to a constant dry weight and the data was recorded to the nearest mg using sensitive electronic balance. All the observations are means of three replications.
Seed Germination Percentage (G %): Percentage of seed germination (G %) was calculated by using the formula: G% = 100 × A / N, where A = Number of seeds found germinated N = Total number of seeds used in the germination test.
Proline accumulation during seedling development The accumulation of proline in the leaves was measured (10). Statistical Analysis Data represents mean± standard error. Dunnet’s test was performed to compare control and treatments. Values were considered significant if p< 0.05
RESULTS The percentage of germination decreased in the stress induced plants when compared to control (Fig 1). There was no germination found at 400ppm cadmium concentration. Hence, data on morphological parameters has not been recorded at 400ppm cadmium concentration. Emergence of radicle started on 3rd day after sowing(3DAS).Brown, stunted roots and leaf chlorosis are the visualsymptoms observed in the cadmium treated plants. Elevation in the concentrations of cadmium resulted in significant decrease in root length (Table 1).Shoots did not arise at 200ppm cadmium concentration. Shoot length, fresh weight, dry weight of Cajanus cajan seedlings decreased with increase of cadmium chloride concentrations (Table 1).The osmolyte proline content increased with high concentration of cadmium (Table 2).
DISCUSSION This study showed increasing levels of cadmium exposure is detrimental to Cajanus cajan which is evident from grad ual decrease in germination percentage and early seedling growth. Concentration dependent decrease in germination percentage might be attributed to physiological disturbance in mobilization of the reserve food materials(11). Reduction in root and shoot length may be due to alteration in water relations, nutrient uptake (12). Similar observations of reduction in root length, shoot length, fresh weight and dry weight with Cdcl2 treatment to Cajanus cajan L. (Upas-120) seeds were noticed (9). Reduction in root and shoot length indicated that Cd concentration produced toxic effects within 7 days. Proline is an aminoacid known to accumulate in plants on exposure to abiotic stress. Accumulation of proline may contribute to osmotic adjustment at the cellular level and enzyme protection stabilizes the structure of macromolecules and organelles. Increase in proline content may be either due to de novo synthesis or decreased degradation or both (7). Similar result has been reported in Brassicajuncea, Triticumaestivum and Vignaradiata in response to cadmium toxicity (13).
CONCLUSION Results of this study show that cadmium reduced seed germination and early seedling growth significantly in Cajanus cajan (L.) (Pushpa).
AKNOWLEDGEMENT Authors acknowledge the immense help received from the scholars whose articles are cited and included in references of this manuscript. The authors are also grateful to authors / editors / publishers of all those articles, journals and books from where the literature for this article has been reviewed and discussed.
1. Meena Deswal, Laura, J.S. Effect of cadmium on growth, yield and dry matter accumulation in Cajanus cajan L. International Journal of Current Research. 2014, 6(11):10019-10024.
2. Zhang G, Fukami M, Sekimoto H. Influence of cadmium on mineral concentrations and yield components in wheat genotypes differing in Cd tolerance at seedling stage. Field Crops Research2002;77:93-98.
3. Wu F, Wu H, Zhang G, Bachir DML. Differences in growth and yield in response to cadmium toxicity in cotton genotypes. Journal of Plant Nutrition and Soil Science 2004; 167:85-90.
4. Metwally A, Safronova VI, Bellimov AA, Dietz KJ. Genotypic variation of the response to cadmium toxicity in Pisumsativum L. Journal of Experimental Botany 2005; 56:167-178.
5. Wu F, Dong J, Jia G, Zheng S, Zhang G. Genotypic difference in the responses of seedling growth and Cd toxicity in rice (Oryza sativa L.). Agricultural Sciences in China 2006; 5:68-76.
6. Wang ME, Zhou QX. Joint stress of chlorimuron-ethyl and cadmium on wheat Triticumaestivumat biochemical levels. Environmental Pollution, 2006; 144:572-580.
7. Faizan S, Kausar S, Perveen R. Varietal differences for cadmium-induced seedling mortality, foliar toxicity symptoms, plant growth, proline and nitrate reductase activity in chickpea (Cicerarietinum L) Biology and Medicine, 3 (2) Special Issue: 196- 206, 2011
8. Ahmad P, John R. Effect of salt stress on growth and biochemical parameters of Pisumsativum L. Archives of Agronomy and Soil Science 2005; 51:665-672.
9. ArunaPatnaik, B. K. Mohanty. Toxic effect of mercury and cadmium on germination and seedling growth of Cajanus cajan L (Pigeon Pea) Annals of Biological Research 2013, 4 (3):123- 126.
10. Bates, L., R. Waldren, I. Teare. Rapid determination of free proline for water-stress studies. Plant and Soil, 1973; 39: 205–206.
11. De Andrade SAR, da Silveira APD. Mycorrhiza influence on maize development under Cd stressand P supply. Braz. J. Plant Physiol.2008; 20: 39-50.
12. Barcelo J, Poschenrieder C. Plant water relations as affected by heavy metal stress: a review. Journal of Plant Nutrition 1990; 13:1-37.
13. Dhir B, Sharmila P, Saradhi PP. Hydrophytes lack potential to exhibit cadmium stress induced enhancement in lipid peroxidation and accumulation of proline. Aquatic Toxicology 2004; 66:141-147.