Effect of Heavy Metals on Seed Germination of Trigonella foenum-graceum L

Abstract

Contamination of soil by heavy metals is an ecological problem on a global level, this contamination affects agricultural crops in the area concerned. In the present study, Copper, Zinc and Chromium being heavy metals have been assessed for their injurious effects on seed germination and seedling growth of Trigonella foenum-graceum L. solutions of the heavy metals were prepared in concentrations ranging from1,3,5,10,50,100,200,300,500ppm for irrigating the seeds of the crop to be germinated in Petri-dishes for seven days. The young seedlings were studied for their response based on seed vigour index, length of radicle, length of plumule and fresh weight against seeds germinated using distilled water as control. It was observed that toxic effect of heavy metals on fenugreek growth was as follows: Cr>Cu>Zn on the basis of a decrease in germination percentage and overall poor health of the seedling. Key-wordsChromium, Copper, Zinc, Germination, Trigonella foenum-graceum L., Toxicity -------------------------------------------------IJLSSR----------------------------------------------INTRODUCTION Heavy metals are not pollutants but a component of the earth’s crust, it’s the excessive rise of anthropogenic activities over the past few decades has led to the contamination of soil and water presenting us with a problem of heavy metal pollution. Heavy are metallic elements with an atomic weight more than five and theyare highly toxic even at low concentration. Plants experience oxidative stress upon exposure to heavy metals that leads to cellular damage and disturbance of cellular ionic homeostasis (1). Some plant species have capacity to grow in the metal contaminated soil and accumulate elevated amount of heavy metals (hyper-accumulation) as an eco-physiological adaptation in metalliferous (2). Sources of Cu contamination include mining and smelting, urban, industrial and agricultural wastes, and the use of agrochemicals. Copper is present in many forms in soils, with free Cu2+ activity considered to be the best indicator of bioavailability (3). The effect of Cu toxicity is largely on root growth and morphology. Access this article online Quick Response Code: Website: www.ijlssr.com DOI: 10.21276/ijlssr.2016.2.4.27 Chromium is an environmental pollutant that ranks seventh in abundance within the earth crust (4). Chromium is used on a large scale in many industries, including metallurgical, electroplating, production of paints and pigments, tanning, wood preservation, chromium chemicals production, pulp and paper production (5). Zinc is an essential nutrient with a vital role as a cofactor of enzymes, synthesis of chlorophyll and carotenoids, regulation of cytoplasmic concentration of nutrients, albeit in high doses it causes abiotic stress and affects plant growth negatively. Considerable work on plants and heavy metals has been reviewed by several authors (6-7). Germination and early seedling growths have been regarded as critical phases, which are greatly influenced by stressful conditions (8). Growth changes are the first most obvious reactions of plants under stress. Heavy metals uptake and accumulation in plants have been shown to result in negative effects on plant growth (9). Several plants such as Amaranthus viridis L., Oryza sativa L., Vigna radiata L., Abelmoschus esculentus, Brassica juncea L. (10) have been studied for their phytotoxic responses to chromium as well as for their phyto-remediation potential. The present study was conducted to investigate and compare the detrimental effects of varying concentrations of chromium, copper and zinc on Trigonella foenum-graecum L. to understand the response of this plant to metal stress and illustrate its tolerance potential for the same. Research Article (Open access) Int. J. Life. Sci. Scienti. Res., VOL 2, ISSUE 4 http://ijlssr.com IJLSSR © 2015 All rights are reserved Page 489 MATERIALS AND METHODS The research was conducted over a period of 10 months at the department of Botany, Rizvi College of arts, science and commerce, Mumbai, India. Seeds of Trigonella foenum-graecum L. were obtained from Namdeo Umaji Agritech (India) Pvt. Ltd. Different concentration solutions of Chromium, Copper and Zinc was prepared using anhydrous potassium dichromate (K2Cr2O7), Copper sulphate pentahydrate (CuSO4.5H2O) and Zinc suphate monohydrate (ZnSO4) of analytical grade obtained from Loba Chemie. 1, 3, 5, 10, 50,100,200,300,500 ppm solutions were prepared for each metal. Ten surface sterilized seeds uniform in colour, weight and size were placed on a Petri dish (9 cm diameter) on double-layered Whatman filter paper No. 1. The seeds were sterilized using Bavistin solution for 5 minutes followed by a through rinse, using distilled water. The filter paper was moistened with varying concentrations of heavy metal solutions, 5mL on the first day followed 2 ml on alternate days for 7 days. Triplicates of each treatment in completely randomized designed were studied along with a separate control series using distilled water. Germination indices i.e. total germination (also known as final germination percentage) (GT) and Seedling vigour index (SVI) (11), length of the radical, length of the plumule and fresh weight were recorded at the end of seven days. Total Germination: the final Germination percentage is a measure of the time for a population of seeds to germinate in order to estimate its viability and is expressed as a percentage (%). The total germination (GT) was calculated using the following formula: GT = No. of seeds germinated/Total seeds x 100 Seedling vigour index was calculated by following formula: SVI = Germination % × Seedling length (cm) Seedling length = RL + SL Where, RL is root length (cm), SL is shoot length RESULTS AND DISCUSSION Effect of Heavy Metals on Total Germination of Trigonella foenum-graceum L. A general trend observed in the present study reveals that higher concentration of Chromium, Copper and Zinc solutions adversely affected the germination of selected angiospermic plants (Table1). Chromium interferes with several metabolic processes, causing toxicity to plants as exhibited by reduced seed germination or early seedling growth (12). Metabolic alteration has also been reported in plants as the direct effect on enzymes and metabolites or by its ability to generate ROS (13). Even tough Cu and Zn are considered to essential micro nutrients, there is a clear decrease in total germination when subjected to higher concentrations. The effects of copper on germination of fenugreek remained fairly unaffected by concentrations below 100ppm with a noticeable drop in the germination percentage thereafter. The reduced germination of seeds under Cr stress would be due to the depressive effect of Cr on the subsequent transport of sugars to the embryo axis (14). Protease activity increases simultaneously with the chromium treatment which could also contribute to the reduction in germination of chromium treated seeds (14). Table 1 – Effect of Heavy Metals on Total Germination of Trigonella foenum-graceum L Total germination (%) ppm Cr6+ Cu2+ Zn2+

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