Indicators of heavy metal toxicity in duckweed (Lemna minor L.) and onion (Allium cepa L.)

Vujčić, Valerija (2008) Indicators of heavy metal toxicity in duckweed (Lemna minor L.) and onion (Allium cepa L.). Diploma thesis, Faculty of Science > Department of Biology.

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Abstract

Duckweed (Lemna minor L.) is often used as a plant model because it is a widely spread monocot, multiplies rapidly and shows tremendous metal accumulating capacity. Onion (Allium cepa L.) is suitable candidate for genotoxicity studies because it has a small number of large chromosoms (2n = 16). Heavy metals enter the plant tissues through the root system and then mobilize to leaves causing chlorosis and growth inhibition. I investigated phytotoxic and genotoxic effects of heavy metals present in chosen surface (Sava Županja, Sava Jesenice i Sutla Prišlin taken every month during 3 months) and waste waters (ZGOS taken every 4 hours during 24 hours and Jakuševac) using duckweed and onion as plant test systems. Plant material was harvested after seven days (duckweed) or 24 hours (onion). Essential and non-eseential heavy metals were determinated by atomic absorption spectrometry. I monitored the relative frond number, relative fresh weight, chlorophyll and carotenoid contents, guaiacol peroxidase activity and cytogenetic analysis. All samples of tested waters caused growth inhibition, decrease of chlorophyll and carotenoid contents and decline of guaiacol peroxidase activity. Activity of that antioxidant enzyme increased only in ZGOS 4 and 5 samples. Water samples containing heavy metals caused the inhibition of onion root length and morfological changes of root tips such as crochet hooks. Consequently, mitotic index declined and the number of cells in each fase of cell cycle decreased as well. Cytogenetic analysis revealed the highest number of chromosome aberrations in both waste waters and surface water Sutla Prišlin. The most frequent chromosome aberrations as sticky chromosomes, c-mitosis and lagging chromosomes were most probably caused by increased quantities of lead, mercury and chromium in water samples. Results obtained in this work indicate that surface and waste waters contains toxic and genotoxic compounds that may impact aquatic ecosystem but also present potential risk to all living organisms.

Item Type: Thesis (Diploma thesis)
Keywords: phytotoxicity, Lemna minor, Allium cepa, genotoxicity
Supervisor: Pevalek-Kozlina, Branka
Date: 2008
Number of Pages: 50
Subjects: NATURAL SCIENCES > Biology
Divisions: Faculty of Science > Department of Biology
Depositing User: Silvana Šehić
Date Deposited: 12 Sep 2014 11:41
Last Modified: 17 Sep 2014 12:48
URI: http://digre.pmf.unizg.hr/id/eprint/2743

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