Journal
CHEMOSPHERE
Volume 131, Issue -, Pages 149-156Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2015.03.008
Keywords
Chloroplast; Cobalt; Lemnaceae; Lemna minor; Phytotoxicity; Starch accumulation
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Funding
- Science and Engineering Research Board, Govt. of India
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Cobalt (Co2+) inhibits vegetative growth of Lemna minor gradually from 1 mu M to 100 mu M. Fronds accumulated up to 21 mg Co2+ g(-1) dry weight at 10 mu M external Co2+ indicating hyperaccumulation. Interestingly, accumulation of Co2+ did not decrease the iron (Fe) content in fronds, highlighting L. minor as a suitable system for studying effects of Co2+ undisturbed by Fe deficiency symptoms unlike most other plants. Digital image analysis revealed the size distribution of fronds after Co2+ treatment and also a reduction in pigmentation of newly formed daughter fronds unlike the mother fronds during the 7-day treatment. Neither chlorophyll nor photosystem II fluorescence changed significantly during the initial 4 d, indicating effective photosynthesis. During the later phase of the 7-day treatment, however, chlorophyll content and photosynthetic efficiency decreased in the Co2+-treated daughter fronds, indicating that Co2+ inhibits the biosynthesis of chlorophyll rather than leading to the destruction of pre-existing pigment molecules. In addition, during the first 4 d of Co2+ treatment starch accumulated in the fronds and led to the transition of chloroplasts to chloro-amyloplasts and amylo-chloroplasts, while starch levels strongly decreased thereafter. (C) 2015 Elsevier Ltd. All rights reserved.
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