Giant Duckweed ( Spirodela polyrhiza ) Root Growth as a Simple and Sensitive Indicator of Copper and Chromium Contamination.

Abstract

Aquatic environment are often contaminated with heavy metals from various industrial sources. However, physicochemical techniques for pollutant detection are limited, thus prompting the need for additional bioassays. We investigated the use of greater duckweed ( Spirodela polyrhiza ) as a bioindicator of metal pollution. We exposed S. polyrhiza to four pollutants (namely, silver, cadmium, copper, and chromium) and assessed metal toxicity by measuring its frond area and the length of its regrown roots. The plant displayed significant differences in both frond size and root growth in response to the four metals. Silver was the most toxic (EC 50 = 23 µg L -1 ) while copper the least (EC 50 = 365-607 µg L -1 ). Direct comparisons of metal sensitivity and the reliability of the two endpoint assays showed that root growth was more sensitive (lower in terms of 50% effective concentration) to chromium, cadmium, and copper, and was more reliable (lower in terms of coefficient of variation) than those for frond area. Compared to conventional Lemna -based tests, the S. polyrhiza test is easier to perform (requiring only one 24-well plate, 3 mL of medium and a 72-h exposure). Moreover, it does not require livestock cultivation/maintenance, making it more suitable for repeated measurements. Measurements of S. polyrhiza root length may be suitable for assessment when copper and chromium in municipal and industrial wastewater exceed the environmentally permissible levels.

Plant phenotyping relevance

薬物汚染評価の生物学的目的を含むが、根長・葉状体面積をエンドポイントとする植物バイオアッセイを比較検証し、感度と再現性を評価しているため、表現型取得法が中心的である。

Code and data availability

The article reports duckweed metal-toxicity bioassays (frond area and root length measurements analyzed with ImageJ, ANOVA in Excel, SSD fitting in R, EC50 via ToxCalc), but no public phenotype dataset, image collection, analysis code, or supplement with such assets is mentioned. The Data Availability Statement only re

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