Journal Article

Root Fungal Endophytes Enhance Heavy-Metal Stress Tolerance of Clethra barbinervis Growing Naturally at Mining Sites via Growth Enhancement, Promotion of Nutrient Uptake and Decrease of Heavy-Metal Concentration

山路 恵子, Yui Hiroshi, Shigeto Arisa, Haruma Toshikatsu, Watanabe Yumiko, Yamaji Keiko, Masuya Hayato

2016

Overview

Clethra barbinervis Sieb. et Zucc. is a tree species that grows naturally at several mine sites and seems to be tolerant of high concentrations of heavy metals, such as Cu, Zn, and Pb. The purpose of this study is to clarify the mechanism(s) underlying this species' ability to tolerate the sites' severe heavy-metal pollution by considering C. barbinervis interaction with root fungal endophytes. We measured the heavy metal concentrations of root-zone soil, leaves, branches, and fine roots collected from mature C. barbinervis at Hitachi mine. We isolated fungal endophytes from surface-sterilized root segments, and we examined the growth, and heavy metal and nutrient absorption of C. barbinervis seedlings growing in sterilized mine soil with or without root fungal endophytes. Field analyses showed that C. barbinervis contained considerably high amounts of Cu, Zn, and Pb in fine roots and Zn in leaves. The fungi, Phialocephala fortinii, Rhizodermea veluwensis, and Rhizoscyphus sp. were frequently isolated as dominant fungal endophyte species. Inoculation of these root fungal endophytes to C. barbinervis seedlings growing in sterilized mine soil indicated that these fungi significantly enhanced the growth of C. barbinervis seedlings, increased K uptake in shoots and reduced the concentrations of Cu, Ni, Zn, Cd, and Pb in roots. Without root fungal endophytes, C. barbinervis could hardly grow under the heavy-metal contaminated condition, showing chlorosis, a symptom of heavy-metal toxicity. Our results indicate that the tree C. barbinervis can tolerate high heavy-metal concentrations due to the support of root fungal endophytes including P. fortinii, R. veluwensis, and Rhizoscyphus sp. via growth enhancement, K uptake promotion and decrease of heavy metal concentrations.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Analysis / Biodegradation, Environmental / Biology and Life Sciences / Branches / Cadmium / Chlorosis / Clethra / Clethra barbinervis / Clethraceae - drug effects / Clethraceae - growth & development / Clethraceae - microbiology / Copper / Endophytes / Endophytes - drug effects / Endophytes - growth & development / Environmental science / Flowers & plants / Food / Fungi / Heavy Metal Poisoning / Heavy metals / Inoculation / Lead / Leaves / Medicine and Health Sciences / Metal concentrations / Metals / Metals, Heavy - toxicity / Microorganisms / Mining / Morphology / Mycoses / Nickel / Nutrient concentrations / Nutrient uptake / Nutrients / Phialocephala fortinii / Physical Sciences / Plant Roots - drug effects / Plant Roots - growth & development / Plant Roots - microbiology / Plant species / Poisoning - etiology / Poisoning - prevention & control / Promotion / Roots / Seedlings / Shoots / Soil contamination / Soil microorganisms / Soils / Species / Statistics / Toxicity / Trees / Zinc