Catechin production in roots of <i>Thujopsis dolabrata</i> var. <i>hondai</i> in soils on Mt. Hayachine with high Ni concentrations

Abstract

Mt. Hayachine in Iwate prefecture is characterized by serpentine site, which is known to have high concentrations of Ni. In general, few plants that can tolerate high concentrations of Ni can grow in serpentine soil. Thujopsis dolabrata var. hondai occurs naturally on Mt. Hayachine. In this study, we hypothesized that T. dolabrata var. hondai shows Ni tolerance due to detoxification by phenolics. We collected T. dolabrata var. hondai seedlings and root-zone soil from the Kadoma National Forest on Mt. Hayachine to analyze the concentrations of Ni, other heavy metals, and macronutrients. The seedling roots had high concentrations of Ni. Further, we conducted a pot experiment by using 1-month-old sterile seedlings grown in three types of sterilized soils-Kadoma soil (obtained from the Kadoma National Forest), Tsugaru forest soil, and nursery soil-and compared the concentrations of Ni, nutrients, and catechin, as well as the growth of seedlings in the different soils. The pot experiment indicated that the roots of seedlings grown in Kadoma forest soil contained high concentrations of Ni and catechin, which could act as an antioxidant and a possible Ni-chelating compound that detoxified Ni in the plant cells. We concluded that T. dolabrata var. hondai seedlings growing in the serpentine site of Mt. Hayachine accumulated Ni and could detoxify it by producing high concentrations of catechin.

Recent advances in woody plant: Preface to a special issue in Plant Root

“…hondai is naturally distributed in serpentine soils with high Ni content. Okimura et al (2015) showed that catechin production in the roots of T. dolabrata var. hondai, which exists naturally in serpentine soil with high Ni concentration, increased in high Ni concentration soil as compared to those in other soil conditions, suggesting that the roots of T. dolabrata var.…”

“…At any scale of study, we-root researchers-are interested in root traits, which contribute to plant functions, although studies at different scales may have different objectives depending on their focus, such as survival, growth, reproduction or harvest of individual plants, production, decomposition, soil formation, and retarding or driving succession through material cycling of ecosystems. This special issue contains four studies on roots of trees in Japan, on different themes and scales: the mechanisms of stress tolerance to excessive heavy metal soil (Okimura et al 2015), anatomical and morphological differentiation within a root system (Tawa and Takeda 2015), root biomass distribution patterns under competition (Hishi et al 2015), and response of tree organs to long-term N saturation (Nagakura et al 2015).…”