The influence of environmental condition on the creation of organic compounds in Pinus sylvestris L. rhizosphere, roots and needles

Zuzanna Magdziak,Bartłomiej Mazela,Andrzej Mocek,Bogusława Waliszewska,Piotr Goliński,Agnieszka Mocek-Płóciniak,Przemysław Niedzielski,Monika Gąsecka,Magdalena Zborowska,Tomisław Kozubik,Mirosław Mleczek,Wojciech J Cichy

doi:10.1007/s00468-020-02046-y

Abstract

Key messageStudied organic molecules in Pinus sylvestris L. seem to have acted as a safety net for metal transport, chelation and sequestration, allowing adaptation and growth under highly polluted conditions.Pinus sylvestris L. is known for its ability to survive in areas of highly elevated metal pollution, such as flotation tailings. The aim of the study was to estimate the content of selected organic molecules (including aliphatic low molecular weight organic acids (ALMWOAs), phenolic compounds and terpenes) and the physiological mechanisms underlying differences in metal/metalloid tolerance of P. sylvestris growing in unpolluted (soil) and polluted (flotation tailings) areas. The dominant ALMWOAs in rhizosphere soil extracts were citric acid followed by malic and oxalic acids, whereas in flotation tailings malic and oxalic acids. In roots and needles, the content of ALMOWAs was significantly higher in P. sylvestris L. tissue from flotation tailings in comparison to soil. Phenolic compounds were detected only in roots and needles, with a generally higher content of nearly all detected compounds from flotation tailings. The composition of roots did not contain all the compounds detected in needles. The profile of needles additionally contained four hydroxybenzoic, protocatechuic and salicylic acids. In pine needles, 24 volatile terpenes were identified in total. The content of these compounds in pine needles from the polluted area was markedly different from the unpolluted area. The dominant volatile monoterpenes in P. sylvestris L. needles from the unpolluted area was three carene, while in pine needles from the polluted area monoterpenes α-pinene was dominant.

Highlights

Soil contamination with toxic trace elements is widespread and has a significant impact on such specific ecosystem functions as found in soil (Huang et al 2016)
In the light of the diverse potential of the studied plants and limited literature data on the creation and exudation by woody plant roots of different organic compounds (aliphatic low molecular weight organic acids (ALMWOAs), enzymes, amino acids, phenolic compounds, simple and complex sugars, vitamins, purines, proteins and flavonoids) into the rhizosphere (Ryan et al 2001; Adeleke et al 2017; Magdziak et al 2017), we investigated the effects of flotation tailings in organic biomolecule activity in the rhizosphere
The results of our study pointed to a significant increase of phenolic compounds, suggesting they have a prevailing role in the defence mechanism connected with antioxidant mechanisms rather than a structural role associated with lignification, the precursors of lignin are present in roots

Summary

Introduction

Soil contamination with toxic trace elements is widespread and has a significant impact on such specific ecosystem functions as found in soil (Huang et al 2016). The above molecules, especially ALMWOAs and phenolic compounds, are essential factors for nutrient acquisition (Dinh et al 2017) They are present in the most abundance and are most reactive with metals (Koo et al 2010); they play a role in alleviation of anaerobic stress in roots as well as mineral weathering (Adeleke et al 2017). They influence several soil processes, e.g. sorption and desorption (Wang et al 2015), oxidation and reduction (Blaylock and James 1994) and precipitation and dissolution (Zhou et al 2007). In some of the previously mentioned studies, ALMWOAs and phenolic compounds have been found in plant tissues (mainly, roots and leaves) (Drzewiecka et al 2017; Magdziak et al 2017), where next to the rhizosphere, plants use ALMWOAs to transport, sequestrate and prevent cytoplasmic precipitation of toxic elements in cells, or in the case of phenolic compounds, in participation in adaptation and detoxification mechanisms mainly related to their structure and antioxidant properties (Ivanov et al 2012; Jiang et al 2017a, b; Benbettaieb et al 2018)

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