Juncus bulbosus as a pioneer species in acidic lignite mining lakes: interactions, mechanism and survival strategies

Abstract

Bulbous rush (Juncus bulbosus) initiates plant colonization in extremely acid lakes resulting from coal mining operations. Various analytical techniques (methylene blue/agar method, Ti³⁺-citrate solution) X-ray diffraction (XRD), scanning electron microscopy (SEM), and Energy-dispersive X-ray (EDX) were used to assess the mechanisms and strategies employed by J. bulbosus to overcome the extreme conditions. The plant releases oxygen into the rhizosphere in turn increasing the redox potential and inducing iron oxide plaque formation. XRD showed that the iron oxide of the plaque is mainly goethite that has been developed in the presence of CO₂; SEM showed that there is a micro-space between the roots and sand grains which is inhabited by microorganisms. Furthermore, SEM-EDX studies on internal iron distribution demonstrate that iron toxicity is delayed by the physiological and biochemical structure of the plant. It is suggested that J. bulbosus uses a variety of mechanisms and strategies (morphological, physiological and biochemical adaptation) which are mainly complementary and which interact with each other to help J. bulbosus to manage its growth and survival in an extreme environment.