According to the ‘novel weapons hypothesis’, invasive success depends on harmful plant biochemicals, including allelopathic antimicrobial roots exudate that directly inhibit plant growth and soil microbial activity. However, the combination of direct and soil-mediated impacts of invasive plants via allelopathy remains poorly understood. Here, we addressed the allelopathic effects of an invasive plant species (Rhus typhina) on a cultivated plant (Tagetes erecta), soil properties and microbial communities. We grew T. erecta on soil samples at increasing concentrations of R. typhina root extracts and measured both plant growth and soil physiological profile with community-level physiological profiles (CLPP) using Biolog Eco-plates incubation. We found that R. typhina root extracts inhibit both plant growth and soil microbial activity. Plant height, Root length, soil organic carbon (SOC), total nitrogen (TN) and AWCD were significantly decreased with increasing root extract concentration, and plant above-ground biomass (AGB), below-ground biomass (BGB) and total biomass (TB) were significantly decreased at 10 mg·mL-1 of root extracts. In particular, root extracts significantly reduced the carbon source utilization of carbohydrates, carboxylic acids and polymers, but enhanced phenolic acid. Redundancy analysis shows that soil pH, TN, SOC and EC were the major driving factors of soil microbial activity. Our results indicate that strong allelopathic impact of root extracts on plant growth and soil microbial activity by mimicking roots exudate, providing novel insights into the role of plant–soil microbe interactions in mediating invasion success.
Cadmium (Cd) and lead (Pb) generally occur simultaneously with low concentration in soil. However, anthropogenic activities have significantly raised these non-biodegradable heavy metals and caused long-term deleterious effects on ecosystem health. To study single or combined effects of Cd and Pb on seed germination, early seedling growth and physiological response in Rhus typhina, a seed germination and sand culture experiment was established completely randomized with 0, 100, 300, and 500 mg•L -1 Pb(NO 3 ) 2 or 0, 25, 75, 125 mg•L -1 CdCl 2 individually or in combination. The present results showed seed germination and seedling growth of Rhus typhina decreased with increasing Cd and Pb, and the joint effect was more serious than single heavy metal stress. The lowest of seed germination rate (GR), germination index (GI), root length (RL) and shoot length (SL) in Rhus typhina decreased 65.85%, 73.46%, 84.33% and 61.95% compared to control in soil supplemented with combined Cd and Pb, respectively. The activity of superoxide dismutase (SOD), peroxidase (POD), malondialdehyde (MDA) and soluble protein (SP) changed significantly with increasing concentration of Cd and Pb, and MDA and POD played important roles in resisting Cd and Pb stress because of their significant correlation with seed germination and early seedling growth.
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