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Premise of the Study Nutrient resorption is essential for plant nutrient conservation. Large‐bodied plants potentially have large nutrient sink pools and high nutrient flux. Whether and how nutrient resorption can be regulated by plant size and biomass allocation are yet unknown. Methods Using the herbaceous plant Amaranthus mangostanus in greenhouse experiments for two consecutive years, we measured plant biomass, height, and stem diameter and calculated the root to shoot biomass ratio (R/S ratio) and nutrient resorption efficiency (NuRE) to assess the effects of plant body size and biomass allocation on NuRE. NuRE was calculated as the percentage reduction in leaf nutrient concentration from green leaf to senesced leaf. Key Results NuRE increased with plant biomass, height, and stem diameter, suggesting that the individuals with larger bodies, which led to a larger nutrient pool, tended to resorb proportionally more nutrients from the senescing leaves. NuRE decreased with increasing root to shoot ratio, which might have reflected the nutrient acquisition trade‐offs between resorption from the senescent leaves and absorption from the soil. Increased root biomass allocation increased the proportion of nutrient acquisition through absorption more than through resorption. Conclusions This study presented the first experimental evidence of how NuRE is linked to plant size (indicated by biomass, height, and stem diameter) and biomass allocation, suggesting that nutrient acquisition could be modulated by the size of the nutrient sink pool and its partitioning in plants, which can improve our understanding of a conservation mechanism for plant nutrients. The body size and root to shoot ratio effects might also partly explain previous inconsistent reports on the relationships between environmental nutrient availability and NuRE.

1. Olfactory cues can determine the host preferences of herbivorous insects, but their role in host shifting is unclear. Host specificity and the potential for host shifts are important criteria for screening and post-release evaluation of biological control agents for invasive plants. However, the role of olfactory cues in mediating host shifts in biological control agents is not well understood. 2. To investigate the role of olfactory cues in host selection of a reportedly monophagous flea beetle (Agasicles hygrophila), an important biocontrol agent for invasive alligator weed (Alternanthera philoxeroides), we extracted and analysed the volatiles produced by the host-plant A. philoxeroides and the non-host plants Alternanthera sessilis, Beta vulgaris and Amaranthus mangostanus. Moreover, we used electrophysiological techniques, behavioural bioassays and field trials to test the antennal responses and behavioural preferences of A. hygrophila to combinations of different plant volatiles and treatments, and pure compounds in different dosages and combinations. 3. We show that A. hygrophila female beetles indeed use olfactory cues to select plants for feeding and oviposition and that the survivorship of larvae on the second preferred non-host plant A. sessilis, a close relative of the first preferred host plant A. philoxeroides, was over 75% in a field trail. Although female beetles responded to many volatile compounds from host and non-host plants, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) positively encouraged the beetle's feeding and oviposition preferences, whereas (Z)-3-hexenol displayed repellent effect. Remarkably, complementation assays with (Z)-3-hexenol on host plant or DMNT on non-host plants significantly shifted A. hygrophila host preferences to non-host plants and resulted in oviposition and egg hatching on the non-host plant A. sessilis in field trials. 4. Synthesis. We demonstrate an olfactory mechanism by which a specialized herbivorous beetle uses the ratio of two common plant volatiles, (E)-4,8-dimethyl-1,3,7-nonatriene and (Z)-3-hexenol, to discriminate between its host and non-host plants in nature. This study highlights an important mechanism by which olfactory cues could lead to undesired host range expansion in biocontrol agent, thus representing an important warning of the potential for a host shift and development of invasiveness in a common biocontrol agent, the flea beetle.

Differences in cellular cadmium (Cd) distribution between Cd-tolerant and Cd-sensitive lines of amaranth ( Amaranthus mangostanus L.) may reveal mechanisms involved in Cd tolerance and hyperaccumulation. We compared the cellular distribution and accumulation of Cd in roots, stems, and leaves between a low-Cd accumulating cultivar (Zibeixian, L-Cd) and a high-Cd accumulating cultivar (Tianxingmi, H-Cd) in a hydroponic experimental system. In all treatments, H-Cd grew better than L-Cd and accumulated more Cd. As the Cd concentration increased, the H-Cd plants grew normally and their biomass increased, except in the 60 μM Cd treatment. The biomass of L-Cd decreased with increasing Cd concentrations. The highest Cd concentration in the roots, stems, and leaves of H-Cd was 950 mg/kg, 305 mg/kg, and 205 mg/kg, respectively, compared with 269 mg/kg, 62.9 mg/kg, and 74.8 mg/kg, respectively, in L-Cd. The Cd distribution differed between the two cultivars. Scanning and transmission electron microscopy and energy-dispersive spectrometry analyses showed that Cd was distributed across the entire cross section of H-Cd roots but largely restricted to the epidermal cells and the exodermis of L-Cd roots. The main Cd storage sites were the root apoplast, cell walls, and intercellular spaces in H-Cd and the root epidermal cells and the exodermis in L-Cd. In H-Cd leaves, Cd accumulated mainly in vacuoles of epidermal cells and, at high external Cd concentrations, in the vacuoles of mesophyll cells.

The effects of different concentrations of cadmium and 2,2′,4,4′,5,5′-hexabrominated diphenyl ether (BDE-153) on the growth and related physiological and biochemical indexes of Amaranthus mangostanus L. (amaranth) were studied. The results showed that the presence of BDE-153 promoted the absorption of Cd by the amaranth and inhibited the migration of Cd from the roots to the shoots. At the same time, 0.1 mg/L of Cd had a synergistic effect on the migration of BDE-153, but 5 mg/L Cd inhibited the accumulation of BDE-153 in the aboveground part of the amaranth. In addition, the kinetics of the uptake of pollutants by the amaranth showed that both Cd and BDE-153 could be transported by amaranth, but Cd and BDE-153 were mainly enriched in the roots, and the presence of Cd may cause a lag in the uptake of BDE-153 in the shoots. Compared with the control group, the biomass of the amaranth affected by BDE-153 and a high concentration of Cd (5 mg/L) decreased by 30.2–49.5%, the chlorophyll content decreased by 43.0–60.3%, the Evans blue increased, and the MDA content was higher. The activities of superoxide dismutase (SOD) and catalase (CAT) also decreased with an increase in the BDE-153 concentration. This indicates that the interaction between BDE-153 and a high concentration of Cd (5 mg/L) is more toxic to amaranth than single Cd pollution. This paper provides the necessary data support for phytoremediation of heavy metal and organic compound pollution.

Bone homeostasis is dynamically balanced between bone forming osteoblasts and bone resorbing osteoclasts. Osteoclasts play an important role in bone destruction and osteoporosis, and they are derived from monocyte/macrophages in response to macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor κB (NF-κB) ligand (RANKL). Amaranthus mangostanus L. (AM) is a plant with powerful antioxidant and other biological activities including anti-inflammatory, antidiabetic, and antihyperlipidemic effects. However, its effects on bone health are unknown. In this study, we explored whether AM could affect RANK-mediated osteoclastogenesis. AM significantly suppressed RANKL-induced osteoclast differentiation and expression of osteoclast-specific genes, TRAP, cathepsin K, NF-activated T-cells (NFATc1), and Dc-stamp in RAW 264.7 cells. Moreover, AM significantly inhibited extracellular signal-regulated kinase (ERK), Akt, and NF-κB signaling pathways in RAW 264.7 cells. In addition, AM preserved ovariectomy-induced bone loss in mice. Taken together, our results suggest that AM might be a potential candidate for the treatment of postmenopausal osteoporosis.

The present study was designed to investigate the residual decline pattern and the risk assessment of 10 different class pesticides, namely azoxystrobin, boscalid, diazinon, diethofencarb, difenoconazole, etofenprox, flubendiamide, paclobutrazol, and pyraclostrobin in young vegetative amaranth ( Amaranthus mangostanus ) sprayed once or twice under greenhouse growing conditions. Field-incurred samples, collected at 3, 7, or 10 days after application of both treatments, were extracted and purified with the quick, easy, cheap, effective, rugged, and safe “QuEChERS” citrate-buffered method and analyzed with liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/MS) in positive ion mode. The linearity was satisfactory with determination coefficients ( R 2 ) falling between 0.9817 and 0.9999 and limits of detection (LOD) and quantification (LOQ) values of 0.0007 and 0.002 mg/kg, respectively. The mean recovery rate at four spiking levels (equivalent to 5, 10, 50, and 100 × LOQ) ranged from 78.1 to 131.6% with a relative standard deviation (RSD) of < 11%. Substantial differences in the initial deposit between the tested analytes were observed and clearly indicated that the structure, as well as the initial concentration of applied products, greatly affected the residue deposit. From the obtained residual data, the provisional marginal maximum residue limits (MRLs) and the pre-harvest intervals (PHI) were proposed. Risk assessment was evaluated by comparing the theoretical maximum daily intake (TMDI) with the acceptable daily intake (ADI). Herein, the TMDI was lower than the ADI (TMDI/ADI ratio ≤ 80% set by the Korean Ministry of Food and Drug Safety) except for difenoconazole (80.92%, marginally higher), indicating that the vegetative amaranth is not hazardous and can be consumed safely by Korean consumers.

Industrial pollutants are known to affect the growth of plants and increase the costing of agricultural production. For ecological risk assessment, the toxicological screening benchmark concentrations of contaminants in soil and soil solution may use as the indicators for potential concern. The benchmark values were derived from the lowest values of the EC30 of the chemicals in tested plant species. As the economically important agricultural plant species in China are quite different from that of the North America, local data on the phytotoxicity of chemicals to local species should be a piece of valuable information. In the present studies, the method of seed germination and root elongation were used to estimate the EC50 and EC30 of 2,4,6-Trichlorophenol (TCP) and Phenol to six economically important local agricultural plants. The lowest EC30 of TCP in tested species was found to be one forth of the reference benchmark values, while the lowest EC30 of Phenol was similar to the benchmark concentration. The phytotoxicity of TCP was found to be more rigorous than that of Phenol in reducing the growth of local agricultural plants. For the tested agricultural species, Raphanus sativus \\“short-leave radish no. 13” was relatively insensitive to the effect of TCP and Phenol, while Amaranthus mangostanus \\“round-leaf green amaranth” was the most sensitive one. For the three species from the genus Brassica, they have similar sensitivity to both of the chemicals.