Inhibition of iron deficiency stress response in cucumber by rare earth elements

Effect of Gallium Exposure in Arabidopsis thaliana is Similar to Aluminum Stress

Although gallium (Ga) is a rare element, it is widely used in semiconductor devices. Ga contamination of the environment has been found in semiconductor-producing countries. Here, the physiological and molecular impacts of Ga in the model plant Arabidopsis thaliana were investigated in medium culture. The primary symptom of Ga toxicity is inhibition of root growth. The increased production of malondialdehyde (MDA) suggests that Ga stress could cause oxidative damage in plants. Roots were the main Ga accumulating sites. The distinctive Ga granules were deposited within the intercellular space in roots. The granules are Ga(OH)₃ precipitation, which indicates immobilization or limited translocation of Ga in A. thaliana. Ga stress induces root secretion of organic acids such as citrate and malate. The expression of the transporters AtALMT and AtMATE, responsible for citrate and malate secretion, respectively, were elevated under Ga stress, so the secretion may play a role in the resistance. Indeed, supplying exogenous citrate significantly enhanced Ga tolerance. The overall response to Ga exposure in A. thaliana is highly similar to that with aluminum stress. Our findings provide information for risk assessment in Ga-contaminated soil.

Distribution of YLOID in soil-grapevine system (Vitis vinifera L.) as tool for geographical characterization of agro-food products. A two years case study on different grafting combinations

The knowledge of a chemistry relationship between the soil and the agricultural products is an important tool for the quality assessment of food. We studied YLOID (Y, La and lanthanoids), recognized as very useful tracers due their coherent and predictable behavior, to trace and evaluate their distribution from soil to the grape in Vitis vinifera L. Because much of the world's viticulture is based on grafting, and rootstocks have proved affect vine growth, yield, fruit and wine quality, we carried out experimental trials to analyse the YLOID distribution of two different red cultivars, grafted onto six different rootstocks, on the same soil. The YLOID amounts, the relationship Heavy vs Light YLOID and the pattern of YLOID were calculated. The results showed that the different grafting combinations were not able to induce significant differences in YLOID uptake from the soil maintaining the same fingerprint (with the exception of Eu).

DNA-protein cross-links involved in growth inhibition of rice seedlings exposed to Ga

Hydroponic experiments were conducted with rice seedlings (Oryza sativa L. cv. XZX45) exposed to gallium nitrate (Ga(3+)) to investigate the accumulation of Ga in plant tissues and phytotoxic responses. Results showed that phyto-transport of Ga was apparent, and roots were the dominant site for Ga accumulation. The total accumulation rates of Ga responded biphasically to Ga treatments by showing increases at low (1.06-8.52 mg Ga/L) and constants at high (8.52-15.63 mg Ga/L) concentrations, suggesting that accumulation kinetics of Ga followed a typical saturation curve. Higher amount of Ga accumulation in plant tissues led to significant inhibition in relative growth rate and water use efficiency in a dose-dependent manner. DNA-protein cross-links (DPCs) analysis revealed that overaccumulation of Ga in plant tissues positively stimulated formation of DPCs in roots. Likewise, the measure of root cell viability evaluated by Evan blue uptake showed a similar trend. These results suggested that Ga can be absorbed, transported, and accumulated in plant materials of rice seedlings. Overaccumulation of Ga in plant tissues provoked the formation of DPCs in roots, which resulted in cell death and growth inhibition of rice seedlings.

Nano-CuO and interaction with nano-ZnO or soil bacterium provide evidence for the interference of nanoparticles in metal nutrition of plants

The expansion of nanotechnology raises concerns about the consequences of nanomaterials in plants. Here, the effects of nanoparticles (NPs; 100-500 mg/kg) on processes related to micronutrient accumulation were evaluated in bean (Phaseolus vulgaris) exposed to CuO NPs, a mixture of CuO and ZnO (CuO:ZnO) NPs, and in CuO NP-exposed plants colonized by a root bacterium, Pseudomonas chlororaphis O6 (PcO6) in a sand matrix for 7 days. Depending on exposure levels, the inhibition of growth by CuO NPs was more apparent in roots (10-66 %) than shoots (9-25 %). In contrast, CuO:ZnO NPs or root colonization with PcO6 partially mitigated growth inhibition. At 500 mg/kg exposure, CuO NPs increased soluble Cu in the growth matrix by 23-fold, relative to the control, while CuO:ZnO NPs increased soluble Cu (26-fold), Zn (127-fold) and Ca (4.5-fold), but reduced levels of Fe (0.8-fold) and Mn (0.75-fold). Shoot accumulations of Cu (3.8-fold) and Na (1-fold) increased, while those of Fe (0.4-fold), Mn (0.2-fold), Zn (0.5-fold) and Ca (0.5-fold) were reduced with CuO NP (500 mg/kg) exposure. CuO:ZnO NPs also increased shoot Cu, Zn and Na levels, while decreasing that of Fe, Mn, Ca and Mg. Root colonization reduced shoot uptake of Cu and Na, 15 and 24 %, respectively. CuO NPs inhibited ferric reductase (up to 49 %) but stimulated cupric (up to 273 %) reductase activity; while CuO:ZnO NPs or root colonization by PcO6 altered levels of ferric, but not copper reductase activity, relative to CuO NPs. Cu ions at the level released from the NPs did not duplicate these effects. Our findings demonstrate that in addition to the apparent phytotoxic effects of NPs, NP exposure may also have subtle impacts on secondary processes such as metal nutrition.

Laboratory assessment of uptake and toxicity of lanthanum (La) in the leaves of Hydrocharis dubia (Bl.) Backer

Increasing amounts of lanthanum (La) is released into aquatic environments. However, little information is available on the influence of La on aquatic plants. In this study, physiological and ultrastructural responses of Hydrocharis dubia (Bl.) Backer leaves to elevated concentrations of La (up to 160 μM) were investigated. The accumulation of La was found to be increased in a concentration-dependent manner. La disturbed the intrinsic balance of nutrient elements (P, Mg, Ca, Fe, K, and Zn). Pigment content decreased with the rise of the La concentrations and the EC(50) value for chlorophyll was 20 μM on day 7. The antioxidants (superoxide dismutase, peroxidase, catalase, reduced ascorbate, and reduced glutathione) exhibited varied response to the La treatments. Malondialdehyde content enhanced gradually at all La concentrations. The enhancement in proline content was found in a concentration-dependent manner. The amounts of three polypeptides with apparent molecular weights of 61.9, 51.5, and 16.7 kDa, respectively, were gradually diminished, as well as one existing polypeptides with apparent molecular weight of 22.3 kDa, elevating in response to increasing La concentrations. Significant damage to the chloroplast, mitochondrion, and nucleus was imposed by La indicated a general disarray in the cellular functions. The negative effects of La on H. dubia unequivocally indicate that La could exert an adverse influence on aquatic ecosystem and should lead to a more careful discharge of such elements into water environment.