HYPERACCUMULATION OF CADMIUM IN MAIZE PLANT (Zea Mays)

Maize plant responses, in terms of growth and metal uptake, to different concentrations of cadmium ions (4, 20 µM) were analyzed in a hydroponic culture, for 2 weeks. For a 4 µM cadmium-contaminated environment, the maize plant presents the highest bioaccumulation level after 192 h, with a recovery degree of 52%, meanwhile, at a 20 µM concentration, the highest bioaccumulation was registered after 366 h, with a corresponding recovery degree after 288 h (10.56%). The translocation factor presented higher values for 20 µM induced contamination than for 4 µM, which means that increasing metal concentration in the medium increased the concentration in the upper parts of the plant. Anatomical sections of a maize plant (in a 4 and 20 µM cadmium-contaminated environment) were observed to evidence the changes in plant morphological structure. The efficiency of phytoextraction is related to the metal concentration in the environment and to the plant's ability to grow on polluted soil sites, concomitantly with a high biomass yield. Keywords: heavy metal, phytoremediation, bioaccumulation, translocation factor INTRODUCTION Heavy metal contamination is a serious environmental problem that limits crop production and threatens human health through the food chain. Cadmium, one of the most toxic environmental pollutants for plants, may interfere with numerous biochemical and physiological processes -including photosynthesis, respiration, nitrogen and protein metabolism, and nutrient uptake. Phytoremediation is an in situ nondestructive technique, characterized by the utilization of hyperaccumulator plant species to remove the heavy metals from soil. The suitability of a certain plant for heavy metal remediation is determined by various plant properties, such as heavy metal tolerance, size, growth rate and rooting depth, heavy metal accumulation in aboveground plant parts and climatic adaptation and pest resistance. 1,2 The aim of this research was to evaluate the maize plant responses to cadmium stress conditions, every 48 h, for 2 weeks, and the efficiency in phytoremediation processes. EXPERIMENTAL Maize seeds (Zea mays) were sterilized in the commercial bleaching agent HOCl (1%) for 30 min and rinsed with distilled water under stirring for 10 min, the process being repeated 3 times. The seeds were placed over moist filter paper disks in Petri dishes and stored in the dark at 25 ºC, with a view to their germination. The , 5 µM Fe) with the pH adjusted 3 to 6.8. The plastic pots were covered with an aluminum foil to prevent the development of photosynthetic algae. After 5 days of germination, seedlings of maize with the same size were assembled in each hydroponic unit. The volume of nutrient solution (150 mL) was not modified throughout the experiments, to avoid the variation of metal concentrations. Every 48 h and at the end of the assay (2 weeks), the contents of cadmium in the roots, stem and leaves, as well as the growth parameters of maize plants, were determined. The plant roots were rinsed in abundant tap and distilled water ALINA STINGU et al. 288 before mineralization. Maize plants separated into roots, stems and leaves were oven-dried at 60 ºC, until constant mass was reached, and then the plant tissues were digested 4 using HNO 3 (65%) and H 2 O 2 (30%), on a hot plate at 120 ºC, for at least 5 h. The measurement of the metal content in the solution was accomplished through AAS (using a GBC Avanta 2003 Atomic Absorption Spectrophotometer). To evaluate the growth rate of the maize plant every 48 h, in a cadmium-contaminated environment, the following formula was used: growth rate, % = 100 x (growth parameters at the beginning of the experiment -growth parameters at a considered time)/growth parameters at a considered time. Spectrophotometric quantification of heavy metal concentration in maize plant tissues permitted the evaluation of cadmium bioaccumulation, translocation factor and recovery: Bioaccumulation coefficient = (cadmium concentration µg/g dry plant tissue)/(cadmium concentration µg/mL nutrient solution); 5 Translocation factor (TF) = ratio of metal concentration in shoots/ratio of metal concentration in roots; 6 Recovery, % = metal content in shoot or root/metal content in the medium. 7 At the end of the experiment, histological cross-sections were obtained for maize roots. The sections were cut manually, using microtome and elder pith as a support. The histological sections were washed in sodium hypochlorite, then in acetic acid (to eliminate the cellular content) and distilled water. The sections were coloured with iodine green (1 min), washed in 90% ethylic alcohol and distilled water, then coloured with ruthenium red (1 min) and again washed in distilled water. RESULTS AND DISCUSSION In the first hours, under 4 µM cadmium stress conditions, an increasing trend in plant growth and development was observed, the maximum growth rate being registered at 144 h. 192 h after the beginning of the experiment, the growth process seemed to stop, being resumed after 48 h. For a 20 µM cadmium-contaminated environment, the maximum growth rate was registered in the first 48 h. After 192 h, a decreasing trend in plant growth was observed. Maize plant growth rate decreased with increasing cadmium concentration in the growth medium Cadmium concentration (μg/g dry mass) and content (μg/plant) in maize plant presented different values, as depending on metal contamination level. The highest values for cadmium concentration and content (390.04 μg/plant), under 4 µM stress conditions (15430.99 μg/g), were registered at 192 h. Reported to the 20 µM cadmiumcontaminated environment, the highest metal content (395.82 μg/plant) and concentration (22443.54 μg/g) were recorded at 228 and 336 h. These results could be correlated with the plant growth rat

Multiomics in the central Arctic Ocean for benchmarking biodiversity change.

Multiomics approaches need to be applied in the central Arctic Ocean to benchmark biodiversity change and to identify novel species and their genes. As part of MOSAiC, EcoOmics will therefore be essential for conservation and sustainable bioprospecting in one of the least explored ecosystems on Earth

Multiomics in the central Arctic Ocean for benchmarking biodiversity change

Multiomics approaches need to be applied in the central Arctic Ocean to benchmark biodiversity change and to identify novel species and their genes. As part of MOSAiC, EcoOmics will therefore be essential for conservation and sustainable bioprospecting in one of the least explored ecosystems on Earth

Antifungal activity of natural phenolic compounds on Saccharomyces Cerevisiae

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Wood Fibres for Papermaking

Firs and pines dominated the global picture of the raw materials for paper industry until the 1950s. At that time, the interest in introducing new species, mostly hardwoods, led the researchers intensify efforts to look for the fibrous characteristics and their combinations that could represent the relationship between fibres, pulp and paper. The pulp and paper industry has shown, mainly in the last two decades, a strong North-South displacement. This is to a large extent due to the favourable climate, which promotes the development of the trees. Similarly, the paper fibres have gone from being almost exclusively softwoods from natural forests of the Northern-Hemisphere cold regions, such as spruce and fir, to fast-growing species of short fibres, such as eucalyptus, and willow and poplar hybrids from plantations...Fil: Area, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Popa, Valentin I.. Technical University of Iasi; Rumani

Enhancing copper and lead bioaccumulation in rapeseed by adding hemp shives as soil natural amendments

The current study reveals the results of a phytoremediation process applied to a multi metal contaminated soil, located in close proximity to an energy power plant. Phytoremediation process was studied using the rapeseed cultivation, both in the presence and absence of hemp shives, considered as potential natural soil amendments. The physiological responses of the rapeseed plants, such as variations in length and accumulation of biomass, as well as the content of assimilating pigments were investigated. The concentrations of Cu (II) and Pb (II) ions have also been determined in soil and plants aiming at locating the metal ions in different organs of the plants. By using hemp shives as amendments, bioaccumulation of copper and lead ions in plant increases. The plants cultivated in the presence of high amounts of heavy metal ions have been characterized by an inhibition of growth and development that consisted in decrease of root and stem lengths, as well in the amount of biomass accumulated in different vegetative organs