Deposition of an iron oxide plaque or coating on roots of rice (Oryza sativa L. cv. M-201 84 Biggs) ameliorated the toxic effects of copper (Cu), nickel (Ni), and Cu + Ni on plant growth and affected patterns of metal uptake and accumulation. Plaque was formed on plants during 24 h in an anaerobic solution containing 20 mg ∙ L−1 iron at pH 5.5. Subsequently two additional coatings were deposited after new growth of roots. Plants were grown hydroponically in one-quarter strength Hoagland's solution and exposed to Cu (0.5 mg ∙ L−1), Ni (2.0 mg ∙ L−1), or Cu + Ni; exposure to metals lasted 21 – 45 days. At the end of the experimental period growth was estimated as total biomass, dry weight of root, dry weight of shoot, length of leaf, and length of root. After harvesting, Fe, Cu, and Ni concentrations in plaque were measured using a dithionite–citrate–bicarbonate extraction, and internal Fe, Cu, and Ni concentrations were measured in roots and leaves using atomic absorption spectrophotometry. Formation of the palque did not affect growth of plants in control solutions. When exposed to Cu, plants with plaque had significantly larger biomass, dry weight of roots, dry weight of leaves, and growth increments of root and leaf than plants without plaque. When exposed to Ni, plants with plaque had signifiantly higher increment in leaf growth than plants without plaque. When exposed to Ni + Cu, plants with plaque had significantly higher biomass than plants without plaque. Toxic symptoms were not observed on plants with plaque grown with excess copper, while all other plants exposed to metals showed chlorosis, necrosis, or both. Metals were detected on the surface of roots, whether plants were allowed to develop a plaque or not. Cu, Ni, and Fe were concentrated in plaque and in roots. Lower concentrations of Cu and Ni were found in leaves of plants with a plaque than in plants without plaque. Comparisons of concentrations of Fe, Cu, and Ni with those of other species grown under field conditions are made. Key words: rice, iron plaque, toxicity of Cu and Ni.
The alien invasive vine Vincetoxicum rossicum (Kleopow) Barbar. is problematic in the Lower Great Lakes Basin of North America. The lack of effective control strategies exacerbates the need for a better understanding of the growth and reproductive potential of V. rossicum. Thus, a 2-year field experiment was performed in a field site in 2003 and 2004 that was densely colonized by V. rossicum. Mean height of V. rossicum stems was 20% and 45% greater in naturally shaded plots compared with plots receiving full sun in 2003 and 2004, respectively. During the 2-year study, the density of stems 10 cm or taller averaged 134 stems·m–2, substantially greater than reported in previous field studies for this species. The high densities of stems and seedlings indicate that this field site may be near or at carrying capacity. Each stem produced, on average, 17 mature follicles with some stems producing as many as 100 follicles. Each follicle yielded an average of 15 seeds, each composed of an average of two viable embryos. A typical V. rossicum stand in this site produced as many as 54 000 seedlings·m–2 annually. More flowers (2400 flowers·m–2), follicles (2250 follicles·m–2), and total seeds (32 000 seeds·m–2) were produced in plots receiving intermediate light compared with plants in full sun (1650 flowers·m–2, 1600 follicles·m–2, and 25 000 seeds·m–2) or shaded (1600 flowers·m–2, 2000 follicles·m–2, and 28 000 seeds·m–2) plots. Seeds harvested from follicles in the low light plots were 41% more likely to be dormant than seeds collected from follicles in full sun plots. Seeds collected from plants in full sun plots had the lowest frequency (∼36%) of single embryo seeds and the highest frequency (∼64%) of multiple embryo seeds. These findings suggest that V. rossicum growth and reproductive output is influenced by light environment. While competitive strategies differ between the light environments, the decrease in viability and germination in shaded sites may not be large enough to affect population growth over multiple generations. The substantially greater growth and reproduction of V. rossicum reported in this study relative to previous research may explain the increasing abundance and range expansion of this species in many Lower Great Lakes regions of Ontario and New York State.
To cite this article: S. Greipsson (1994) Effects of iron plaque on roots of rice on growth and metal concentration of seeds and plant tissues when cultivated ABSTRACT: Deposition of iron (Fe) plaque on roots of rice before exposure to excess of copper (Cu) was found to lessen the toxic effects of Cu. In the excess of Cu, plants with Fe plaque had significantly greater dry weight of roots and leaves, longer leaves, and roots, and higher concentration of Fe in leaves than plants without plaque. In the excess of Cu, plants without Fe plaque had more leaves showing chlorosis than plants with plaque. Iron plaque on roots appeared to be beneficial for seed formation, since plants with plaque grown without exposure to excess Cu had highest seed weight, although differences were not significant. In the excess Cu solution, plants with plaque had significantly more Fe in seeds and more Cu in roots and in the DCB (dithionite-citrate-bicarbonate) wash than plants without plaque.
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