Influence of iron on mineral status of two rice (Oryza sativa L.) cultivars

Abstract

Iron is an essential nutrient for plants. In aerobic conditions, Fe is highly unavailable for plant uptake, and Fe deficiency can be severe in plants grown in calcareous soils. In waterlogged soils, however, Fe availability increases and can reach toxic concentrations. Rice is an important staple crop worldwide and faces iron deficiency or excess, depending on the growth conditions. To contribute to the study of mechanisms involved in response to Fe deficiency and resistance to Fe excess, experiments were carried out with rice cultivars BR-IRGA 409 (I409, susceptible to Fe toxicity) and EPAGRI 108 (E108, resistant to Fe toxicity) grown in culture solutions and submitted to Fe excess, control concentration or deficiency (500, 6.5 or zero mg L-1 Fe, respectively). Analysis of shoot dry weight confirmed the resistance of E108 plants to Fe excess. Mössbauer spectroscopy analysis indicated the presence of four different Fe3+compounds. The parameters obtained match those expected for ferrihydrite, lepidocrocite (and/or citrate) and Fe-nicotianamine. Mineral concentrations were determined using the PIXE (Particle Induced X-Ray Emission) technique. E108 plants had lower Fe concentrations than I409 plants when exposed to excess Fe. Except for lower Mn levels in roots and shoots, the excess of Fe did not result in lower nutrient concentrations in the susceptible cultivar compared to the resistant one. I409 plants seem to be affected directly by Fe toxicity rather than by secondary effects on mineral nutrition, whereas E108 plants seem to make use of the avoidance mechanism in the resistance to Fe overload. Both cultivars responded to Fe deficiency with allocation of P from roots to shoots. In addition to being more resistant to iron overload, E108 plants seem to be more efficient in inducing Fe deficiency responses.

Whole-plant mineral partitioning during the reproductive development of rice (Oryza sativa L.)

“…First, Fe, Zn, Cu and Ni were preferentially accumulated in roots. Silveira et al (2007) also detected higher Fe levels in roots than in shoots of different rice cultivars. Fe is mainly required for photosynthesis, respiration, sulphate assimilation, hormone synthesis, nitrogen fixation, as well as DNA synthesis and repair (Puig et al, 2007;Sperotto et al, 2010).…”

Role of ferritin in the rice tolerance to iron overload

“…Seemingly, E108 plants were able to restrict Fe accumulation, reaching lower shoot Fe concentrations when submitted to Fe overload than the I409 plants. Silveira et al (2007) had already suggested that E108 plants rely mostly on avoidance of Fe uptake into the plant and decreased translocation to shoots when coping with Fe overload. Based on results herein presented, we suggest that the tolerance mechanism to excess Fe in E108 includes both restricted Fe translocation and increased ferritin accumulation.…”

“…indica) seeds from cultivars EPAGRI 108 (E108) and BR-IRGA 409 (I409) were provided by IRGA (Instituto Rio Grandense do Arroz, Brazil). These cultivars have been previously characterized as tolerant and susceptible to Fe toxicity (Nava & Bohnen, 2002;Silveira et al, 2007). After germination and growth in vermiculite and nutrient solution (Yoshida et al, 1976) for 14 days in an incubator (28°C, first two days in the dark and remaining days with 16 h of light), plants were transferred to glass pots covered with aluminum foil and containing 500 mL of nutrient solution.…”

“…Fe concentrations were determined in roots and shoots by the Particle Induced X-Ray Emission (PIXE) technique, as described by Silveira et al (2007). Sampled roots or shoots from four plants were dried, ground and pressed into pellets.…”

Ecophysiology of iron homeostasis in plants

“…Fe toxicity in leaves causes necrotic spots, dark roots, inhibition of plant growth (Dobermann and Fairhurst 2000) and cationic unbalance, which promotes nutritional imbalances. In rice, excess of Fe has resulted in a reduction in the absorption of P, K, Ca and magnesium (Mg) (Silveira et al 2007). In Beta vulgaris under the effects of Fe toxicity, changes in chloroplast structure were observed, with reduced numbers of grana and stromal lamellae per chloroplast, and of thylakoids per grana, and also reduced numbers of P 700 molecules and cytochrome f per unit of area.…”