Direct Fe Deficiency Research Articles

Direct and Bicarbonate-Induced Iron Deficiency Differently Affect Iron Translocation in Kiwifruit Roots.

Bicarbonate-induced iron (Fe) deficiency (+Bic) is frequently observed in kiwifruit orchards, but more research attention has been paid to direct Fe deficiency (-Fe) in plants, including kiwifruit. Here we compared the differences of kiwifruit plants between -Fe and +Bic in: (1) the traits of 57Fe uptake and translocation within plants, (2) Fe forms in roots, and (3) some acidic ions and metabolites in roots. The concentration of 57Fe derived from nutrient solution (57Fedfs) in roots was less reduced in +Bic than -Fe treatment, despite similar decrease in shoots of both treatments. +Bic treatment increased 57Fedfs distribution in fine roots but decreased it in new leaves and stem, thereby displaying the inhibition of 57Fedfs translocation from roots to shoots and from fine roots to xylem of coarse roots. Moreover, +Bic imposition induced the accumulation of water-soluble Fe and apoplastic Fe in roots. However, the opposite was observed in -Fe-treated plants. Additionally, the cell wall Fe and hemicellulose Fe in roots were less reduced by +Bic than -Fe treatment. +Bic treatment also triggered the reduction in H+ extrusion and the accumulation of NH4+, succinic acid, and some amino acids in roots. These results suggest that, contrary to -Fe, +Bic treatment inhibits Fe translocation to shoots by accumulating water-soluble and apoplastic Fe and slowing down the release of hemicellulose Fe in the cell wall in kiwifruit roots, which may be related to the decreased H+ extrusion and the imbalance between C and N metabolisms.

Oxidative stress and antioxidant responses to direct and bicarbonate-induced iron deficiency in two quince rootstocks

The aim of this research was to investigate some physiological parameters underlining the differences in the sensitivity of quince rootstocks to iron (Fe) deficiency. Two quince rootstocks, Fe-chlorosis tolerant “hawthorn” and Fe-chlorosis sensitive “quince” were subjected to direct or bicarbonate-induced Fe deficiency. One-year-old seedlings of each rootstocks were grown in nutrient solution containing 50 μM Fe-EDTA, pH 5.5 (control), 5 μM Fe-EDTA, pH 5.5 (direct Fe-deficiency) or bicarbonate-lime-induced Fe-deficiency including 5, 10, 15, or 20 mM NaHCO3 in the absence or presence of 0.5 g l−1 CaCO3, containing 50 μM Fe-EDTA, pH 7.8. Both Fe-deficiency treatments decreased leaf chlorophyll, carotenoid and Fe concentrations in quince seedlings, whereas the presence of bicarbonate had no or small effect on these parameters in hawthorn leaves. In both rootstocks, leaf malondialdehyde and hydrogen peroxide (H2O2) concentration were increased in response to direct Fe-deficiency and HCO3- induced Fe-deficiency, though to a higher level in the quince seedlings. Iron-deficiency (direct and indirect) conditions resulted in an increase in the leaf superoxide dismutase activity in both rootstocks, whereas catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX) activities decreased significantly, but only in leaf of sensitive quince seedlings. This proposed that CAT, APX, and GPX activities could be an important feature associated with the tolerance to Fe deficiency by inhibiting an increase in H2O2 concentration and protect the cell from oxidative injury.

Inoculation with Efficient Nitrogen Fixing and Indoleacetic Acid Producing Bacterial Microsymbiont Enhance Tolerance of the Model Legume Medicago truncatula to Iron Deficiency.

The aim of this study was to assess the effect of symbiotic bacteria inoculation on the response of Medicago truncatula genotypes to iron deficiency. The present work was conducted on three Medicago truncatula genotypes: A17, TN8.20, and TN1.11. Three treatments were performed: control (C), direct Fe deficiency (DD), and induced Fe deficiency by bicarbonate (ID). Plants were nitrogen-fertilized (T) or inoculated with two bacterial strains: Sinorhizobium meliloti TII7 and Sinorhizobium medicae SII4. Biometric, physiological, and biochemical parameters were analyzed. Iron deficiency had a significant lowering effect on plant biomass and chlorophyll content in all Medicago truncatula genotypes. TN1.11 showed the highest lipid peroxidation and leakage of electrolyte under iron deficiency conditions, which suggest that TN1.11 was more affected than A17 and TN8.20 by Fe starvation. Iron deficiency affected symbiotic performance indices of all Medicago truncatula genotypes inoculated with both Sinorhizobium strains, mainly nodules number and biomass as well as nitrogen-fixing capacity. Nevertheless, inoculation with Sinorhizobium strains mitigates the negative effect of Fe deficiency on plant growth and oxidative stress compared to nitrogen-fertilized plants. The highest auxin producing strain, TII7, preserves relatively high growth and root biomass and length when inoculated to TN8.20 and A17. On the other hand, both TII7 and SII4 strains improve the performance of sensitive genotype TN1.11 through reduction of the negative effect of iron deficiency on chlorophyll and plant Fe content. The bacterial inoculation improved Fe-deficient plant response to oxidative stress via the induction of the activities of antioxidant enzymes.

Physiological responses of hawthorn (Crataegus persica Pojark.) and quince (Cydonia oblonga Mill.) rootstocks to bicarbonate‐induced iron deficiency in nutrient solution

AbstractHawthorn (Crataegus persica Pojark.) is used as a quince (Cydonia oblonga Mill.) rootstock in order to reduce the severity of iron (Fe) chlorosis in quince orchards in alkaline calcareous soils in central Iran. This study was conducted to investigate physiological responses of Fe‐chlorosis resistant hawthorn and Fe chlorosis‐sensitive quince cultivars to Fe‐deficiency and different levels of (5, 10, 15, and 20 mM NaHCO3), in the presence or absence of 0.5 g CaCO3 L−1 in a CO2‐buffered pH 7.8 nutrient solution containing 50 μM Fe(III)‐EDTA. A separate set of two free‐bicarbonate controls containing deficient [5 μM Fe(III)‐EDTA] and sufficient [50 μM Fe(III)‐EDTA] Fe concentrations was also used. Chlorosis symptoms appeared on the rootstocks exposed to and in the 5 μM Fe(III)‐EDTA treatment. In response to ‐induced Fe deficiency, hawthorn roots released high amounts of H+ and phenolic compounds to the surrounding medium, while no such response was observed in quince. The higher resistance to bicarbonate of hawthorn was also related with a higher root activity of the ferric chelate reductase (FCR), associated to a higher Fe(OH)3 solubilization. Accordingly, hawthorn seedlings in the ‐induced Fe deficiency had higher leaf and root Fe concentrations in comparison to those in the direct Fe deficiency. The addition of CaCO3, in general, had no or small effect on the root release of H+ and phenolic compounds. The effectiveness of Fe‐deficiency resistance mechanisms described for hydroponically grown hawthorn have to be evaluated under soil conditions.

Structural and functional integrity of Sulla carnosa photosynthetic apparatus under iron deficiency conditions.

The abundance of calcareous soils makes bicarbonate-induced iron (Fe) deficiency a major problem for plant growth and crop yield. Therefore, Fe-efficient plants may constitute a solution for use on calcareous soils. We investigated the ability of the forage legume Sulla carnosa (Desf.) to maintain integrity of its photosynthetic apparatus under Fe deficiency conditions. Three treatments were applied: control, direct Fe deficiency and bicarbonate-induced Fe deficiency. At harvest, all organs of deficient plants showed severe growth inhibition, the effect being less pronounced under indirect Fe deficiency. Pigment analysis of fully expanded leaves revealed a reduction in concentrations of chlorophyll a, chlorophyll b and carotenoids under Fe deficiency. Electron transport rate, maximum and effective quantum yield of photosystem II (PSII), photochemical quenching (qP), non-photochemical quenching (qN) as well as P700 activity also decreased significantly in plants exposed to direct Fe deficiency, while qN was not affected. The effects of indirect Fe deficiency on the same parameters were less pronounced in bicarbonate-treated plants. The relative abundances of thylakoid proteins related to PSI (PsaA, Lhca1, Lhca2) and PSII (PsbA, Lhcb1) were also more affected under direct than indirect Fe deficiency. We conclude that S.carnosa can maintain the integrity of its photosynthetic apparatus under bicarbonate-induced Fe deficiency, preventing harmful effects to both photosystems under direct Fe deficiency. This suggests a high capacity of this species not only to take up Fe in the presence of bicarbonate (HCO3- ) but also to preferentially translocate absorbed Fe towards leaves and prevent its inactivation.

Effect of sodium nitroprusside on responses of Melissa officinalis to bicarbonate exposure and direct Fe deficiency stress

In our study, one-month-old Melissa officinalis plants were subjected to Fe-deficiency treatments, such as 10 µM Fe (as direct iron deficiency, DD), and 30 µM Fe + 10 mM NaHCO3 + 0.5 g l−1 CaCO3 (as indirect iron deficiency, ID), and 30 µM Fe (as control) for 14 d. Both Fe-deficiency types reduced plant growth, photosynthetic pigment contents, an active Fe content in roots and leaves, root Fe(III)-reducing capacity, Fe-use efficiency, maximal quantum yield of PSII photochemistry, a ratio of variable to basic fluorescence, and activities of antioxidant enzymes, while they increased lipid peroxidation and a H2O2 content in leaves. These effects were more pronounced in plants exposed to ID with bicarbonate than those of DD plants. We showed that sodium nitroprusside (SNP), as NO donor, could ameliorate the adverse effects of bicarbonate on above traits. The methylene blue, as NO blocker, reversed the protective effects conferred by SNP in the ID-treated plants as well as DD plants. These findings suggests that NO protects photosynthesis and growth of IDtreated plants as well as DD plants by contribution in availability and/or delivery of metabolically active iron or by changing activities of reactive oxygen species-scavenging enzymes.

Comparison of two chickpea varieties regarding their responses to direct and induced Fe deficiency

The effects of Fe deficiency (whether direct or bicarbonate-induced) on plant morphology, growth parameters, photosynthesis-related pigment contents, gas exchange, and water relations were addressed in two contrasting chickpea varieties (INRAT88 and Chetoui, respectively tolerant and sensitive to Fe deficiency). A marked decrease in the whole plant Fe content was observed in the Fe deprived plants of both varieties, especially the bicarbonate-treated ones, which showed a slower growth development and water deficit stress symptoms (increased leaf tissue osmolality associated with decreased shoot height, increased leaf mass to area ratio, and decreased water content). Both Fe shortage and bicarbonate addition resulted in both varieties in the decline of the photosynthetic pigment contents, contributing to lower photosynthetic efficiency ( φ c) and lower net photosynthesis ( A). Fe deficiency reduced the water use efficiency and physiological availability of water too. However, INRAT88 was more tolerant to Fe deficiency than Chetoui, by maintaining a higher growth rate associated with lower respiration rate ( R D), higher chlorophyll a and b concentrations, higher A, lower transpiration rate ( E) and a higher water use efficiency ( A/E). The present data suggest that the efficient utilisation of Fe for the synthesis of chlorophyll together with the effective control of electron-transport chains at chloroplasts (high A) and mitochondria (low R D) may account for the higher tolerance of INRAT88 to direct Fe deficiency. Further investigations with respect to oxidative stress and ROS generation, or about photorespiration would be helpful for a better understanding of their interaction with Fe deficiency in this grain legume.

Biochemical Responses to True and Bicarbonate-Induced Iron Deficiency in Grapevine Genotypes

ABSTRACT Biochemical responses to direct or bicarbonate-induced iron (Fe) deficiency were compared in two Tunisian native grapevine varieties, Khamri (tolerant) and Balta4 (sensitive), and a tolerant rootstock, 140Ru. Woody cuttings of each genotype were irrigated with a nutrient solution containing one of the following: 20 μM Fe (control), 1 μM Fe (direct Fe-deficiency), or 20 μM Fe + 10 mM HCO3 − (indirect bicarbonate-induced Fe-deficiency). Under direct Fe-deficient conditions, lower leaf chlorosis score and higher chlorophyll and leaf Fe contents were found in Khamri and 140Ru compared with Balta4. Moreover, indirect Fe deficiency caused similar effects on these parameters, which were more pronounced in Balta4. Both tolerant genotypes, Khamri and 140Ru, showed higher roots-acidification capacity and phenol release under the direct Fe deficiency compared with the bicarbonate-induced condition. In the sensitive variety, Balta4, no significant changes were found between the control and Fe-deficient plants. Root Fe(III)-reductase activity was strongly stimulated by both types of Fe deficiency in Khamri and 140Ru, and displayed no significant changes in Balta4. In the three genotypes, root and leaf activities of two Fe-containing enzymes, catalase and guaiacol peroxidase, were significantly affected under Fe deficiency (either direct or induced), though to a greater extent in the sensitive variety, Balta4. The latter also displayed higher leaf malonyldialdehyde (MDA) content, traducing an important membrane lipid peroxidation.