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Iron (Fe) deficiency leads to an overproduction of reactive oxygen species (ROS) in plants that activate their antioxidant systems to control oxidative burst. In this study, contrasting Medicago truncatula genotypes, A17 and TN8.20 (tolerant) and TN1.11 (sensitive), were grown under Fe deficiency. The superoxide dismutase (SOD: EC1.15.1.1) activity, their isoforms’ coding genes, the copper chaperone expression patterns, and leaf phenolic contents were analysed. Our results showed that Fe deficiency decreases the photosynthetic capacity and plant biomass production with a prominent effect on TN1.11 genotype. The tolerance of A17 and TN8.20 was correlated with a maintenance of Fe content and the photosynthetic apparatus and an increase of Cu concentration compared with the sensitive genotype. We revealed a significant increase of H2O2 in Fe-deficient plants, mainly in TN1.11 sensitive genotype. TN8.20 and A17 tolerance were concomitant with a significant increase of SOD activities (SOD, Cu/Zn-SOD, and Mn-SOD) under Fe deficiency. This increment was correlated to an induction of the copper chaperone gene expression level, as well as an accumulation of isoquercitin phenolic compound. Our study provides new insights into the orchestration of SOD’s isoforms activities, the expression of the copper chaperone, FeSOD, Cu/ZnSOD genes, and the leaf phenolic compounds accumulation that allows Medicago truncatula to overcome Fe deficiency.

The first experiment was conducted to evaluate the impact of seed priming on germination behavior and seedling establishment in Vicia faba and Vicia sativa, for that, seeds priming was done using SA (100 µM) and KH2PO4. In order to determine the optimal concentration of KH2PO4 for improving germination, different concentrations were used: 25 µM, 50 µM, and 100 µM. The best germination behavior and seedling establishment were obtained with 25 and 50 µM KH2PO4, respectively for Vicia faba and Vicia sativa. Moreover, data showed that 100 µM of SA improved seed germination as well as the seedling establishment for both species. The second experiment was carried out to investigate the influence of seed priming for improving phosphorous (P) deficiency tolerance. To do, seedling obtained from primed and nonprimed seeds were grown in a hydroponic culture system with three different treatments: control (C, medium containing sufficient P concentration: 360 µM KH2PO4), direct phosphorus-deficient (DD, medium containing only 10 µM KH2PO4), and induced P deficiency by bicarbonate (ID, medium containing sufficient P concentration: 360 µM KH2PO4 + 0.5 g L-1 CaCO3 + 10 mM NaHCO3). Furthermore, the role of exogenous SA applied to P deficiency tolerance enhancement was explored. Seed priming or the exogenous application of SA significantly reduced the severity effect of P deficiency. In fact, the pretreated plants were observed more tolerant to P deficiency as reflected from the significant increase in plant biomass, P uptake, and an efficient antioxidant system. Overall, this paper highlights the beneficial effect of seeds priming or the exogenous application of SA in the improvement of plant tolerance to phosphorus deficiency. A deficiência de fósforo (P) é um fator ambiental adverso comum que limita a produção agrícola em todo o mundo. Este estudo é uma avaliação do efeito benéfico da técnica de priming de sementes para tolerância à deficiência de P em Vicia faba e Vicia sativa. Para avaliar o impacto do condicionamento das sementes no comportamento germinativo de Vicia faba e Vicia sativa, suas sementes foram imersas em diferentes concentrações de KH2PO4 (25 µM, 50 µM e 100 µM) e em 100 µM de ácido salicílico (SA) por 24 h. Os resultados obtidos definiram KH2PO4 50 µM (para Vicia sativa) e KH2PO4 25 µM (para Vicia faba) como as concentrações ótimas que garantem uma melhor germinação das sementes. Além disso, os dados mostraram que a SA melhora a germinação de sementes e o estabelecimento de mudas. Posteriormente, para investigar a contribuição dessa técnica no aumento da tolerância à deficiência de P, sementes preparadas e não preparadas foram cultivadas em solução hidropônica com três tratamentos diferentes: controle (C, meio contendo concentração suficiente de P: KH2PO4 360 µM), deficiente em fósforo direto (DD, meio contendo apenas 10 µM de KH2PO4) e deficiência induzida de P por bicarbonato (ID, meio contendo concentração suficiente de P: 360 µM de KH2PO4 + 0,5 g l-1 de CaCO3 + 10 mM de NaHCO3). Além disso, o papel da SA exógeno aplicada no aumento da tolerância à deficiência de P foi explorado. A preparação das sementes ou a aplicação exógena de SA reduziu significativamente o efeito da severidade da deficiência de P. De fato, as plantas pré-tratadas foram observadas mais tolerantes à deficiência de P, refletidas no aumento significativo da biomassa da planta, na absorção de P e em um eficiente sistema antioxidante. No geral, este artigo destaca o efeito benéfico da priming de sementes ou a aplicação exógena de SA na melhoria da tolerância das plantas à deficiência de fósforo.

According to the United Nations estimation, the human population will be reaching 9.7 billion by mid-century and 11.2 billion by century’s end...

The aim of this study was to assess the effect of symbiotic bacteria inoculation on the response ofMedicago truncatulagenotypes to iron deficiency. The present work was conducted on threeMedicago truncatulagenotypes: 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 melilotiTII7 andSinorhizobium medicaeSII4. Biometric, physiological, and biochemical parameters were analyzed. Iron deficiency had a significant lowering effect on plant biomass and chlorophyll content in allMedicago truncatulagenotypes. 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 allMedicago truncatulagenotypes inoculated with bothSinorhizobiumstrains, mainly nodules number and biomass as well as nitrogen-fixing capacity. Nevertheless, inoculation withSinorhizobiumstrains 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 the halophyte Suaeda fruticosa cultivated under combined effects of salinity and iron deficiency were addressed. Plants were grown hydroponically for one month with a complete nutrient solution containing iron (Fe) of 0 or 30 μM, without or with salinity (100 and 400 mM NaCl). Growth parameters, chlorophyll concentration, mineral status, Fe(III) chelate reductase (FCR) activity and the acidification capacity were evaluated. Fe deficiency restricted significantly the plant biomass production as well as Fe uptake. Interestingly, the exposure to salinity mitigated the impact of Fe shortage on the plant growth whereas the impacts of salinity and Fe deficiency were not additive with respect to the plant Fe status. Salinity had no effect on the root proton release except a slight reduction at 400 mM and the FCR activity. Interestingly, both Fe absorption and use efficiencies were significantly higher in salt-treated plants under optimal Fe supply.

Iron deficiency is an important environmental factor restricting plant productivity. Selecting tolerant genotypes is one of the possible ways to solve this problem. Many studies reported the effects of Fe deficiency on photosynthesis and anti-oxidative defense system. Yet, there is little information available on the use of these attributes as selective criteria. In the present study, we aim to determine some physiological and biochemical traits conferring Fe deficiency tolerance at leaf level in two lines of Medicago ciliaris. Our results showed that Fe deprivation had a lowering effect on photosynthesis (chlorophyll, photosynthetic electron transport activity and chlorophyll fluorescence) in both lines studied. However, the sensitive line TN8.7 was more affected. Hydrogen peroxide concentration was negatively correlated with the activities of antioxidant enzymes and with the concentration of some non-enzymatic antioxidant. The tolerant line TN11.11 was characterized by a more efficient antioxidant defense system in comparison with the sensitive line TN8.7. The main conclusion of this study is that photosynthesis and antioxidant defense system could be used as physiological and biochemical indicators of Fe deficiency tolerance in Medicago ciliaris plants.

a b s t r a c t The aim of this work was to explore leaf characteristics underlining the difference in the sensitivity of pea cultivars (cv. Kelvedon, Douce and Lincoln) to Fe deficiency. Plants were grown in a greenhouse under controlled conditions in continuously aerated solution. Three treatments were used: 30 M Fe (+Fe), 0 M Fe (−Fe); direct deficiency and 30 M Fe + 10 mM NaHCO3 (+Fe+Bic); indirect deficiency for 12 days. Growth parameters, iron status, potassium content, chlorophyll fluorescence and photosynthetic capacity were studied. Our results showed that Fe deficiency led to a significant decrease of chlorophyll index (SPAD readings) and bivalent iron content in all Pisum sativum cultivars. The lower reduction was observed in Fe-deficient plants of Kelvedon and Douce. In addition, shoot length and whole plant dry weight were not affected by Fe deficiency in the latter cultivars. Both tolerant cultivars showed higher accumulation of potassium content in their leaves compared with the sensitive one. Moreover, both chlorophyll fluorescence ratios (Fv/Fm and Fv/F0) were significantly decreased in all cultivars under both Fe deficiency treatments. The photosynthetic electron transport activity was reduced in the sensitive cultivar, especially in the absence of iron. The adverse effect of bicarbonate-induced Fe deficiency on the above mentioned parameters were more pronounced than that of the direct one. The capacity of both tolerant cultivars to preserve adequate chlorophyll synthesis, photosynthetic capacity and plant growth under iron-limiting conditions is related to the suitable nutrition of their leaves in ferrous iron, due to (at least partially) their higher potassium content.

The aim of this research was to study the responses of two lines of Medicago ciliaris: TN11.11 and TN8.7 to iron deficiency under saline conditions. However; the paper showed also the results of a preliminary study which report the contrastive responses of the two lines to salinity. We found that plant growth and chlorophyll content of TN11.11 line were more affected by salinity than TN8.7. The severity of symptoms was linked to the sodium accumulation in shoots as well as a limitation of potassium uptake. Our data allowed us to note that TN8.7 line is less sensitive and can better cope with the salinity. Concerning the effect of salinity on iron deficiency responses, we noted that root PM H+-ATPase and FCR activities were reduced when iron deficiency was associated with salinity. This probably explained the decrease of Fe uptake. On the contrary, PEPC activity was not affected.

Our study investigates the effect of iron deficiency on morpho-physiological and biochemical parameters of two Medicago ciliaris ecotypes (Mateur TN11.11 and Soliman TN8.7). Iron deficiency was imposed by making plants grow, either in an iron free or by the addition of CaCO3/NaHCO3 to the Hoagland nutrient solution. Our results showed that both true and bicarbonate Fe-deficiency induced the characteristic iron-chlorosis symptoms, although the intensity of the symptoms was ecotype-dependent. This variability in tolerance to iron deficiency was also displayed by other morphological parameters such as root biomass and chlorophyll concentration. Besides, iron chlorosis induced an increase in biochemical parameters: the iron reducing capacity (measured in vivo on root segments and in vitro on plasma membrane enriched vesicles) and rhizosphere acidification by enhancement of H+-ATPase activity were more pronounced in Mateur ecotype. These findings suggest that Soliman ecotype was more sensitive than Mateur one to iron chlorosis.

The aim of this work was to evaluate the effects of Fe deficiency on the activity of several metabolic enzymes (PEPC, PK, PFK, G6PDH and G3PDH), along with the function of the antioxidant enzymes (SK, SDH and PAL) in two lines of Medicago ciliaris, TN11.11 and TN8.7. Plants were grown in a greenhouse under controlled conditions. After germination and pre-treatment, plants were transferred for hydroponic culture. Three treatments were used: 30 μM Fe (+Fe), 0 μM Fe (−Fe) and 30 μM Fe + 10 mM NaHCO3 (+Bic.). Our results showed that all the enzymatic activities increased in extracts of Fe-deficient roots when compared to the control. The above increases in the activity were particularly evident for the bicarbonate-treated roots of TN11.11. PEPC activity was increased by 277% in TN11.11 plants with the addition of bicarbonate to the nutrient solution. Our results indicate also that, in the two lines of Medic, the activity of SK, SDH and PAL in leaves and roots were increased under Fe deficiency (either direct or induced by bicarbonate), to a greater extent in TN11.11 plants. Furthermore, a considerable increase in lipid peroxidation of roots and leaves of Fe-deficient plants was observed in TN8.7 when compared to TN11.11 plants. Our data suggest that the TN11.11 line is more effective in overcoming Fe deficiency than TN8.7. The tolerance of TN11.11 to Fe deficiency is related to its ability to modulate the carbohydrate metabolism and to increase secondary metabolism pathways.

The main objective of this work was to compare the tolerance to lime-induced Fe deficiency of two lines of Medicago ciliaris (TN11.11 and TN8.7). We studied the effects of Fe deficiency on: (1) root biomass and rhizosphere acidification, (2) accumulation in the roots and the exudation into the rhizosphere of organic compounds (citric acid, malic acid and phenols), (3) changes under Fe deficient conditions in the activities of two enzymes, the first related to organic acid metabolism (malate dehydrogenase: MDH) and the other to proton extrusion (H+-ATPase activity). After a pre-treatment of one week, plants were transferred into hydroponic culture under three treatments: +Fe, −Fe and +Fe +lime. Iron deficiency led to 40% increase in root biomass in TN11.11 line in the presence of lime. Both the omission of Fe and the addition of lime to the nutrient solution increased the H+-ATPase activity more in TN11.11 than in TN8.7. In addition, Fe deficiency increased accumulation of organic acids as well as phenols in roots, and stimulated the MDH activity more in TN11.11 than in TN8.7 (+75% and +41% in TN11.11 and TN8.7, respectively). Iron deficiency also increased the amounts of citrate, malate and phenols in root exudates. Our data allowed us to note that the TN11.11 line is more effective in overcoming Fe deficiency than TN8.7.