14 research outputs found
Physiological and antioxidant responses of the sabkha biotope halophyte Limonium delicatulum to seasonal changes in environmental conditions
No full textIn saline biotopes, different mechanisms may contribute to the tolerance of halophytes to high soil salinity and temperature, drought and other abiotic stresses, but their relative responses and their ecological plasticity for a given species remain unknown. In this study, we examined the responses of the salt marsh halophyte Limonium delicatulum to changing environmental conditions of its natural habitats (Sabkha “El Kalbia”, Tunisia). The specific aim of the work was to check whether statistically significant correlations could be established between particular stress response mechanisms (ion uptake, activation of antioxidant systems) and soil parameters and climatic data associated with environmental stress. The results showed that the salinity of the soil increased during the months of June, July and August (dry period), concomitantly with a strong accumulation of salt ions in the aerial parts of the plant. Moreover, the highest antioxidant capacity of this halophyte (enzymes and antioxidant molecules) was reached during the same period of the year. The remaining periods (corresponding to the rainy season) did not show a significant difference in enzymes activities and level of antioxidants, with a minimum observed in the months of January and February. These results show a remarkable effect of salinity in the natural habitat on the activity of enzymes and antioxidant molecules. Other edaphic and climatic factors could also be involved to increase antioxidant capacity, such as nutrient deficiency, temperature and precipitation
Seed priming mitigates high salinity impact on germination of bread wheat (Triticum aestivum L.) by improving carbohydrate and protein mobilization
No full textSalinity is increasingly considered as a major environmental issue, which threatens agricultural production by decreasing yield traits of crops. Seed priming is a useful and cost-effective technique to alleviate the negative effects of salinity and to enable a fast and uniform germination. In this context, we quantified the effects of priming with gibberellic acid (GP), calcium chloride (CP), and mannitol (MP) on seed germination of three bread wheat cultivars and investigated their response when grown at high salinity conditions (200 mM NaCl). Salt exposure strongly repressed seed imbibition and germination potential and extended germination time, whereas priming enhanced uniformity and seed vigor. Seed preconditioning alleviated the germination disruption caused by salt stress to varying degrees. Priming mitigating effect was agent-dependent with regard to water status (CP and MP), ionic imbalance (CP), and seed reserve mobilization (GP). Na+ accumulation in seedling tissues significantly impaired carbohydrate and protein mobilization by inhibiting amylase and proteases activities but had lesser effects on primed seeds. CP attenuated ionic imbalance by limiting sodium accumulation. Gibberellic acid was the most effective priming treatment for promoting the germination of wheat seeds under salt stress. Moreover, genotypic differences in wheat response to salinity stress were observed between varieties used in this study. Ardito, the oldest variety, seems to tolerate better salinity in priming-free conditions; Aubusson resulted the most salt-sensitive cultivar but showed a high germination recovery under priming conditions; Bologna showed an intermediate behavior
Seed priming mitigates high salinity impact on germination of bread wheat (Triticum aestivum L.) by improving carbohydrate and protein mobilization
No full textAbstract Salinity is increasingly considered as a major environmental issue, which threatens agricultural production by decreasing yield traits of crops. Seed priming is a useful and cost‐effective technique to alleviate the negative effects of salinity and to enable a fast and uniform germination. In this context, we quantified the effects of priming with gibberellic acid (GP), calcium chloride (CP), and mannitol (MP) on seed germination of three bread wheat cultivars and investigated their response when grown at high salinity conditions (200 mM NaCl). Salt exposure strongly repressed seed imbibition and germination potential and extended germination time, whereas priming enhanced uniformity and seed vigor. Seed preconditioning alleviated the germination disruption caused by salt stress to varying degrees. Priming mitigating effect was agent‐dependent with regard to water status (CP and MP), ionic imbalance (CP), and seed reserve mobilization (GP). Na+ accumulation in seedling tissues significantly impaired carbohydrate and protein mobilization by inhibiting amylase and proteases activities but had lesser effects on primed seeds. CP attenuated ionic imbalance by limiting sodium accumulation. Gibberellic acid was the most effective priming treatment for promoting the germination of wheat seeds under salt stress. Moreover, genotypic differences in wheat response to salinity stress were observed between varieties used in this study. Ardito, the oldest variety, seems to tolerate better salinity in priming‐free conditions; Aubusson resulted the most salt‐sensitive cultivar but showed a high germination recovery under priming conditions; Bologna showed an intermediate behavior
Adjustment of photosynthetic carbon assimilation to higher growth irradiance in three-year-old seedlings of two Tunisian provenances of Cork Oak (Quercus suber L.)
No full textAdjustment of photosynthetic carbon assimilation to higher growth irradiance in three-year-old seedlings of two Tunisian provenances of Cork Oak (Quercus suber L.)
No full textThree-year-old seedlings of two Tunisian provenances of cork oak (Quercus suber L.) differing in climatic conditions at their geographical origin were subjected to increasing light intensities. Ga’four was the provenance from the driest site and Feija from the wettest site. Low-light adapted seedlings from both provenances were exposed to two light treatments: full sunlight (HL) and low light (LL, 15% sunlight) for 40 days. The CO2-response curve of leaf net photosynthesis (An-Ci curve) established under saturated photon flux density was used to compare photosynthetic parameters between leaves subjected to continuous low light (LL leaves) and leaves transferred from low to high light (HL leaves). Transfer from low to high light significantly increased net photosynthesis (An) and dark respiration (Rd) in Ga’four provenance but not in Feija. After transfer to high irradiance, specific leaf area (SLA) did not change in either provenance. This suggested that the increase in photosynthetic capacity on a leaf area basis in HL leaves of Ga’four provenance was not due to increased leaf thickness. Only the seedlings from the Ga’four provenance were able to acclimate to high light by increasing Vcmax and Jmax
Effect of seed priming with auxin on ROS detoxification and carbohydrate metabolism and their relationship with germination and early seedling establishment in salt stressed maize
No full textAbstract As crucial stages in the plant ontogeny, germination and seedling establishment under adverse conditions greatly determine staple crop growth and productivity. In the context of green technologies aiming to improve crop yield, seed priming is emerging as an effective approach to enhance seed vigor and germination performance under salt stress. In this study, we assess the efficiency of seed priming with indole-3-acetic acid (IAA) in mitigating the adverse effects of salt stress on maize (Zea mays L.) seedlings during germination and early seedling stages. In unprimed seeds, salt stress reduced germination indices, and seedling (both radicle and coleoptile) growth, together with decreased tissue hydration. However, seed priming using IAA significantly improved maize salt response, as reflected by the increased seed germination dynamics, early seedling establishment, and water status. Besides, seedlings from IAA-primed seeds showed a higher activity of α-amylase, resulting in increased sugar contents in roots and coleoptiles of salt-stressed plants. Further, IAA-seed priming stimulated the accumulation of endogenous IAA in salt-stressed seedlings, in concomitance with a significant effect on reactive oxygen species detoxification and lipid peroxidation prevention. Indeed, our data revealed increased antioxidant enzyme activities, differentially regulated in roots and coleoptiles, leading to increased activities of the antioxidant enzymes (SOD, CAT and GPX). In summary, data gained from this study further highlight the potential of IAA in modulating early interactions between multiple signaling pathways in the seed, endowing maize seedlings with enhanced potential and sustained tolerance to subsequent salt stress
Structural and functional integrity of<i>Sulla carnosa</i>photosynthetic apparatus under iron deficiency conditions
No full textDifferential performance of two forage species, Medicago truncatula and Sulla carnosa, under water-deficit stress and recovery
No full textThe response patterns during water deficit stress and subsequent recovery of two forage species, Medicago truncatula and Sulla carnosa, were studied. After germination and pre-treatment, seedlings were individually cultivated for two months under two irrigation modes: 100% and 33% of field capacity. Measured parameters were plant growth, water relations, leaf osmotic potential, lipid peroxidation, and leaf inorganic (Na+ and K+) and organic (proline and soluble sugars) solute contents, as well as delta-1-pyrroline-5-carboxylate synthase (P5CS) and proline dehydrogenase (PDH) activities. Our results showed that under control conditions, and in contrast to roots, no significant differences were observed in shoot biomass production between the two species. However, when subjected to water-deficit stress, M. truncatula appeared to be more tolerant than S. carnosa (reduction by 50 and 70%, respectively). In the two studied species, water-deficit stress led to an increase in root/shoot ratio and leaf proline and soluble sugar contents, and a decrease in leaf osmotic potential. Enzymatic assay revealed that in the two species, P5CS activity was stimulated whereas that of PDH was inhibited under stress conditions. Despite greater accumulation of proline, sugar, and potassium in leaves of S. carnosa, M. truncatula was more tolerant to water deficit. This was essentially due to its capacity to control tissue hydration and water-use efficiency, in addition to its greater ability to protect membrane integrity. Following stress relief, M. truncatula and S. carnosa showed partial re-establishment of growth capacity
Plant Growth-Promoting Rhizobacteria Alleviate High Salinity Impact on the Halophyte Suaeda fruticosa by Modulating Antioxidant Defense and Soil Biological Activity
No full textPlant growth-promoting rhizobacteria (PGPR) are considered as bio-ameliorators that confer better salt resistance to host plants while improving soil biological activity. Despite their importance, data about the likely synergisms between PGPR and halophytes in their native environments are scarce. The objective of this study was to assess the effect of PGPR (Glutamicibacter sp. and Pseudomonas sp.) inoculation on biomass, nutrient uptake, and antioxidant enzymes of Suaeda fruticosa, an obligate halophyte native in salt marshes and arid areas in Tunisia. Besides, the activity of rhizospheric soil enzyme activities upon plant inoculation was determined. Plants were grown in pots filled with soil and irrigated with 600 mM NaCl for 1 month. Inoculation (either with Pseudomonas sp. or Glutamicibacter sp.) resulted in significantly higher shoot dry weight and less accumulation of Na(+) and Cl(–) in shoots of salt-treated plants. Glutamicibacter sp. inoculation significantly reduced malondialdehyde (MDA) concentration, while increasing the activity of antioxidant enzymes (superoxide dismutase; catalase; ascorbate peroxidase; and glutathione reductase) by up to 100%. This provides strong arguments in favor of a boosting effect of this strain on S. fruticosa challenged with high salinity. Pseudomonas sp. inoculation increased shoot K(+) and Ca(2+) content and lowered shoot MDA concentration. Regarding the soil biological activity, Pseudomonas sp. significantly enhanced the activities of three rhizospheric soil enzymes (urease, ß-glucosidase, and dehydrogenase) as compared to their respective non-inoculated saline treatment. Hence, Pseudomonas sp. could have a great potential to be used as bio-inoculants in order to improve plant growth and soil nutrient uptake under salt stress. Indole-3-acetic acid concentration in the soil increased in both bacterial treatments under saline conditions, especially with Glutamicibacter sp. (up to +214%). As a whole, Glutamicibacter sp. and Pseudomonas sp. strains are promising candidates as part of biological solutions aiming at the phytoremediation and reclamation of saline-degraded areas
Significance of photosystem integrity and reducing Cd accumulation in mitigating Cd stress on olive tree inoculated with soil-borne bacteria consortium is variety-dependent
No full textRhizosphere microbial community role in boosting fruit tree ability to cope with heavy metals is gaining interest. Here, we address the effects of in-frame holobiont microbial inoculation on two Tunisian olive tree varieties (Olea europaea L. cv. Chemlali and Chetoui) exposed to CdCl for one month. Shoot Cd content, leaf pigment contents, chlorophyll fluorescence, and energy conversion-related traits in photosystems I and II (PSI and PSII) were considered. Following pyrosequencing-based 16S rRNA analysis, Proteobacteria, and to a lesser extent Firmicutes phylums, were the most abundant. Both Cd-treated olive varieties showed a significant decrease in leaf pigment contents, however, this depressive effect was significantly mitigated following inoculation. PSI and PSII activities were more altered in Cd-treated Chetoui as compared to Chemlali. Quantum yield and electron transport of PSI and PSII were also more impacted in Chetoui, whereas the limitation of the donor side of PSI increased in the latter. Yet, Cd impact on these parameters was significantly reduced in inoculated plants. The quantum yield of nonregulated non-photochemical energy loss in PSII significantly increased in both olive varieties under Cd stress, but values were markedly restored with inoculation. High Cd accumulation observed in Chetoui shoots upon Cd exposure was significantly lower in inoculated plants. Overall, the consortium used improved olive tree Cd tolerance likely due to the restoration of leaf pigment contents and the better integrity of photosystems in both varieties, whereas lowering Cd translocation to shoots would be more prominent in Chetoui. Long-term experiments will be conducted to confirm these results.This work was funded by the Tunisian Ministry of Higher Education and Scientific Research (LR15CBBC02)
