Effect of phosphorus deficiency induced in calcareous soil on plant growth, phosphorus use efficiency and acid phosphatase activity of Medicago truncatula.

Calcareous soils, characterized by a higher pH, are frequent in the North West of Tunisia. Large concentrations of calcium carbonate in calcareous soils result in accumulation of high levels of bicarbonate ions, which complex with phosphate, resulting in phosphorus deficiency (induced P deficiency) for plants. The impact of calcareous soil on plant growth, photosynthetic activity and acid phosphatase activity was explored in two lines of Medicago truncatula: TN6.18 and Jemalong. Calcareous soil significantly restricted shoot growth only in Jemalong (-45 % of the control). When grown on calcareous soil, root length was stimulated, this effect being more pronounced in TN6.18. Under calcareous soil, net CO2 assimilation declined more in Jemalong (-40 % of the control) than in TN6.18 (-20 % of the control). CO2 accumulation was increased in Jemalong (+35% of the control) plants grown in calcareous soil. The acid phosphatase activity was higher in plants cultivated under calcareous soil. This increased phosphatase activity was more pronounced in TN6.18, which showed higher accumulation of Pi in shoots and roots than Jemalolng.  In the light of these results, the present study proposes acid phosphatase as a useful candidate for improving Pi acquisition and utilization under calcareous soil

Upshot of the ripening time on biological activities, phenol content and fatty acid composition of Tunisian Opuntia ficus-indica fruit

Total phenol content and the antioxidant activities of three cultivars of Opuntia ficus-indica (L.) Mill. were evaluated. The results show that the ecotypes were significantly different according to their fatty acid composition, antioxidant and antibacterial activity, as well as their polyphenol profiles. Rossa fruit collected in August exhibited the higher phenolic content (15.48 mg GAE g−1 DW) with a stronger antioxidant activity. Bianca fruit collected in August exhibited a lower phenolic content (3.13 mg GAE g−1 DW) together with the stronger antiradical activity (96.14%). The advantage of this ecotype was more discernible as compared to positive controls butylated  hydroxytoluene (BHT, 79.75%). Likewise, CpG chromatogram identification revealed also an important difference between the ecotypes on oleic and linoleic acids.Keywords: Opuntia ficus-indica, variability, phenol content, fatty acid, antioxidant activity.African Journal of Biotechnology Vol. 12(40), pp. 5875-588

The phenolic compounds and compositional quality of Chétoui virgin olive oil: Effect of altitude

The differences in the chemical composition of virgin olive oils (VOO) obtained from trees of the Chetoui variety cultivated at different altitudes in Tunisia were evaluated. All samples were harvested using the same controlled procedures and were submitted to a controlled processing in the same laboratory mill. Several analytical parameters such as fatty acid composition, amounts of phenols; o-diphenols and pigments were analyzed. All these parameters showed an important effect on the fatty acids and phenols content of the oils. The total phenol content was positively correlated with the altitude, ranging from 817.33 mg/kg (403 m) to 131.91 mg/kg (10 m). However, the results of the regulated parameters in the potential quality classified all the analyzed oils into the ‘‘extra virgin’’ category.Key words: Orchard elevation, total antioxidant capacity, phenolic compounds, quality index

Morphological and physiological behaviour of sea barley (Hordeum marinum ssp marinum) genotypes originating from Soliman Sebkha under increasing salinity

Evaluation of germplasm in salt stress environment may help identifying salt-tolerant genotypes. In this study, we analyzed the genetic diversity of Hordeum marinum, genotypes originated from Soliman Sebkha in response to salinity (0, 250 and 400 mM) by measuring a set of parameters related to growth, water statue and photosynthetic activity. Results of ANOVA showed that variability of measured parameters was explained by the effects genotypes, treatment and their interaction, with treatment factor recorded the highest values. Salinity significantly reduced the photosynthetic rate and related parameters, including stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration (E). Several indices for salt tolerance indices comprising tolerance index (TOL), stress tolerance index (STI) and Salt Tolerance (ST) were calculated based on drought biomass (ADW) under non-stressed and under stress conditions. Results showed that lower values of TOL and higher values of ST and STI indicate the superiority of the genotypes having enough plasticity to respond to extreme conditions. Principal Component Analysis clustered genotypes into sensitive (21.43%), moderately tolerant (50%), and highly tolerant (28.57%) groups, depending on their relative potential to sustain good growth under high salinity. Results indicating sufficient genetic variability for salinity tolerance among the studied genotypes, hence tolerant genotypes can be good candidates in future breeding programs

Secondary metabolism responses in two Pisum sativum L. cultivars cultivated under Fe deficiency conditions

The present study was carried out to investigate the Fe deficiency effect on the secondary metabolism  responses in two Pisum sativum cultivars characterized by different tolerance to Fe deficiency. Previous study  investigating the physiological responses to Fe deficiency in these two pea cultivars showed that Kelvedon was  more tolerant than Lincoln. Both cultivars were grown in the absence or presence of Fe with the addition of bicarbonate for twelve days. Higher concentrations of phenols and flavonoids were observed in Fe-deficient  tissues of both cultivars; however, the increase was greater in the tolerant cultivar than in the susceptible  one. The activity of shikimate pathway enzymes tested was more enhanced in the tolerant cultivar. In  addition, lipid peroxidation and H2O2 concentrations were more increased in the susceptible cultivar when  compared with the tolerant one. Peroxidase activity was increased in the tolerant cultivar grown under  bicarbonate supply, while a considerable diminution was observed in the susceptible one, suggesting the  involvement of this antioxidant enzyme in the tolerance of pea to Fe deficiency. The lignifying peroxidases  activity was more decreased in Lincoln than in Kelvedon, especially in the presence of bicarbonate. Our data  suggest that the tolerance of Kelvedon was related to its ability to modulate the phenolic metabolism pathway and to enhance the antioxidant potentials.Key words: Iron deficiency, bicarbonate, phenolic metabolism, antioxidative enzymes, Pisum sativum

Interactive Effects of Cd and NaCl on Growth and Mineral Nutrition in Hordeum vulgare L. (Var. Raihane)

In this work, we investigated the combined effect of salt and cadmium on plant nutrition and Cd accumulation in the most cultivated barley variety in Tunisia, Raihane. Seedling were hydroponically subjected to four different treatment: the control without salt and Cd, 50mM NaCl alone, 10µM Cd alone and to the combination of Cd (10 µM) and NaCl (50 mM) during 1 month. At the harvest, plant growth, Cd content in shoots and roots and tissue nutrient concentrations in shoots(Ca, Fe, Mn and Zn) were measured. 50 mM NaCl alone does not significantly affected the morphology and the biomass of plants. However, when subjected to 10 µM Cd alone, plants of barley were less developed and produced low biomass as compared to control ones. NaCl addition to the Cd-treated plants further reduces the development and biomass production. With respect to nutrient acquisition results showed that NCl alone reduced Ca2+ and Fe2+ concentration in the shoots but not affected that of Zn and Mn. But Cd, applied alone or combined with NaCl disturbed all measured element concentration in the shoots. However, the addition of salt to the Cd-containing medium reduced significantly Cd accumulation in the roots and the shoots of plants. In conclusion, salt in the water irrigation is able to reduce Cd accumulation in this barley variety but it accentuated in the same time the toxic effect of this heavy metal in barley. View Article DOI: 10.47856/ijaast.2022.v09i10.00