Effectiveness of soil conditioners to enhance salt extraction ability of Salicornia ramosissima in saline-sodic soil for different soil moisture contents.

Soil salinity is considered one of the main types of soil degradation in semiarid environments around the globe. This work aims to evaluate the effectiveness of soil conditioners to enhance the growth and salt extraction ability of Salicornia ramosíssima for different soil moisture contents. Salicornia plants were cultivated in pots in which the soils were treated with the following conditioners: control; gypsum + organic matter; elemental sulfur + organic matter; and gypsum + elemental sulfur + organic matter. Salicornia plants were subjected to two soil moisture rates - at 35 and 85% field capacity. Soil conditioners associated with higher contents of soil moisture promoted significant increases, compared to control, in fresh (6.20 - 11.13 g) and dry matter (1.20 - 2.07 g), relative biomass (100 - 179%) as well as significantly increased the concentrations of Na+ (56.09 - 65.64 mg kg-1) and Cl- (110.83 - 150.0 mg kg-1) in plant tissues. Soil conditioners significantly increased salt extraction ability under the two moisture levels, mainly by promoting higher values for both transfer factor and phytoremediation potential. The best performance of Salicornia in terms of plant yield and salt extraction, regardless of the moisture level, was the gypsum + organic matter.Novelty statementThere are no studies in the literature relating the use of conditioners as a strategy to enhance Salicornia's ability to extract salts.This work contributes to the management of salinized areas around the globe in two main aspects. The first is that many of these salt-degraded areas are desertified and through this study, it is possible to revegetate and recover them. The second one is that, since Salicornia is a plant with economic value, this can serve as an incentive for farmers to grow Salicornia in saline areas.

Use of the abrasion technique in minimal processing as an alternative to increase purchase acceptability and minimize browning in yam.

BACKGROUND: The present study investigated the sensory acceptance, oxidative damage and protection, and possible anatomical-structural damage of cells from the surface of shapes of minimally processed yam. The tubers were minimally processed into the peeled rondelle, dice and 'chateau cut' (chateau) shapes, the latter of which was obtained after performing the abrasion technique. Control treatment corresponded to the rondelle shape with the periderm. The pieces were kept packed at 5 ± 2 °C for 14 days. RESULTS: Peeled rondelle and chateau were sensorially the most well-accepted yam shapes and achieved the highest purchase intention. The enzymes were partially modulated by the detected H2 O2 levels. Oxidative burst lasted longer in the minimally processed tissues than in the control. Polyphenol oxidase activity showed a clear difference in behavior between the minimally processed pieces and the control. Minimal processing induced transient increases in phenolic compounds, for which the expression was lowest in the abraded pieces. On the other hand, these pieces exhibited greater cell collapse on the surface of the amyliferous parenchyma. CONCLUSION: Based on the results of the trained panel, the abrasion technique is an alternative to provide shapes that are better accepted and marketable, more resistant to browning, and can be stored for up to 12 days. Resistance to browning may be related to a more efficient modulation of enzymatic antioxidant systems and intense deposition of cell debris on the surface of the amyliferous parenchyma. © 2021 Society of Chemical Industry.

Phosphate Fertilization as a Modulator of Enzymatic Browning in Minimally Processed Cassava.

This study proposes to relate the increase in phosphorus (P) supply in the soil, via phosphate fertilization, to oxidative damage and protection, phenylpropanoid metabolism, and enzymatic browning in minimally processed cassava. The roots were grown with 0, 60, and 120 kg ha-1 P2O5. The roots were harvested, and the yield and P content in the root, stem, and leaves were quantified. The roots were minimally processed and stored for 12 days at 5 °C. The higher supply of P in the soil increased the P content of roots and stems but not the agro-industrial yields. Roots grown at 120 kg ha-1 P2O5 showed higher detection of hydrogen peroxide, which was accompanied by increased phenolic compounds, soluble quinones, and antioxidant capacity and increased activities of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, polyphenol oxidase, and peroxidase. The present study thus demonstrates the role of phosphorus application, induction of the synthesis of phenolic compounds, and quality of fresh-cut cassava.

Genotypic differences relative photochemical activity, inorganic and organic solutes and yield performance in clones of the forage cactus under semi-arid environment.

Plants with the crassulacean acid metabolism commonly present good adaptation to arid and semi-arid environments, but it highly depends on the type of species. In this study, chlorophyll fluorescence, the concentration of inorganic and organic solutes and the productive performance were evaluated along with their relationships in different clones of the genera Opuntia and Nopalea. The experiment was conducted from 2016 to 2018. Four clones of genus Opuntia were evaluated: 'Orelha de Elefante Mexicana' (OEM), 'Orelha de Elefante Africana' (OEA), V19 and F8; and two clones of genus Nopalea: 'IPA Sertânia' and 'Miúda'. The experiment was arranged in a randomised block design, with six treatments and three replications. The following parameters were measured when harvesting: initial, maximum and variable fluorescence; the quantum yield of PSII (Fv/Fm); light-induction curves of the photochemical parameters (ΔF/Fm', qP, NPQ and ETR); the chlorophyll and carotenoid content; carbohydrates; the sodium (Na+) and potassium (K+) content; morphometry; and dry matter accumulation. The values for the effective quantum yield of PSII (ΔF/Fm') and the alterations in photochemical quenching were higher in the OEM clone (P < 0.05). There was a difference between clones for non-photochemical quenching, with the F8 clone having the highest values. The Fv/Fm was 0.87 for the OEM. 'IPA Sertânia' obtained the greatest Chl a/b, and the highest values for carbohydrate concentration were found in the OEA clone. The OEM clone showed the greatest accumulation of K+, in addition to a higher cladode area index and greater dry matter accumulation. The results of this study show the high physiological tolerance of the forage cactus to a semi-arid environment, which varies according to the clone.

Association of preharvest management with oxidative protection and enzymatic browning in minimally processed cassava.

The aim of this study was to examine oxidative protection and enzymatic browning in the storage of minimally processed cassava and their relationship with population density and harvest age. Population densities were 1.0, 1.25, 1.5, and 1.75 plants m-2 . After being harvested at 300, 360, or 420 days after planting, cassava were minimally processed and stored at 5 ± 2°C. It was observed that superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) play key roles in the tolerance of young roots to browning. Planting density, however, does not appear to be a key factor modulating the activity of the enzymes studied. PRACTICAL APPLICATIONS: Younger harvested cassava roots, harvested at 300 days, are more tolerant to enzymatic browning. This appears to be in part due to enzymatic activity modulation of the SOD, CAT, and POD enzymes. In addition, it has been demonstrated that agronomic techniques aimed at increasing productivity, such as increasing the planting density of cassava, do not alter the biomarkers of postharvest quality. In summary, evidence that field management may be an efficient approach to improving the conservation of minimally processed cassava is provided. We believe that the findings of this paper will be of great interest regarding the influence of field management on the postharvest quality of freshly cut cassava and will also provide applicable results relating to its production chain.

Exogenous ornithine is an effective precursor and the δ-ornithine amino transferase pathway contributes to proline accumulation under high N recycling in salt-stressed cashew leaves.

The role of the δ-ornithine amino transferase (OAT) pathway in proline synthesis is still controversial and was assessed in leaves of cashew plants subjected to salinity. The activities of enzymes and the concentrations of metabolites involved in proline synthesis were examined in parallel with the capacity of exogenous ornithine and glutamate to induce proline accumulation. Proline accumulation was best correlated with OAT activity, which increased 4-fold and was paralleled by NADH oxidation coupled to the activities of OAT and Δ(1)-pyrroline-5-carboxylate reductase (P5CR), demonstrating the potential of proline synthesis via OAT/P5C. Overall, the activities of GS, GOGAT and aminating GDH remained practically unchanged under salinity. The activity of P5CR did not respond to NaCl whereas Δ(1)-pyrroline-5-carboxylate dehydrogenase was sharply repressed by salinity. We suggest that if the export of P5C from the mitochondria to the cytosol is possible, its subsequent conversion to proline by P5CR may be important. In a time-course experiment, proline accumulation was associated with disturbances in amino acid metabolism as indicated by large increases in the concentrations of ammonia, free amino acids, glutamine, arginine and ornithine. Conversely, glutamate concentrations increased moderately and only within the first 24h. Exogenous feeding of ornithine as a precursor was very effective in inducing proline accumulation in intact plants and leaf discs, in which proline concentrations were several times higher than glutamate-fed or salt-treated plants. Our data suggest that proline accumulation might be a consequence of salt-induced increase in N recycling, resulting in increased levels of ornithine and other metabolites involved with proline synthesis and OAT activity. Under these metabolic circumstances the OAT pathway might contribute significantly to proline accumulation in salt-stressed cashew leaves.

Photosynthetic changes and protective mechanisms against oxidative damage subjected to isolated and combined drought and heat stresses in Jatropha curcas plants.

Photosynthetic changes and protective mechanisms against oxidative damage were evaluated in Jatropha curcas leaves subjected to drought and heat stresses, both individually and combined, in order to elucidate the synergistic and antagonistic mechanisms involved with these abiotic factors. Both the drought and heat stresses caused significant damage to the leaf membrane integrity and lipid peroxidation, and the combination of these stresses greatly enhanced these physiological disturbances. The leaf CO(2) assimilation rate, stomatal conductance and instantaneous carboxylation efficiency (P(N)/C(I)) were significantly decreased in all plants subjected to stressful conditions in comparison to unstressed plants (reference). In contrast, a reduction in photochemical activity was observed only in plants exposed to drought and drought+heat conditions. Catalase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities were stimulated only under heat stress, whereas APX activity was increased in all treated plants in comparison to the references. Moreover, the leaf H(2)O(2) content was increased similarly under all studied stresses. However, the balance of reduced and oxidized ascorbate did not show significant differences between reference and stressed plants. Although J. curcas plants acclimated to the studied stresses, they did not present an efficient mechanism for protection against drought-induced oxidative stress, especially when at high temperatures. However, heat-treated plants triggered an efficient enzymatic antioxidant system of reactive oxygen species scavenging and an effective protection against photochemical damages. The combination of drought and heat most significantly impaired the photosynthetic assimilation of CO(2) and the photochemical activity. These results indicate that drought greatly disturbs photosystem II activity and oxidative metabolism and that these negative effects are strongly stimulated by heat stress. The data also evidence that the combination of heat and drought triggers an intricate response involving antagonistic and synergistic interactions.

Cytosolic APx knockdown indicates an ambiguous redox responses in rice.

Ascorbate peroxidases (APX, EC 1.1.11.1) are class I heme-peroxidases, which catalyze the conversion of H(2)O(2) into H(2)O, using ascorbate as a specific electron donor. Previously, the presence of eight Apx genes was identified in the nuclear genome of rice (Oryza sativa), encoding isoforms that are located in different sub-cellular compartments. Herein, the generation of rice transgenic plants silenced for either both or each one of the cytosolic Apx1 and Apx2 genes was carried out in order to investigate the importance of cytosolic Apx isoforms on plant development and on plant stress responses. Transgenic double Apx1/2-silenced plants exhibited normal development, even though these plants showed a global reduction of Apx activity which strongly impacts the whole antioxidant system regulation. Apx1/2-silenced plants also showed increased H(2)O(2) accumulation under control and stress situations and presented higher tolerance to toxic concentration of aluminum when compared to wild type plants. On the other hand, silencing OsApx1 and OsApx2 genes individually resulted in strong effect on plant development producing semi-dwarf phenotype. These results suggested that the double silencing of cytosolic OsApx genes induced compensatory antioxidant mechanisms in rice while single knockdown of these genes did not, which resulted in the impairing of normal plant development.

Roots and leaves display contrasting oxidative response during salt stress and recovery in cowpea.

In this study, we compare some antioxidative responses of leaves and roots associated to growth reduction in cowpea plants (Vigna unguiculata) during short-term salt stress and recovery. The salt treatment was imposed (200 mM NaCl) for six consecutive days and the salt withdrawal after 3 d. The salt treatment caused an almost complete cessation in the relative growth rate of both leaves and roots. Although NaCl withdrawal has induced an intense reduction in the Na(+) content from the leaves and roots, the growth recovery was slight, after 3 d. The leaf lipid peroxidation was increased in salt-stressed plants and slightly reduced in recovered plants after 3 d. Surprisingly, in the salt-stressed roots it decreased markedly after 3 d treatment and in the pre-stressed/recovered roots it was restored to levels near to the control. In leaves, catalase (CAT) activity showed a rapid and prominent decrease after 1 d of NaCl treatment and salt withdrawal had no effect on its recovery. In contrast, the root CAT activity was not changed by effects of both NaCl and salt withdrawal, over time interval. Leaf superoxide dismutase (SOD) activity did not change in all treatments, whereas in roots it significantly decreased after 3 d of salt treatment and recovered after NaCl withdrawal. Contrasting to the other enzymes, the guaiacol-peroxidase activity increased in leaves and roots, reaching almost 200% of control values and it significantly decreased in both organs from the pre-stressed/recovered plants. In conclusion, cowpea roots and leaves present distinct mechanisms of response to lipid peroxidation and CAT and SOD activities during salt stress and recovery. However, these responses and/or the oxidative damages caused by reactive oxygen species were not related with the growth reduction.