Josemir Moura Maia

Partial oxidative protection by enzymatic and non-enzymatic components in cashew leaves under high salinity

The work evaluated the role of enzymatic and non-enzymatic antioxidants in cashew (Anacardium occidentale) leaves under 0, 50, 100, 150 and 200 mM NaCl. Salt stress increased protein oxidation and decreased the lipid peroxidation, indicating that lipids are less susceptible to oxidative damage. The superoxide dismutase (SOD) activity was not changed, ascorbate peroxidase (APX) activity steadily decreased while the catalase (CAT) activity strongly increased with the increasing NaCl concentration. High salinity also induced alterations in the ascorbate (AsA) and glutathione (GSH) redox state. The salt resistance in cashew may be associated with maintaining of SOD activity and upregulation of CAT activity in concert with the AsA and GSH antioxidants.

Salt-induced changes in antioxidative enzyme activities in root tissues do not account for the differential salt tolerance of two cowpea cultivars

The salt stress effect in root growth and antioxidative response were investigated in two cowpea cultivars which differ in salt tolerance in terms of plant growth and leaf oxidative response. Four-day-old seedlings (establishment stage) were exposed to 100 mM NaCl for two days. The roots of the two cultivars presented distinct response in terms of salt-induced changes in elongation and dry weight. Root dry weight was only decreased in Perola (sensitive) cultivar while root elongation was mainly hampered in Pitiuba (tolerant). Root relative water content remained unchanged under salinity, but root Na+ content achieved toxic levels as revealed by the K+/Na+ ratio in both cultivars. Then, root growth inhibition might be due to ionic toxicity rather than by salt-induced water deficit. Although electrolyte leakage markedly increased mainly in the Perola genotype, lipid peroxidation decreased similarly in both salt-stressed cultivars. APX and SOD activities were reduced by salinity in both cultivars reaching similar values despite the decrease in Pitiuba had been higher compared to respective controls. CAT decreased significantly in Pitiuba but did not change in Perola, while POX increased in both cultivars. The salt-induced decrease in the CAT activity of Pitiuba root is, at principle, incompatible to allow a more effective oxidative protection. Our results support the idea that the activities of SOD, APX, CAT and POX and lipid peroxidation in cowpea seedling roots were not associated with differential salt tolerance as previously characterized in terms of growth rate and oxidative response in plant leaves.

Differences in Cowpea Root Growth Triggered by Salinity and Dehydration are Associated with Oxidative Modulation Involving Types I and III Peroxidases and Apoplastic Ascorbate

The aim of this work was to investigate the balance between the activities of ascorbate peroxidase (APX) and phenol peroxidases (POD) and cowpea root growth in response to dehydration and salt stress. Root growth and indicators of oxidative response were markedly changed in response to salinity and dehydration. Salt treatment strongly inhibited root elongation, which was associated with an increase in lignin content and a significant decrease in the concentrations of apoplastic hydrogen peroxide (H2O2) and ascorbate. In conditions of extreme salinity, cytosol–APX activity was significantly decreased. In contrast, cell-wall POD activity was greatly increased, whereas lipid peroxidation was unchanged. These results indicate that POD could be involved in both H2O2 scavenging and the inhibition of root elongation under high salinity. In contrast, dehydration stimulated primary root elongation and increased lipid peroxidation and apoplastic ascorbate content, but it did not change APX and POD activities or H2O2 concentration. When cowpea roots were subjected to salinity followed by dehydration, the water and pressure potentials were decreased, and lipid peroxidation was markedly increased, highlighting the additive nature of the inhibitory effects caused by salt and dehydration. The proline concentration was markedly increased by dehydration alone, as well as by salt followed by dehydration, suggesting a possible role for proline in osmotic adjustment. Salinity and dehydration induce contrasting responses in the growth and morphology of cowpea roots. These effects are associated with different types of oxidative modulation involving cytosolic-APX and cell-wall POD activities and apoplast H2O2 and ascorbate levels.

Atividade de enzimas antioxidantes e inibição do crescimento radicular de feijão caupi sob diferentes níveis de salinidade

Phenol peroxidase (POX) is a dual enzyme that is involved with hydrogen peroxide scavenging and lignin biosynthesis, contributing to growth inhibition by secondary wall thickening. In order to relate growth inhibition to salt-induced oxidative modulation, the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and POX were evaluated in cowpea roots under salinity. Four-day-old seedlings of the Pitiuba and Perola cultivars were exposed to 0, 25, 50, 75 and 100 mM NaCl in germination paper under controlled conditions. After two days of treatment, root length was reduced under 100 mM NaCl by 56 and 26% in Pitiuba and Perola, respectively, which was associated with enhanced electrolyte leakage and cell death in the root apex. NaCl salinity did not trigger lipid peroxidation, indicating that cell death was probably due to membrane damage instead of oxidative stress. Salt stress reduced the activity of SOD, CAT and APX and increased the POX activity, demonstrating that this enzyme plays a role in oxidative protection in cowpea roots exposed to NaCl salinity. In conclusion, salt-induced growth inhibition in cowpea roots could be attributed, at least in part, to a coordinate action involving an increase in POX activity and a drop in CAT and APX activities.

Salt-induced delay in cotyledonary globulin mobilization is abolished by induction of proteases and leaf growth sink strength at late seedling establishment in cashew.

Seedling establishment in saline conditions is crucial for plant survival and productivity. This study was performed to elucidate the biochemical and physiological mechanisms involved with the recovery and establishment of cashew seedlings subjected to salinity. The changes in the Na+ levels and K/Na ratios, associated with relative water content, indicated that osmotic effects were more important than salt toxicity in the inhibition of seedling growth and cotyledonary protein mobilization. Salinity (50mM NaCl) induced a strong delay in protein breakdown and amino acid accumulation in cotyledons, and this effect was closely related to azocaseinolytic and protease activities. In parallel, proline and free amino acids accumulated in the leaves whereas the protein content decreased. Assays with specific inhibitors indicated that the most important proteases in cotyledons were of serine, cysteine and aspartic types. Proteomic analysis revealed that most of the cashew reserve proteins are 11S globulin-type and that these proteins were similarly degraded under salinity. In the late establishment phase, the salt-treated seedlings displayed an unexpected recovery in terms of leaf growth and N mobilization from cotyledon to leaves. This recovery coordinately involved a great leaf expansion, decreased amino acid content and increased protein synthesis in leaves. This response occurred in parallel with a prominent induction in the cotyledon proteolytic activity. Altogether, these data suggest that a source-sink mechanism involving leaf growth and protein synthesis may have acted as an important sink for reserve mobilization contributing to the seedling establishment under salinity. The amino acids that accumulated in the leaves may have exerted negative feedback to act as a signal for the induction of protease activity in the cotyledon. Overall, these mechanisms employed by cashew seedlings may be part of an adaptive process for the efficient rescue of cotyledonary proteins, as the cashew species originates from an environment with N-poor soil and high salinity.

CHANGES IN OSMOTIC AND IONIC INDICATORS IN Ananas comosus (L.) cv. MD GOLD PRE-TREATED WITH PHYTOHORMONES AND SUBMITTED TO SALINE MEDIUM

ABSTRACT- The production of fruits and seeds of many crops is increased when bees visit their flowers pollinating them. The aim of this study was to evaluate the effect of different pollination treatments on ‘Bordo’ grapevine ( Vitis labrusca L.) fruit quantity and quality. Quantitative and qualitative fruit production parameters of plants visited by Apis mellifera L., manually self- and cross-pollinated plants and plants without pollination were analyzed and compared. Fruit production was high for all treatments and all fruits presented four seeds per fruit, on average, confirming that this grape cultivar is autogamous. However, fruit set after spontaneous self-pollination was statistically lower than that of all other treatments, and pollination by A. mellifera showed the highest fruit production. Furthermore, pollination by honey bees resulted in increased biomass, reflected on fruit weight, but the content of soluble solids remained unchanged. The results of this study showed that there is no need of pollinators for fruit production of ‘Bordo’ cv., but the presence of these agents, in particularThe aim of this study was to evaluate the effect of NaCl on the hydroponic culture of cv. MD Gold pineapple pretreated with the phytohormones naphthaleneacetic acid (NAA) and 6-benzylaminopurine (BAP) using indicators of water stress and osmotic adjustment. Pineapple seedlings from saline treatments in the absence (-NB) and presence (+NB) of the phytohormones during the in vitro culture were grown in Hoagland & Arnon (1950) nutrient solution in the absence and presence of different NaCl concentrations (50; 100 and 150 mM) for 10 days in a greenhouse. Plants obtained from in vitro culture pretreated with phytoregulators (+NB) showed distinct physiological responses compared to non-treated plants (-NB) in relation to dry mass (DM) in roots, electrolyte leakage (EL) and Na+ and K+ concentrations in leaves and roots, and also regarding soluble sugars (TSS), free amino acids (TFAA) and proline (PRO) concentrations in leaves. Additionally, salt treatments induced similar responses in -NB and +NB plants, however differing in relation to intensity and the studied organs. The presence of NaCl in the solution reduced leaf DM in the -NB treatment, the leaf relative water content in -NB and +NB, and root RWC only in the -NB treatment. High levels of NaCl increased leaf EL in the +NB treatment. Potassium levels decreased with the increase of NaCl concentrations in nutrient solution for leaves and roots submitted to -NB treatment and for roots submitted to +NB treatment. Leaf potassium levels increased in +NB treatment regardless of salt treatment. No ionic toxic effects were identified except for roots subjected to 150 mM NaCl solution both for -NB and +NB conditions. TSS concentrations decreased with increasing NaCl concentration in leaves for both -NB and +NB treatments. Furthermore, TFAA and PRO showed increased levels in leaves subjected to saline stress, being more expressive in -NB treatment. In conclusion, pretreatment with growth regulators in pineapple plants minimized the effects of NaCl, despite higher concentrations of this salt affecting most of the evaluated parameters. Additionally, we conclude that the osmotic effect of salt stress was determinative for the physiological changes and that roots have different outcomes regarding the increment of growth regulators and NaCl concentrations.

Antioxidant Protection of Photosynthesis in Two Cashew Progenies Under Salt Stress

The present work evaluated the indicators of photosynthetic efficiency and antioxidative protection in cashew tree seedlings subjected to salinity stress. The study was conducted with seedlings of two advanced dwarf cashew clones (CCP09 and CCP76) subjected to salt stress with increasing doses of NaCl (0, control; 25; 50; 75; 100 mM) in the nutrient solution for 30 days under greenhouse conditions. The variables of gas exchange, CO2 assimilation (PN), stomatal conductance (gS), transpiration (E), intercellular CO2 concentration (CI), photochemical activity, potential quantum efficiency (Fv/Fm), effective quantum efficiency (ΔF/Fm’) of photosystem II (PSII), photochemical quenching (qP), non-photochemical quenching (NPQ) electron transport rate (ETR) as well as the indicators of damage and oxidative protection were measured. Under these conditions, there was an intense accumulation Na+ associated with a reduction in the K+/Na+ ratio in the leaves of both clones in response to salt, with higher values for this ratio in clone CCP09 than in CCP76 the highest concentration of NaCl (100 mM). Salinity reduced PN, gS and E in the two clones evaluated, with lower reductions in CCP09 than in CCP76 at the highest salt dose. Instantaneous carboxylation (PN/CI) and water use (PN/E) efficiencies were strongly restricted by salinity but were less affected in CCP09 than in CCP76. Salinity stress also increased hydrogen peroxide (H2O2) levels in CCP09, whereas lipid peroxidation decreased in both progenies. The clones presented specific antioxidant responses due to greater enzymatic and non-enzymatic activity in CCP76, in addition to the activity of phenol peroxidase (POX) in CCP09.

TOLERÂNCIA DO FEIJÃO-CAUPI AO ESTRESSE SALINO SOB MARCADORES FENOLÓGICOS

Introdução Dentre a produção mundial o Brasil destaca-se como o maior produtor de feijão. No qual abrangeu uma área semeada no ano de 2017 de 1.111mil hectares, com uma produtividade média de 1243 kg/há. No entando a área plantada de feijão caupi no estado da Paraíba é de apenas 63,2 mil hectares, devido à prolongada estiagem nas últimas safras, com produtividade média estimada em 261 kg/ha (CONAB 2017). Entre tanto, a região semiárida prevaleci várias condições adversas, como, alta insolação, altas temperaturas, baixa pluviosidade e excesso de sais na água de irrigação, onde as mesmas são responsáveis pela perca de produtividade das culturas (MEDEIROS et al., 2012; NETO SILVA et al., 2012). Dentre as condições adversas, a salinidade apresenta natureza osmótica e iônica, podendo afetar a disponibilidade de água no solo, bem como, efeitos específicos de íons que podem ocasionar toxidez ou desequilíbrio nutricional nas plantas (GHEYI, 2000), sendo considerada então quando uma espécie moderadamente tolerante à salinidade, entretanto o grau de tolerância do caupi ao estresse salino varia entre genótipos (DANTAS 2002). Com o acréscimo dos problemas de salinização dos solos no Nordeste, se faz necessário a adoção de práticas que viabilizem o cultivo