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 Pérola (sensitive) cultivar while root elongation was mainly hampered in Pitiúba (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 Pérola 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 Pitiúba had been higher compared to respective controls. CAT decreased significantly in Pitiúba but did not change in Pérola, while POX increased in both cultivars. The salt-induced decrease in the CAT activity of Pitiúba 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.

The objective of this work was to evaluate the vegetative development and determine the concentration of sodium, potassium, and calcium in watermelon (Citrullus lanatus) grown on two organic substrates and under increasing saline concentrations. The substrates were soil + earthworm humus (S₁) and soil + bovine manure (S₂), and the saline treatments consisted of irrigation water with different electrical conductivities: 1.36 (control), 3.56, 5.76, and 7.96 dS m^-1. The experimental design used was a randomized complete block in a 2×4 (substrate × conductivity) factorial arrangement with five replicates. Main branch length, root length, stem diameter, leaf number, leaf area, and fresh matter mass of shoots and roots, as well as the sodium, potassium, and calcium contents in the plants, were determined. All phenological parameters showed interaction with the substrates, and S₁ improved plant performance. Substrates interacted significantly with: leaf area; leaf number; stem diameter; main branch length; root length; fresh matter mass of shoots and roots; and the contents of sodium, potassium, and calcium, in both shoots and roots of watermelon irrigated with saline water for up to 27 days after emergence. There are also interactions between substrates and salinity for stem diameter, main branch length, fresh matter mass of roots, and calcium contents in both shoots and roots, and potassium and sodium contents in the roots.

Nesse trabalho propõe-se contribuir com as discussões sobre a exploração sustentável da Caatinga através de uma atualização bibliográfica sobre o tema, destacando a importância desse bioma, suas potencialidades e a necessidade de sua preservação e conservação. Foram abordadas a importância socioeconômica do bioma, as estratégias de subsistência e geração de renda (como o extrativismo e bioprodutos de valor econômico), as políticas públicas e ameaças, além de avaliar o seu uso sustentável. Com base no exposto, compreende-se que o manejo sustentável é uma possibilidade real, tecnicamente comprovada. Faz-se necessário um intenso processo de conscientização e capacitação de todos os atores envolvidos por meio da formulação de políticas públicas, que priorizem a realidade ambiental e socioeconômica do bioma, da geração, sistematização e disseminação de informações, da construção de uma matriz de incentivos adaptados à realidade local e do fortalecimento institucional, como forma de garantir a sobrevivência do ecossistema.

Considering the cashew tree’s relevance and the limitations imposed by salinity stress in semi-arid regions, the use of alternatives capable of mitigating the harmful effects due to salinity is of great importance to the production sector. The use of grafted plants, especially with rootstock made of tolerant materials, influences the accumulation of toxic ions in leaves of grafted seedlings. Thus, the objective of this work was to evaluate morphophysiological characteristics and leaf concentrations of Na+, K+ and Ca+2 of combinations of scion and rootstock of early dwarf cashew, contrasting in terms of salinity tolerance. The experiment was carried out in a completely randomized design with five replicates, in a 4 × 3 factorial arrangement, corresponding to four dwarf cashew scion/rootstock combinations (self-graft CCP 09, CCP 09/CCP 76, self-graft CCP 76, and CCP 76/CCP 09) and three NaCl concentrations (0, 50, and 100 mM L-1). Height, number of leaves, leaf area, dry matter, tolerance index and leaf concentrations of Na+, K+ and Ca+2 were evaluated after 30 days of application of NaCl concentrations. The scion/rootstock combination CCP 76/09 showed tolerance to 50 mM L-1, due to the increase of leaf area and number of leaves. The scion/rootstock combination CCP 76/09 was more suitable, as it kept the leaf K+ concentration and had the lowest Na+ concentration.

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.

Salinity in soil can affect Jatropha seedling metabolism, interfering with plant establishment. In this study, the effect of salinity on the mobilization of reserves during the development of Jatropha seedlings was tested. Two genotypes of Jatropha were used and three concentrations of NaCl were applied between the 4th and 8th days after germination. The effects of salinity on seedling growth, in terms of fresh and dry phytomass, ionic partition, and sugar quantification, starch, proteins, amino acids, and lipids were evaluated in cotyledon leaves, hypocotyls, and roots. There was an increase in the content of all classes of macromolecules analyzed in at least one of the organs. It is hypothesized that the hypocotyls acted as an accumulating organ of Na⁺. The accumulations of amino acids and protein in roots suggest that metabolic responses occurred in response to the ionic and osmotic effects of NaCl, although this accumulation did not appear to prevent biomass losses in seedlings. Furthermore, the findings of this study demonstrate that salinity inhibits the mobilization of lipids and carbon stocks from cotyledon leaves to the rest of the plant, and together with the synthesis of proteins and amino acids that occurred primarily in roots, contributed to response of these plants to salinity.