This study aimed to evaluate the effect of stress attenuators on the tolerance and antioxidant activity of watermelon cultivars under water deficit. The experiment was conducted in two stages, Stage I corresponding to water deficit levels (N1 = 0; N2 = −0.1; N3 = −0.2 MPa) and six watermelon cultivars. Stage II comprises two cultivars selected in Stage I (one sensitive and one tolerant) and the combination of water restriction with attenuators (T1 = 0.0 MPa (control), T2 = −0.2 MPa (water deficit), T3 = −0.2 MPa + hydropriming, T4 = −0.2 MPa + gibberellic acid, T5 = −0.2 MPa + salicylic acid, and T6 = −0.2 MPa + hydrogen peroxide). The concentration and exposure times of the attenuators were determined through preliminary tests. In Stage I, physiological and biochemical analyses were performed. In Stage II, in addition to these tests, hydrogen peroxide content, malondialdehyde levels, and the activity of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) were assessed. Water deficit impaired germination and seedling vigor of watermelon, with Crimson Sweet, Omaru, Charleston Gray, and Congo being the most sensitive cultivars, while Fairfax was the most tolerant. For Crimson Sweet, pre-germination treatments reduced oxidative stress and enhanced tolerance by stimulating antioxidant enzyme activity, with GA and H₂O₂ providing the most effective results. For Fairfax, greater tolerance was associated with osmotic adjustment through the accumulation of compatible solutes, a mechanism further enhanced by the use of attenuators.

Salinization of agricultural areas is one of the main abiotic factors responsible for the reduction of seed germination and vigor. In this context, the use of stress attenuators applied to seeds may contribute to mitigating the effects of salinity and improving the physiological and antioxidant performance of seedlings. This study aimed to evaluate the effects of stress attenuators on the tolerance and antioxidant activity of watermelon Citrullus lanatus (Thunb.) Matsum & Nakai cultivars under saline conditions. The study was conducted in two stages. In the first stage, a 3 × 6 factorial scheme was used to evaluate three salinity levels (0, −0.2, and −0.4 MPa) and six watermelon cultivars. In the second stage, in a 2 × 6 factorial scheme, two cultivars (sensitive and tolerant) were subjected to the combination of salinity (−0.4 MPa) and attenuators: hydropriming, gibberellic acid, salicylic acid, and hydrogen peroxide. Physiological and biochemical traits were evaluated, including hydrogen peroxide content, lipid peroxidation, and the activity of the enzymes, superoxide dismutase, catalase, and ascorbate peroxidase. Salinity reduced germination and seedling vigor, with Crimson Sweet, Charleston Gray, and Charleston Super being the most sensitive cultivars, whereas Congo and Omaru exhibited greater tolerance, and Fairfax also showed good performance under saline conditions. The selection of cultivars for the second stage was based not only on physiological tolerance but also on agronomic and commercial relevance, including post-harvest resistance traits. Seed treatment of Crimson Sweet with salicylic acid and hydrogen peroxide increased antioxidant enzyme activity, with increases of up to 103% in ascorbate peroxidase activity, and reduced oxidative damage, with reductions of 44% in hydrogen peroxide and 49% in malondialdehyde levels. In Fairfax, gibberellic acid contributed to osmotic adjustment, promoting increase of up to 76% in total soluble sugars, while pre-germinative treatment with salicylic acid and hydrogen peroxide promoted higher enzyme activity, contributing to the reduction of oxidative stress.

Erythrina velutina Willd. is a xerophytic plant native to the Caatinga, whose seeds show heteromorphism in seed coat color, varying between reddish and orangish. This study aims to analyze the influence of seed coat color on the physical characteristics, dormancy and physiological potential of the seeds of this species. The seeds were evaluated for length, width, moisture content, hundred-seed weight, water absorption curve, first count, germination, hard seeds, shoot and root length, and shoot and root dry mass. In addition, cross-sectional fragments of 10 seeds of each color were examined by means of a scanning electron microscope (SEM), which was used to visualize the epidermis, palisade layer and parenchyma cell layers. The experimental design was completely randomized with four replications of 25 seeds in a 2 x 2 factorial scheme, considering seed coat color (orangish and reddish) and dormancy overcoming (intact and scarified seeds). The data were subjected to analysis of variance and compared by Tukey test at 5% probability level. There was no significant influence of seed coat color on the physical characterization of the seeds. It was found that reddish seeds have greater dormancy and lower physiological potential when compared to orangish seeds.

Moringa oleifera Lam. is an arboreal forest species of great economic potential, adapted to the climatic conditions of the Brazilian semi-arid region, whose multiplication is mainly by seeds. Rapid viability and vigor tests help in the choice of lots. Thus, the objective of this study was to assess the efficiency of the pH of exudate and primary root protrusion tests in the evaluation of viability and vigor, respectively. Two seed lots were initially evaluated for moisture content, germination, first count, germination speed index, seedling length, seedling dry mass and electrical conductivity. For the pH of exudate test, phenolphthalein (1%) and sodium carbonate (2 and 4 g L-1) solutions were prepared, with three soaking periods (1, 3 and 5 h) and three temperatures (25, 30 and 35 °C). Exudate solution in strong to light pink color indicated viable seeds, whereas very light pink color to colorless indicated non-viable seeds. The primary root protrusion test was performed under 25, 30 and 35 °C, evaluating the primary root protrusion of at least 2 mm, every 12 h until 196 h. The experimental design was completely randomized, with four replicates. pH of exudate test with 1 h of soaking at 25 or 30 °C with 2 g L-1 sodium carbonate solution was promising, but further studies are needed before it is indicated as routine use for the species. Primary root protrusion test is efficient and can be conducted at 35 °C with evaluation after 48 h. A Moringa oleifera LAM. é uma espécie florestal arbórea de grande potencial econômico, adaptada às condições climáticas do semiárido. A principal forma de multiplicação desta é por sementes, a realização de testes de viabilidade e vigor, auxiliam na escolha dos lotes. Assim, objetivou-se verificar a eficiência dos testes de pH de exsudato e de precocidade de emissão da raiz primária na avaliação da viabilidade e vigor, respectivamente. Foram utilizados dois lotes, caracterizados quanto ao grau de umidade, germinação, primeira contagem, índice de velocidade de germinação, comprimento e massa seca de plântulas e condutividade elétrica. Para o pH de exsudato foram preparadas soluções indicadoras, fenolftaleína (1%) e carbonato de sódio em duas concentrações (2 e 4g/L), três períodos de embebição (1, 3 e 5h) e três temperaturas (25, 30 e 35°C). A solução rosa forte a claro indicou sementes viáveis e os rosa muito fraco a incolor, inviáveis. O teste de precocidade de emissão da raiz primária foi realizado sob temperaturas de 25, 30 e 35°C, avaliado a cada 12h, até 196h, sendo utilizado o critério de 2mm de emissão de raiz. O delineamento experimental foi o inteiramente casualizado, com quatro repetições. O pH de exsudato com 1h de embebição a 25 ou 30°C, com solução de carbonato de sódio 2g/L foi promissor, porém estudos complementares são necessários antes de ser indicado como uso rotineiro para a espécie. O teste de precocidade de emissão de raiz primária é eficiente, podendo ser conduzido a 35°C com avaliação após 48 horas de instalação.

Salinity compromises seed germination and early seedling growth, highlighting the need to identify tolerant cultivars and effective management strategies. This study aimed to evaluate tolerance to salt stress, antioxidant activity, and the effectiveness of seed-applied stress attenuators in pumpkin cultivars. The research was conducted in two stages. In the first stage, six cultivars (Tetsukabuto, Soberana, Kin, Bahiana Tropical, Sergipana, and Adele) were subjected to three levels of osmotic potential induced by NaCl (0.0, −0.2, and −0.4 MPa). Germination, growth, and biochemical variables were evaluated. In the second stage, two contrasting cultivars were subjected to six treatments: control (0.0 MPa), salt stress (−0.4 MPa), hydropriming, gibberellic acid, ascorbic acid, and salicylic acid, all under salt stress (−0.4 MPa). In addition to germination and growth variables, oxidative damage (H₂O₂ and lipid peroxidation) and antioxidant activity (SOD, CAT, and APX) were evaluated. Salt stress significantly reduced germination, growth, and biomass accumulation. Cultivar Adele showed greater tolerance, whereas Tetsukabuto was more sensitive. Hydropriming, gibberellic acid, ascorbic acid, and salicylic acid mitigated the effects of salinity, with hydropriming showing the greatest reduction in lipid peroxidation. It is concluded that Adele, combined with gibberellic acid, and Tetsukabuto, combined with hydropriming and gibberellic acid, showed better performance under salinity stress, highlighting the potential of physiological and biochemical traits for identifying contrasting responses to salinity.

Among the main factors affecting maize (Zea mays L.) productivity, water scarcity stands out, especially during the early stages of development. This study aimed to evaluate the tolerance of maize cultivars subjected to water deficit conditions during germination and early seedling growth. The experiment followed a completely randomized design in a 20 × 3 factorial arrangement, consisting of twenty maize cultivars (‘BRS 2022’, ‘BRS 4103’, ‘BRS Cruzeta’, ‘BRS Gorutuba’, ‘Capo 22’, ‘HTC697’, ‘HTC717’, ‘HTC795’, ‘MC 70’, ‘PF 7008’, ‘Potiguar, Sintético 91801587’, ‘Sintético 91801590’, ‘Sintético 91801592’, ‘Sintético 91801596’, ‘Sintético 91801599’, ‘Sintético 91801600’, ‘Sintético 91801601’, ‘Sintético PESAGRO-RIO’, and ‘UFLA JM100 POP AXB’) and three polyethylene glycol (PEG-6000) concentrations at water potentials of 0.0, −0.2, and −0.4 MPa to simulate water deficit. The analyzed variables included germination, first germination count, germination speed index, shoot and root length, root volume, shoot and root fresh and dry mass, and electrolyte leakage. Water deficit reduced germination and vigor in the maize cultivars. The potential of -0.4 MPa had a significant impact on shoot length and shoot fresh mass of the cultivars, causing mean reductions 75%. The cultivars ‘BRS 2022’, ‘UFLA JM100 POP AXB’, ‘Sintético PESAGRO-RIO’, ‘PF 7008’, ‘HTC697’, ‘BRS Gorutuba’, ‘Sintético 91801596’, ‘MC 70’, ‘Capo 22’, ‘BRS Cruzeta’, and ‘Potiguar’ were the most tolerant at −0.2 and −0.4 MPa. The cultivars ‘HTC717’, ‘HTC795’, ‘Sintético 91801587’, ‘Sintético 91801590’, ‘Sintético 91801599’, and ‘Sintético 91801600’ were the most sensitive under more severe water deficit conditions (−0.4 MPa).