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.

Physalis angulata L. (Solanaceae), known as ‘camapu’, has pharmacological and agroindustrial potentials, but information on the ecophysiological aspects that influence germination is scarce. In this context, the objective was to evaluate the expression of the physiological potential of P. angulata seeds as a function of the maturation stage, temperature, substrate and light condition. Four experiments were conducted: in the first, the maturation stages (green calyx + fruit, yellow calyx + fruit and light brown calyx + fruit) were evaluated at temperatures of 25, 30 and 35 °C, separately; in the second, the interaction between the temperatures of 35, 40 and 45 °C and types of substrate (on paper, between paper and between vermiculite) was tested in a 3x3 factorial scheme (temperatures as the first factor and types of substrates as the second factor); in the third experiment, the effect of light (absence of light, white light, red and far-red light) was evaluated; and, in the fourth, increasing values of photoperiods (0, 8, 12 and 16 hours) were used. In all experiments, the design was completely randomized with four replicates of 50 seeds. Analysis of the results showed that there was no interaction between the temperatures and the substrates tested, demonstrating the isolated action of the factors. P. angulata seeds expressed better physiological potential when the calyx and fruit are yellow. In the germination test, the seeds should be sown between paper towels, under temperature of 35 °C and absence of light.

Este relato apresenta os resultados do trabalho realizado por um grupo de alunos do curso de Ciências biológicas do IFPI - São João do Piauí, que desenvolveram um filtro de água caseiro e de baixo custo para auxiliar a população da cidade no tratamento complementar da água distribuída. Tal medida foi exitosa e se mostrou bastante viável no que diz respeito a melhoria das condições de saúde da população. DOI: http://dx.doi.org/10.35700/ca.2020.ano7n12.p52-56.2611

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.

Semiarid regions are frequently affected by low water availability, which hinders the development of horticultural species such as melon (Cucumis melo L.). In this context, techniques that enhance drought tolerance are essential for more effective crop management. This study aimed to evaluate the tolerance and antioxidant activity of different melon cultivars using seed pre-treatment with stress-attenuating agents. The experiment was conducted in two stages, both arranged in a completely randomized design with four replicates of 50 seeds. In the first stage, a 3 × 5 factorial scheme was used, combining three levels of water deficit (0.0, −0.15, and −0.3 MPa) and five melon cultivars (“Dali”, “Premier”, “Supreme”, “Imperial 45”, and “Asturia”). The second stage consisted of the two previously selected cultivars (one sensitive and one tolerant), subjected to combinations of water deficit and attenuating agents: T1 = 0.0 MPa (control), T2 = −0.15 MPa (water deficit), T3 = −0.15 MPa + hydropriming (12 h), T4 = −0.15 MPa + gibberellic acid, T5 = −0.15 MPa + ascorbic acid, T6 = −0.15 MPa + salicylic acid, and T7 = −0.15 MPa + hydrogen peroxide. In the first stage, morphological and biochemical variables were evaluated. In the second stage, the same variables were analyzed, along with citrulline content, hydrogen peroxide and malondialdehyde levels, and the activity of superoxide dismutase, catalase, and ascorbate peroxidase. Overall, salicylic acid mitigated the effects of water stress on germination, seedling length, and dry mass in the cultivar Dali. For the sensitive cultivar (Imperial 45), hydrogen peroxide reduced the production and accumulation of H2O2, mainly through the action of the enzymatic antioxidant system, resulting in improved germination performance under water deficit.

As one of the most economically important cucurbit crops, melon (Cucumis melo L.) is extensively cultivated in semi-arid and tropical regions where high evaporative demand frequently intensifies salt accumulation. These conditions promote the evaporative concentration of salt, leading to salt accumulation in soil and irrigation water, which can impair crop development. Therefore, identifying approaches capable of maintaining seedling establishment under saline conditions is crucial for sustainable melon production. This study evaluated tolerance and antioxidant responses in different melon cultivars using seed treatments to mitigate salt stress effects. The experiment was conducted in two stages under a completely randomized design with four replicates of 50 seeds. In the first stage, a 3 × 5 factorial design tested three salinity levels (0, 60, and 120 mM NaCl) and five cultivars (‘Dali’, ‘Premier’, ‘Supreme’, ‘Imperial 45’, and ‘Asturia’), assessing morphological, physiological, and biochemical traits. In the second stage, two contrasting cultivars (‘Imperial 45’ (sensitive) and ‘Asturia’ (tolerant)) were exposed to salinity combined with stress attenuators, including hydropriming, gibberellic acid, ascorbic acid, salicylic acid, and hydrogen peroxide. Additional biochemical markers and antioxidant enzyme activities were analyzed. Results showed that gibberellic acid and ascorbic acid enhanced antioxidant activity and reduced oxidative damage, particularly in Imperial 45, whereas hydrogen peroxide was more effective in Asturia. Based on their physiological and biochemical responses during germination and early seedling development, Asturia and Imperial 45 were identified as tolerant and sensitive to salt stress, respectively. These findings indicate that the effectiveness of seed treatments depends on cultivar-specific physiological characteristics at the seedling stage.