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.

The accelerated aging test consists of evaluating the vigor of the seeds under conditions of high temperature and humidity, with the purpose of identifying the physiological quality of lots with similar germination. The objective of this study was to evaluate the efficiency of the accelerated aging test for classifying seed lots of P. moniliformis at different levels of vigor. Initially, the seed lots were assessed by means of seedling emergence, life velocity index, shoot length and root length, total dry mass of seedlings and determination of water content, before and after each period of aging. The experimental design for the whole world was based on a 3 × 4 factorial scheme (three seed lots and four periods of 24, 48, 72 and 96 h duration), with separate evaluations at temperatures of 38 °C and 41 °C. The accelerated aging test conducted at a temperature of 41 °C for 24 h was a more suitable combination for separating batches of P. moniliformis according to different levels of vigour, and made it possible to obtain results similar to the classification of lots in relation to the initial quality.

Melon is one of the most consumed cucurbits and commercially significant cucurbits in the world. It is planted predominantly through seedlings, and seed quality is essential in this process. Among the rapid tests used in seed analysis, the pH testing of exudate has shown promise for several cultivated species. Thus, this study aimed to verify the viability of melon (Cucumis melo L.) seeds through the pH testing of exudate. For this, seeds of the hybrids Premier and Supreme (three lots each) were subjected to germination and vigor tests (first germination count, tetrazolium, accelerated aging, emergence speed index, and emergence). The pH testing of exudate was evaluated using phenolphthalein and sodium carbonate solutions. The results indicated the possibility of classifying the lots into three quality levels for both hybrids, similar to most tests used to assess initial quality. Therefore, the pH testing of exudate was effective in determining the viability of lots of melon seeds and can be conducted with a soaking period of 120 minutes at 25 or 30 °C.

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.