Seed germinability of Stylosanthes spp. (Fabaceae) accessions under water stress conditions

Tolerance to water and salt stress during germination and growth of agricultural species might have superior results when seeds are submitted to priming processes. The objective of the present study was to evaluate the use of hydropriming and hormonal priming with gibberellic acid (GA3) on the tolerance of divergent genotypes of sorghum to salt and water stress during germination and seedling growth. The genotypes analyzed were cultivar BRS 330 and lineage 201420, which are the most and least tolerant to water and salt stress, respectively. Sowing was undertaken under control (no stress), water stress (-0.6 MPa), and salt stress (20 dS·m-1) conditions, and the seeds were subjected to the following treatments: control-no immersion; hydropriming-immersion for 2 hours in distilled water; and hormonal priming-immersion in GA3 solutions, at concentrations of 50, 75, and 100 ppm, for 2 hours. After soaking, the seeds were dried for 24 hours at a temperature of 30°C ± 2°C. The variables analyzed were percentage and germination speed index, root and shoot lengths, and root/shoot ratio. The stress conditions analyzed negatively affected the two genotypes; however, the seeds that underwent priming processes improved the performance of the genotypes under salt and water stress conditions, especially when using seeds of the more tolerant genotype (BRS 330) subjected to hormonal priming at 100 ppm GA3 concentration.

Salinity and water deficiency are abiotic factors which have a strong impact on agricultural activities, especially in arid and semi-arid regions. The aim of this research was to analyse the tolerance of two genotypes of forage sorghum, EA 116 and BRS Ponta Negra, to different levels of water and salt stress during germination. The conditions of water and salt stress were simulated by moistening the substrate with a solution of mannitol and of sodium chloride (NaCl) respectively, with the water potential adjusted to 0 (distilled water), -0.1, -0.2, -0.3, -0.4, -0.5 and -0.6 MPa. The variables under analysis were germination percentage, first count, germination speed index, shoot and root length, seedling dry weight, electrolyte leakage and leaf Na+/K+ ratio. The experiment was conducted in a completely randomised design, and distributed in a 2 (genotypes) × 2 (stress condition) × 7 (osmotic potential) factorial scheme, with four replications. The EA 116 and BRS Ponta Negra genotypes show greater tolerance to water stress. The EA 116 cultivar maintained germination under water stress from 0 to -0.6 MPa and saline stress from 0 to -0.4 MPa.

The use of discontinuous hydration cycles can act in improving seed germination and seedling initial growth under water stress. In this context, the objective of this study was to evaluate the effect of discontinuous hydration on the germination of Mimosa caesalpiniifolia and Pityrocarpa moniliformis seeds under water stress. For this, seeds of these species were subjected to 0 (without hydration), 2 and 4 hydration cycles (18 h) and dehydration (12 and 18 h, respectively), with subsequent germination under water stress simulated for osmotic potentials of 0.0 (distilled water), -0.2, -0.4, -0.6 and -0.8 MPa. Seedlings were evaluated using tests of germination, germination speed index, mean germination time and seedling length. Discontinuous hydration in M. caesalpiniifolia and P. moniliformis seeds hampers germination and vigor of seedlings under water stress up to -0.6 MPa. However, the use of two cycles in P. moniliformis favors germination under more severe water stress (-0.8 MPa).

Information on the effects of climate conditions on the survival of species grown in semi-arid regions is essential and at the same time scarce, especially regarding rustic species such as West Indian gherkin (Cucumis anguria L.). Thus, this study aimed to evaluate germination, growth and biochemical alterations in C. anguria seeds under water stress and different temperature regimes. The experimental design was completely randomized, in 5 x 5 factorial scheme, composed of five osmotic potentials (0.0; -0.1; -0.2; -0.3 and -0.4 MPa) and four temperatures (20; 25; 30 °C and alternating temperatures of 20-30 oC), with each treatment composed of four replicates of 50 seeds. The seeds were sown on paper towel (Germitest®) and germinated in Biochemical Oxygen Demand (B.O.D.) germinators, under 8-h photoperiod. Germination percentage, germination speed index, mean time of germination, seedling length and contents of chlorophylls, carotenoids, proline, free amino acids and free sugars were determined along the experiment. Decrease in osmotic potential reduced germination, growth and contents of chloroplast pigments of C. anguria seedlings, but was more drastic at levels lower than -0.2 MPa. Low temperatures intensify the effects of water stress on the germination of C. anguria seeds. The synthesis of protecting osmolytes increased in C. anguria seedlings but these components did not promote efficient osmotic adjustment in their initial development stage.

Water is considered the most important environmental resource for the germination process. This study aimed to evaluate the germination performance of Parkia platycephala seeds under different conditions of water and saline stress. Seed germination was tested with solutions of poly (ethylene glycol) 6000 and sodium chloride (NaCl) at seven osmotic potentials [0.0, -0.2, -0.4, -0.6, -0.8, -1.0, and -1.2MPa (megapascal)] and four replicates with 25 seeds in a completely randomized design, simulating the water and saline stress levels, respectively. The following seedling variables were evaluated: germination percentage, germination speed index, length, and dry mass. Results showed significant interaction between the agent and the osmotic potential for all evaluated variables. P. platycephala seeds presented higher tolerance to saline stress simulated by NaCl than to water stress, showing germination performance appropriate for glycophyte plants.

Water stress limits the initial growth and development of maize mass and grain, as well as the physiological process for absorbing the amount of mineral elements. The objective was to evaluate the effect of silicon on germination and growth of corn seedlings submitted to water deficit. The experiment was carried out in the laboratory and the experimental design was completely randomized (factorial 3 × 4), with three concentrations of calcium silicate (0.0; 1.0 and 2.0 mM) and 4 solutions of PEG-6000 to simulate different osmotic potentials (0, 0; -0.3; -0.6; -0.9 MPa). Germination percentage, germination speed index (GSI), mean germination time (MGT), percentage of non-germinated and abnormal germinated, length and dry matter of shoot, root and total seedlings were evaluated. Water deficiency reduced the parameters TG, GSI and MGT. The water deficit reduce the MSPA, MSR and MST with more than 80% reduction in mass from seedlings without deficiency to seedlings with deficiency. For CPA, CR and CT there was a reduction of at least 87%, 70% and 77%, respectively, among seeds without deficiency compared to seeds submitted to deficiency. The use of silicon in corn seeds did not attenuate the stress caused by water deficit simulated by PEG-6000.

Tamarind (Tamarindus indica L.) is a fruit species native to Equatorial Africa, India and Southeast Asia. Its seeds experience slow germination, thus, study on the influence of environmental factors, such as water and salt stresses, on seed germination, is required to assess the tolerance of these seeds to storage, and to maintain the vigor and the viability in the period between harvesting and sowing. The objective of this study was to evaluate the performance of tamarind seeds subjected to salt and water stresses and to storage. Three experiments were carried out in a completely randomized design with four replications of 25 seeds, totaling 100 seeds per treatment. For stress conditions, treatments consisted of moistening of the substrate with different concentrations of PEG 6000 (experiment 1) and NaCl (experiment 2) - 0 (control); -0.3; -0.6; -1.2. For the storage trial (experiment 3), seeds remained stored for 0 (control), 12, 24, 36 and 48 months. In the germination test, the percentage of germination, the speed of germination index, the mean speed and the mean germination time were assessed. All variables were influenced by the water and salt stress, and the seeds of tamarind sensitive to potential used in this work. As in the test with water and saline potential storage trials showed that the physiological seed quality was impaired when they were subjected to long storage period. Key words: Tamarindus indica L, salinity, polyethyleneglycol, stress, storage.

This study aimed to evaluate the allelopathic effects of aqueous extracts of Tectona grandis L.F. in various concentrations produced from leaves and flowers. Seeds of lettuce (Lactuca sativa L.) and germitest paper as substrate were used, the germitest paper was moistened with distilled water, and aqueous extract in concentrations of 100%, 75%, 50%, 25% and 0% (distilled water). The extracts were homogeneously deposited on twenty-five seeds evenly distributed in gerbox-type boxes. The materials used in the experiment were previously sterilized with alcohol (70%). A completely randomized experimental design with four replicates was used and the experiment was conducted under natural conditions of temperature and humidity. The tests were carried out in the laboratory, the experiment was watched for 10 days always at the same hour and the variables analyzed were Germination Percentage (%G), Speed of Germination Index (SGI), Mean germination time (MGT) and Mean speed of germination (MSG). The data were submitted to Analysis of Variance and compared by Tukey test considering 95% of probability. It was observed that there were no significant differences in leaf and flower extracts for the variables %G, MGT and MSG, however, in SGI aqueous leaf extract differed significantly at the highest concentrations (75% and 100%). It was concluded that aqueous extracts of leaves and flowers of T. grandis had no inhibitory potential in relation to the percentage and average germination time of lettuce seeds at any of the concentrations.

Germination test is used to assess the physiological quality of seeds; however, since it is carried out under ideal conditions, this test has not been shown sufficient for this purpose. Instead, it is possible to use vigor tests, although the lack of standardized methodologies has reduced their applicability and reproducibility. Thus, this study aimed to develop methodologies for conducting tests of germination, accelerated aging, and electrical conductivity for the evaluation of the physiological quality of pitaya seeds. For this purpose, seeds from ripe Hylocereus undatus fruits were used. A completely randomized experimental design was used with four replications. The physiological quality of the seeds was assessed using germination, accelerated aging, and electrical conductivity tests, and the speed of germination index (SGI) and mean germination time (MGT) were determined for both the germination test and accelerated aging test. For the statistical analysis, we performed regression model adjustments and calculated the Pearson correlation coefficient (p < 0.05). The germination test for H. undatus seeds can be performed at 25 °C, with the aim of reaching the highest SGI and lowest MGT values. The accelerated aging test can be conducted at 43 °C for 48 h, because combining these factors favors the expression of seed vigor, allowing seeds to achieve the maximum SGI and minimum MGT, while reducing the time of the assay. The electrical conductivity test can be performed using 25 seeds at a temperature of 30 °C and a water volume of 10 mL, since under these conditions there is less interference from external factors on the leachate content of the solution.

<p>Germination test is used to assess the physiological quality of seeds; however, since it is carried out under ideal conditions, this test has not been shown sufficient for this purpose. Instead, it is possible to use vigor tests, although the lack of standardized methodologies has reduced their applicability and reproducibility. Thus, this study aimed to develop methodologies for conducting tests of germination, accelerated aging, and electrical conductivity for the evaluation of the physiological quality of pitaya seeds. For this purpose, seeds from ripe <em>Hylocereus undatus </em>fruits were used. A completely randomized experimental design was used with four replications. The physiological quality of the seeds was assessed using germination, accelerated aging, and electrical conductivity tests, and the speed of germination index (SGI) and mean germination time (MGT) were determined for both the germination test and accelerated aging test. For the statistical analysis, we performed regression model adjustments and calculated the Pearson correlation coefficient (p < 0.05). The germination test for <em>H. undatus </em>seeds can be performed at 25 °C, with the aim of reaching the highest SGI and lowest MGT values. The accelerated aging test can be conducted at 43 °C for 48 h, because combining these factors favors the expression of seed vigor, allowing seeds to achieve the maximum SGI and minimum MGT, while reducing the time of the assay. The electrical conductivity test can be performed using 25 seeds at a temperature of 30 °C and a water volume of 10 mL, since under these conditions there is less interference from external factors on the leachate content of the solution.</p>

Lack of water and salinity are commonly encountered problems in many regions worldwide. For this reason, certain robust cactus species may represent promising crops. Because it is necessary to assess the ability of cactus species to survive and adapt under conditions of natural stress, the present study aimed to evaluate the effect of water and salt stress on the vigor and viability of seeds of pitaya genotypes using different osmotic potential gradients and different osmotically active agents. The experiment had a completely randomized design with a 3 × 6 × 4 factorial scheme corresponding to three pitaya genotypes (white, hybrid I, and hybrid II), six osmotic potential gradients (0.0, -0.2, -0.4, -0.6, -0.8, and -1.0 MPa), and four osmotically active agents (PEG 6000, KCl, NaCl, and MgCl2), with four replicates. The following variables were analyzed: germination percentage, germination speed index (GSI), and mean germination time (MGT). Statistical analyses were performed for each pitaya genotype. The data pertaining to germination were fitted to a binomial model; the data pertaining to GSI and MGT were fitted to regression models. The germination, GSI, and MGT values for all three pitaya genotypes were optimal with the osmotically active agents KCl and NaCl, regardless of the osmotic potential gradient. At osmotic potential gradients lower than -0.2 MPa, the PEG 6000 polymer was detrimental to pitaya seed vigor and viability. The pitaya hybrid I seeds were more resistant to the adverse conditions, exhibiting higher rates of germination and GSI than those of the other genotypes. The osmotic effect negatively influenced the vigor and viability of seeds of the three pitaya genotypes to a greater extent than the salt effect. Key words: Cactaceae, Hylocereus undatus, Hylocereus costaricensis, polyethylene glycol, vigor.

This study aimed to evaluate the physiological quality of green corn seeds subjected to water stress. The experimental design used was completely randomized, in a 2 x 5 factorial arrangement, consisting of two corn hybrids (AG1051 and BRS3046) and five osmotic potentials (0; -0.4; -0.8; -1.2 and – 1.6 MPa) simulated with aqueous solutions of polyethylene glycol 6000 (PEG 6000), with four replications of 50 seeds per treatment, totaling 40 experimental units. The analyzed variables were: water content, germination, root protrusion, final root protrusion, germination speed index, root length and coleoptile length. There was a significant effect of the interaction between hybrid factors and osmotic potentials for all analyzed variables, except for final root protrusion, which showed an isolated effect for the two factors studied. The results obtained indicated a higher percentage of germination and initial development of green corn seedlings for green corn seeds, hybrids AG1051 and BRS3046 at the osmotic potential of 0.0 MPa. The germination and vigor of green corn seeds decrease under water stress conditions from the osmotic potential of -0.4 MPa induced by PEG 6000, inhibiting the development of normal seedlings, affecting seed viability. Hybrid AG1051 presents superior germination and vigor compared to BRS3046.

Environmental factors affect the germination process, like the presence of seed coat and the quality of light; these informations are still scarce for many native species from Brazil, especially for Senna cana, which there are no adequate standards and methodologies to be used in germination tests. The aim of this research was to recommend adequate pre-germinative treatment(s) to overcome seed dormancy, and determine the degree of influence of different light regimes in seed germination of S. cana. Two experiments were carried out: T1-evaluation of different methods of dormancy overcoming (intact seeds (control), T2-imbibition of the intact seeds for 24 hours (in distilled water), T3-scarified seeds with sandpaper n° 100 in the hilum opposite region, T4-scarified seeds with sandpaper n° 100 in the region the hilo opposite region and imbibition in water (in distilled water) for 24 hours; T5-imbibition in water at 80°C); 2-Influence of light quality on seed germination and vigor (white light, red light, far red light and absence of light). The evaluated parameters were: first germination count, percentage of germination, IVG (Germination speed index), MGT (Mean germination time). Treatments were compared by Tukey at 5% probability. The best method for overcoming seed dormancy was mechanical scarification with sandpaper nº 100. The germination of the seeds of S. cana can be classified as indifferent to the luminosity, despite germinative response be greater under white and red light.

Water is one of the factors that most influences the seed germination process; however, its excess can cause injuries to cell membranes due to rapid imbibition. On the other hand, water restriction limits seed germination, promoting a reduction in cell water potential that disrupts physiological and metabolic reactions. Thus, the objective of this study was to evaluate the physiological quality of sunflower seeds subjected to water stress induced by polyethylene glycol 6000 (PEG 6000). The experimental design used was completely randomized, consisting of six treatments consisting of osmotic potentials (0; -0.3; -0.6; -0.9; -1.2; and -1.5 MPa) simulated with aqueous solutions of PEG 6000. Germination, radicle protrusion, first count, germination speed index, abnormal seedlings, shoot length, and root length were evaluated. Water stress induced by PEG 6000 solutions affects the physiological quality of sunflower seeds, being proportional to the reduction of osmotic potential. Germination and seed vigor decrease under water stress conditions from an osmotic potential of -0.4 MPa, with the most negative potentials (-1.2 and -1.5 MPa) preventing seed germination.

The experiment was conducted into two stages, the first being the barley seed production and application of glyphosate and the second the vigour tests in the laboratory. Both stages were performed at the Experimental Farm of Agrarian Sciences at Grand Dourados Federal University (UFGD). In field, four cultivars of barley was sowing being: BRS Cryst, BRS Kallibre, BRS Demeter, BRS Sampa. For desiccation, the glyphosate herbicide (480 g L-1 of active ingredient) was used, applied using a backpack sprayer at dose of 5 L ha-1. The experimental design used was randomized blocks, and each cultivar was divided into five replications, applying the herbicide in four of them leaving one without application for control. The application was made when seeds presented water content close to 50%. At second stage, eight evaluation were made being one at the day of glyphosate application, one, two, three, eight, ten and fourteen days after application and without application in natural physiological maturity. In each evaluation, sowing was performed according to Rules to Seed Analysis. The analyses were: First count, percentage of germination, germination speed index, mean germination time, mean germination speed, accelerated aging and synchronization index. Glyphosate has interfered negatively in the physiological maturation of barley seeds when the herbicide was applied in pre-harvest. The results obtained showed that there was an increase in seeds germination after 14 days of application, however, the means were significantly smaller in relation to seeds harvested at the point of physiological maturation without glyphosate application.