Action of nitric oxide on the physiological potential and biochemical mechanisms of pea seeds

Nitric oxide (NO) can act in biochemical pathways of the germination process; however, there is little information about how it acts on the performance of pea seeds. The aim of this study was to evaluate the physiological and biochemical effects of NO on pea seed germination and vigor. Pea seeds cv. Itapuã 600 obtained from three seed lots with different levels of physiological quality were sown in a substrate moistened with water (control) or sodium nitroprusside (SNP) solution, a NO donor (50 μM), to assess germination, vigor, activity of antioxidant enzymes, reactive oxygen species, lipid peroxidation, and amylase activity. NO application does not alter pea seed germination, but it increases vigor. It is more effective in seeds with lower physiological potential. In addition, NO leads to reduction in oxidative stress, favors the translocation of reserves to the embryo, and has potential for use in the treatment of pea seeds to increase seed vigor.

Effect of Gluconacetobacter diazotrophicus inoculation and reduced nitrogen fertilizer on yield and growth parameters of rice varieties

This study aimed to investigate effects of nitrogen (N) fertilizer rates and inoculation of rice seeds with N-fixing bacterium Gluconacetobacter diazotrophicus on the growth parameters and yield of OM5451 and OM6976 rice varieties in the Vietnamese Mekong Delta region. Nitrogen fertilizer rates of 50 kg N.ha-1 and 100 kg N.ha-1 were used, with latter reflecting farmer practice. Three rice seed inoculation methods were also employed: Seeds soaked in water for 24 hours and allowed to stand for 30 hours (control) (B0); Seeds soaked in water for 24 hours and inoculated with G. diazotrophicus for 30 hours (B1); Seeds soaked with G. diazotrophicus in water for 24 hours and allowed to stand for 30 hours. Applying 50 kg N.ha-1 without combining with NFB bacterium in this experiment generally resulted in less tillers, shorter plants, a lower SPAD index, and lower grain yield. Combining G. diazotrophicus bacterium with reduced N fertilizer of 50 kg N.ha-1 demonstrated rice growth and yield may be maintained in both varieties compared to 100 kg N.ha-1. These results providing a firm foundation for future research of adding NFB to paddy soils to decrease the N fertilizer requirement.

Metabolites of the phenylpropanoid pathway and physiological quality of soybean seeds in storage

The aim of this study was to evaluate changes in the physiological quality of soybean seeds throughout a storage period in two environments, and to evaluate how these changes are related to metabolites of the phenylpropanoid pathway. A completely randomized experimental design was used in a 4 × 8 factorial arrangement (storage periods × cultivars) with four replications. We used seeds from cultivars with contrasts in lignin content, color, and presence of anthocyanin in the seed coat, and isoflavone content in the seed. The seeds were kept for six months under cold and dry storage and in a non-controlled environment. Germination, first germination count, seedling emergence, and tetrazolium testing were performed on the seeds every two months. The physiological quality of the seeds declines during the storage period, with higher rates of decrease in the non-controlled environment. The metabolites of the phenylpropanoid pathway that were studied, especially lignin, affect seed storage potential. Cultivars with higher lignin content show greater storage potential, especially in a non-controlled environment.

Effect of priming and different types of drying on the physiological quality of Urochloa ruziziensis seeds

Seed vigor is one of the main limitations to meet the demanding forage market. In order to boost the productive potential and provide the satisfactory development of quality seeds and seedlings, it is necessary to develop techniques that provide quality and high productivity. With the Urochloa genus stands out in the seed production and quality, this study aimed to evaluate the effect of seed priming with sodium nitroprusside and to define the best drying method that allows the maintenance of the changes of this treatment in Urochloa ruziziensis seeds. The seeds were conditioned in sodium nitroprusside solution, as a nitric oxide donor, for 42 hours and later submitted to the following procedures: no drying, initial reduction of water content, thermal shock, slow and fast drying. The design was completely randomized, with ten treatments and four replications. Water content, germination, emergence and biochemical evaluations were performed. As results, it was observed that all drying methods evaluated reduced the water content of the seeds to 12%, recommended range for storage, with the exception of the treatment without drying that presented 30%. Regarding germination parameters, the treatment of initial reduction and quick drying obtained the best performance in germination and emergence. Moreover, the types of drying presented high rate of enzymatic activity of the antioxidant system, thus helping in the maintenance of redox homeostasis. According to the enzymatic activity and germination rates, it suggests that the rapid drying method after priming with nitric oxide is the best method for Urochloa ruziziensis.

Chitosan coating on bean and maize seeds: release of agrochemical fungicide and post-storage condition

Chitosan is a biopolymer obtained from deacetylation of chitin; it has multiple applications in agriculture as an antifungal, soil conditioner, inducer of defense mechanisms, fruits postharvest coating, leaves and seeds, among others. The objective in this research was to evaluate the effect of chitosan coatings mixed with fungicide (dithiocarbamate) on the germination and germination speed of bean and maize seeds in storage and to determine the retention capacity of the fungicide in the coated seeds under different times of imbibition. Two coating treatments at concentrations of 0.1 and 0.5% chitosan in water, two coatings treatments at 0.1 and 0.5% chitosan supplemented with 0.5% fungicide and a coating without chitosan using only 0.5% fungicide in water were used in bean and maize seed; and as control seeds imbibed in distilled water were used; after treatments, germination percentage and germination speed were determined, also fungicide release were determined at 0, 1, 2 and 6 h of imbibition, and the effect of storage time on germination and germination speed was determined at 30, 60, 90, 120, 150 and 180 days of storage at 4 °C and 45% relative humidity. The fungicide release effect was determined by inhibiting Fusarium oxysporum conidia germination. There were no negative effects of coatings on seed germination after storage. The treatment that provided both greater retention of the fungicidal agent and released it gradually, was 0.5% chitosan mixed with fungicide concentration. Chitosan coating seeds mixed with fungicide do not cause negative changes in seed germination or germination rate.

Physiological and biochemical responses of “mofumbo” seeds during storage

“Mofumbo” (Combretum leprosum Mart. (Combretaceae) is a neotropical species of wood, pharmacological, beekeeping and environmental importance. Thus, the objective was to evaluate the biochemical and physiological responses in C. leprosum seeds under different storage environments. The experiment was carried out in a factorial (2 x 7), with two storage conditions (natural and climate-controlled environments) and seven storage periods (0; 60; 120; 180; 240; 300 and 360 days), in four replications per treatment. At the beginning of storage and at 60-day intervals, the seeds were analyzed for water content, physiological potential (germination, germination speed index, root and shoot lengths and seedling dry mass) and biochemical (neutral lipids, lipid peroxidation, total and reducing sugars, total free amino acids, and starch). The results indicated that storing “mofumbo” seeds for 360 days reduced viability, being more pronounced after 180 days, regardless of the storage environment. “Mofumbo” seeds were stored in a natural environment for 180 days, resulting in less lipid degradation. After this period, the reduction was associated with the attack of reducing sugars on amino acids. Thus, it is concluded that “mofumbo” seeds must be stored in a natural environment for up to 180 days.

Effect of seed vigor and sowing densities on the yield and physiological potential of wheat seeds

Initial seed vigor and sowing density interact in establishment of plants in the field, and can thus affect expression of the plasticity of the wheat crop and the yield and physiological quality of the seeds produced. The aim of this study was to evaluate the effect of seed vigor levels in combination with sowing densities on the yield and physiological potential of wheat seeds. The cultivars BRS Gralha-Azul and BRS Sabiá were used in a randomized block experimental design in a 2 × 4 factorial arrangement, with four replications. The treatments consisted of seeds of high and low vigor and four sowing densities (150, 250, 350, and 450 seeds.m-2). The following evaluations were made: seed yield, germination, first germination count, seedling length, seedling dry matter, accelerated aging, emergence speed index, and seedling emergence in sand. An increase in sowing density favors the seed yield of both cultivars; however, it reduces the vigor of the seeds produced by the cultivar BRS Gralha-Azul, especially of the seeds produced by plants originating from high vigor seeds. For the cultivar BRS Sabiá, an increase in sowing density decreases the germination performance of seeds produced by plants originating from low vigor seeds.

Is it possible to estimate longevity through the analyses used to measure the initial physiological potential in soybean seeds?

The analysis of longevity can support decisions about the length of seed lot storage until commercialization, since this characteristic implies the maintenance of viability over time. Seed longevity is analyzed by the p50 test, which expresses the time to lose 50% of the initial viability. Seeds with high vigor and germination have greater physiological potential and, thus, a greater capacity to maintain quality throughout the storage period. However, there has been little research on the correlations between the analysis of p50 (longevity) and the tests used to measure physiological potential (germination and vigor) of lots, which can be used as a tool to make inferences about longevity using the most traditional tests. Thus, the objective of this study was to investigate which tests used to measure the potential of lots can estimate p50. To this end, germination and vigor were evaluated using traditional tests while longevity was assessed in eight soybean seed lots. Correlations and linear regression were tested for the traditional variables versus p50. It was found that the use of accelerated aging, electrical conductivity, and time to 50% radicle protrusion has high potential to estimate longevity as measured by p50.

Quantification and conceptual validation of the inoculum potential of Sclerotinia sclerotiorum in soybean and bean seeds

The fungus Sclerotinia sclerotiorum, the causal agent of white mold, is widespread throughout the world. The disease is considered to be one of the major diseases of soybean and bean crops in Brazil. The pathogen S. sclerotiorum is spread by soybean and bean seeds both in the form of sclerotia and dormant mycelium inside the seeds. The objective of this work was to evaluate the relationship between different potentials of S. sclerotiorum in soybean and bean seeds and the performance of these seeds, as well as to verify the localization and quantification of the inoculum of the pathogen in the seeds inoculated by Real-time PCR (qPCR), validating the term inoculum potential. Soybean and bean seeds were inoculated with the fungus by the osmotic conditioning method based on the exposure of the seeds to the fungus for periods of 24 h, 48 h, 72 h, and 96 h. Molecular analysis was carried out by means of qPCR in whole seeds and dissected in the integument, cotyledon and embryonic axis. The results showed that the effects of S. sclerotiorum on seed germination and vigor were progressive and proportional to the increases in inoculum potentials, since there was more severe damage to the seeds and consequently to the emerged plants at the highest potential (P96). The inoculum of the pathogen was found in all parts of the evaluated seeds, even at its lowest inoculum potential (P24), with an increasing DNA concentration, and the integument obtained a greater amount of DNA than the embryo, in comparison.

Morphological parameters of image processing to characterize primary root emergence in evaluation of tomato seed vigor

The use of computational tools has become notable in seed quality control to assist in confirming seed lots of higher potential. Thus, the aim of this study was to use a computational approach to investigate analysis of morphological parameters that characterize primary root emergence in evaluation of tomato seed vigor. For that purpose, five seed lots were analyzed for germination and vigor (seedling emergence and analysis of seedling images). A parallel analysis of primary root emergence was made using computer-assisted imaging; the images recorded as germination proceeded were processed with the ImageJ® software to obtain aspect ratio and seed area parameters. Vigor differences among tomato seed lots can be identified based on primary root emergence, and computer image processing based on aspect ratio proves to be an efficient procedure to characterize emergence of the primary root in evaluation of tomato seed vigor.