Plant biostimulants have been increasingly used in agriculture. Plant biostimulants have been mostly investigated regarding their stress attenuation and only a few reports have brought information on their effects on fruit quality, which is related to appearance, chemical and physical attributes. Due to their organic nature, they have a sustainable appeal, attending the demand of consumers worried about the beneficial effects of healthier foods. This review turns evident the little information available on this matter. As fruits have differentiated metabolism, from pollination to harvest and after-harvesting, it is suggested that further research should focus separately on each stage. Thus, research should aim at quality formation, when the fruits are still attached to the plant, and shelf life extension, after harvesting.

Computerized systems for image analysis are alternatives to decrease the subjectivity and speed of assessment of seed physiological potential. The aim of this study was to determine the efficiency of the Seed Vigor Automated Analysis System (Vigor-S) to identify differences in vigor among soybean seed lots compared to results of the Seed Vigor Imaging System - SVIS® and tests recommended for evaluation of soybean seed vigor. Two cultivars were used, BMX Potência RR and 7166 RSF IPRO, each one represented by ten seed lots with similar germination and vigor differences. The seeds were evaluated regarding germination, vigor (tetrazolium, accelerated aging), seedling emergence in the field and SVIS® and Vigor-S analysis, in three experimental periods. Analysis of variance was used on the data in a completely randomized experimental design (laboratory tests) and in randomized blocks (field tests), and the mean values were compared by the Tukey test (p ≤ 0.05). Separation of the seed lots by Vigor-S was consistent with the results obtained in tests recognized as effective in evaluating the physiological potential of soybean seeds, and there was no interference of the different cultivars on the response pattern for vigor. Analysis through Vigor-S proved to be effective in determination of physiological potential and for composition of quality control programs established by soybean seeds production companies.

Algae extract biostimulants increase nutrient uptake, stress tolerance, and productivity in several crops. However, there is still a gap in the knowledge of the mechanisms of action of algae extracts on nitrogen plant metabolism. This study aimed to evaluate the effect of a commercial Ascophyllum nodosum algae extract on nitrogen metabolism in nodulating soybean plants and their productivity. Two concentrations of algae extract (0.25% and 0.50%) were used, which were applied via seeds and leaf spray. Seeds were treated at sowing, and plants were sprayed twice at two vegetative phenological stages. Plants were harvested at the R5 phenological stage for leaf biochemical and enzyme activity analyses and leaf and root gene expression analyses. The experiment was carried out a second time to evaluate productivity. There was an increase in leaf and stem biomass, number of pods and seeds, weight of pods and seeds, and productivity in plants treated with both concentrations. Biochemical analysis showed increased amino acid content in leaves after extract application. No marked differences were found regarding the parameters related to nitrogen metabolism when the data were analysed individually. However, principal component analysis and gene expression heatmaps supported the conclusion that N metabolism was affected by algae extract application, leading to higher seed production.

Protein hydrolysates are plant biostimulants containing amino acids, oligopeptides, and peptides in their composition. When supplied to plants, protein hydrolysates (HPs) have been identified to improve nitrogen metabolism, enhance the activity of antioxidant enzymes, boost plant defense response to stresses, and positively impact the quantity and quality of products. Soybean is a crucial global commodity, with nitrogen being the primary nutrient for crop development as it directly affects productivity. This study aimed to evaluate the effect of an HP-based biostimulant on the N metabolism in nodulated soybean plants and their productivity. A greenhouse experiment was conducted to test two modes of application of the 0.20% HP-based biostimulant. Soybean plants, growing in pots, were treated with 0.20% HP either via seed treatment or foliar application (at growth stages V3 and V5). Activities of enzymes and compounds related to N metabolism, gene expression, and productivity components were analyzed. It was observed that the mode of application did not significantly influence the results. The application of HPs increased the concentration of nitrate, amino acids, and ureides in soybean leaves. It also positively altered the expression of genes such as nitrate reductase, urease, and asparagine. Additionally, it enhanced productivity, resulting in plants with a greater number and weight of pods and grains. Therefore, it is possible to consider HPs as a stimulator for increasing soybean productivity, even under non-stressing conditions.

The study was carried out in Selvíria-MS, in the 2011/12 and 2012/13 agricultural years, aiming to evaluate the efficiency of Azospirillum brasilense in nitrogen fixation in upland rice, as a function of doses and application methods of the inoculant containing this diazotrophic bacterium. The experimental design was randomized blocks, arranged in a 4 x 4 factorial scheme, with 4 doses of inoculant (control without inoculation, 100, 200 and 300 mL of the commercial product ha^-1) and 4 application methods (seed inoculation, application in the sowing furrow, soil spraying after sowing, and foliar spraying at the beginning of plant tillering), with 4 replicates. During the experiment, the agronomic characteristics, production components and yield of the rice crop were evaluated. It was concluded that the inoculant containing Azospirillum brasilense promotes increase (19%) in the yield of upland rice under sprinkler irrigation when used at the dose of 200 mL ha^-1, regardless of the application methods.

The accelerated aging test is widely used to evaluate the vigor of soybean seeds. Currently, the methodology recommended in the literature is to set up the germination test at most one hour after the seed aging process, which makes it difficult to set up and evaluate a large number of samples. The aim of this study was to assess the effect of delay in setting up the germination test after the process of accelerated aging of soybean seeds, specifically its effect on seed physiological performance. We tested three seed lots of the soybean cultivars BRS 397, BRS 399 RR, BRS 1007 IPRO, BRS 1010 IPRO, and BRS 388, all within the standards required for commercialization. The seed lots were physiologically characterized by evaluation of moisture content, germination, seedling vigor classification, tetrazolium test (viability and vigor) and accelerated aging test. The treatments consisted of hours (0, 1, 2, 3, 4, 5, 6, 7, and 8) of delay in setting up the germination test after accelerated aging. A delay of up to eight hours in setting up the germination test after the accelerated aging process of soybean seeds has no direct relationship with the result of assessment of the physiological performance of the seed lot.