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.

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.

A qualidade da semente impacta diretamente nas características agronômicas e na produtividade final da cultura da soja. Diante disso o objetivo do trabalho foi avaliar diferentes parâmetros fitotécnicos e a produtividade final para diferentes cultivares de soja obtidos de forma certificada e salvas pelo produtor rural. O trabalho foi realizado na Área Experimental da Universidade de Cruz Alta. Durante a safra 2017/2018, foram avaliados os parâmetros fitotécnicos: altura de plantas, diâmetro da haste, número de ramos, número de vagens, acamamento e produtividade final para as cultivares NA5909RG, NS5959IPRO, NS5445IPRO e NS6909IPRO sob diferentes formas de obtenção, sendo estas, “sementes salvas” e “sementes certificadas”. Os parâmetros fitotécnicos avaliados foram influenciados pela forma de obtenção da semente para as cultivares NS5445IPRO e NS6909IPRO. Dentre as cultivares avaliadas, verificou-se que as produtividades de NS5445IPRO e NS6909IPRO foram superiores em plantas oriundas de sementes certificadas.