Foliar application of plant growth regulators changes the nutrient composition of sweet pepper (Capsicum annuum L.)

• GA3 reduces yield and carbohydrate content.
• GA3 and ABA reduce pepper colour.
• GA3 increases P and Fe content in pepper.
• Tyrosine content is quadrupled by GA3 foliar application.

Plant growth regulators (PGRs) may have an important role in regulating both yield and fruit quality during the production of sweet pepper in controlled-environment greenhouses, but the uncertainly of results – due to the specificity of the plant response – could limit their use and potential benefits. Therefore, we investigated the effect of the foliar spraying of abcisic acid (ABA), gibberellic acid (GA3) and indole-3-acetic acid (IAA) on fruit colour, concentrations of carbohydrates, ions and amino acids, plant growth and total fruit yield. Although yield was decreased by the GA3 and ABA treatments, GA3 augmented plant height and the levels of tyrosine, phosphate, sulphate, iron and phosphorus while decreasing the amounts of glucose and fructose. The foliar applications of IAA did not produce any change when compared with the control plants, while plants treated with ABA had decreased levels of sucrose but higher levels of iron. GA3, applied fortnightly, produced a significant improvement in the fruit quality of sweet pepper but did not significantly increase total yield. Further studies will be necessary to determine the best GA3 concentration and frequency of application, to obtain greater benefits for human consumption this important crop.

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