Plant Growth Regulators and Biostimulants as Alternatives for Managing Flowering and Fruiting of Mandarins

The chapter explores the use of plant growth regulators (PGRs) and biostimulants to manage mandarins flowering and fruit set in mandarins, addressing challenges such as alternate bearing, where irregular fruit production occurs between harvests. PGRs, such as gibberellins and auxins, are used to regulate fruit set, fruit size and quality, while mitigating alternate production by thinning fruit or inhibiting excessive flowering. Biostimulants, including humic substances and coumarins, have the potential to be used in the management of citrus flowering and fruit set, although their exact modes of action are still partially understood. Humic substances, derived from organic matter, have growth-regulating properties similar to those of PGRs, while coumarins, secondary metabolites, have antioxidant and gibberellin-like effects. The study highlights the importance of timing and methods of application of PGRs and biostimulants to optimize fruit production and quality, particularly in citrus cultivars with a tendency to alternate production. Integrating these tools offers a sustainable approach to improving citrus productivity while addressing environmental and agricultural challenges.