Role of plant growth regulators in fruit crop production: Physiological mechanisms and practical applications

Introduction

The discovery of plant hormones during the early twentieth century fundamentally changed understanding of how plants coordinate growth and development [1] . These naturally occurring compounds including auxins, gibberellins, cytokinins, ethylene, and abscisic acid regulate virtually every aspect of plant life from seed germination through senescence. The subsequent development of synthetic analogs and commercial formulations enabled practical application of hormone manipulation in agricultural production systems [2] . Fruit production presents unique opportunities and challenges for growth regulator applications. Unlike annual crops where manipulation targets primarily vegetative development, fruit crops require coordinated management of perennial woody structure, annual reproductive cycles, and fruit maturation processes [3] . The extended production life of orchards justifies investment in sophisticated management inputs, while high crop values support premium pricing of growth regulator products. Commercial growth regulator applications in fruit crops target multiple objectives including regulation of vegetative vigor, flower induction and enhancement, fruit set improvement, control of fruit development and quality, and manipulation of harvest timing and post-harvest behavior [4] . Each objective requires understanding of the specific physiological processes involved and selection of appropriate compounds, concentrations, and application timing to achieve desired outcomes. This review examines the physiological mechanisms through which major growth regulator categories affect fruit crop production, synthesizes evidence regarding practical applications across important fruit species, and identifies best management practices for integration into commercial production programs [5] . The goal is to provide both theoretical understanding and practical guidance for optimizing growth regulator use in modern fruit production systems.

Material and Methods

Material

This review synthesizes published research on plant growth regulator applications in fruit crops from peer-reviewed journals, institutional publications, and industry technical reports. Literature searches were conducted using standard databases including CAB Abstracts, Web of Science, and Google Scholar using keywords related to specific growth regulators, fruit species, and physiological processes [6] . Studies were selected based on relevance to commercial fruit production, quality of experimental design, and practical applicability of findings.

Methods

Information was organized by growth regulator category and application objective to facilitate comparison across studies and identification of consistent patterns. Quantitative data on response magnitudes were extracted where available to characterize typical ranges of effects achievable under commercial conditions [7] . Recommendations were formulated based on convergent evidence from multiple sources, with recognition of variability introduced by environmental and management factors.

Physiological Mechanisms

Growth regulators exert effects through specific receptormediated signaling pathways that modify gene expression and cellular processes. Auxin perception involves the TIR1/AFB receptor complex that targets transcriptional repressors for degradation, releasing expression of auxinresponsive genes [8] . Gibberellin signaling similarly involves receptor-mediated destruction of DELLA repressor proteins. Understanding these molecular mechanisms explains the concentration-dependent nature of growth regulator responses and guides development of improved compounds with enhanced specificity.

Results

Discussion

The effectiveness of growth regulator applications depends critically on matching compound selection and application timing to specific physiological objectives [9] . Gibberellic acid remains the most versatile compound with documented benefits across numerous species and production objectives. However, its effectiveness varies substantially with cultivar genetics, tree age, nutritional status, and environmental conditions prevailing during and following application.

Growth retardants including paclobutrazol have gained popularity for managing tree vigor in high-density plantings and inducing flowering in irregular bearing species [10] . The soil application method provides extended activity but raises concerns about persistence and potential groundwater contamination. Foliar applications offer shorter residual activity suitable for seasonal management without accumulation issues. Integration of multiple growth regulators in programmed sequences can achieve outcomes not possible with single applications. For example, paclobutrazol application during the rest period followed by gibberellin at bud swell can both enhance flowering intensity and improve fruit set in mango [11] . Such integrated approaches require careful attention to compound interactions and cumulative residue management.

Limitations

This review draws primarily from published research that may not fully represent commercial production conditions. Variability in experimental protocols limits direct comparison across studies. Newer compounds and formulations may not have sufficient research history for definitive recommendations. Regional differences in climate, cultivars, and management practices require local validation of general recommendations.

Conclusion

References

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