Flower senescence: A comprehensive update on hormonal regulation and molecular aspects of petal death

Abstract

Senescence marks the final phase in the ontogeny of flower development, characterized by a cascade of physiological, biochemical, and molecular changes that lead to cellular degradation and subsequent death of petal tissues. This process, widely regarded as a developmental form of programmed cell death (PCD), parallels apoptosis, involving a succession of metabolic shifts, ROS accumulation, lipid peroxidation, and the breakdown of essential cellular components such as proteins, nucleic acids, and carbohydrates. The crosstalk of various plant growth regulators (PGRs), such as ethylene, abscisic acid (ABA), gibberellic acid (GA), and cytokinins (CK) during floral senescence are well-established. However, a comprehensive understanding of flower senescence at the molecular level is anticipated to elucidate the underlying mechanisms. While the role of ethylene is well-documented in ethylene-sensitive flower senescence, less is known about its role—or lack thereof—in ethylene-insensitive flowers, where hormones like ABA regulate this process. Several genes, transcription factors, and enzymes associated with ethylene- and ABA-mediated senescence have been identified. Interestingly, the targeted genetic manipulation of these components has potentially delayed flower senescence and extended flower longevity. Despite significant advances in understanding flower senescence, comprehensive studies on ethylene-sensitive and ethylene-insensitive species remain limited. In this context, the current review offers a detailed understanding of the physiological, biochemical, and molecular mechanisms orchestrating flower senescence. Besides, it emphasizes the intricate crosstalk among PGRs and other cellular processes that converge to initiate senescence and PCD in flowers. The review also highlights the importance of interdisciplinary approaches to further elucidate these mechanisms and proposes future research directions to advance the field. These insights are expected to facilitate the development of predictive models for PCD and senescence across various plant families and to propose novel strategies for enhancing the postharvest quality and longevity of cut flowers.