Which hormone is present in pears? A detailed guide to fruit ripening

November 30, 2025 •

3 min read

While many enjoy the sweet taste and soft texture of a ripe pear, few consider the complex biology behind its transformation. A key part of this process involves the plant hormone ethylene, which triggers and regulates the fruit's ripening. However, ethylene does not act alone; a complex network of phytohormones orchestrates the pear's entire life cycle from fruit set to senescence.

Quick Summary

Pears contain the gaseous plant hormone ethylene, which is crucial for triggering and accelerating ripening. Other phytohormones, such as auxin and abscisic acid, also regulate various developmental stages through a complex network of interactions.

Key Points

Primary Ripening Hormone: Pears are climacteric fruits that produce ethylene, a gaseous hormone that initiates and accelerates ripening, leading to changes in texture, color, and aroma.
Supporting Phytohormones: Beyond ethylene, pears contain a suite of other plant hormones, including auxins, gibberellins, abscisic acid, and cytokinins, all of which regulate different stages of fruit development.
Hormonal Crosstalk: The ripening process is regulated by a complex interplay, or crosstalk, between these different hormones. For example, the balance of auxins and gibberellins during early growth shifts to favor ethylene and abscisic acid during maturation.
Maturation Signal: Abscisic acid (ABA) levels accumulate as the pear matures, working synergistically with ethylene to promote ripening, including fruit softening and flavor development.
Phytoestrogens Present: Pears also contain phytoestrogens, which are plant-derived compounds with mild estrogen-like effects in the human body, but they are not the same as human hormones.
Controlling Ripening: The production of ethylene is why storing unripe pears with other ethylene-producing fruits like bananas can speed up their ripening in a concentrated environment, such as a paper bag.
Impact on Quality: The intricate hormonal balance throughout the pear's development significantly influences its final quality, including texture, flavor profile, and post-harvest behavior.

The Primary Ripening Hormone: Ethylene

Pears, like bananas, apples, and tomatoes, are classified as climacteric fruits. This means they exhibit a rise in respiration and ethylene production after harvest, which drives ripening. Ethylene ($C_2H_4$) is the main hormone orchestrating this process, impacting color, texture, and aroma.

Autocatalytic Process: Ripening is autocatalytic; small amounts of ethylene stimulate further production, leading to rapid changes.
Softening: Ethylene causes softening by promoting enzymes that break down cell walls.
Aroma and Flavor: The hormone triggers the creation of volatile compounds giving pears their characteristic scent and taste.

The Complex World of Plant Hormones in Pears

Pear development involves a sophisticated interaction between numerous phytohormones, not just ethylene. These hormones have roles throughout the fruit's life, and their balance affects quality and shelf-life.

Auxins (especially IAA): Important early for fruit growth and cell expansion, influencing size. They also interact with ethylene later to modulate ripening.
Gibberellins (GAs): Crucial for fruit set and early cell expansion. In some varieties, GAs can inhibit ripening.
Abscisic Acid (ABA): Levels are high during early development and late maturation. ABA works with ethylene and can speed up softening.
Cytokinins (CKs): Known for promoting cell division. They can affect fruit size and, synthetically applied, induce fruit development without fertilization.
Jasmonic Acid (JA) and Salicylic Acid (SA): While often involved in defense, SA can inhibit ethylene production in pear cells, and JA may also inhibit ripening in some cases.

Understanding the Hormonal Crosstalk

Pear ripening is a coordinated process dependent on the balance of these hormones. Early growth sees high levels of auxins and gibberellins, while maturation increases the influence of ethylene and ABA. This balance varies by cultivar, impacting characteristics like chilling needs and shelf life.

Key functions of phytohormones in pears:

Ethylene: Triggers and accelerates ripening, including texture, flavor, and color changes.
Auxin (IAA): Promotes cell division and expansion, affecting fruit size and shape.
Gibberellins (GAs): Involved in fruit set and early growth; can inhibit ripening.
Abscisic Acid (ABA): Regulates maturation and works with ethylene to promote ripening and softening.
Cytokinins (CKs): Promote cell division during fruit development.
Jasmonic Acid (JA) & Salicylic Acid (SA): Involved in defense and potentially ripening inhibition.

Do Pears Contain Human-Like Hormones? Phytoestrogens Explained

Plant hormones (phytohormones) are distinct from human hormones. Pears contain phytoestrogens, natural compounds found in many plants.

Phytoestrogens vs. Hormones: Phytoestrogens weakly bind to human estrogen receptors due to similar structures but have a much milder effect than human estrogen.
Dietary Role: These are found in small amounts in diets and are generally considered beneficial. Eating pears won't disrupt the endocrine system but adds nutrients and fiber.

Plant Hormones in Pears: A Comparison


Hormone	Primary Function in Pears	Role in Ripening	Effect on Fruit Growth	Notes
Ethylene	Gaseous Ripening Agent	Initiates and accelerates ripening	Minimal direct effect during growth	Promotes autocatalytic process; climacteric signal
Auxin (IAA)	Cell Division & Expansion	Modulates ethylene signal during ripening	Drives early fruit growth and size	Level changes during development influence ripening onset
Gibberellins (GAs)	Fruit Set & Expansion	Can inhibit ripening, especially in certain cultivars	Critical for early fruit enlargement	Balance with other hormones controls development stages
Abscisic Acid (ABA)	Maturation & Senescence	Promotes ripening synergistically with ethylene	High in early and late stages; dips during middle growth	Level increases signal the onset of maturity and ripening
Cytokinins (CKs)	Cell Division & Growth	Minor direct role in ripening	Contributes to fruit growth and cell proliferation	Synthetic versions can induce parthenocarpy

Conclusion

The hormone primarily present in pears is ethylene, which drives the ripening process, but other phytohormones like auxins, gibberellins, abscisic acid, and cytokinins play crucial supporting roles throughout development. This complex hormonal network ensures the pear ripens in a controlled way. Pears also contain phytoestrogens, which are plant compounds distinct from human hormones and are not associated with hormonal disruption. Understanding this biochemical symphony enhances the appreciation of a ripe pear.

For more detailed information, the article "Interplay between hormones and assimilates during pear fruit development and the determination of its postharvest ripening behaviour" provides a deep dive into these dynamics.

Frequently Asked Questions

No, pears do not contain human hormones. They contain phytohormones, which are plant-specific chemical messengers, and phytoestrogens, plant-derived compounds that are distinct from animal hormones and have a much weaker effect on the human body.

Placing a pear in a paper bag traps the ethylene gas that the fruit naturally produces. This concentrated ethylene signals the fruit to speed up its own ripening process, leading to accelerated softening and sweetening.

While the chemical compound is the same ($C_2H_4$), the ethylene produced naturally by a pear is a benign, biologically-produced plant hormone. In car exhaust, it is part of a complex mixture of harmful pollutants. One is a natural part of a fruit's life cycle; the other is a man-made toxin.

The phytoestrogens in pears are mild and bind to human estrogen receptors differently than natural hormones. For most people, consuming them as part of a balanced diet is not associated with significant hormonal disruption.

Gibberellins (GAs) play crucial roles in promoting initial fruit set and development in pears, particularly by affecting cell expansion. In some varieties, GAs can also inhibit ripening, a role that varies with the specific cultivar and stage of development.

Without ethylene, a climacteric fruit like a pear would not ripen properly. The fruit would remain hard, lack its characteristic flavor and aroma, and not undergo the typical color changes associated with maturity.

Yes, ripening can be controlled artificially. The application of exogenous ethylene gas in commercial ripening rooms is a common practice to ensure uniform ripening. Conversely, ethylene inhibitors like 1-MCP can be used to delay ripening and extend shelf life.