Ethephon is a widely used plant growth regulator that has both beneficial and potential detrimental effects on plant growth and development. It is commonly used in agriculture and horticulture for various purposes, including promoting flowering, fruit ripening, inducing leaf drop, and increasing abiotic stress tolerance. However, the application of ethephon can also lead to negative impacts on plants and the environment if not used properly. Understanding the effects of ethephon is crucial for maximizing its benefits while minimizing its risks.

One of the main benefits of ethephon is its ability to promote flowering in plants. It can be used to induce flowering in crops that require specific photoperiods or temperate species that require cold temperatures to initiate flowering. Ethephon triggers the synthesis and release of ethylene, a plant hormone that plays a crucial role in flower induction. This application can be particularly useful in commercial flower production and fruit production, where the timing of flowering is essential for high yields and marketability.

In addition to promoting flowering, ethephon is commonly used to enhance fruit ripening. It stimulates ethylene production in fruits, leading to accelerated ripening processes, such as color development, softening, and sugar accumulation. This application is widely employed in the fruit industry to ensure timely fruit maturation and uniform ripening, which facilitates harvesting, transportation, and marketing. However, it is important to note that the application of ethephon for fruit ripening should be carefully controlled to avoid over-ripening or premature fruit drop.

Moreover, ethephon can be used to induce leaf drop in deciduous trees, such as those grown in urban areas or orchards. It stimulates the production of ethylene, which triggers the abscission process, resulting in the shedding of leaves. This application is commonly used to facilitate easier leaf removal, reduce the risk of disease and pests during winter, and prepare plants for dormancy. However, excessive or mistimed application of ethephon can lead to premature leaf drop or damage to the plant's health, so it should be applied with caution.

Ethephon can also boost plants' tolerance to various abiotic stresses, such as drought, heat, and salinity. Ethylene production induced by ethephon application enhances the synthesis of protective proteins and antioxidants, as well as the activation of stress-response pathways. This can help plants survive under adverse environmental conditions and improve their overall resilience. However, the concentration and timing of ethephon application should be carefully adjusted depending on the tolerance level and sensitivity of the plant species to prevent potential phytotoxic effects.

Despite the many benefits of ethephon, its improper or excessive use can pose risks to both plants and the environment. Over-application of ethephon can lead to phytotoxicity, causing growth inhibition, leaf chlorosis, and even plant death. Additionally, the excessive release of ethylene from ethephon-treated plants can negatively affect nearby non-target plants, leading to a series of physiological and morphological abnormalities. It is crucial to strictly follow the recommended application rates and guidelines to prevent these risks.

In conclusion, ethephon provides various benefits for plant growth and development in agriculture and horticulture. It can promote flowering, enhance fruit ripening, induce leaf drop, and increase abiotic stress tolerance. However, the use of ethephon should be carefully controlled to avoid negative effects such as phytotoxicity and environmental contamination. Understanding the effects of ethephon and adhering to proper application practices are essential to harness its benefits and mitigate potential risks.