What is the role of ethylene in plant growth and development?

Ethylene is a plant hormone that regulates growth, ripening and response to stress in plants.

Ethylene, a gaseous plant hormone, plays a crucial role in various aspects of the plant life cycle, including seed germination, root growth, flowering, fruit ripening, and senescence. It is one of the simplest molecules that regulate plant growth and development, and its effects can be seen in almost all areas of plant growth.

In seed germination, ethylene helps break dormancy and stimulate the germination process. It promotes the growth and elongation of the embryonic axis and enhances the growth of the radicle, the embryonic root. This is particularly important in conditions where the seed is buried deep in the soil and needs to push through the soil surface.

Ethylene also plays a significant role in root growth and development. It influences root hair formation, which increases the root's surface area and enhances the plant's ability to absorb water and nutrients from the soil. Additionally, ethylene can stimulate the formation of adventitious roots, which are roots that form from non-root tissues, such as stems or leaves. This can be particularly beneficial in stressful conditions, such as flooding, where the primary root system may be damaged or insufficient.

One of the most well-known roles of ethylene is in fruit ripening. It triggers the ripening process in many fruits, leading to changes in colour, texture, flavour, and aroma. This is why fruits often ripen faster when placed in a bag, as the ethylene gas is trapped and concentrates around the fruit.

Ethylene also regulates plant responses to stress. It can promote leaf and flower senescence, the process of ageing and eventual death of plant tissues. This can be beneficial in conditions of stress, as it allows the plant to conserve resources by shedding non-essential tissues. Furthermore, ethylene can stimulate the plant's defence responses to pathogen attack, enhancing its resistance to disease.

In summary, ethylene is a versatile plant hormone that regulates a wide range of growth and developmental processes, from seed germination to fruit ripening, and plays a crucial role in plant responses to environmental stress.