Ethylene a. causes the triple response in seedlings growing...

Ethylene
$a$. causes the triple response in seedlings growing underground.
$b$. is liquid at room temperature.
$c .$ delays the ripening of fruits.
$d$. generally promotes stem elongation.
e. inhibits the swelling of stems, in opposition to cytokinin's effects.

Key Concepts

Role in Fruit Ripening

Ethylene is a critical regulator of fruit ripening in climacteric fruits, initiating processes that lead to changes in color, texture, and flavor. Rather than delaying ripening, ethylene accelerates this process, marking the transition from unripe to ripe status, which is important for seed dispersal and ensuring fruit quality.

Gaseous Nature at Room Temperature

Chemically, ethylene is a gas at room temperature, which allows it to move easily between cells and tissues. Its gaseous state contrasts with many other phytohormones that are in liquid or crystalline forms and explains its rapid and widespread action within plant systems.

Interaction with Other Hormones

Ethylene does not act in isolation; its effects are part of a complex network of hormonal interactions. For instance, its influence on cell expansion and differentiation can counteract or modify the effects of other hormones like cytokinin, demonstrating how plants integrate multiple signals to fine-tune growth and developmental outcomes.

Ethylene as a Plant Hormone

Ethylene is a simple gaseous hormone that plays a crucial role in a variety of plant developmental processes. Unlike hormones that are stored in vacuoles or synthesized on demand, ethylene diffuses readily throughout plant tissues and can trigger responses with quick onset, making it a key regulator in growth, development, and stress responses.

Triple Response in Seedlings

The triple response is a well-known reaction of seedlings to ethylene that involves inhibition of stem elongation, radial swelling of the stem, and enhanced formation of an apical hook. This coordinated response helps seedlings navigate obstacles while growing underground, ensuring that emerging shoots are better prepared to reach the soil surface.

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