What are Plant Hormones?

Questions and Answers

What is the primary function of plant hormones?

To replicate cells in plants

To respond to light and darkness

To promote and regulate functions in different parts of the plant (correct)

To protect plants from environmental changes

In which parts of the plant are hormones synthesized?

In all parts of the plant, including roots, stems, and leaves (correct)

Only in the roots

Only in the stems

Only in the seeds

Why are plant hormones important in horticulture and agriculture?

Because they help plants adapt to extreme temperatures

Because they help plants respond to predators

Because they allow humans to produce excess or synthesize hormones to trigger desired effects (correct)

Because they help plants grow faster

What is a unique characteristic of plant growth compared to animal growth?

Plants can continue to grow throughout their life Signup and view all the answers

What is an example of a function regulated by plant hormones?

Ripening of fruit Signup and view all the answers

What is the primary function of auxins in plant growth?

To promote cell elongation in response to phototropism and gravitropism Signup and view all the answers

What is the main function of cytokinins in plant growth?

To regulate cell division and differentiation Signup and view all the answers

What is the function of gibberellins in plant growth?

To regulate stem, fruit, and seed growth Signup and view all the answers

Where are plant hormones typically produced?

In the stems, buds, and root tips of the plant Signup and view all the answers

What is the consequence of removing the above stem of a plant?

It promotes the growth of the lateral buds Signup and view all the answers

What is the primary function of gibberellins in plants?

To stimulate shoot elongation and flower and fruit maturation Signup and view all the answers

What is unique about the hormone ethylene?

It is a gaseous hormone Signup and view all the answers

What is the primary role of abscisic acid in plants?

To induce dormancy in seeds and other plant organs Signup and view all the answers

What is salicylic acid used for by humans?

As a medicine with anti-inflammatory properties Signup and view all the answers

What would happen to plant growth if there were no hormones to inhibit it?

Plant growth would be unfettered and uncontrolled, leading to an excess of resource use Signup and view all the answers

Study Notes

What Are Plant Hormones?

Plant hormones are chemicals produced in many parts of the plant that promote and regulate functions in other parts of the plant.
Hormones are chemical messengers that tell different parts of the plant to do different things, depending on the type of hormone.
Functions regulated by plant hormones include promotion and inhibition of growth, protection from pathogens, repair from damage, ripening of fruit, and start or delay of senescence.

Where Are Hormones Synthesized in Plants?

Hormones are synthesized in many parts of the plant, including roots, stems, and leaves.
Hormones are then transported to the part of the plant that needs a specific hormone through vascular tissues, such as phloem and xylem.

Types of Plant Hormones

There are five types of hormones in plants: auxins, cytokinins, gibberellins (GAs), ethylene, and abscisic acid (ABA).
Each type of hormone has a specific function, with several secondary functions that help the plant in its life.

Plant Hormones for Growth

Three plant hormones fall under the category of growth promotion: auxins, cytokinins, and gibberellins.
Auxins are responsible for cell elongation in response to phototropism and gravitropism, and are produced in the stems, buds, and root tips of the plant.
Cytokinins are responsible for cell division and are most abundant in areas of the plant that produce cells, such as seed embryo, fruit, and root and shoot tips.
Gibberellins are responsible for stem, fruit, and seed growth, and are produced in the roots of plants.

Plant Hormones for Inhibiting Growth

The two main hormones synthesized by plants and used for growth inhibition are ethylene and abscisic acid.
Ethylene is responsible for aging in plants, ripening fruit, and is released as a gas.
Abscisic acid is responsible for dormancy of different organs within the plant, and causes leaves to drop in response to environmental factors such as cold, heat, dehydration, or nutrient deficiency.

Other Uses of Plant Hormones

Plant hormones are used for protection from pathogens, and many hormones act as the plant's immune system.
Plant hormones are used by humans as medicine, such as salicylic acid, which is a powerful anti-inflammatory used in painkillers.