Did you know plants have hormones?

And did you know how they affect plant growth?

Hormones are chemical messenger molecules that help organisms respond to stimuli in their environment. For plants to be able to use this, cells must communicate with each other. Hormones facilitate this process, meaning they can respond to stimuli and activate specific responses.

Below we’ve broken down some of the key plant hormones and the effects they have, to give you an easy reference point when brushing up on your plant knowledge.

Cytokinins

• This hormone causes plant cells to divide
• Produced in growing areas
• Prevents the process of aging – used in floristry to cut flowers for longevity

Gibberellins

• Implicated in plant growth, particularly the length of stems
• Small plants, such as bonsai trees, have low levels of gibberellins
• Stops dormancy of seeds and buds, and signals it is time for a seed to germinate or for a bud to open

Abscisic acid

• Opens and closes the small openings in leaves, called stomata, as leaves wilt
• When a plan is stressed due to lack of water, this hormone prevents water loss through those stomata
• Also signals dormancy in buds and seeds when environmental conditions are not ideal for germination and growth
• When conditions improve, abscisic acid levels drop, and levels of gibberellins increase

Ethylene

• Helps ripen fruit
• Involved in the process of dropping leaves, fruits and flowers after they have ripened or bloomed – known as abscission
• Unusual in that it is a gas, and its presence can cause nearby fruit to also ripen, or spoil

Auxins

• Key role in plant growth
• Promotes stem elongation
• Produced at the tip of the plant, and ensure the main central stem is stronger than other stems and branches – inhibits the growth of lateral buds
• If the tip of the plant is removed, then the auxins are no longer present – results in the side branches developing
• Hence why pruning a plant and removing branches produces a fuller plant
• Also involved in tropisms - Eg. Auxin will move to the darker side of a plant, causing cells there to grow larger, producing a curving of the plant stem tip towards the light – phototropism

Is there anything else about plants you’d like to understand further? Let us know in the comments.