Plant Hormones & Movement

HormonesWhat do you need to know?

1. Where are they produced?2. How are they transported?3. How does the plant respond?4. Commercial usesStart with the definition – a chemical that

is produced in one part of the plant, then transported to another where it causes a physiological change.

Auxins

1. Apical meristems2. Active transport3. Weakens fibers to allow growth4. Promotes rooting, inhibits

branching, delays fruit formation & leaf/fruit drop

Gibberellins

1. Location unknown2. Vascular issue3. Stimulate cell division & elongation4. Increased production of grapes,

more malt production in barley (more beer!), increased production of sugar in sugar cane. Breaks dormancy in seeds

Application of gibberellins

Cytokinins1. Roots2. Xylem3. Stimulates mitosis & cell

division when combined with auxins

4. Prolong the storage life of green vegetables (asparagus, broccoli & celery)

Ethylene Gas1. Produced by ripening or dying

tissues2. Diffusion3. Promotes ripening in fruit4. Makes mechanical harvesting

of fruits and veggies easier

Plant responsesTropic response

Slow movement caused by growth - irreversible

Positive tropism – growth is towards stimulus

Negative tropism – growth is away from stimulus

Ex. Phototropism & gravitropism

Nastic movement

Rapid movement caused by change in water pressure - reversible

Response is always the same – not towards or away from stimulus

Ex. – Venus flytrap & Mimosa plants