Plant Growth

Meristems

What environmental factors affect plant growth?

Environmental Factors…

• light

• nutrients

• temperature

• soil

• What was the factor that you studied in your lab?

Tropisms

• change in the growth of a plant in response to a stimulus

Phototropism

Gravitropism

Thigmotropism

Plant Growth Regulators

Auxins

• promote cell elongation

• occurs on “dark side” causing phototropism

Gibberellins

• action variable

• promotes cell division & elongation

• plays role in flowering & fruit production

• gibberellin spray induces fruit production & elongates fruit stems in grapes

Cytokinins

• promote cell division

• found in growing tissues such as meristems, young leaves, growing seeds

• slow cell aging

• sprayed on mushrooms & lettuce to prevent spoiling

Ethylene

• gas that is produced at various stages of plant growth

• “plant stress hormone”

• also stimulates fruit ripening, and many other developmental stages

• ethylene levels controlled so that fruit is ripe when sold at the store

Abscisic Acid (ABA)

• inhibits growth

• maintains dormancy in seeds and leaf buds

• levels rise in response to temperature & light changes (e.g., seasonal change)

• sometimes used on plants that are being shipped