PLANT RESPONSES

Do plants have minds?

???Read the article and decide for yourself

Do plants have stress? Do they respond?

What are some abiotic stresses faced by plants?

*Turn to a partner

& list some

abiotic stresses faced by plants*

Abiotic Environmental Stresses

-temperature (too hot, too cold)-amount of sunlight (too much, too little)-water availability (too much, too little)-lack of nutrients in soil-others you came up with??

What are some biotic stresses faced by plants?

*Turn to a partner

& list some

biotic stresses faced by plants*

Biotic Environmental Stresses

• predators (omnivores/herbivores)• disease (caused by bacteria, fungi,

viruses and/or animals)• competition with other plants• others you came up with??

How do plants deal with these stresses?

ADAPTATIONS!

Tropisms

Tropisms

A tropism is “the turning of all or part of an

organism in a particular direction in response to an external stimulus.”

It is derived from Greek tropos meaning “turning”

Tropisms Can be Positive or Negative

If a plant turns towards the stimulus, then it is a

positive tropism.

If a plant turns away from a stimulus, then it is a

negative tropism.

Phototropism

Phototropism is “the orientation of a plant or other

organism in response to light, either toward the source of light (positive phototropism) or away

from it (negative phototropism).”

Positive Phototropisms

Stems exhibit positive

phototropism when leaning towards light

Negative Phototropisms

http://leavingbio.net/Plant%20Responses.htm#tropisms

Roots exhibit negative

phototropism when growing away from the

light

Gravitropism

Gravitropism is “the growth of a plant or other

organism in response to gravity, either being pulled down by gravity (positive

gravitropism) or growing against it (negative gravitropism).”

Positive Gravitropism

Roots exhibit positive

gravitropism when growing down towards

gravity

Negative GravitropismStems & leaves exhibit

negative gravitropism

when growing up

against gravity

Thigmotropism

Thigmotropisms are growth responses to touch

Positive Thigmotropisms

Plant stems (tendrils) exhibit positive

thigmotropism when they coil around an object.

Venus fly traps exhibit positive thigmotropismwhen they snap shut at the touch of an insect

landing inside

Negative ThigmotropismsRoots exhibit negative thigmotropisms when they grow away from or around

an object in the soil