Nastic Movement Definition

¤ Nastic Movements are plant movements that are in response to a stimulus (non-directional)¤Examples:. Temperature,

Humidity, & Light Irradiance

¤ The movement can be caused by turgor or changes in growth

Plants That Have Nastic Movement

Prayer Plant (Flat) Prayer Plant (Vertical) Due to Daytime Due to Nighttime

VENUS FLYTRAP

Nastic Movement vs.

Tropic Movement¤ Nastic Movements differ from Tropic

Movements in that the direction of Tropic Responses depend on the direction of the stimuli, whereas the direction of Nastic Movements are independent of the stimuli.

Nastic Responses¤ The frequency of these responses increases as intensity

of the stimulus increases.¤ Example of Nastic Response: Opening and closing of

flowers (Photonastic response)¤ Nastic Responses are usually associated with plants:

1. Photonasty: Response to light2. Nyctinasty: Movements at night or in the dark3. Chemonasty: response to chemicals or nutrients4. Hydronasty: response to water5. Thermonasty: Reponse to temperature6. Geonasty/Gravinasty: Response to gravity7. Thigmonasty/Seismonasty/Haptonasty: Response to

touch¤ Notice that the Nastic Responses are named with the

suffix “-nasty” and have prefixes that depend on the stimuli

PhotoPeriodicity

¤ Photoperiodicity is the physiological reaction of organisms to the length of day or night.

¤ Examples:

1.Shortday plants-Morning Glory, Tulip

2.Longday plants-Potato, Poppy3.Day Neutral-Tomato,

Dandelion, Corn

-The term auxin is derived from the Greek word auxein which means to grow.

- Auxins were the first plant hormones discovered

Functions of Auxins:

-Stimulates cell elongation

-Stimulates cell division in the cambium

-Stimulates differentiation of phloem and xylem

-initiates response of bending in response to gravity and light

•Coleoptile or stem tip

Agar block prevents the movement of auxins in the stem

If auxins cannot move through the stem than the stems ability to respond to, say light ,is inhibited. This means that the plant will not be able to grow towards the light as it normally would. Place the tip back on the plant and all is well!!

If the agar block is placed partially on the stem than the response would be as shown.

As the auxin (which is in the agar block) diffuses into that side of the coleoptile, it stimulates cell elongation and the coleoptile bends away from the block.

Cytokinin Functions:

-Stimulates cell division

Ethylene :

-Ethylene, unlike the rest of the plant hormone compounds is a gaseous hormone

- stimulates the ripening of the fruit

Gibberellins:

- stimulates flowering, stem elongation, dormancy, and germination.

Abscisic acid :

-causes trees to lose their leaves in response to winter -buds to go dormant

Phototropism—the way a plant grows or bends in response to light -Stems are positively phototropic.

-Roots are negatively phototropic.

Geotropism—the way a plant grows or bends in response to gravity -Stems are negatively gravitropic -roots are positively gravitropic.

Hydrotropism—the way a plant grows or bends in response to water ex.willow trees roots grow towards water making them great for areas that are very wet

Thigmotropism—the way a plant grows or bends in response to touch ex. Venus fly trap or sweet pea whose tendrils climb in response to the feel of the area they are growing

** remember a tropism is a response directly related to the direction of the stimulus, unlike nastic response which are independent to the direction of the stimulus