Nastic Movements

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NASTIC
MOVEMENTS
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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

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Plants That Have Nastic Movement
Prayer Plant (Flat) Prayer Plant
(Vertical) Due to Daytime Due
to Nighttime
VENUS FLYTRAP
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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.

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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
• Photonasty Response to light
• Nyctinasty Movements at night or in the dark
• Chemonasty response to chemicals or nutrients
• Hydronasty response to water
• Thermonasty Reponse to temperature
• Geonasty/Gravinasty Response to gravity
• 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

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PhotoPeriodicity

• Photoperiodicity is the physiological reaction of
  organisms to the length of day or night.
• Examples
• Shortday plants-Morning Glory, Tulip
• Longday plants-Potato, Poppy
• Day Neutral-Tomato, Dandelion, Corn

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Plant Hormones
-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
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Experiment showing effects of auxins on plants

Agar block prevents the movement of auxins in the
stem
Coleoptile or stem tip
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!!
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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.
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Other plant hormones
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
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Tropisms
Phototropismthe way a plant grows or bends in
response to light -Stems are positively
phototropic. -Roots are negatively
phototropic. Geotropismthe way a plant grows or
bends in response to gravity -Stems are
negatively gravitropic
-roots are positively
gravitropic. Hydrotropismthe 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 Thigmotropismthe 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