Plants in Motion

1
Plants in Motion

• http//plantsinmotion.bio.indiana.edu/plantmotion/
  starthere.html

2
Germination

• Germination is the process where growth emerges
  from a resting state.
• If germination occurs in darkness, root growth
  slows after the shoot emerges and shoot
  elongation accelerates.
• This behavior increases the chance that the
  seedling will emerge from soil into the light
  where it will be able to obtain energy from
  sunlight by photosynthesis.
• Once a seedling emerges into the light, the plant
  undergoes dramatic changes such as turning green
  and producing leaves. This light-dependent
  developmental transformation is called
  photomorphogenesis.

3
Corn Seed Germinating

• This short movie shows corn seeds germinating and
  growing in darkness over a period of a few days
  starting 36 hours after being planted in wet
  soil. The time between images in this movie was 1
  hour.
• Note that the root is the first part of the
  seedling to emerge from the seed.
• The seed on the left was planted with the embryo
  aligned with its root pointing down.
• The seed on the right was oriented with the
  embryo upside down.
• As the movie shows, the roots from both seeds
  grew down regardless of the initial orientation
  of the embryo. Also, the shoots that emerged
  later grew up from both seeds.
• The ability of the seedling to orient its growth
  occurs as a result of the process of
  gravitropism. Gravitropism is the process by
  which plants sense and respond to the direction
  of gravity.

http//plantsinmotion.bio.indiana.edu/plantmotion/
earlygrowth/germination/germ.html
4
Sunflower Germination

• This movie shows germination and early growth of
  sunflower seedlings under low intensity white
  light. The time between images in this movie was
  1 hour and they are shown at 6 frames per sec
• As the seedlings emerge from the soil, they are
  already beginning to make chlorophyll and turn
  green. The cotyledons and apical hook unfold as
  the plant emerges into the light.
• One of the more striking things is the robust
  nutational movement (rotation of the stem) shown
  by these seedlings under continuous dim light. In
  darkness and in bright light, the nutational
  movement is present but less robust (see
  photomorphogenesis movie for comparison). It is
  almost like the seedlings are searching for a
  better light source..

http//plantsinmotion.bio.indiana.edu/plantmotion/
earlygrowth/germination/germ.html
5
Arabidopsis thaliana Germination

• This short movie shows Arabidopsis thaliana seeds
  germinating in the light.
• Once the root has emerged and anchored the plant,
  the shoot begins to grow. As the shoot is exposed
  to the light, the plant undergoes the process
  called photomorphogenesis.
• As the seedlings emerge from the soil, they are
  already beginning to make chlorophyll and turn
  green.
• The cotyledons and apical hook unfold as the
  plant emerges into the light. and the cotyledons
  expand and turn green and the seedling begins to
  grow photosynthetically and no longer depends on
  food stored in the seed

http//plantsinmotion.bio.indiana.edu/plantmotion/
earlygrowth/germination/germ.html
6
Photomorphogenesis

• Plant development is dependent on the
  environmental conditions where it is growing. The
  process by which plant development is controlled
  by light is called photomorphogenesis. Typically,
  photomorphogenic responses are most obvious in
  germinating seedlings but light affects plant
  development in many ways throughout all stages of
  development. The movies in this section will
  demonstrate some of the photomorphogenic
  responses in plants.

http//plantsinmotion.bio.indiana.edu/plantmotion/
earlygrowth/photomorph/photomorph.html
7
Sunflower germination dark

• The movie on the left documents the growth of
  sunflower seedlings in darkness. Because the
  seedlings were imaged with infrared illumination,
  the movie is in black and white. However, the
  seedlings did not turn green like the light-grown
  seedlings in the other movie.
• While in the darkness of the soil, seedlings are
  dependent on stored food reserves in the embryo.
• Plants put most of their energy into stem
  elongation and suppress leaf development and
  chlorophyll production (i.e. they do not turn
  green).
• In addition, dark-grown dicotyledonous plants
  keep the end of the stem hooked and their
  cotyledons closed together. Presumably, this
  growth strategy is an adaptation for rapidly
  emerging from the dark soil.

http//plantsinmotion.bio.indiana.edu/plantmotion/
earlygrowth/photomorph/photomorph.html
8
Sunflower germination light

• The movie on the right documents the growth of
  sunflower seedlings under white light.
• The movie shows shows approximately 2 days of
  growth. By advancing the movie frame by frame,
  the effects of light on plant development can
  readily be seen.
• When a seedling emerges from the soil into the
  light, growth and development changes
  dramatically.
• Elongation is suppressed, the apical hook opens
  and the cotyledons separate, enlarge and turn
  green as chloroplast's develop for carrying out
  photosynthesis.

http//plantsinmotion.bio.indiana.edu/plantmotion/
earlygrowth/photomorph/photomorph.html
9
Tropism

• Tropisms are directional movement responses that
  occur in response to a directional stimulus. One
  of the most commonly observed tropic responses in
  plants is phototropism, in which plant stems grow
  towards light.

http//plantsinmotion.bio.indiana.edu/plantmotion/
movements/tropism/tropisms.html
10
Cool Corn

• After 3 days of growth in darkness, the pot of
  corn seedlings in this movie were exposed to
  light from a single light bulb placed in the
  center of the pot just above the seedling. The
  plants were then imaged at 10 min intervals for
  about 18 hours.
• For the first 14 hours the seedlings appear to be
  worshiping the light as they maintain phototropic
  curvature.
• After 14 hours, the point light source was turned
  off and diffuse room lighting was turned on and
  the seedlings quickly return to a vertical
  orientation.

http//plantsinmotion.bio.indiana.edu/plantmotion/
vegetative/veg.html
11
Vegetative Phase

• The period of growth between germination and
  flowering is known as the vegetative phase of
  plant development.
• During the vegetative phase, plants are busy
  carrying out photosynthesis and accumulating
  resources that will be needed for flowering and
  reproduction.
• Different types of plants show different growth
  habits.
• The movies in this section will document various
  growth processes that occur during the vegetative
  phase of development.

http//plantsinmotion.bio.indiana.edu/plantmotion/
vegetative/veg.html
12
Rosette Plant

• The time-lapse movie shows the development of a
  rosette over a period of approximately 13 days,
  starting from about a week after germination.
• The seedlings were grown in continuous light for
  the movie but had been in a 12 h photoperiod
  prior to filming.
• If you look closely at the cotyledons and leaves
  as they grow, you can see that the leaves exhibit
  brief periods of movement (they appear to wiggle)
  approximately every 24 hours.
• These movements are most likely due to the action
  of the circadian clock that had been entrained
  prior to moving the plants to continuous light.
  The time interval between images in the movie is
  4 hours.

http//plantsinmotion.bio.indiana.edu/plantmotion/
vegetative/veg.html
13
Time Course of leaf area increase

• The graph above shows the time-course of the
  increase in leaf area of the plants shown in the
  time-lapse movie.
• The data shown were obtained from images captured
  every hour (the movie only shows images 4 hours
  apart).
• In addition, data from several seedlings were
  averaged with the data obtained from the seedling
  in the time-lapse movie.
• After about 12 days, it appears that growth
  starts to decrease. However, this apparent
  decrease is the result of leaves overlapping each
  other as the leaves expanded so that they were no
  longer detected by the automated technique used
  to measure the leaf area.

http//plantsinmotion.bio.indiana.edu/plantmotion/
vegetative/veg.html
14
Root Growth

• The main root of a plant typically grows
  downwards towards earths gravity.
• This downwards oriented growth is termed positive
  gravitropism.
• As a root elongates, the cells behind the root
  apical meristem differentiate, with some
  epidermal cells forming root hairs.
• Root hairs are thought to function in uptake of
  water and minerals from the soil.

http//plantsinmotion.bio.indiana.edu/plantmotion/
vegetative/veg.html
15
Wilting

• Water makes up about 95 of the fresh weight of a
  plant.
• Water is essential for plants to take up
  nutrients from the soil and deliver them through
  the plant body.
• When water becomes limiting, plants are said to
  "wilt". Wilting occurs when water availability is
  seriously limiting and can lead to damage or
  death if wilting goes on too long.
• Fortunately, if additional water is provided
  before serious damage occurs, a plant will
  quickly rehydrate and resume normal growth and
  metabolism.
• The time-lapse movie here shows a coleus plant
  wilting as the soil in the pot become
  progressively drier.

http//plantsinmotion.bio.indiana.edu/plantmotion/
vegetative/veg.html