Plants in Motion

Plants in Motion

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

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.

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

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..


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


PhotomorphogenesisPlant 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

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.


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.


TropismTropisms 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

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

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.


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.


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.


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.


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.


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Plants in Motion