Cell Communications- Mimosa Pudica

Mimosa pudica is very well known for its capabilities to move. It has two kinds of movement.

• the leaves close when they are touched, shaken, blown, or when they sense heat.

how it works

• In mere seconds, the leaf exhibits movement based on the loss of fluid within the vacuole of the cell.
• Aquaporins transport water across the cell membrane and change the turgor pressure.
• Two aquaporins known to be involved in the Mimosa pudica are:
• Plasma membrane intrinsic proteins (PIPs)
• Tonoplast intrinsic proteins (TIPs)

• On the left we see loss of water as well as Cl- and K+ ions. Notice the size of the vacuole compared to that on the right. This is a Mimosa pudica leaf in its resting state.
• The cell on the right represents a flexed or closed leaf after losing water and ions.
• Protons are pumped either in or out of the cell via H+-ATPase

evolutionary adaptations

seismonastic movement

nyctinastic movement

• When the plant is not exposed to light the leaves close up. When it is exposed to light the leaves open up again. It is also described as plant "sleep".

Other Contributing Factors

• Research has shown calcium ions also play a role.
• Calcium channels exist in the tannin vacuoles
• Calcium ions are an important regulator of turgor changes in pulvinus and are responsible for the closure of inward-directed K+ channels causing cell shrinking.

Mimosa Pudica

Experiment!

• Another study suggested that pulvini movements are controlled by auxin.
• Auxin is a plant hormone involved in cell growth, division and cell differentiation.
• In order to see if Mimosa pudica is controlled by auxin researchers simply applied auxin to a cut end of a leaflet.
• Auxin caused the leaflet to open and swelling at the pulvinus was present.
• A second experiment used an inhibitor of H+-ATPase called vanadate which caused the leaves to close and the swelling to cease.
• The swelling response depends on K+ and Cl- changes but auxin stimulated vacuolor H+-ATPase activity

(Touch-me-not plant)

Current Research

Mechanisms of the Seismonastic Reaction

• Seismonastic movement is cause by a change in turgor pressure in the motor cells of the pulvinus at the base of each leaf.
• External stimuli (touch) causes an electrical signal that converts to a chemical signal which increases the cell permeability.
• Water and K+, Cl- ions move from the symplast into the apopolasts.

References

Current Research

1. Teale WD, Paponov IA, Palme K. (2006) Auxin in action: signalling, transport and the control of plant growth and development. Nat Rev Mol Cell Biol 7: 847–859.

2. Hager A. (2003) Role of the plasma membrane H+-ATPase in auxin-induced elongation growth: historical and new aspects. J Plant Res 116: 483–505.

3. Plants on the move towards common mechanisms governing mechanically-induced plant movements. Plant Signal Behav. 2011 December 1; 6(12): 1979–1986.

doi: 10.4161/psb.6.12.18192

4. Darwin C. The power of movement in plants. New York: D. Appleton and Company, 1880.

5. Braam J. In touch: plant responses to mechanical stimuli. New Phytol. 2005;165:373–89. doi: 10.1111/j.1469-8137.2004.01263.x.

10-26 pairs of leaflets

per pinna

seeds

Images

Why is Plant Movement Important?

Mechanism of Seismonastic Reaction in Mimosa pudica

1. http://amirshahrokhi.christopherconnock.com/wp-content/uploads/turgor-pressure-diagram1.jpg

2. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3337191/

3. http://www.sciencedirect.com/science/article/pii/S1360138510000944

4. http://en.wikipedia.org/wiki/File:Apoplast_and_symplast_pathways.svg

5.

• Darwin believed that rapid movement in plants was the product of natural selection.
• Some plants have the ability to induce rapid movement in response to their environment.
• This enables them to capture food (venous fly traps) or in the case of Mimosa pudica escape predation
• Insects will have trouble landing and staying on the plant and therefore leave it alone.
• The leaves collapse when exposed to extreme cold or heat. This is a method of self preservation and in hot circumstances it is a strategy to reduce water loss.

By Josh Beaton