The Touch-Me-Not (Mimosa pudica) commonly introduced sensitive plant is an amazing piece of work of nature which has taken the attention of nature lovers worldwide. The plant is well known for its leaf and branch folding mechanism. When the branches or the leaves of the plant are touched, it responds to the touch quickly, like a response from an animal. Let’s explore the science behind this amazing phenomenon shown by this plant through this article.
This plant is native to South and Central American regions but can now be found around the globe. Mimosa pudica is a leguminous plant with green compound leaves of multiple leaflets joined by thin thorny branches. Mimosa is famous for its medicinal value and a nitrogen enhancer in the soil while fixing atmospheric nitrogen. Also, its widely spread root system protects the soil from erosion.
The Mimosa pudica plant folds its leaves in response to touch as well as other stimuli like external shock or heat. The affected leaflets fold inward and droop downward when the plant is touched, creating the impression that the plant has perished. This touch-induced nastic movement of Mimosa pudica is known as thigmonasty.
Water flow, ion fluxes, and cellular changes interact dynamically to control Mimosa pudica‘s leaf folding mechanism. At the base of every leaflet, specialized cells called motor cells or pulvinus cells are stimulated to initiate the plant’s reaction. There are two kinds of pulvinus cells called extensor cells and flexor cells. The movements are created by the flexing of extensor cells and stretching of flexor cells.
These motor cells receive mechanical and electrical impulses when a leaf is touched. This initiates a chain of events that includes potassium ions leaving the cells quickly. Turgor pressure in the motor cells instantly drops as a result of water leaving the cells by osmosis with the potassium ions. The cells become flaccid and bend as a result of the decrease in turgor pressure, these changes in the turgor pressure manage the folding of the leaves and leaflets.
Also, the leaves of Mimosa pudica move in response to changes in light conditions throughout the day. They fold at night and reopen during the day. This adaptation is regulated to maximize photosynthesis efficiency and minimize unnecessary water loss in the plant. This operation of the natural clock inside the plant is known as nyctinasty. This phenomenon is not only an interesting adaptation but also serves several core functions. Another main function of this mechanism is to protect the plant from herbivores and other threats. When a plant is touched, the leaflets fold inward, making it hard for herbivores to consume. So, this reaction helps to chase away the insects that may feed on the plant. Also, this phenomenon helps the Mimosa pudica plant to conserve water. While the plant is experiencing high temperatures or dry conditions, the leaflets fold inward, exposing a minimum surface area of the leaves and minimizing water loss through transpiration. This adaptation helps the plant to survive in arid conditions.
Finally, it can be concluded that the leaf-folding mechanism of the Touch-me-Not plant is a wonderful adaptation that enables the plant to respond to touch and other stimuli uniquely. The leaf folding mechanism is just one of the many fascinating features that make it a plant worthy of studying and admiring.
References
01. Gupta, R. et al. (2012) ‘Mimosa pudica L. (Laajvanti): An overview’, Pharmacognosy Reviews, 6(12), p. 115. doi:10.4103/0973-7847.99945.
02. Fleurat-Lessard, P. and Bonnemain, J.L., 1978. Structural and ultrastructural characteristics of the vascular apparatus of the sensitive plant (Mimosa pudica L.). Protoplasma, 94, pp.127-143.
03. L, W. (2015) Mimosa pudica: U Can’t touch this!, Tropical Biodiversity. Available at: https://blogs.reading.ac.uk/tropical-biodiversity/2014/02/mimosa-pudica-u-cant-touch-this/ (Accessed: 19 February 2024).
04. A, A. (2016) Sensitive Mimosa pudica Electrophysiology, Sensitive mimosa pudica electrophysiology. Available at: https://backyardbrains.com/experiments/Plants_SensitiveMimosaPudica (Accessed: 19 February 2024).
05. Kirton , J. (2022) What is mimosa pudica? everything you need to know, Micro Farm Guide. Available at: https://www.microfarmguide.com/mimosa-pudica/ (Accessed: 19 February
