NASTIAS: TYPES, CHARACTERISTICS AND EXAMPLES - BIOLOGY - 2025

The nasties, nastismos or nastic movements are a form of motion of plants resulting from the perception of an external stimulus in a way, but where the direction of the resultant movement is independent of the perceived stimulus. They occur in virtually all plant organs: leaves, stems and branches, flowers, tendrils, and roots.

Among the mechanisms that plants have to adapt to the environment that surrounds them are some forms of movements that, reversibly or irreversibly, result from the perception of light, thermal, chemical, water, tactile, gravitational stimuli, product of wounds caused by herbivores. when feeding, among others.

Carnivorous plant Drosera rotundifolia (Source: pixabay.com/)

Movement in plants is traditionally classified into two types: tropisms and nastias. Tropisms, unlike nastias, are functionally defined as movements or growth responses of plant organs to physical stimuli and are directly related to the direction in which they are perceived.

Both nastias and tropisms can be the result of movements due to growth or turgor changes in the cells of the moving organ, so that some movements could be considered reversible and others irreversible, as the case may be.

Charles Darwin in his 1881 work - The Power of Movement in Plants - described plant movements resulting from environmental changes, especially those related to tropical responses. However, the mechanisms underlying these movements have been described by various authors since then until the present time.

Types

A plant can receive a great diversity of stimuli for which it can trigger a great variety of responses. The classification of the different nastic movements has been done mainly on the basis of the nature of the stimuli, however, the scientific description of the response mechanisms presents many ambiguities.

Among the best known types of nastias are:

• Nictinastia: when the leaves of some species of leguminous plants fully expand during the day and fold or close at night.
• Thigmonastia / Seismonastia: movements that result from stimuli by direct physical contact in certain organs of some species.
• Thermonastia: reversible movements dependent on thermal fluctuations.
• Photonastia: it is considered a special type of phototropism; the leaves of some species under conditions of high light intensity can be arranged parallel to the incidence of light.
• Epinastia and hyponastia: they are foliar movements that some species have in the face of conditions of extreme humidity in the roots or high concentrations of salt in the soil. Epinasty has to do with exaggerated growth of the adaxial region, while hyponastia refers to the growth of the abaxial region of the leaf blade.
• Hydronastia: movement of certain plant organs that depends on hydric stimuli.
• Chemionastia: movement response related to concentration gradients of some chemical substances. Some authors refer rather to internal movements and signaling pathways.
• Gravinastia / Geonastia: reversible temporal movement of some plants in response to gravitational stimuli.

Features and examples

Many of the nastic movements depend on the existence of a particular organ: the pulvínulo. Pulvinules are specialized motor organs located at the base of the petioles of simple leaves, and petioles and leaflets in compound leaves.

Anatomically speaking, they consist of a central cylinder, surrounded by layers of collenchyma, and a motor cortical zone that has parenchymal cells that are susceptible to changes in size and shape.

Cells of the pulvinular cortex that change in size and shape are known as motor cells, among which are the extensor and flexor motor cells. Normally the movement of these depends on turgor changes due to the entry and / or exit of water from the protoplast.

Below is a brief description of the nastias whose cases could be considered classic examples.

Nictinastias or "sleep movements" of plants

They were initially discovered in Mimosa pudica and are very common in legumes. They have to do with the "rhythmic" movement of the leaves, which close at night and fully expand during the day. The most studied have been those of Albizzia julibrissim, A. lophantha, Samanea saman, Robinia pseudoacacia and Phaseolus coccineus.

The phenomenon is well known in plants and is thought to have adaptive reasons: the expansion of the leaf blades during the day allows a maximum of light energy to be captured during sun exposure, while the closure at night seeks to avoid caloric loss important.

When the leaves are expanded, the pulvinules are in a horizontal position (diurnal) and when they are closed they have a "U" shape (nocturnal), or that is related to an increase in turgor in the extensor cells during opening, and an increase in turgor in flexor cells during closure.

Graphic description of the nictinastic movement (Charles Darwin, LL.D., FRS assisted by Francis Darwin, via Wikimedia Commons)

Such turgor changes occur due to the movement of water that depends on the intracellular movement of ions such as K + and Cl-, malate and other anions.

K + enters the motor cells by an increase in the negative charge on the inner face of the cytoplasmic membrane, which is achieved through the action of ATPases responsible for expelling protons from the cytoplasm.

The loss of turgor occurs due to the inactivation of the proton pump, which depolarizes the membrane and activates the potassium channels, promoting the exit of this ion towards the apoplast.

These movements depend on the action of photoreceptors composed of phytochromes, since experiments have shown that prolonged radiation stimulates leaf opening.

Nictinastic movement has a certain “rhythmicity”, since plants subjected to permanent darkness present these movements every 24 hours, so a kind of “biological clock” must participate in the regulation of turgor changes in the pulvinule motor cells.

Thigmonasties or touch movements

One of the most popular tigmonastic responses in the literature is the one presented by the carnivorous plant Dionaea muscipula or "Venus flytrap", where the insects are trapped in its hinged bilobed leaves.

When an insect climbs toward the ventral surface of the leaf and encounters three delicate hairs that trigger the motor response, intercellular electrical signals are generated and initiates differential elongation of the cells in each leaf lobe, resulting in the closure of the "Cheat" in less than a second.

Dinoaea muscipula, Venus flytrap (Venus flytrap) (Source: pixabay.com/)

Carnivory gives D. muscipula enough nitrogen to survive, so these plants can settle without problem in soils poor in this mineral. It is important to note that this movement is very specific, which means that stimuli such as raindrops or strong winds do not trigger the closing of the lobes.

Another carnivorous plant, Drosera rotundifolia, has hundreds of mucilaginous tentacles on the surface of its modified leaves, attracting the attention of hundreds of potential prey, which become trapped in the mucilage of the "tentacles."

The sensory tentacles detect the presence of the prey and the adjacent tentacles bend towards the one that has been stimulated, forming a cup-shaped trap that traps the insect inside.

Differential growth is thought to occur that is controlled by changes in auxin levels since the addition of exogenous auxins triggers the closing of the leaves, and by adding blockers of the transport of the same hormone, movement is inhibited.

Mimosa pudica is also the protagonist of the best described tigmonastic movements. The touch of one of its leaflets promotes the immediate closure of its compound leaves.

It is thought that this response to tactile stimuli can serve to scare off possible predators or as a defense mechanism that allows the exposure of their defensive spines.

The folding of the leaves depends on changes in turgor. The pulvinules in this case lose turgor, specifically, the flexor cells stretch in response to the loss of volume of the extensor cells.

Mimosa pudica or the "sensitive plant" (Source: pixabay.com/)

The volume change occurs due to a discharge of sucrose in the phloem, which forces the osmotic transport of water and the passive transport of potassium and chlorine ions.

An electrochemical gradient is also generated in this movement thanks to the participation of proton pumps in the membrane (ATPases). Growth factors, cytoskeleton and actin filaments, among others, are involved.

Thermonasties

It has been detailed in Crocus flowers and tulips. It occurs due to a differential growth on the opposite sides of the petals that react to the thermal stimulus and not due to changes in turgor. The difference in response occurs since the two sides of the organ have growth optimum at very different temperatures.

Crocus flowers (Source: pixabay.com/)

During this movement no significant changes occur in the osmotic, pH or permeability values ​​of the protoplasts. Significant increases in intracellular CO2 have also been observed, which appears to be the factor that sensitizes tissues to changes in temperature.

Closed tulips (Source: pixabay.com/)

This movement is independent of the light intensity and strictly dependent on the increase in temperature. The convention between different authors is that the thermal variation must be between 0.2 ° C and 0.5 ° C to observe a movement of the flowers. A drop in temperature of the same magnitude causes its closure.

References

1. Azcón-Bieto, J., & Talón, M. (2008). Fundamentals of Plant Physiology (2nd ed.). Madrid: McGraw-Hill Interamericana of Spain.
2. Braam, J. (2005). In touch: plant responses to mechanical stimuli. New Phytologist, 165, 373–389.
3. Brauner, L. (1954). Tropisms and Nastic movements. Annu. Rev. Plant. Physiol., 5, 163-182.
4. Brown, AH, Chapman, DK, & Liu, SWW (1974). Comparison of Leaf Epinasty Induced by Weightlessness or by Clinostat Rotation. Bioscience, 24 (9), 518–520.
5. Dubetz, S. (1969). An unusual photonastism induced by drought in Phaseolus vulgaris. Canadian Journal of Botany, 47, 1640–1641.
6. Dumais, J., & Forterre, Y. (2012). "Vegetable Dynamics": The Role of Water in Plant Movements. Annu. Rev. Fluid Mech., 44, 453-478.
7. Enright, JT (1982). Sleep movements of leaves: In defense of Darwin's interpretation. Oecologia, 54 (2), 253–259.
8. Esmon, CA, Pedmale, U. V, & Liscum, E. (2005). Plant tropisms: providing the power of movement to a sessile organism. Int. J. Dev. Biol., 49, 665-674.
9. Firn, RD, & Myers, AB (1989). Plant movements caused by differential growth- unity of diversity of mechanisms? Environmental and Experimental Botany, 29, 47–55.
10. Guo, Q., Dai, E., Han, X., Xie, S., Chao, E., & Chen, Z. (2015). Fast nastic motion of plants and bioinspired structures. JR Soc. Interface, 12.
11. Hayes, AB, & Lippincott, JA (1976). Growth and Gravitational Response in the Development of Leaf Blade Hyponasty. American Journal of Botany, 63 (4), 383–387.
12. Koukkari, WL, & Hillman, WS (1968). Pulvini as the Photoreceptors in the Phytochrome Effect on Nyctinasty in Albizzia julibrissin. Plant Physiology, 43 (5), 698–704.
13. Sandalio, LM, Rodríguez-Serrano, M., & Romero-Puertas, MC (2016). Leaf epinasty and auxin: A biochemical and molecular overview. Plant Science. Elsevier Ireland Ltd.
14. Schildknecht, H. (1983). Turgorins, Hormones of the Endogenous Daily Rhythms of Higher Organized Plants-Detection, Isolation, Structure, Synthesis, and Activity. Angewandte Chemie International Edition in English, 22 (9), 695–710.
15. Ueda, M., Takada, N., & Yamamura, S. (2001). Molecular approach to the nyctinastic movement of the plant controlled by a biological clock. International Journal of Molecular Sciences, 2 (4), 156–164.
16. Wood, WML (1953). Thermonasty in Tulip and Crocus Flowers. Journal of Experimental Botany, 4 (10), 65–77.