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at a temperature of 15 C. As the temperature increases, the strength of the response decreases. With continually temperature increases, a lack of thermotropic response is observed and occurs once a temperature threshold is reached. This threshold is dependent on the thermal gradient, with the threshold being colder with smaller gradients. For example, a gradient of 4.2 C per cm had a threshold value of 30 C while a gradient of 0.5 C per cm had a threshold value of 24 C. It is thought that this lack of thermotropic response is due to the lack of sufficient stimuli to induce root curvature. Negative thermotropic behavior was recorded and was shown to occur at higher temperature, but the conditions to establish such behavior is less defined.
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153:, have been shown to bend differently when exposed to different temperature conditions. In general, growing roots tend to bend away from warmer temperatures, and towards cooler temperatures, within a normal range. It has been suggested that this growth behavior is beneficial because in most natural environments, soil closer to the ground's surface is warmer in temperature, while deeper soil is cooler.
123:. As the turgor pressure increases, the leaves roll up, making it tighter to the stem. The leaf also droops perpendicular to the ground. There are predictions on the mechanism of this behavior. Regional changes of cell hydration can cause the inward curling. Another prediction is a change in cell wall physiology. These predictions are very broad, indicating the need for further research.
57:
could not only represent the movement in organism level, thermotropism could also represent an organ level of movement, such as movement of leaves and roots toward or away from heat; but thermotaxis can only represent locomotion at the organism level, such as the movement of a mouse away from a warm environment.
156:
Experimentation with maize has demonstrated the existence of thermotropic responses in roots, with stronger responses seen when the thermal gradient increases. Positive thermotropism, or growth towards higher temperatures, was shown to occur at lower temperatures, with the strongest response observed
207:
movements in the
Phaseolus genus (beans) coincided with regulating leaf temperatures to improve photosynthesis efficiency and heat avoidance in hot, sunny, and arid environments. These movements worked to avoid photo-inhibition and keep leaf temperature lower than the air temperature. In sunflowers,
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The definition of thermotropism can sometimes be confused with the term, thermotaxis, a mechanism by which temperature gradients can alter the behavior of cells, such as moving toward the cold environment. The difference between them is that thermotropism is more commonly used in botany because it
126:
There are currently two hypotheses to why
Rhododendrons do this. The first is that the shape is more effective for snow shedding and better protects the more sensitive areas. Another hypothesis for leaf rolling called the desiccation theory, circulating in recent years, is to prevent membrane and
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Within the same experiment, roots were capable of undergoing positive thermotropism away from gravitational force. The inhibition of normal gravitropic curvature was seen when temperatures were 18 C and lower, with stronger curvature away from gravity seen with lower temperature. This overriding
107:
Research on
Rhododendron leaf thermotropism suggests that the curling response might help prevent damage to cell membranes caused by rapid thawing after a freeze. During the winter months, wild Rhododendrons in the Appalachian Mountains regularly drop to freezing temperatures at night, then thaw
134:
decreased, while proteins for cell permeability increased. The same study showed the highest increase in proteins were responsible for transcription and translation regulation. Thermotropic response in rhododendron leaves protects cells by changing leaf shape and protein levels.
108:
again in the early morning. Because a curled leaf has less of its surface area exposed to the sunlight, the leaf will thaw more slowly than it would if it were unfurled. Slower thawing minimizes damage caused to leaf cell membranes by ice crystal formation.
212:
heating the plant. This resulted in more pollinators being attracted. A study showed this by forcing some floral heads to the west leaving other floral heads to warm illustrating varied pollinator choice. Though these findings are in correlation with
53:. Van Tieghem stated that a plant irradiated with an optimum growth temperature on one side laterally, and a much higher or lower temperature on the opposite side, would exhibit faster growth on the side exposed to optimum temperature.
217:, these heat avoidance and acquisition strategies are entwined with thermotropism as well. With further research, more examples can be found that can definitively detail the thermotropic role in heat avoidance and acquisition.
161:
behavior indicates integration of the plant's gravitropic and thermotropic system and suggests that the sensory systems are an interconnected network of responses rather than separate stimulation response pathways.
60:
The precise physiological mechanism enabling plant thermotropism is not yet understood. It has been noted that one of the earliest physiological responses by plants to cooling is an influx of
104:
during warm versus cold weather. In warm weather, the leaf has a flat oblong shape. As the temperature of the leaf drops, the blade curls inward, giving the leaf a tubular, cigar-like shape.
84:, which allows calcium ion channels to open. From this information, a hypothesis has formed that the plant cell plasma membrane is an important site of plant temperature perception.
26:
is the movement of an organism or a part of an organism in response to heat or changes from the environment's temperature. A common example is the curling of
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is responsible for the leaf movement. The exact stimulus for this output is not understood, but it is known that freezing cold temperatures causes an
621:"Characterization of thermotropism in primary roots of maize: Dependence on temperature and temperature gradient, and interaction with gravitropism"
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we find a different relation involving floral warming. The floral heads of these plants follow the sun from east to west causing increased
341:
746:
Atamian, Hagop S.; Creux, Nicky M.; Brown, Evan A.; Garner, Austin G.; Blackman, Benjamin K.; Harmer, Stacey L. (2016-08-05).
485:"Proteome dynamics of cold-acclimating Rhododendron species contrasting in their freezing tolerance and thermonasty behavior"
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292:"Photostimulation and thermotaxis of sperm: Overview and practical implications in porcine reproduction"
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Gardening hobbyists have frequently noted the dramatic change in the shape of
Rhododendron or "Rhodie"
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376:"Ambient Thermometers in Plants: From Physiological Outputs towards Mechanisms of Thermal Sensing"
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Although there is little known about the molecular mechanisms of this rolling behavior,
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van Zanten, Martijn; Ai, Haiyue; Quint, Marcel (11 May 2021).
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Zanten, Martijn van; Ai, Haiyue; Quint, Marcel (2021-05-11).
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Rhododendron leaves curling in response to cold temperatures.
554:. Vol. 18. Ames, Iowa: Blackwell Pub. pp. R275-7.
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Die, Jose V.; Arora, Rajeev; Rowland, Lisa J. (2017-05-23).
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The term "thermotropism" was originated by French botanist
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Robertson McClung, C.; Davis, Seth J. (21 Dec 2010).
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238:(9 ed.). Boston: McGraw-Hill. p. G1.
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340:Nilsen, Erik Tallak (Winter 1990).
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619:Fortin, M.-C.; Poff, K.L. (1991).
417:"Why Do Rhododendron Leaves Curl?"
342:"Why do Rhododendron Leaves Curl?"
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510:10.1371/journal.pone.0177389
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415:Nilsen, Erik (1990-01-01).
259:Hooker, Jr., H. D. (1914).
234:Stern, Kingsley R. (2004).
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236:Introductory Plant Biology
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42:, when temperature drops.
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560:10.1016/j.cub.2008.02.033
393:10.1016/j.cub.2010.10.035
261:"Thermotropism in Roots"
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88:Thermotropism in leaves
684:"Six Ways Plants Grow"
139:Thermotropism in roots
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119:of water to the leaf
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49:in his 1884 textbook
24:thermotropic movement
47:Philippe Van Tieghem
764:2016Sci...353..587A
724:10.1093/jxb/erab209
501:2017PLoSO..1277389D
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386:(24): R1086–R1092.
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51:Traité de botanique
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179:. You can help by
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915:Phototropism
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900:Gravitropism
895:Chemotropism
819:Leaves Curl?
817:Rhododendron
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