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Thermonasty
Thermonasty is a nondirectional response in plants to temperature. It is a form of nastic movement, not to be confused with thermotropism, which is a directional response in plants to temperature. A common example of this is in some ''Rhododendron'' species, but thermonasty has also been observed in other plants, such as ''Phryma leptostachya''. Flower opening in certain crocus and tulip species is also known to be thermonastic. These movements are thought to be regulated by having unequal cell elongation in certain plant tissues, causing different tissues to bend. In other processes, like in the temperature regulation of flower openings, movement has instead been shown to be a result of irreversible cell growth, a growth type not typically associated with plant movement. Furthermore, thermonasty has been shown to be independent of other environmental signals, such as light and gravity. Thermonasty is generally considered to be an adaptation for protection against colder temperatur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nastic Movements
Nastic movements are non-directional responses to stimuli (e.g. temperature, humidity, light irradiance), and are usually associated with plants. The movement can be due to changes in turgor. Decrease in turgor pressure causes shrinkage while increase in turgor pressure brings about swelling. Nastic movements differ from tropic movements in that the direction of tropic responses depends on the direction of the stimulus, whereas the direction of nastic movements is independent of the stimulus's position. The tropic movement is growth movement but nastic movement may or may not be growth movement. The rate or frequency of these responses increases as intensity of the stimulus increases. An example of such a response is the opening and closing of flowers (photonastic response), movement of euglena, chlamydomonas towards the source of light. They are named with the suffix "-nasty" and have prefixes that depend on the stimuli: * Epinasty: downward-bending from growth at the top, fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermotropism
Thermotropism or thermotropic movement 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 ''Rhododendron'' leaves in response to cold temperatures. ''Mimosa pudica'' also show thermotropism by the collapsing of leaf petioles leading to the folding of leaflets, when temperature drops. The term "thermotropism" was originated by French botanist Philippe Van Tieghem in his 1884 textbook ''Traité de botanique''. 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. 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 tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhododendron
''Rhododendron'' (; from Ancient Greek ''rhódon'' "rose" and ''déndron'' "tree") is a very large genus of about 1,024 species of woody plants in the heath family (Ericaceae). They can be either evergreen or deciduous. Most species are native to eastern Asia and the Himalayan region, but smaller numbers occur elsewhere in Asia, and in North America, Europe and Australia. It is the national flower of Nepal, the state flower of Washington and West Virginia in the United States, the state flower of Nagaland in India, the provincial flower of Jiangxi in China and the state tree of Sikkim and Uttarakhand in India. Most species have brightly colored flowers which bloom from late winter through to early summer. Azaleas make up two subgenera of ''Rhododendron''. They are distinguished from "true" rhododendrons by having only five anthers per flower. Species Description ''Rhododendron'' is a genus of shrubs and small to (rarely) large trees, the smallest species growing to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adaptation
In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the population during that process. Thirdly, it is a phenotypic trait or adaptive trait, with a functional role in each individual organism, that is maintained and has evolved through natural selection. Historically, adaptation has been described from the time of the ancient Greek philosophers such as Empedocles and Aristotle. In 18th and 19th century natural theology, adaptation was taken as evidence for the existence of a deity. Charles Darwin proposed instead that it was explained by natural selection. Adaptation is related to biological fitness, which governs the rate of evolution as measured by change in allele frequencies. Often, two or more species co-adapt and co-evolve as they develop adaptations that interlock with those of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoprotection
Photoprotection is the biochemical process that helps organisms cope with molecular damage caused by sunlight. Plants and other oxygenic phototrophs have developed a suite of photoprotective mechanisms to prevent photoinhibition and oxidative stress caused by excess or fluctuating light conditions. Humans and other animals have also developed photoprotective mechanisms to avoid UV photodamage to the skin, prevent DNA damage, and minimize the downstream effects of oxidative stress. In photosynthetic organisms In organisms that perform oxygenic photosynthesis, excess light may lead to photoinhibition, or photoinactivation of the reaction centers, a process that does not necessarily involve chemical damage. When photosynthetic antenna pigments such as chlorophyll are excited by light absorption, unproductive reactions may occur by charge transfer to molecules with unpaired electrons. Because oxygenic phototrophs generate O2 as a byproduct from the photocatalyzed splittin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquaporin
Aquaporins, also called water channels, are channel proteins from a larger family of major intrinsic proteins that form pores in the membrane of biological cells, mainly facilitating transport of water between cells. The cell membranes of a variety of different bacteria, fungi, animal and plant cells contain aquaporins through which water can flow more rapidly into and out of the cell than by diffusing through the phospholipid bilayer. Aquaporins have six membrane-spanning alpha helical domains with both carboxylic and amino terminals on the cytoplasmic side. Two hydrophobic loops contain conserved asparagine- proline-alanine ("NPA motif") which form a barrel surrounding a central pore-like region that contains additional protein density. Because aquaporins are usually always open and are prevalent in just about every cell type, this leads to a misconception that water readily passes through the cell membrane down its concentration gradient. Water can pass through the cell m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
