Adaptations of Plant Sensory Systems, Physiological Regulation and Environmental Response<br />-How do plants respond to stimuli?<br />-What are the major plant hormones?<br />-How do plants tell time?<br />
How do Plants Respond to Stimuli?<br />Tropism: “An involuntary orientation by an organism or one of its parts that involves turning or curving by movement or by differential growth and is a positive or negative response to a source of stimulation” <br />-Merriam-Webster<br />Plants respond to different stimuli such as light, gravity, touch and desiccation in ways that benefit their survival.<br />
Plant Response to Light<br />Phototropism: The growth of a plant in the direction of a light source.<br />Plants grow towards the light for the maximum amount of photosynthesis to occur.<br />Caused by the hormone Auxin<br />http://www.doctortee.com/dsu/tiftickjian/bio100/cell-communication.html<br />http://www.gettyimages.com/detail/686097-001/Stone<br />
Plant Response to Gravity<br />Gravitropism: The plants growth direction in response to gravity.<br />Plants use gravity to guide their growth direction in the absence of phototropism.<br />Plants sense of gravity allows shoots to grow straight up and roots straight down.<br />http://www.darienps.org/teachers/otterspoor/botany/tropisms/<br />
Plant Response to Touch<br />Thigmotropism: A plants growth response to touch.<br />Roots use thigmotropism to find the path of least resistance.<br />Caused by the plant hormones Auxin and Ethylene.<br />http://visualsunlimited.photoshelter.com/image/I0000cjwWdVtlI5M<br />
Plants Response to Desiccation<br />Desiccation: A period of extreme dryness.<br />Like the human body, plants will begin to shut down various parts of their body to survive.<br />Plants will open and close their stomata to regulate the amount of water loss that occurs.<br />http://www.labtechindia.net/stomata-1657.html<br />
Five Major Plant Hormones<br />There are five major plant hormones that are recognized in modern plant biology<br />The list includes:<br />1)Auxin 2)Abscisic Acid<br /> 3)Cytokinin 4)Gibberellins<br /> 5)Ethylene <br />These hormones are important in the growth and well being of the plant system.<br />
Five Major Plant Hormones<br />1) Auxin: One of the most important plant hormones, this chemical helps in the growth of plant parts and the cell elongation process.<br />Synthetic auxin is commercially used as a pesticide. <br />Most common auxin is indoleacetic acid (IAA), however there are other types of auxin.<br />The hormone responsible for many tropisms.<br />http://www.pherobase.com/database/compound/compounds-detail-3-indoleacetic%20acid.php<br />
Five Major Plant Hormones<br />2) Abscisic Acid:brings dormancy to a plant in certain conditions, and causes a plant’s stomata to open or close.<br />Was originally thought to be the cause of abscission.<br />3) Cytokinin: Regulates plant growth, cell division, and lateral bud growth in plants containing flowers.<br />Found mostly in plant roots.<br />Works with the hormone Auxin.<br />
Five Major Plant Hormones<br />4) Gibberellins:Regulates growth and developmental stages in the plant.<br />Found in meristems and roots of plants<br />Commercially used to increase the size of fruits and plants.<br />5) Ethylene:Promotes abscission and the growth of fruits.<br />Abscission occurs when a plant need to separate its self from an appendage.<br />Too much ethylene causes fruits to rot.<br />
How do Plants Tell Time?<br />Like humans, plants have a type of internal biological clock that is part of the Circadian Rhythm.<br />The Circadian Rhythm is defined as a physiological cycle of about 24 hours that is present in all eukaryotic organisms and that persist even in the absence of external cues.<br />These external cues such as light, temperature, and humidity are not what tell the plant what to do, they are used only to “set” the internal clock to a certain time period.<br />
Circadian Rhythm<br />Thought to work in three phases.<br />Phase 1: An input “sets” the internal clock.<br />Phase 2: The plant modifies proteins in the central oscillator<br />Phase 3: The oscillator outputs the proteins to various parts of the plant body.<br />http://howplantswork.wordpress.com/2009/01/25/how-plants-tell-time/<br />
Sources<br />-2008. Science Clarified. http://www.scienceclarified.com/Oi-Ph/Phototropism.html. January 20, 2011<br />-2004. Space Garden. Planet LLC. http://www.spacegarden.net/downloads/Gravitropism.pdf. January 21, 2011<br />-Vartanian, Steffan. 1997. Thigmotropism in Tendrils. Kenyon College. http://biology.kenyon.edu/edwards/project/steffan/b45sv.htm. January 21, 2011<br />-Oliver,Melvin, Velten, Jeff, Mishler, Brent. 2005. Integrative and Comparative Biology. Oxford Journals. http://icb.oxfordjournals.org/content/45/5/788.full. January 21, 2011.<br />-Moneo, Marta. 2004. ESPERE-ENC. http://www.atmosphere.mpg.de/enid/b53941b75a5c58a972d7e308d37e88c3,0/Food___Climate/more_pi.html. January 22, 2011<br />-2005, Biology Online, http://www.biology-online.org/11/10_growth_and_plant_hormones.htm. January 24, 2011<br />-Urry, Cain, Wasserman, Minorsky, Jackson. 2008. Biology. 8th Edition. Person. See page 838-839.<br />-Gardner, Michael, Hubbard, Kathy, Hotta, Carlos, Dodd, Tony, Webb, Alex. 2006. How Plants Tell Time. PubMed Central. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1479754/. January 24, 2011.<br />
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