Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Interactions of Vascular Plants with Their Environment By Ashley Nunez Tropisms Tropism: is an invariable growth response to an environmental stimulus occurring in plants and primitive invertebrates. Irritable Reaction: is the capacity to respond in a characteristic way to changes in the environment. “Positive” “Negative” http://cccmkc.edu.hk/~sbjbiology/AL%20BIO/Continuity%20of%20life%20growth% 20and%20development/Tropism_hydrotropism%20and% 20geotropism%20competing.htm Geotropism A.B. Franck, 1869 (introduced geotropism as a term). Statolith Theory: postulates that plant organs perceive gravity through the movement of starch grains (not universally accepted). Centrifugal force, mutant plants, and golgi bodies. Environmental Changes Vascular Plants (tracheophytes): Have evolved an apparatus of conducting tubules. The link between animals (heterotrophs) and plants (autotrophs). Plants do detect changes in their environment and react to these changes in a specific way. Types of Responses: Movement (but not usually locomotion). Alteration of growth patterns. Developmental phenomena. Change in the state of particular plant structures. Hydrotropism http://www.studentsguide.in/biology/growth-development-angiosperms/paratonicgrowth-movements.html Phototropism http://botit.botany.wisc.edu/images/130/Tropisms/Phototropism/P hototropism_MC_.html http://www.cartage.org.lb/en/themes/Sciences/BotanicalScienc es/PlantHormones/Nutrition/Nutrition.htm Thigmotropism http://www.science-projects-resources.com/simple-science-fairprojects.html Plant Hormones Tropisms, as well as other phenomena occurring in the plant, are probably mediated by plant hormones. One of the first hormones to be discovered in plants was auxin, by Fritz Went in 1926. Hormone: is a substance produced in one part of a living organism that has profound metabolic effects throughout the organism as it travels through the vascular system. Hormones are chemical mediators of function and behavior. Relatively slow responses compared to faster neural responses (found only in animals). Auxin Auxin effects: The suppression of the lateral buds along the stem. The development of the root and shoot system. The growth of the fruit. Dropping off of the leaves and fruit (abscission). Division of cells in the cambium. Auxin Continued.. Auxin-like substances were produced as weed killers. Acted primarily on broad-leaved varieties of weeds. Agent Orange Cytotoxins First discovered in the tissue cultures laboratories of Folke Skoog et al. at the University of Wisconsin. Isolated as breakdown products from plant nucleic acids. Dr. D.S. Letham of New Zealand isolated zeatin from corn seeds (active cytotoxin). Work in conjunction with auxins. Cytotoxins Effects: Focused effects on cell division. http://www.mesoblast.com/images/imagesmesoblast_cell_division_still.jpg Gibberellins Originally associated with a fungus named Gibberella fujikuroi (caused rice plants to be abnormally high) . Various gibberellins have also been found in plant tissues themselves. Termed “Foolish-seeding disease” by the Japanese. Increase of stem length in various dwarf plants. The green revolution and its effect on dwarf strains of rice and other agricultural staples. May also increase plant height and alter both vigor and nutritional yield. Gibberellins Continued…. The effects of gibberellins is not confined to increasing plant height. Gibberellins also: Influence the formation of enzymes (hydrolyze starch). May break down the dormancy of seeds. Bring about flowering under certain conditions. In their absence, produce no flowers at all. http://belladia.typepad.com/photos/uncategorized /2007/08/13/flowermosaic.jpg Gibberellins Continued…. Negative effect on plant vigor because it limits their application on agriculture. Synthesized in a manner similar to steroid hormones in vertebrates. Resemble sex steroids in structure. They transverse cell membranes rapidly. http://4e.plantphys.net/images/ch20/wt2002b_s.jpg Ethylene A unique hormone, because it exists as a gas rather than a liquid. Associated with rapid ripening of fruit. Produced by the plant itself, usually when the fruit has reached its maximum size. Also added externally by handlers to bring about ripening. http://www.iesnz.co.nz/webfiles/IES/webpages/im ages/2185/ethylene.jpg Ethylene Continued… Senescence (aging and degradation): is the change in the biology of an organism as it ages after its maturity (http://en.wikipedia.org/ wiki/Senescence). Leaf abscission is mediated by ethylene. Termed “chief messenger of death” by botanists. Marks the end of each growing season http://www.biologyreference.com/images/biol_04_img0409.jpg http://botit.botany.wisc.edu/images/130/Leaf/Leaf_abscission_M C.low.jpg Inhibitors A variety of inhibitors, which are not primary hormones, may also play a role in maintaining dormancy and resisting growth. Inhibitor hormones complement the influence of ethylene. http://wwwmgs.bionet.nsc.ru/mgs/papers/goryachkovsky/plant-trrd/image6.gif Abscisic Acid (ABA) Synthesized by chloroplasts, but small amounts are also synthesized by apical meristems in the root and shoot. A single compound unlike auxins, gibberellins, and cytotoxins. Induces dormancy in seeds, buds, and cambial layers. Stress hormone. Leaf abscission and adverse conditions. High concentrations of ABA: protective scales, watertight resins increase, and stomata closes. Photoperiodism The ability to respond to relative periods of light and darkness (not confined to plants). Flowering is a specific example of photoperiodism. Flowering response (three separate groups): Long-day plants (e.g., beet and clover). Short-day plants (e.g., chrysanthemum and ragweed). Neutral plants (e.g., sunflower and tomato) http://ashoutinthestreet.files.wordpress.com/2009/06/beet.j pg http://wendyusuallywanders.files.wordp ress.com/2009/07/4-leaf-clover.jpg http://www.discoverplants.com/planttypes/flowers/chrysanthemum/pictures/chrysanthe mum-01.jpg http://weeds.cropsci.illinois.edu/images/Commo n%20ragweed/images/Common%20ragweed% 20vegetative%20plants.jpg Photoperiodism Continued… Span of continuous darkness is crucial. Short-day plants should be exposed to a minimum period of darkness. Long-day plants have a maximum limit on the period of darkness consistent with flowering. http://image.tutorvista.com/content/plant-growth-movements/photoperiodismlong-day-short-day-plants.jpeg H.A. Borthwick and S.B. Hendricks Discovered that red light (660 nm) and far-red light ( 730 nm) were most effective in mediating photoperiodicity. Red light effects: Most effective in interrupting the minimal period of darkness required for short-day plants. Most effective component in inducing light exposure in long-day plants. Far-red light has the exact opposite effects as red light. Phytochrome Borthwick and Hendricks hypothesized that this could be best explained by the existence of a single pigment that acts as a light receptor. This pigment, which they named phytochrome, must exist in two forms. Pr: absorbs red light. Pfr: absorbs far-red light. Recent research suggests that phytochrome is a conjugated protein. Initial Synthesis of Phytochrome When Pr absorbs red light, it is converted to Pfr form. Pfr will absorb light in the far-red to reconstitute the more stable Pr molecule. Pfr will revert to Pr in the dark. Most of the phytochrome exists as Pfr in the light. At night, Pfr levels are low. Two forms of pigment enable the plant to distinguish between day and night. Duration of Night or Day Periods The determination of the duration of night or day periods in plants by the plant is more complex. Likely involves an interaction between phytochrome and an internal clock mechanism. Biological clocks: exist as endogenous (internal) rhythms of fairly intense activity and usually follow a circadian (24-hour) cycle. The phyochrome system functions to mark dark and light period, but does not provide the measure of duration. Biological Clock Biological clock effects: Membrane function. Permeability characteristics of the membrane. Metabolism. Related to alterations in protein structure. Change concentration/characteri s-tics of phospholipids of the membrane. http://www.cartoonstock.com/newscartoons/cartoonists/rma/lowres/rman5560l.jp g Plant Diseases All plants require water, light, and a variety of nutrients optimum growth and development. The short supply or absence of any of these factors challenges the survival of the plant. If plants are grown without light, they are said to be etiolated. http://www.uwsp.edu/biology/courses/botlab/images/Lab12Growth/12D%20 etiolate.jpg Chlorosis http://plantpath.wsu.edu/whatsnew/images/Pre%202006%20images/IW000032.jpg Take on a yellowish hue when the fail to form chlorophyll in sufficient amounts. Arises from short supplies of mineral nutrients in the soil. Iron shortages are a major cause as well. Ergot A bizarre social phenomenon is sometime elicited by a fungus (ergot) that attacks such monocot crops as wheat, rye, barley, and malt. Produces mind-altering products if ingested by humans. Mass waves of psychosis (ergotism) swept through Europe during the Middle Ages and have occurred more recently. Ergotate (a derivative of ergot) is used as a vasoconstrictor to control bleeding, help treat migraine headaches, and stimulate uterine contractions. http://www.botany.hawaii.edu/faculty/wong/BOT135/ErgotonRye.gif Wheat Rust http://www.sciencedaily.com/images/2007/11/071126151723.jpg http://www1.fccj.cc.fl.us/dbyres/images/rust100.jpg Puccinia graminis Affects wheat crops worldwide. Mosaic Disease Mosaic virus is caused by a variety of viruses which attack and can destroy many vegetable and fruit crops. If infected plants are not cleared from the garden the disease will spread. Aphids and cucumber beetles spread the disease as they feed going from infected plant to healthy plant. Spraying has been reasonably successful in stopping the spread of some of these infectious diseases. http://www.aragriculture.org/images/diseases/image_library/ Tomato_Vegetables/squash/V20b_Squash.jpg Developmental Abnormalities Plants exhibit developmental abnormalities. Are particularly evident in tissue cultures. When plants are wounded, they often develop masses of amorphous material with very poor cellular differentiation known as calluses. Plant tumors and cancers. http://mbbnet.umn.edu/firsts/plant-gen.jpeg http://www.rense.com/general82/agrobacterium.jpg Galls http://www.plantanswers.com/Oak_leaf_galls2.j pglg.jpg http://www.elkhornslough.org/journal/jour nalpix/050908wasp-galls1.jpg http://www.wildliferanger.com/users/www.w ildliferanger.com/upload/Silk%20Button%2 0Spangle%20Galls%20001%20249.JPG Growth on a plant that are induced by parasites and are usually highly organized. Crown Galls Are tumors caused by bacteria. They are usually less well differentiated than other types of galls. http://www.sactorose.org/ipm/22bacteria/2 2bacterialcrowngall-stem.jpg Infectious Diseases Infectious diseases of plants may arise from infestation from viruses, bacteria, or fungi. Serious economic effects. Large-scale death and starvation. Ireland mid-1840s fungal blight that destroyed that potato crop (~1 million people died). Mainly responsible for the mass emigration of Irish people to the United States. References Fried, George and Hademenos, George. Schaum’s Outline to Biology. New York: McGrawHill, 2009>