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6/5/2014 Introduction Plant Hormone Presentation Ethylene by Natalie, Amy, Yamuna When and where ethylene is produced? • A hydrocarbon with carboncarbon double bond • A gaseous plant hormone, which regulates a number of developmental process in plants • Early observation during the 1800s, coal gas leakage from gas pipes caused nearby trees to drop leaves prematurely • In 1901, the Russian scientist demonstrated the gas ethylene as the active factor in the coal gas Function: leaf abscission • It is produced by almost all parts of the plants • It is biologically active at very low concentrations • Plants produce ethylene in response to stresses: drought, flooding, mechanical pressure, injury and infection A change in the ratio of ethylene to auxin controls abscission: - less auxin in aging leaf, rendering the cells of the abscission layer more sensitive to ethylene. ethylene on the abscission layer induces cells to produce enzymes that digest the cellulose and other components of cell walls Functions ● ● ● ● ● ● Breaking of dormancy Development of adventitious root formation Inhibits root growth, stops mitotic processes Internode shortening Fruit and leaf degreening Promotes stem growth in some aquatic species Formation of Ethylene 3 STEP PROCESS: ● ATP and water are added to methionine resulting in loss of the three phosphates and Sadenosyl methionine. ● 1-amino-cyclopropane-1carboxylic acid synthase (ACCsynthase) facilitates the production of ACC from SAM. ● Oxygen is then needed in order to oxidize ACC and produce ethylene. This reaction is catalyzed by an oxidative enzyme called ethylene forming enzyme. 1 6/5/2014 Triple Response ● Slowing of stem elongation ● Thickening of stem ● Stem start to grow horizontally ● Together these responses strengthen the seedling stem and root Applications of Ethylene ● Used in agricultural industry to accelerate fruit ripening after shipment ■ “Degreens” unripe fruit ■ Causes trees to shed their leaves prematurely ■ Mainly used for bananas, tomatoes and citrus fruits Factors Controlling Synthesis of Ethylene ● CO2 and KMnO4 inhibit ethylene actions. These bind to ethylene receptors or otherwise interfere with the mechanism of ethylene action ● Ethylene is controlled by auxin and by red light ● Auxin acting to induce a labile enzyme needed for ethylene synthesis ● Red light to repress ethylene production ● CO2 as a competitive inhibitor of ethylene action ● 02 also is needed for ethylene production Sources Website: http://vannocke.hrt.msu.edu/plb865/30nov/fruit%20abscission.html Ethylene in Plant Growth BY STANLEY P. BURG The Fairchild Tropical Garden, and University of Miami, Miami, Florida 33156 Barnes, R. (2013, January 14). Seattle Community Colleges | Libraries | Remote Access. Seattle Community Colleges |Libraries|RemoteAccess.RetrievedMay22,2014,from http://www.accessscience.com.ez.sccd.ctc.edu:3048/content/ethylene/243500 Campbell, N. A. (2011). Chapter 39. Campbell Biology (9th ed., ). San Francisco, Calif.: Benjamin Cummings Kevany, B. (2013, January 1). Seattle Community Colleges | Libraries | Remote Access. Seattle Community Colleges | Libraries|RemoteAccess.RetrievedMay22,2014,from http://www.accessscience.com.ez.sccd.ctc.edu:3048/content/ethylene-plantphysiology/900120 http://vannocke.hrt.msu.edu/plb865/30nov/fruit%20abscission.html 2
