All You Need To Know About: Abscisic Acid

1. All You Need To Know About: Abscisic Acid • What it is: • ABA is a Plant Growth Regulator • Chemical formula: C15H20O4 • Mainly acts to inhibit growth and cellular activities • Helps plants survive through environmental distresses • (BSCS Biology) Plant in hot sun with ABA • Which Plant Organs are targeted: • The stomata in leaves (BSCS Biology) • Embryos in seeds (BSCS Biology) • Shoots • Vascular cambium (What is Abscisic Acid?) • Apical Meristem (Abscisic Acid (ABA)) Plant in hot sun without ABA • Why is it Important? • Allows plant to stay alive and conserve water during dry times • Ensures maximum chance of survival when growing from seed into plant • Allows embryo to stay alive and nourished through stimulation of storage proteins • Assists plant in living through harsher conditions • ie. Winter • (BSCS Biology) Structural formula for ABA • When is it produced? • Synthesized in dry conditions • ie. Drought • Higher water stress causes increase in ABA synthesis • During embryo formation in seeds • (BSCS Biology) Fun Fact: When rats and pigs brains were purified using radioimmunoassay in an experiment, they began to show the same characteristics as ABA. (Rouvier 1986) • PGR- Targeted Organ’s Responses: • ABA causes the stomata on leaves to close • Reduces water loss • Inhibits photosynthesis because less gas exchange • Causes seed embryos to become dormant when ABA accumulates • During embryo formation, ABA stimulates the synthesis of storage proteins • Prevents embryo from germinating until it is mature and conditions are favorable • (BSCS Biology) • Induces gene transcription • Especially for proteinase inhibitors • Inhibits seedling growth • (Abscisic Acid) • Inhibits division of cells in vascular cambium • Adjusts to colder conditions during winter by suspending primary and secondary growth (What is Abscisic Acid?) • ABA can cause the apical meristem to become a dormant bud that will protect it and prevent it from drying during cold periods like winter (Abscisic Acid (ABA)) A seed embryo and Its endosperm (Nat. Tree Centre) • Where is it produced? • Produced in all parts of the plant (PC) • Produced in chloroplasts and plastids • In leaves, made from ground tissue • (Abscisic Acid) • Produced in the terminal buds in preparation for winter • (What is Abscisic Acid?) • Produced in the roots when there is dry soil during times like drought • (What is Abscisic Acid?) • Flows through xylem to leaves by transpiration • Works Cited: • BSCS Biology: A Molecular Approach. Columbus: Glencoe/Mcgraw- Hill Companies, Inc., 2006. • Abscisic Acid. Mendipweb. 4 April 2008. • <http://www.plant-hormones.info/abscisicacid.htm> • What is Abscisic Acid?. 2002. Pagewise, Inc. 4 April 2008 • <http://www.essortment.com/all/whatisabscisic_rjdl.htm > • Abscisic Acid (ABA). April 3 2007. April 4 2007. • http://www.users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ABA.html • JSTOR. E. Rouvier/1986. Version number 83. National Academy of Sciences. 4/6/08. http://www.jstor.org/pss/27114 • National Tree Seed Centre. March 13 2007. Natural Resources Canada. April 4 2008. <http:// cfs.nrcan.gc. • ca/images/4867 To protect the plant from water loss, ABA shrinks the guard cells causing the stomata to close. (Abscisic Acid 2007)

2. CYTOKININS Definition: a class of plant hormones that promotes tissue growth and slows tissue aging. It is found in almost all plants and has a structure resembling the DNA base adenine. Where are cytokinins produced? Cytokinins are produced in the roots through biochemical modification of adenine. How are cytokinins transported? Cytokinins are moved from the roots of the plant to the shoots of the plant through the xylem via plant transport. What parts of a plant do cytokinins target and how do those parts respond? Cytokinins are plant hormones that stimulate stem and root growth as well as chloroplast development. Cytokinins as promote the growth of lateral branches and opposes the aging of plant tissues. These PGRs can do this because they increase cell division, which then means more growth. Cytokinins target root tips, and germinating seeds as well as the stems and leaves of a plant. Why are cytokinins important for the life of the plant? Cytokinins play an important role in the life a plants. They are one of the hormones that contribute greatly to the development of a seed into a mature plant. Cytokinins also extend the longevity of plant tissues, making them last longer. Flowers sprayed with cytokinins tend to stay green for a longer period of time. Fun Fact: What is the relationship between auxins and cytokinins? While auxins prevents axillary buds from growing, cytokinins stimulate the growth of axillary buds. Once cytokinins have activated the growth of the buds, auxin cannot stop it. This is the same with lateral branches and lateral roots. Cytokinins stimulate the growth of lateral branches while auxin stimulates the growth of lateral roots. In this way, plants achieve a balance of growth between the shoots and root systems. Fig. 1 Bibliography: "Cytokinins." Plant Hormones Info. 2003. 4 Apr. 2008 <http://www.plant-hormones.info/cytokinins.htm>. Palmer, Chelsea. "What are Cytokinins?" Essortment. 2002. 5 Apr. 2008 <http://www.essortment.com/all/cytokinins_rfjy.htm>.