07 Plant Growth and Mineral Nutrition - part 13 - Grwoth Harmone - Abscissic Acid

07 Plant Growth and Mineral Nutrition - part 13 - Grwoth Harmone - Abscissic Acid


Abscissic Acid : 
  • It is a natural growth inhibiting hormone. 
  • Carns and Addicott (1961-65) observed that the shedding of cotton balls was due to a chemical substance abscisin I and II. 
  • Wareing (1963) isolated a substance from buds of Acer that can induce bud dormancy and named it dormin. 
  • These two identical chemical substances were given the common name abscissic acid. 
  • It is synthesized in leaves, fruits, roots, seedsetc. 
  • Chemically, it is a 15-carbon sesquiterpenoidand is synthsized from mevalonic acid. 
Physiological effects and application of ABA: 
  • It promotes abscission of leaves and induces dormancy in many plants. 
  • Controls the dormancy in buds and seeds by inhibiting growth processes. 
  • accelerates the senescence of leaves, flowers and fruits. 
  • Inhibits and delays cell division and cell elongation and suppresses cambium activity by inhibiting mitosis in vascular cambium. 
  • ABA could cause efflux of k+ ions from the guard cells and result in closure of stomata. So, it is known as an antitranspirant. 
  • Acts as a stress hormone by inducing the plant to bear the adverse environmental conditions. 
  • Inhibits flowering in long day plants but stimulates flowering in short day plants.

Do you know ?
Bioassays for : 
  • Auxins - Avena curvature test. 
  • Gibberellins - Alpha amylase bioassay. 
  • Cytokinins - Chlorophyll retention test. 
  • Ethylene - Tripple pea test. 
  • ABA - Inhibition of alpha amylase test.

Comments

Post a Comment

Popular posts from this blog

6. Biomolecules - part 01 - Carbohydrates

Image
  6. Biomolecules - part 01 - Carbohydrates Introduction : Our planet is having a wide diversity of living organisms that are classified as - unicellular  (consisting of a single cell; including bacteria and yeast) or  multicellular  having many cells (e.g. plants and animals).  living organisms have cell as the basic structural and functional unit.  The cells have protoplasm containing numerous chemical molecules, the biomolecules. Biochemistry  : Biochemistry is  biological chemistry  that provides us the idea of the chemistry of living organisms and molecular basis for changes taking place in plants, animals and microbial cells.  It develops the foundation or understanding  all biological processes  and communication within and between cells as well as chemical basis of inheritance and diseases in animals and plants. Chemical analysis of all living organisms indicates presence of the most common elements like  carbon, h...
Read more

6. Biomolecules - part 02 - Lipids

Image
  6. Biomolecules - part 02 - Lipids B. Lipids : These are group of substances with greasy consistency with  long hydrocarbon chain containing carbon, hydrogen and oxygen. In lipids, hydrogen to oxygen ratio is  greater than 2:1  (in carbohydrates it is always 2:1). Lipid is a broader term used for fatty acids and their derivatives.  They are soluble in organic solvents (non-polar solvents).  Fatty acids are organic acids which are composed of hydrocarbon chain  ending in carboxyl group (-COOH).  They can be  saturated fatty acids  with no double bonds between the carbon atoms of the hydrocarbon chain.  Palmitic and stearic acids  found in all animal and plant fats are examples of saturated fatty acids. Unsaturated Fatty Acids  are with one or more double bonds between the carbon atoms of the hydrocarbon chain.  Oleic acid  found in nearly all fats and  linoleic acid  found in many seed oils are example...
Read more

6. Biomolecules - part 05 - Enzymes

Image
  6. Biomolecules - part 05 - Enzymes Enzymes : Thousands of different chemical reactions take place automatically at a given time in a tiny living cell. The reactions take place at the body temperature.  If these enzymes were not present in the cell, either the reactions would not occur or if they occur they would occur at a  very very slow rate . Know the scientists : German chemist  Edward Buchner  discovered enzymes by accident.  Buchner discovered that living cells were not necessary but that  yeast  extract could bring about fermentation.  He then coined the term Enzyme (Gk. En = in, zyma = yeast i.e. in yeast). This term is now commonly used for all biocatalysts. Each enzyme catalyzes a small number of reactions, specifically perhaps only one. Substrate :  The substance upon which an enzyme acts is termed as the substrate.  Endo-enzymes :  The enzymes which act within the cell in which they are synthesizedare known as en...
Read more