Title: Effect of extracted growth hormones on nodulation and Stem length of Oryza sativa (Rice).
Subjects: Chemistry, Biology
Topics covered: Alcohol extraction (chemistry), HPLC (Chemisty), Plant development and growth (Biology)
To determine the effect of extracted growth hormones (Auxins & Gibberlins) on root and shoot formation.
Higher plants undergo a complex pattern of growth and development during their life cycle. For more than 100 years, plant physiologists have tried to understand the mechanisms by which this pattern of growth and development is regulated. During this time, various endogenously produced molecules have been identified as having the property of altering one or more aspects of growth and development. These molecules are called plant hormones, plant growth substances, or phytohormones. Most experiments with phytohormones have involved exogenous application of extracted hormones of synthetic analogues to plants or plant tissues. These experiments have demonstrated numerous dramatic effects of hormones on plant growth and development. Relatively little is known about the mechanisms by which these molecules exert their effects. This problem of mechanism of action is compounded by the fact that each phytohormone usually produces multiple effects, so the initial site of action is often obscured. The observation that phytohormones are active at very low concentrations, 10-6 M or less, suggests that phytohormones act by binding tightly to specific “receptor” molecules. The receptor might be, for example, a protein, that is activated by the binding of a particular phytohormone.
Groups of Phytohormones
To date, five major groups of phytohormones have been established. These groups are listed
here, together with a brief description of the physiological effects that they evoke.
Indole-3-acetic acid (IAA) is a naturally occurring auxin. IAA is synthesized from trytophan in the above-ground meristematic tissues and then undergoes polar transport down the stem. Stimulation of cell elongation in stems is the best known effect of auxin, but it also plays a role in other processes such as apical dominance. The chemical 2,4-dichlorophenoxyacetic acid (2,4 D) and ?-naphthaleneacetic acid (?-NAA) are two of the many synthetic auxins that are known.
Gibberellic acid (GA3) is only one of more than 60 naturally occurring gibberellins. These diterpenoid compounds are synthesized from geranylpyrophosphate in leaf primordia and roots. GA3 is readily translocated throughout most parts of the plants. Gibberellins cause profound stem elongation and, in some plants, enhance other processes such as seed germination and fruit set.
Zeatin was the first naturally occurring cytokinin to be identified in plants. Synthetic cytokinins such as kinetin and N6-benzyladenine (BA) were discovered previously. The major effect of cytokinins is a stimulation of cell division. Cytokinins also have other effects, however, including cell enlargement and regulation of senescence. Zeatin and most synthetic cytokinins are thought to be synthesized in roots and also in developing fruits. D. Abscisic Acid Abscisic acid (ABA) is another naturally occurring phytohormone. ABA is an isoprenoid compound and is synthesized in both roots and leaves. This hormone is translocated readily in the plant. ABA acts to inhibit, rather than stimulate, many physiological functions. Effects of ABA include closure of stomata, dormancy of axillary buds, abscission of certain fruits, and inhibition of seed germination.
Ethylene gas is produced by many plant tissues, although ripening fruits are an especially rich source of this phytohormone. The immediate biosynthetic precursor of ethylene on plants is 1-aminocyclopropane-1-carboxylic acid which itself is formed from S-adenosylmethionine. Ethylene stimulates fruit ripening, accelerates senescence, and alters other processes such as bud growth in pea seedlings. Ethylene moves readily through the plant by the process of diffusion.
- Coconut water –From young green tender coconuts.
- Appropriate solvent extraction reagents required to extract growth hormones from coconut water.
- Fertile soil.
- Plastic cups.
- Fertilizer solution.
- Green house for incubating seedlings.
Principle: Plant hormones affect seed germination and dormancy by acting on different parts of the seed.
Chemistry Lab Investigation:
- Step 1 – Extraction of auxins and gibberllins by suitable solvent extraction method.
- Step 2: Purifications of growth hormones.
Biology Lab Investigation:
Step 3 – Control: Add Distilled water ( 3/4th of boiling tube) in a boiling tube and then add some cotton (Substratum), to this add some surface sterilized seeds (Rice seeds) .(You could also inoculate these seeds on tissue culture media with amount of distilled water poured after inoculation of seeds). …………………..X 4 (Tubes).
Step 4 – Coconut Water: Add coconut water ( 3/4th of boiling tube) in a boiling tube and then add some cotton (Substratum), to this add some surface sterilized seeds (Rice seeds) .(You could also inoculate these seeds on tissue culture media with addition of coconut water poured after inoculation of seeds). …………………..X 4 (Tubes)
Step 5:Coconut Water extract (Growth hormones) : Coconut Water extract ( 3/4th of boiling tube) in a boiling tube and then add some cotton (Substratum), to this add some surface sterilized seeds (Rice seeds) .(You could also inoculate these seeds on tissue culture media with amount of Coconut Water extract poured after inoculation of seeds).
…………………..X 4 (Tubes)
- Plug all the Boiling tubes with cotton plugs to avoid contamination.
- Leave the set up in a greenhouse with standard incubation condition for Rice seeds.
- Constant monitoring of tubes for addition of Distilled water, Coconut Water, and Coconut Water extract.
Coconut Water extract
Average Hypocotyl Length (mm)
Average Radicle Length (mm)
Average Stem Length(mm)