Preparation of Plant Growth Regulators and their Uses

Preparation of Plant Growth Regulators and their Uses

Growth regulator is a broad term and all growth-regulating compounds either endogenously or exogenously produced come under this category. In relation to plants, terms like hormones or phytohormones are synonymous to each other. Plant hormones or Plant Growth Regulators are organic compounds, other than nutrients, produced endogenously by plants, which in low concentrations regulate plant physiological processes. 

The horticulture industry is indirectly dependent on plant growth regulators as these are exclusively used for different purposes in all stages of the plant growth for desired manipulations viz., treatment of seeds for enhancing their germination, rooting of cuttings, induce flowering, deblossming, fruiting, yield, ripening, improving fruit quality and as postharvest treatments for better shelf-life. For the propagation of cuttings and layers, treatments of IBA growth regulators are used for inducing roots early rooting. 

These Growth Regulators are applied as powder form, solutions form, and paste form. Most of the hormones are not easily dissolved in water. Thus, it is necessary to dissolve them first in a suitable solvent viz., acetone or ethanol or alcohol. The growth regulators are required in a very minute quantity; therefore, precise weighing is of utmost importance and any mistake can be harmful to the plant. The different heopreparations of growth regulators are as follows;

Peparation of Growth Regulators

1. Powder Form:

The required quantity of the hormone is weighed precisely with the help of sensitive balance for the preparation of hormonal powders. It is dissolved in ½ litre ethanol, methanol or acetone in a beaker. This material is poured into one kilogram of talc taken in mortar and mixed thoroughly with a glass rod. After mixing, the mixture is kept open in air for few hours. The alcohol will evaporate soon, after which, the dried talc is ground to a fine powder. This fine powder should be kept in air tight containers to avoid moistening and can be used as and when required.

2. Solution Form:

For the preparation of hormonal solutions, the required quantity of hormone is weighed accurately in a physical or electronic balance. It is then dissolved in few drops of acetone or alcohol or ethanol. The final volume is made with distilled water after the complete dilution of contents. The pH of the solution should be neutral. In case, the pH of the solution would be high or less, it may not serve the purpose, rather it would affect the process adversely. The pH of the solution can be adjusted with the help of 0.1 N HCl or 0.1 N KOH. All the hormonal solutions should preferably be prepared fresh and can be stored at low temperatures in a refrigerator for some time but stored preparations may loose their properties and become inactive.

3. Paste Form:

        The required quantity of the hormone is weighed and dissolved completely in a few drops of alcohol/ethanol/acetone. The required quantity of the lanolin (a product similar to grease and greenish-yellow in colour) is also weighed and heated slightly in a beaker under a gentle flame. When the lanolin is slightly liquidified, the dissolved hormone is poured into it. The contents are dissolved thoroughly with constant stirring with a glass rod. The contents are then allowed to cool down. The paste is thus ready for use.

Methods of Application:

1. Lanolin paste

        This technique is most common for laboratory experiments. As this paste is prepared from fat the growth regulator doesn't dry out, thereby maintaining a constant concentration of the compund in contact with the treated organ.

2. Immersion into dilute or concentrated solutions

        The cuttings or the seeds can be soaked in the dilute solution of the growth regulator for 10-24 hrs. Dipping in a concentrated solution is recommended for rapid action. The proximal end of the cutting should be dipped in the solution.

3. Spraying method

        This method of growth regulator application is comparatively easy and quick. The dilute solutions are sprayed on the crop foliage with several types of sprayers. The effectiveness of the application depends on the ability of the growth regulator to penetrate through leaf cuticles into the mesophyll cells.

4. Dust method

        The growth regulator is dusted over the surface of the plant in the form of powder. This method is commonly used in rooting of cuttings. The cuttings may first be moistened with water at the basal end and then dipped in powder and planted on the lower end in the soil.

5. Aerosol and vapour method

       These methods are widely adopted in green house plants for promoting fruitsetting, inducing parthenocarpy and controlling the fruit drop. The aerosol method is based on preparing a growthregulater solution of low boiling point.For vapour form the active compound must be volatile.

Calculation for Plant Growth Regulators:

            Q1. 1pppm of Growth Regulator preparation


            1ppm = 1mg of growth regulator in 1 lit of water

        Q2. Prepare a GA3 growth regulator at the concentration of 10ppm and the final volume of solution should be 5 lit. (Try to solve it)

Answer: ?

Precautions to be taken

Ø  A proper solvent like acetone or ethanol etc should be used so as to dissolve the growth regulators.

Ø  At once, a minute quantity of hormone is used. So, don't buy more than what is required.

Ø  Check the date of expiry of the hormone.

Ø  The weighing of growth regulators should be done precisely and accurately on an electronic balance.

Ø  These hormones are photo-sensitive and photo-degradation occurs if exposed to light. Thus, these should be stored in dark or amber-coloured bottles. The solutions should always be made fresh.

[Preparation and application of PGR for a part of M.Sc. Research work in Acid lime@OUAT] by subhrajyoti's horticulture

Hello friends, I'am Dr. Subhrajyoti , from Odisha, India. I have completed my UG & PG from OUAT and Ph.D. from JAU. During my early year of teaching, I loved to provide important information to the young agriculturists and farmers. With the suggestions from my best friend Mr. S. R. Biswal, (Ph.D. Research Scholar; website designer & content editor of (blog &YouTube), I got interested to create such an amazing platform, where I can share my knowledge to a greater range of audience and also get enriched with new ideas and knowledge. I feel privileged to be in contact with you all. I would like to thank you all for your valuable support and encouragement through viewing my articles. I will always try my best to provide the quality and latest information on this website. Thank you….

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