Exercise 3

Exercise 3: Preparation and application of Plant growth regulator solutions for seed germination and Vegetative propagation

    Exercise: Preparation and application of plant growth regulator solutions for seed germination and vegetative propagation.
    Materials Required: Plant growth regulator(s), measuring cylinder, volumetric flask, beaker(s), electronic balance, distilled water.
    Preparation of growth regulator solution:
    • The strength of growth regulators is calculated in ppm (parts per million). One ppm means 1.0mg of chemical dissolved in one litre of water.
    • After weighing the required quantity of growth regulator transfer it to a beaker and dissolve it with the small quantity of solvent.
    • Auxins are soluble in alcohol or 0.1% NaOH. Gibberellins are soluble in absolute alcohol, while, cytokinins can be dissolved in 1-2 ml N/10 HCl.
    • Abscisic acid is highly soluble in NaOH. Shake the beaker till the growth regulator/chemical is fully dissolved. Now transfer it into volumetric flask and make final volume with distilled water to one litre.
    • For every use one should prepare fresh solution. Following formula is used for conversion of hormonal strength.
    I) Percent solution = ppm 10,000
    II) ppm solution = % x 10000 = % x 104
    Preparation of hormonal powder:
    • For preparation of hormonal powder, the required quantity of hormone is weighed precisely with the help of sensitive balance.
    • 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.
    Preparation of hormonal paste:
    • For preparing hormonal pastes, the required quantity of the hormone is weighed accurately and dissolved completely in a few drops of alcohol.
    • The required quantity of lanolin (wool fat, a product similar to grease and is greenish-yellow in colour) is weighed and heated slightly in a beaker under gentle flame.
    • When the lanolin is slightly liquefied the dissolved hormone is poured in it.
    • The mixture is dissolved thoroughly with constant stirring with a glass rod. The mixture is allowed to cool down.
    The paste is ready for use. Until use, the paste may be kept for few months in a cool dry place but one should prefer to use fresh paste.
    • First of all check the expiry date of the hormone powder.
    • The weight should be taken precisely, preferably on electronic balance.
    • Proper solvent should be used to avoid precipitation.
    • Hormones deteriorate under high temperature, so store in cool and dry place.
    • Hormones are photosensitive; therefore they must be stored in dark or amber colored bottles.
    • Use hormonal solutions for treatment of cuttings and lanolin paste for layers.
    • Solutions should be prepared fresh. If required to store for some time use, refrigerators.
    • The treated cuttings should be planted with the help of some stick to make hole, so as to avoid removal of solution from basal end of cutting.
    Method of application of growth regulators:
    The effectiveness of growth regulators not only depend the concentration, but also on the method of application. Auxins are most effectively and widely used rooting hormone. Among synthetic auxins IBA and NAA are found to be most effective for inducing rooting. The different methods used for treatment of cuttings and layers are as under:
    Prolonged soaking method:
    • In this method, the basal end of cuttings is dipped in the dilute solution of the hormone for 24 hours in a cool dry place.
    • The concentration of hormone or growth regulator usually varies from 20ppm to 200 ppm, depending upon plant species and type of cutting.
    • After treatment cuttings are planted in growing medium. The concentration is usually low in growing medium.
    • The concentration is usually low for easy to root species and vice versa.
    • This method is very useful for difficult to root species, where some materials like vitamins, sugars and nitrogenous compounds are also used along with the growth regulators for facilitating rooting.
    Plate 3.1. Cuttings of Merton 793 immersed in IBA solution
    Quick dip method:
    • In this method, the basal end of cuttings is dipped in the concentrated solution of a hormone for a short time, usually for 5 seconds to 2 minutes depending upon the species to be propagated.
    • Treated cuttings are planted in the rooting medium or field. The concentration of hormone for quick dip method may vary from 500 to 10,000 ppm depending upon the type of cutting and species, but generally a concentration of 3000 to 5000 ppm is used.
    Powders dip method:
    • In this method also basal ends of cuttings are dipped in the hormonal powder which carries (talc) for some time.
    • After treatment of cuttings, extra amount of powder adhering to the cuttings should be removed by shaking and cuttings are immediately inserted into the rooting medium.
    • For effective rooting, the cut ends of the cuttings should be moistened before the treatment and care should be taken that extra powder adhered to cuttings should be shaken off, otherwise, it may cause adverse effect on the rooting process.
    • Seradix, Rootex or many other formulations are available in the market as powders.
    Lanolin paste method:
    • As described under preparation of hormonal paste, the paste of growth regulators made in lanolin is applied to the girdled portion of a layer or stool for inducing rooting in them.
    Spray method:
      • Spraying of growth regulators is sometimes done to mother plants before taking cuttings from them. Spraying of stock plants with 2,4,5-T in concentrations ranging from 25 to 100 ppm is done about 30 to 40 days before taking cuttings from them, Cuttings taken from such plants root better as compared to untreated plants.

Last modified: Thursday, 20 September 2012, 4:48 AM