Use Of Plant Growth Regulators In Quality Production Of Vegetable Crops
Author: Pravin L. Deshmukh

Till recently, enhanced crop yields were achieved through the use of fertilizers, pesticides, better crop management and exploitation of genetic resources to develop highly yielding varieties. Plant growth regulators are one of the emerging biotechnologies that could possibly boost crop productivity. Plant growth regulators are chemicals, which are naturally occurring endogenous plant hormones or are synthetic plant growth regulators, which have potential for improving the productivity of different crop species. These chemicals are applied directly to the target plant to change its life process leading to improve the quality of its produce. It is generally suggested that synthetic plant growth regulators cause their effects through changing the endogenous levels of naturally occurring hormones and hence modify growth and development of the plant in a desired director and to a desired extent.

The crop productivity under field condition is dependent upon many factors like prolonging photo synthesis, delaying senescence, reducing photorespiration bringing about better partitioning of photo assimilates, stimulating mineral uptake and invigorating nitrogen metabolism. These factors could improve the physiological efficiency of a plant resulting in higher yields and quality produce. Just like with animal hormones, plant growth regulators come in a wide variety, producing different and often antagonistic effects. In short, the combination of hormones is vital to achieve the desired behavioural characteristics of cells and the productive development of plants as a whole.

Plant Growth Regulators

They are produced in plants in very small quantities. In addition to light, carbon dioxide, water and minerals, plants need certain chemicals in order to grow. These substances are called growth regulators or hormones.

A plant growth regulator is an organic compound, either natural or synthetic, that modifies or controls one or more specific physiological process within a plant. If the compound is produced within the plant it is called a plant hormone. Although photosynthesis supplies the carbon and respiration supplies the energy for plant growth, a group of chemicals produced by plants known as plant growth regulators control the growth and development of vegetables. These chemicals act on plant processes at very low concentrations. Often these are produced at one location and translocated to another where they exact their influence; however, they may also act on the same tissue in which they are produced.

Classification for plant growth regulators

The different categories of substances affecting plant growth are known which can be broadly classified into growth promoting and growth retarding substances or into naturally occurring growth substances and synthetic growth substances. Growth regulating substances may be classified into following categories:

  1. Auxins, e.g. Indole acetic acid (IAA)
  2. Gibberellins, e.g. Gibberellic acid (GA)
  3. Cytokinins, e.g. Kinetin, Zeatin etc.
  4. Ethylene, e.g. Ethylene
  5. Dormin, e.g. Abscisic acid (ABA), Xanthoxin, Phaseic acid etc.
  6. Flowering hormones, e.g. Florigen, Anthesin, Vernalin.
  7. Miscellaneous natural substances. e.g. Cyclitols, Vitamins, Phytochromes etc.
  8. Phenolic substances, e.g. Coumarin
  9. Synthetic growth retardants, e.g. CCC, AMO 1618, Phosphone D, Morphactins, Malformins, Maleic hydrazide (MH) etc.
  10. Miscellaneous synthetic substances, e.g. Synthetic auxins, synthetic cytokinins etc.

    Table: Plant growth regulators used in vegetable production;
Crop PGR's Dosage Time of spray Remarks
Solanaceous Vegetables
Tomato Triacontanol 1.25 ml/L of water 30,60 DAT Antitranspirant
NAA 0.25 ml/L of water 70,90 DAT Reduce flower and fruit drop
Brinjal Triacontanol 1.25 ml/L of water 20,40 DAT Antitranspirant
NAA 0.25 ml/L of water 60,90 120 DAT Reduce flower and fruit drop
Chilli Triacontanol 1.25 ml/L of water 20,40,60,80 DAT Antitranspirant
NAA 0.25 ml/L of water 60,90 DAT Reduce flower and fruit drop
Capsicum & Paprika Triacontanol Planofix 1.25 ml/L of water 0.25 ml/L of water 30,60,90 DAT 70,85 DAT Antitranspirant Reduce flower and fruit drop
Cucurbits
Watermelon Ethrel 2.5 ml/10 L of Water 2 true leaf stage (15 days) 3 times @ 1 week interval Modification of sex expression
Cucumber Ethrel 2.5 ml/10 L of Water 2 true leaf stage (15 days) 3 times @ 1 week interval Modification of sex expression
Gourds
Bitter Gourd Ethrel 2.5 ml/ 10L of water 2 true leaf stage (15 days) 3 times @ 1 week interval Modification of sex expression
Ridge gourd Ethrel 2.5 ml/ 10L of water 2 true leaf stage (15 days) 3 times @ 1 week interval Modification of sex expression
Snake gourd Ethrel 1 ml/ 10L of water 2 true leaf stage (15 days) 3 times @ 1 week interval Modification of sex expression
Pumpkin & Ash gourd Ethrel 1 ml/ 10L of water 2 true leaf stage (15 days) 3 times Modification of sex expression
Foliar spraying of PGR's as specified in above table, would be beneficial in enhancing the yield and quality of vegetables. Vegetables contribute to the food and nutritional security of the people in both developed and developing countries. By adopting PGR's in vegetables, a remarkable change in production and quality of vegetables can be assured.



About Author / Additional Info:
Ph.D. Scholar, Department of Horticulture, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, Maharashtra-444104.