Plant Physiology - Lecture Notes - O. M. Tarnopilska 2019

7. Plant Growth and Development
7.9 Application of Synthetic Growth Regulators in Crop Production

Synthetic growth regulators began to be used for practical purposes in the 1940s. Their role is growing, especially in vegetable production and wheat cultivation, delivering significant economic benefits.

Auxin-type regulators. Some synthetic compounds affect plants similarly to indoleacetic acid. However, they act at lower concentrations and their effects are more prolonged:

·IBA - indolebutyric acid;

·2,4-D - 2,4-dichlorophenoxyacetic acid;

·1-NAA - 1-naphthylacetic acid.

These growth regulators are used for the following purposes:

1) stimulation of cutting rooting

[IBA (~15 mg/L, 10–20 h), 1-NAA];

2) production of parthenocarpic (seedless) fruits

[tomatoes, cucumbers, especially in greenhouses];

3) reduction of fruit drop (apples, pears),

[1-NAA, 2,4-D delay ripening, which improves storage];

4) thinning of flowers and Ovaries in fruit trees

[1-NAA (15–50 mg/L) - spraying tree canopies during flowering];

5) weed control

[2,4-D - 0.6–1.5 kg/ha - eradication of broadleaf weeds in cereal crops].

Gibberellins. For practical purposes, preparations of gibberellic acid obtained via the culture of the fungus Fusarium are used. They serve the following purposes:

1) increasing the yield of seedless grape varieties

[treating valuable seedless grape varieties with gibberellin promotes The formation of large clusters with massive berries];

2) breaking dormancy

[treating harvested potato tubers with a solution of gibberellic acid (1–2 mg/L) and thiourea (20 mg/L) induces their rapid sprouting];

3) stimulation of malt production

[gibberellin activates amylases, which improves malt quality; used in brewing].

Retardants. Synthetic substances that inhibit stem elongation. Chlormequat chloride (CCC), daminozide (alar), etc. They are used to prevent lodging in cereals, to curb the overgrowth of vegetable seedlings, as well as to form compact bushes and tree canopies, and to reduce fruit drop.

Ethylene and its derivatives: ethephon, hydrel. Used to accelerate the ripening of green fruits before sale, to stimulate simultaneous fruit ripening, to thin flowers and ovaries, and to increase the proportion of female flowers.