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About PGRs

Plant growth regulators (PGRs) are crop protection products used in a wide variety of crops worldwide. They modify plant growth by interfering with plant hormones.

A field of green crops at sunset

How PGRs work

Auxins

Auxins are commonly found in the growing regions of the plant such as the tip of the leaves, the tip of the shoot or the buds. When auxins accumulate in the plant cell, its growing regions elongate, i.e., grow taller.

Gibberellins

Gibberellins also cause cell elongation but are usually concentrated on the stem in the areas where new leaves, also known as nodes, are formed. Under the effect of gibberellins, the stem between the nodes elongates, i.e., the internode distance becomes longer. The more gibberellins, the longer the plant.

Gibberellins also influence seed germination. A seed will only start growing when enough gibberellins accumulate.

Gibberellins are present across all growth stages of the plant. Their concentration is highest during periods of rapid growth (Feekes 4‒6, Zadoks 30‒32).

Cytokinins

Cytokinins promote cell division. If cytokinins are present in one cell, they divide it into two cells. Cell division means new cells and the emergence of new leaves, fruits and branches (tillers).

Abscisic acid

During periods of draught, abscisic acid will accumulate at cell borders to keep the stomata of the plant cells closed. Stomata are small openings in the leaf that allow it to breathe but simultaneously cause it to lose water. Another function of abscisic acid is to inhibit seed germination (e.g., until growing conditions are optimal).

Ethylene

Ethylene is a gas that, once released, breaks down the cell walls of a fruit, making them softer. Ethylene also helps release sugar, making fruit taste sweet. The most common use of ethylene is on bananas, which are commonly shipped green from country of origin and given ethylene treatment to ripen shortly before reaching supermarkets. In cereals, ethylene induces ripening and stops further plant growth.

Different PGRs interfere with different plant hormones and have different effects on plant growth. Even if two PGRs target the same hormone, their underlying chemistry can interfere differently with the targeted plant hormone.

Mode of action of cereal PGRs registered in the United States
Adjust™ SL
(proprietary chlormequat chloride)
Trinexapac-ethyl Ethephon
Inhibits early stages of gibberellin biosynthesis to reduce plant height and increase stem thickness Inhibits late stages of gibberellin biosynthesis to reduce plant height and increase stem thickness Releases ethylene to reduce crop height
Long residual activity Short residual activity
Has a slow onset of action, creating a more gradual response as it acts in the early stages of gibberellin biosynthesis Has a rapid onset of action as it acts in the late stage of gibberellin synthesis
Formulated to work effectively at temperatures as low as 34°F Harsh field conditions at or following application timing can cause crop damage Induces ripening and consequently stops further plant growth
Wheat growth stages and application timing of different plant growth regulators
Graph explaining how Adjust SL has an application window of Feekes 1-9, compared to other solutions with shorter windows.

A plant growth regulator can be a valuable cereal management tool for growers looking to:

  • Maximize yield potential
  • Protect investments on crop input
  • Improve harvest efficiency
  • Increase grain quality
  • Reduce disease risk
  • Reduce lodging risk
Evaluating your lodging risk
When am I at risk for root lodging? When am I at risk for stem lodging?
Cereal crops are planted late (backward crop), and the focus is to maximize tillers. Cereal crops are planted early and show lots of growth.
Season is wet, resulting in less compact soil conditions. Spring is warm, promoting lots of growth.
  Cereal fields are highly populated (due to overseeding or heavy nitrogen levels), resulting in weak stems.
Cereal variety is prone to lodging when working with high-yield wheat management.


PGRs can be applied via ground boom or aerial application. For specific uses and tank mixing, always read and follow label directions. For more user instructions on Adjust SL, go to application recommendations.

Auxins

Auxins are commonly found in the growing regions of the plant such as the tip of the leaves, the tip of the shoot or the buds. When auxins accumulate in the plant cell, its growing regions elongate, i.e., grow taller.

Gibberellins

Gibberellins also cause cell elongation but are usually concentrated on the stem in the areas where new leaves, also known as nodes, are formed. Under the effect of gibberellins, the stem between the nodes elongates, i.e., the internode distance becomes longer. The more gibberellins, the longer the plant.

Gibberellins also influence seed germination. A seed will only start growing when enough gibberellins accumulate.

Gibberellins are present across all growth stages of the plant. Their concentration is highest during periods of rapid growth (Feekes 4‒6, Zadoks 30‒32).

Cytokinins

Cytokinins promote cell division. If cytokinins are present in one cell, they divide it into two cells. Cell division means new cells and the emergence of new leaves, fruits and branches (tillers).

Abscisic acid

During periods of draught, abscisic acid will accumulate at cell borders to keep the stomata of the plant cells closed. Stomata are small openings in the leaf that allow it to breathe but simultaneously cause it to lose water. Another function of abscisic acid is to inhibit seed germination (e.g., until growing conditions are optimal).

Ethylene

Ethylene is a gas that, once released, breaks down the cell walls of a fruit, making them softer. Ethylene also helps release sugar, making fruit taste sweet. The most common use of ethylene is on bananas, which are commonly shipped green from country of origin and given ethylene treatment to ripen shortly before reaching supermarkets. In cereals, ethylene induces ripening and stops further plant growth.

Different PGRs interfere with different plant hormones and have different effects on plant growth. Even if two PGRs target the same hormone, their underlying chemistry can interfere differently with the targeted plant hormone.

Mode of action of cereal PGRs registered in the United States
Adjust™ SL
(proprietary chlormequat chloride)
Trinexapac-ethyl Ethephon
Inhibits early stages of gibberellin biosynthesis to reduce plant height and increase stem thickness Inhibits late stages of gibberellin biosynthesis to reduce plant height and increase stem thickness Releases ethylene to reduce crop height
Long residual activity Short residual activity
Has a slow onset of action, creating a more gradual response as it acts in the early stages of gibberellin biosynthesis Has a rapid onset of action as it acts in the late stage of gibberellin synthesis
Formulated to work effectively at temperatures as low as 34°F Harsh field conditions at or following application timing can cause crop damage Induces ripening and consequently stops further plant growth
Wheat growth stages and application timing of different plant growth regulators
Graph explaining how Adjust SL has an application window of Feekes 1-9, compared to other solutions with shorter windows.

A plant growth regulator can be a valuable cereal management tool for growers looking to:

  • Maximize yield potential
  • Protect investments on crop input
  • Improve harvest efficiency
  • Increase grain quality
  • Reduce disease risk
  • Reduce lodging risk
Evaluating your lodging risk
When am I at risk for root lodging? When am I at risk for stem lodging?
Cereal crops are planted late (backward crop), and the focus is to maximize tillers. Cereal crops are planted early and show lots of growth.
Season is wet, resulting in less compact soil conditions. Spring is warm, promoting lots of growth.
  Cereal fields are highly populated (due to overseeding or heavy nitrogen levels), resulting in weak stems.
Cereal variety is prone to lodging when working with high-yield wheat management.


PGRs can be applied via ground boom or aerial application. For specific uses and tank mixing, always read and follow label directions. For more user instructions on Adjust SL, go to application recommendations.

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Adjust SL

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FAQs

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Certain statements may not be applicable in all geographical regions. Product labeling and associated claims may differ based on government requirements.
Pending EPA registration, Adjust SL is not yet registered for sale or use in the U.S.