Biology

Difference between Auxin and Gibberellin

Main difference

Auxins and gibberellins are two of the five major plant hormones. Auxins are present in higher plants, while gibberellins are found in some plants and fungi.

Comparative chart

Auxin Gibberellin
Location Upper floors Fungi (Gibberella fujikuroi) and some higher plants
Structure Single or double unsaturated ring structure with side chain Tetracyclic structure of gibbane with one side chain. At some point unsaturation is present.
Etymology The Greek word “auxein” means “to grow.” Latin word “Gibberella”.
Transport Basipetal (polar) Basipetal and acropetal (transport of channels in different directions)
Function Role in growth and function Role in growth and in different functions.
Discovery 1926 1938

What is auxin?

Auxin was discovered in 1926 and is the first group of plant hormones. Auxins are previously known as plant hormone regulators. Auxin is present in the form of indole acetic acid in plants. However, some other chemical compounds also exhibit the functions of auxins. One of the important functions is to stimulate the cell lengthening of the young shoots. Auxins are synthesized in apical meristems and young leaves. The developing seeds and fruits also contain high levels of auxins. It is transported through the cells of the parenchyma and translocates through the tracheal elements of the xylem and the sieve elements of the phloem. The transport is known as unidirectional and occurs from end to base. Auxins are used commercially in plant nurseries and crop production. Its IAA form is used as a hormone to promote root growth in cuttings and shed leaves. Synthetic auxins are also used in greenhouses to promote normal fruit development of tomato plants. The flowers of unfertilized plants are treated with auxins to bear fruit on the plants. Synthetic auxins are also used as herbicides.

What is gibberellin?

In 1926, a Japanese botanist, Kurosawa managed to obtain a filtered extract (gibberellin) of mushrooms while researching the disease of silly rice seedlings. In 1938, two scientists, Yabuta and Sumiki, discovered gibberellin in crystalline form. The biological activity and functions of these hormones were studied and reported by Japanese workers for the first time. Gibberellins are a group of plant hormones (about 125 closely related plant hormones) that promote plant growth primarily through cell elongation. Gibberellins are produced mainly in the meristems of the apical buds and roots, young leaves, and developing seeds. The translocation of gibberellin is acropetal, that is, from the base to the top. Gibberellins are produced in the apical stem and root meristem, in seed embryos, and in young leaves. These hormones perform a wide range of functions in plants, for example, cell elongation, internode elongation, increased fruit size, bud breakage and seed dormancy, gender expression, modification of the expression of the sex of the flower, effect on the development and growth of pollen and improvement of growth in cereal seedlings by stimulating digestive enzymes (amylase). Gibberellins also increase the elongation of the internodes of genetically dwarf plants. Gibberellins break dormancy in the seeds of plants that need exposure to light and cold to germinate. Abscisic acid is used as a strong antagonist of the action of gibberellins. It is applied to trees under power lines to control growth and decrease the frequency of pruning in urban areas. effect on the development and growth of pollen and improvement of growth in cereal seedlings by stimulating digestive enzymes (amylase). Gibberellins also increase the elongation of the internodes of genetically dwarf plants. Gibberellins break dormancy in the seeds of plants that need exposure to light and cold to germinate. Abscisic acid is used as a strong antagonist of the action of gibberellins. It is applied to trees under power lines to control growth and decrease the frequency of pruning in urban areas. effect on the development and growth of pollen and improvement of growth in cereal seedlings by stimulating digestive enzymes (amylase). Gibberellins also increase the elongation of the internodes of genetically dwarf plants. Gibberellins break dormancy in the seeds of plants that need exposure to light and cold to germinate. Abscisic acid is used as a strong antagonist of the action of gibberellins. It is applied to trees under power lines to control growth and decrease the frequency of pruning in urban areas. Gibberellins break dormancy in the seeds of plants that need exposure to light and cold to germinate. Abscisic acid is used as a strong antagonist of the action of gibberellins. It is applied to trees under power lines to control growth and decrease the frequency of pruning in urban areas. Gibberellins break dormancy in the seeds of plants that need exposure to light and cold to germinate. Abscisic acid is used as a strong antagonist of the action of gibberellins. It is applied to trees under power lines to control growth and decrease the frequency of pruning in urban areas.

Auxin vs. Gibberellin

  • Auxin accelerates growth in shoot segments while gibberellin promotes growth in intact shoots.
  • Auxin shows little effect on leaf growth, while gibberellin improves leaf growth.
  • Auxin has an effect on apical dominance while gibberellin has no effect on apical dominance.
  • Auxin does not cause bolting in root plants or rosette plants, while gibberellin causes stem elongation or bolting in rosette plants and root crops.
  • Auxin does not influence the vernalization requirement, whereas gibberellin can replace the vernalization requirement in most plants.
  • Auxin does not break dormancy in seeds and sprouts, while gibberellin helps to break dormancy.
  • Auxin is necessary for callus growth and formation, while gibberellin has no effect on callus growth.
  • Auxin has no effect on the flowering of long-day plants, while gibberellin can replace the need for a prolonged photoperiod in
  • Auxin shows the effect on root growth in low concentration, while gibberellin has no effect on root growth.
  • Auxin does not produce hydrolyzing enzymes to mobilize the food reserve during seed germination, whereas gibberellin produces hydrolyzing enzymes.
  • Auxin has a feminizing effect on some plants, while gibberellin has a masculinizing effect on plants.
  • Auxin does not cause cell division in plants, while gibberellin promotes cell division in plants.

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