Plant hormones: what are they and what are their functions?

Pflanzenhormone: Welche gibt es und was sind ihre Funktionen? - FARBIO® - Nachhaltige Bio-Flüssigdünger aus Hamburg

The hormones in plants are also called phytohormones. They are plant-specific chemical compounds that control important processes within the plant. Plant hormones are messenger substances that pass on important information and regulate growth. Many different hormones work together, which is why it is not only relevant whether a hormone is present, but also in what concentration.

What are Gibberellins?

Gibberellins are the hormones in a plant that are responsible for the germination of seeds and buds. They also promote the formation of a plant's flowers. Gibberellins give plants the impetus for the longitudinal growth of shoots, especially in young plants. This plant hormone is mainly produced by growing plant parts. The hormone is involved in the process that makes a plant grow towards the sun.

And auxins?

Auxins are other phytohormones. If it is shady on one side of the shoot axis, the auxins migrate there. In doing so, they activate the local gibberellins, which ensure linear growth. This is how the plant bends towards the sun.

Auxins are among the first plant hormones discovered. Because they are synthesized in the shoot tip, plants can no longer grow without them. Auxins are also involved in the growth of a plant by promoting the expansion of cells and thus the longitudinal growth of the shoot axis and roots. With their presence, auxins also influence the growth of flowers and fruits.

How are cytokinins related to auxins?

Cytokinins are the hormones in a plant that ensure balance between roots and shoots. In this context, the cytokinins work together with the auxins. Because of the concentration balance between the two, a plant can determine whether it needs to develop more roots or shoots. Since cytokinins are produced in the roots, an excess signals the plant to produce more shoots. If there are more auxins, which are produced in the shoot tips, the growth of the roots is stimulated. The phytohormone particularly promotes the growth of the side shoots of a plant. Furthermore, cytokinins slow down the aging process of a plant.

What is the function of ethylene?

Ethylene is not only active within a plant, but also serves as a messenger between plants. The amino acid methionine is produced within the plant. Fruits ripen through the stimulation of ethylene, which is responsible for breaking down cell walls. This ensures softer fruits and a higher sugar content. The plant hormone causes the aging of leaves and flower organs and ultimately promotes leaf fall. Ethylene is also important for sprout germination and growth. It causes the thickening, shortening and curvature of the sprouts.

What is abscisic acid?

In response to stress, the plant produces the phytohormone abscisic acid in the chloroplasts. Stress factors for plants include drought or cold. Abscisic acid helps the plant regulate its water balance. Stomata, the stomata of a leaf, close as soon as the plant does not receive enough water. There is no loss of water through transpiration. In response to low temperatures, the hormone ensures that buds and seeds do not germinate in winter. This is the initiation of the dormant state, the so-called seed dormancy.

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