The type of plant hormone that controls the cell elongation in plants during phototropism and gravitropism is known as Auxin. Another type of plant growth hormone ‘Gibberellin‘ regulates the seed germination shoot elongation, flower, and fruit maturation.
Such important biochemicals that influence plant growth and cell differentiation, tissues, and organs under various conditions are known as Plant hormones. The term was elaborated by the German botanist ‘Julius von Sachs’ who pointed out that plants can produce a chemical substance, which is carried by plant tissues, resulting in the growth and formation of the plant and its various parts.
Plant hormones are also known as Plant growth regulators or Phytohormones which play the role of chemical messengers in plants. They are of five types: auxins, gibberellins, cytokinins, abscisic acid (ABA), and ethylene. These hormones coordinate work together for the growth and development of plant cells.
Based on their action, plant growth regulators are also of two types: Plant Growth Promoters and Plant Growth Inhibitors. Plant Growth Promoters enhance cell enlargement, division, fruiting, flowering, and seed formation.
Plant Growth Inhibitors promote dormancy to inhibit the growth and abscission in plants. Auxins, cytokinins, gibberellins are examples of plant growth promoters, while abscisic acid is the example of inhibitors.
We all are aware of the extrinsic factors that a plant needs to grow, which are air, water, and sunlight. But apart from these essentials, intrinsic factors such as the growth hormones also play a vital role from their side. In this article, we will be highlighting two types of hormones which are Auxins and Gibberellin, how they vary from each other, and their functions.
Content: Auxin Vs Gibberellin
Comparison Chart
| Basis for Comparison | Auxin | Gibberellin |
|---|---|---|
| Meaning | Auxins is the plant hormone that induces cell division, cell elongation, and cell differentiation and support formation of shoot segments. | Gibberellin is also the class of plant hormone that induces stem growth, germination and flowering. |
| Found in | Auxin is present in higher plants. | Gibberellin is present in fungi as well in higher plants. |
| Consist of | Auxin has a ring structure along with side chain, and this ring is indole (benzopyrrole), attached to the side chains of fatty acids to the pyrrole part of carbon 3 of indole. | It has saturated tetracyclic gibbane structure. |
| Type of transport | Auxins show basipetal transport. | Gibberellin shows acropetal and basipetal transport. |
| Role | Auxins play role in cell division, cell differentiation, cellular expansion, lateral expansion, axial elongation, and isodiametric exapnsion in plants. | Gibberellin plays a role in germination, flowering, elongation of the stem, enzyme induction, sex expression, and fruit and leaf senescence. |
| It promotes | Auxin enhances the growth of shoot segments. | Gibberellin only enhances the growth of the intact shoot. |
| Effect on leaf | There is less impact on leaf growth. | Gibberellin promotes leaf growth. |
| Apical dominanace | Auxin causes apical dominance. | Gibberellin does not affect or causes apical dominance. |
| Other features |
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Definition of Auxin
The first growth hormone discovered and derived its name from the Greek word ‘auxein‘ which means ‘to grow‘. These were observed by Charles Darwin and Francis Darwin. They observed that the coleoptile tip in canary grass bends and grows towards the source of light, and the phenomenon is known as ‘phototropism’.
From this observation, it was concluded that auxins are responsible for cell growth and its division in gravitropism and phototropism. They also play a role in leaf development and the differentiation of vascular tissues.
Indole-3-acetic-acid (IAA) and Indole butyric acid (IBA) are the only natural auxin produced by the plants. These auxins are present in stem and rots and then are carried to the site where they are required. The synthetic auxins are 2, 4-dichlorophenoxyacetic acid (2, 4-D) and Naphthalene acetic acid (NAA).
Uses
- It is helpful in plant propagation.
- It is used to kills weeds (2, 4-D is used as a herbicide).
- It stimulates plant propagation.
- It is helpful in parthenocarpy (production of fruits without fertilization).
Outcomes
- Auxins promote rooting.
- It stimulates flowering in plants such as pineapples.
- Auxin promotes the natural dropping or detachment of fruits and older leaves.
- Supports during cell division and in xylem differentiation.
Definition of Gibberellin
Gibberellins are the set of around 125 closely associated compounds and are found in numerous fungi, lower as well as in higher plants. It mainly plays a role in shoot elongation, seed germination, and the maturation of fruits and flowers. Due to their acidic properties, they are denoted as – GA1, GA2, GA3, etc. Gibberellic acid (GA3) is the most studied and critical one, as it was first to be discovered.
Another compound of GA4+7 is used in plant tissue culture; gibberellin is also used in adventitious root formation, and in the stimulation of organogenesis.
Uses
- Help to induce bolting in rosette plants.
- The use of gibberellins also increases the yields of the sugarcane by strengthening the stem.
- GA3 is also used industrially to boost up the malting process.
- It also promotes early seed production.
Outcomes
- Delay fruit senescence due to which market period is extended.
- Gibberellins improve the shapes of fruits such as apples.
Key Differences Between Auxin and Gibberellin
The following points will highlight the critical distinctions between the two types of plant hormones, which are Auxin and Gibberellin:
- Auxins is the plant hormone that induces cell division, cell elongation, and cell differentiation and supports the formation of shoot segments. Gibberellin is also a class of plant hormones that induces stem growth, germination, and flowering.
- Auxin is present in higher plants, whereas Gibberellin is present in fungi as well in higher plants in small proportions.
- Auxin has a ring structure along with a side chain, and the ring is indole (benzopyrrole), attached to the side chains of fatty acids to the pyrrole part of carbon 3 of indole, whereas gibberellin has a saturated tetracyclic gibbane structure.
- Auxins show basipetal transport, while Gibberellin shows acropetal and basipetal transport.
- Auxins play a role in cell division, cell differentiation, cellular expansion, lateral expansion, axial elongation, and isodiametric expansion in plants. Gibberellin plays a role in germination, flowering, elongation of the stem, enzyme induction, sex expression, and fruit and leaf senescence.
- Auxin enhances the growth of shoot segments. Gibberellin only enhances the growth of the intact shoot.
- Auxin causes apical dominance, whereas gibberellin does not affect or causes apical dominance.
- The presence of auxins inhibits root growth, required for callus formation and its growth. The presence of Gibberellin leads to bolting in root crops and rosette plants, and it has no role in callus growth and development, rather it is required in the germination of seed and in breaking of bud dormancy.
Similarities
- Auxin and Gibberellin are the types of plant growth hormone or phytohormone.
- Both are cell responsible for the development of shoot.
- Both the hormones also promotes the cell division, elongation, and differentiation.
- These hormones are responsible for the formation of flowers, stems, leaves, and fruits.
Conclusion
We can conclude that among the five types of hormones found in plants, auxins and gibberellins play a major role in regulating the growth and development of plants; though they are found in small amounts but are considered to be an essential one. These are required to carry out various biochemical reactions and in coordinating and responding to the signals provided by different parts of the plant.
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