Introduction
Auxin and Gibberellin both are a type of plant hormones that occurs naturally and synthesises artificially. These hormones help the plant in the plant growth processes like flowering, root initiation, organogenesis and many more. Both of these hormones fall under the category of phytohormones. They also have major roles to mediate the responses of the shading adaptation of plants.
What is Auxin?
The word auxin means growing or enlarging. This hormone is situated in the growing roots of apice. It changes location later to promote growth in the plant. It is acquired from tryptophan, a type of amino acid and plays a significant role in plant development. Auxin never breaks seed and bud dormancy. On the other hand, it has a significant role in axial elongation, cell differentiation, cell division, cellular expansion, isodiametric expansion and lateral expansion among plants. They commonly help in the production of apical meristem of shoots, young leaves and seeds.
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Functions of Auxin
The functions of auxin are the following −
- It helps to improve cell elongation in shoots and coleoptiles.
- It increases morphogenesis and helps to create callus formation if mixed with cytokinin.
- It enhances secondary growth and controls cell division in the vascular cambium region.
- NAA is a highly used component for root formation stimulation while cutting the stems.
- It can be extracted from seeds and can be mixed with gibberellins to improve the development of fruit.
- Synthetic auxins can destroy weeds but it is ineffective on grasses. Examples: 2,4- D and 2,4,5-T.
- Auxin helps to blossom litchi and pineapple trees. It has a feminine effect on them.
- It causes phototropism, gravitropism and thigmotropism. It means auxin causes the plants to react to light, gravity and touch.
- The proportion of auxin increase on the dark side of the plant which causes higher cell elongation in that part.
What is Gibberellin?
Gibberellin is a type of diterpenoid. It creates vitamin molecules like Vitamine A and Vitamine E. Gibberellin has different side groups linked to it. The linked group differentiates its unique functions. The main function it has in plant growth is stem elongation. This stimulates the stem to grow and if applied only in a low concentration then too it the stem starts growing. Gibberellin helps to grow the dwarf shoots and internodes. There are around more than 70 isolated gibberellins such as GA1, GA2, GA3 and others. GA3 is the most frequently examined plant growth regulator among them.
Gibberellin: Applications
The main applications of gibberellin are the following −
- Grapevines can be enlarged by spraying gibberellins on them.
- It helps in the seed germination process. Fungi are the commercial source to produce gibberellin.
- Cucumber plants can develop all-male flowers with the help of this hormone. It can be used in the hybridization process for the desired pollen characteristics obtainment.
- It helps biennial plants to produce flowers at low temperatures as well.
- Genetic mutants like dwarf varieties of plants can be stimulated for growth by gibberellin application.
Differences between Auxin and Gibberellin
The differences between auxin and gibberellin are the following −
| Characteristics | Auxin | Gibberellin |
|---|---|---|
| Structure | Auxin has an unsaturated structure attached to a side chain. The unsaturated structure can be single or double. | Gibberellin doesn’t have a side chain. It has a saturated tetracyclic gibbane structure. |
| Location | It can be only located in higher plants. | It is located both in higher plants and in |
| Apical dominance | It can create apical dominance. | It does not create apical dominance. |
| Root Growth | Auxin helps in root growth if it is at a normal concentration. | Gibberellin does not have any function in it. |
| Shoot Growth | It helps in the shoot segment growth. | It helps to grow an intact shoot. |
| Leaf Growth | It doesn’t have a huge role in leaf growth. | It plays a huge role in leaf growth. |
| Stem Elongation | It doesn’t help in stem elongation. | It helps in stem elongation. |
| Bolting | It cannot create bolting | It creates bolting in rosette plants. |
| Callus Growth | It has the most signification role in the growth of callus. | It plays no such role in the growth of the callus. |
| Root Formation | It stimulates the formation process of roots. | It does not stimulate the formation of roots. |
| Hormonal Effects | Auxin creates a feminine effect among plants. | Gibberellin creates a masculine effect among plants. |
| Transport | It only has the basipetal transport method. | It has both the basipetal and acropetal transport method. |