Auxin is a type of phytohormone in plants that controls various physiological activities in plants. Its function is to control cell enlargement and stimulate cell elongation behind the meristematic areas like root tips and stem tips.
Auxin hormone is produced in coleoptiles like stem tips, root tips, and other tissues that are meristematic in their characteristics.
Here’s a more extensive list on the functions of auxin hormone in plants:
- Prevent flowers, leaves, and fruits from falling off (abscission)
- Stimulate cambium activity for secondary growth
- Stimulate flowers, leaves, and fruits formation
- Stimulate cell elongation, cell division, elongation of buds at the tip of plants
- Help in parthenocarpy
- Stimulate the formation of fibrous roots, calyptras, and lateral buds
- Accelerate seed germination
- Control apical dominated activities on root tips and stem tips
Auxin hormone’s work and activity are very affected by light condition and earth’s gravitational pull. Its ties with gravitational pull is that for example, when a plant that used to stand straight up then it is made to recline, auxin hormone will accumulate in the down side of the plant so that’s the part that will have more accelerated growth. That’s what causes stems to bend upwards: the imbalance in cell growth.
On the other hand, auxin hormone is very sensitive to sun light or other kinds of lights. Exposed to sun light, auxin hormone is easily destroyed. Thus, plants put under direct sun light will no longer experience cell elongation while other shaded parts will continue to elongate, causing stems to bend towards sun light.
Further example is when soybean seeds are placed in dark or shaded area, their auxin hormones are more active. That’s why soybean seeds germinates faster in shaded area, with tall, thin stems because of etiolating.
The work of auxin hormone can be seen on the dynamics of apical dominated root tips and stem tips. If one of those is cut off, there will grow lateral buds and that particular stem will not grow perfectly because the auxin hormone has been accumulated by other parts of the stem.