Question

Mention any two physiological effects of auxins.

Answer 1

1. Cell division of elongation: It increases cell division and elongation in shoots. It promotes stem growth and differentiates xylem and phloem tissues.
2. Apical dominance: Apical dominance refers to a phenomenon where the apical bud grows faster than the lateral buds. Removing apical buds causes a rapid growth of lateral buds.
3. Root initiation: A higher concentration of auxin inhibits root growth, but increases the number of lateral roots.
4. Prevention of abscission: Abscission is the term used to describe the separation of plant organs like leaves, flowers, and fruits. Natural auxins in plants stop the abscission layer from forming, which would otherwise cause the leaves, flowers, and other parts of the plant to abscise. Because they cease to produce auxin, leaves shed seasonally.
5. Parthenocarpy: Spraying of auxin (IAA) can induce the formation of parthenocarpic fruits (seedless fruits).
6. Potato dormancy: Potatoes can be preserved for a longer period of time because MH (maleic hydrazide) and α-NAA (alpha naphthalene acetic acid) cause the lateral buds in potato tubers to go dormant.
7. Flower initiation and sex expression: In general, auxins prevent flowers from flowering. However, they encourage consistent flowering in lettuce, pineapple, and litchi. When applied to cucurbits, they enhance the number of female flowers while decreasing the number of male flowers.
8. Eradication of weeds: Dicot broad-leaf weeds can be eradicated by some synthetic auxins like 2,4-D and 2,4,5-T. These do not affect monocot plants.