Chapter 45, Problem 1FIB

Summary Introduction

Introduction:

The plant hormones also called as phytohormones. The plant hormones are chemical substances that regulate the growth of plants. There are five types of hormones present in plants: Auxin, Gibberellins, cytokinins, abscisic acid and ethylene. Auxins regulate as the growth of roots and fruits, it also prevents the abscission of new or young leaves.

Answer to Problem 1FIB

Correct answer:

Auxin produced by the apical meristem of the shoot inhibits sprouting of lateral branches; this phenomenon is called apical dominance. In roots, auxin stimulates development of root side branches. The discovery of auxin by the Darwins was based on its ability to stimulate phototropism.

Explanation of Solution

Auxin is a plant growth hormone that promotes the plant growth. The auxin is produced by the shoot apical meristem, young leaves, fruits, flower and root apical meristem (in lower concentration). Auxin inhibits the growth of lateral bud and promotes the growth of the apical meristem which is known as apical dominance.

The lower concentration of auxin hormone around root meristem stimulates lateral branching of roots. The hormones produced by the plants are chemical substances that coordinate with the stimuli. The plant hormones produced in lower concentration could bring a large change in the form of response in plant cells. Example: lower concentration of auxin hormone cause the movement of plants toward the light which is known phototropism.

Conclusion

Auxin inhibits lateral bud growth and stimulates lateral branching of roots. Auxin cause the weakened of stem cell wall which result in the bending of stem toward the light or phototropism.