Which is the correct order of events during auxin-mediated cell elongation?
A: Proton pump gene expression → expansin activation → ATP hydrolysis → H+ movement into the cell wall
B: expansin activation → proton pump gene expression → H+ movement into cell wall → ATP hydrolysis
C: ATP hydrolysis → expansin activation → proton pump gene expression → H+ movement into the cell wall
4: Proton pump gene expression → ATP hydrolysis → H+ movement into cell wall → expansin activation
The correct option is D.
The correct order is:
Proton pump gene expression → ATP hydrolysis → H+ movement into cell wall → expansin activation
At the first stage, auxin stimulates proton pump gene expression. It releases hydrogen ions with ATP hydrolysis in the cell wall. As a result PH of the cell wall reduces and expansion enzyme activated. The expansion in the cell wall elongates the cell, and thus the cellulose loosens.
Auxin is a plant hormone. Auxin is produced in buds, stems, and root tips. It promotes stem elongation and inhibits the growth of lateral buds. An example of an Auxin hormone is Indole Acetic Acid (IA).
Auxin plays a pivotal role in maintaining apical dominance. Most plants have lateral buds located at nodes. Buds are embryonic meristems maintained in a dormant state. Auxin maintains this dormancy.
As long as enough auxin is produced the lateral buds remain dormant. If the apex of the shoot is removed, the auxin production gets to stop. It will cause the lateral buds to break the dormancy and begin to grow. As a result, the plant becomes bushier. When a gardener trims a hedge, they are applying apical dominance.