Practice important
Adventitious rooting
MCQ questions and answers.
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MCQ Questions
1. A stem cutting is treated with an auxin paste only on its basal end before planting. Which outcome most directly demonstrates auxin-induced adventitious rooting?
A.
Formation of lateral roots from the intact leaves
B.
Initiation of roots from tissues near the treated basal region
C.
Conversion of all stem cells into mature xylem
D.
Suppression of cell division in the basal stem
Correct Answer:
Initiation of roots from tissues near the treated basal region
Explanation:
Auxin applied to the basal region of a stem cutting promotes the initiation of adventitious roots from tissues that normally do not produce roots at that position.
2. Why is auxin commonly applied to the basal portion rather than the apical portion of a stem cutting when the objective is adventitious root formation?
A.
Basal application places the auxin near the region where root initials are expected to develop
B.
Apical tissues are completely incapable of responding to auxin
C.
Auxin can move only upward through a stem cutting
D.
The basal end contains mature roots that become activated by auxin
Correct Answer:
Basal application places the auxin near the region where root initials are expected to develop
Explanation:
Root initiation is promoted near the basal end of many cuttings, so localized auxin treatment there increases the effective concentration at the prospective rooting region.
3. A cutting receives progressively increasing concentrations of an auxin rooting treatment. Rooting improves up to an intermediate concentration but declines at the highest concentration. Which explanation best fits this result?
A.
Auxin promotes adventitious-root initiation only within an appropriate concentration range; excessive levels inhibit rooting or damage tissues
B.
High auxin concentrations always accelerate root elongation but prevent stem elongation
C.
Auxin becomes a nutrient only at low concentrations and a sugar at high concentrations
D.
The highest concentration prevents water absorption by permanently closing every stomatal pore
Correct Answer:
Auxin promotes adventitious-root initiation only within an appropriate concentration range; excessive levels inhibit rooting or damage tissues
Explanation:
Auxin has a concentration-dependent effect on adventitious rooting. An optimum promotes root initiation, whereas excessive auxin may inhibit development or cause tissue injury.
4. Which treatment would most directly improve the success of propagating a difficult-to-root stem cutting through adventitious rooting?
A.
Apply a suitable auxin formulation to the basal cut surface before placing the cutting in a moist rooting medium
B.
Apply auxin to the leaf tips and keep the basal cut surface dry
C.
Remove the basal region and treat only the newly formed shoot apex
D.
Expose the basal cut surface to a concentrated auxin solution indefinitely
Correct Answer:
Apply a suitable auxin formulation to the basal cut surface before placing the cutting in a moist rooting medium
Explanation:
Basal auxin treatment is a standard application for stimulating adventitious roots in cuttings, while adequate moisture supports the initiation and development of those roots.
5. In a stem cutting, auxin treatment increases the number of root initials but the roots fail to emerge because the substrate is waterlogged. What is the most appropriate interpretation?
A.
Auxin may have promoted root initiation, but unsuitable aeration restricted subsequent adventitious-root development
B.
Waterlogging proves that auxin can initiate roots only in completely dry tissues
C.
Auxin-induced root initials necessarily develop normally regardless of the rooting medium
D.
The observed root initials must be lateral roots formed on a pre-existing root
Correct Answer:
Auxin may have promoted root initiation, but unsuitable aeration restricted subsequent adventitious-root development
Explanation:
Auxin can stimulate adventitious-root initiation, but successful emergence and growth also depend on suitable environmental conditions, including moisture and aeration.
6. A horticulturist compares two otherwise identical cuttings: one receives auxin at the basal end, and the other receives the same dose at the apical end. The basal-treated cutting roots more effectively. Which conclusion is best supported?
A.
The response depends partly on the location of auxin application relative to the prospective rooting zone
B.
Auxin functions only after being converted into a mineral nutrient at the basal end
C.
Apical application always destroys all cells in the cutting
D.
Rooting is independent of auxin concentration and depends only on leaf number
Correct Answer:
The response depends partly on the location of auxin application relative to the prospective rooting zone
Explanation:
Localized treatment is more effective when it delivers auxin to tissues capable of producing adventitious-root initials, making application position important.
7. Which observation would provide the strongest evidence that an auxin treatment specifically enhanced adventitious rooting in a stem-cutting experiment?
A.
A greater percentage of treated cuttings develop roots from the stem base than untreated cuttings under the same conditions
B.
Treated cuttings produce larger leaves before any roots appear
C.
Treated cuttings show increased chlorophyll concentration in their leaves
D.
Treated cuttings have longer internodes but no difference in basal root formation
Correct Answer:
A greater percentage of treated cuttings develop roots from the stem base than untreated cuttings under the same conditions
Explanation:
Adventitious rooting is directly measured by the initiation and development of roots from non-root stem tissue, especially at the basal region of cuttings.
8. Why are auxin-containing rooting powders often applied as a brief basal dip rather than continuously immersing the entire cutting in a concentrated solution?
A.
A localized, controlled dose can stimulate adventitious-root initiation while reducing the risk of inhibitory effects from excessive auxin exposure
B.
Continuous immersion prevents auxin from entering any living stem cells
C.
Auxin is active only when applied to dry leaves and inactive at cut surfaces
D.
A basal dip converts the cutting directly into a rooted plant without cell division
Correct Answer:
A localized, controlled dose can stimulate adventitious-root initiation while reducing the risk of inhibitory effects from excessive auxin exposure
Explanation:
Rooting formulations are designed to deliver an effective auxin dose to the basal region; excessive or prolonged exposure can reduce rooting success.
9. A stem cutting retains leaves during auxin treatment, but excessive leaf removal greatly reduces adventitious-root formation. Which inference is most appropriate?
A.
Leaves can support the cutting during root initiation, while auxin still acts at the basal region to promote adventitious rooting
B.
Auxin can induce adventitious roots only when all leaves are removed
C.
Leaves directly become roots after absorbing the auxin treatment
D.
Leaf removal increases auxin transport to the apex and therefore must always improve rooting
Correct Answer:
Leaves can support the cutting during root initiation, while auxin still acts at the basal region to promote adventitious rooting
Explanation:
Retained leaves may provide photosynthates and other supportive factors during rooting, whereas auxin applied basally promotes the formation of adventitious-root initials.
10. In vegetative propagation, the principal practical value of treating a stem cutting with a suitable auxin is that it can:
A.
Increase the probability and uniformity of adventitious-root formation in cuttings that root poorly without treatment
B.
Replace the need for a viable stem and produce roots from an inert support
C.
Ensure that every treated cutting forms roots regardless of species and concentration
D.
Prevent all callus formation while automatically producing a complete mature plant
Correct Answer:
Increase the probability and uniformity of adventitious-root formation in cuttings that root poorly without treatment
Explanation:
Auxin rooting treatments are applied commercially and experimentally to enhance the frequency and uniformity of adventitious-root formation during vegetative propagation.
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