Speeding meristem culture in sweet potato (<i>Ipomoea batatas</i>) Which supplement(s) are commonly added to accelerate shoot initiation and multiplication during meristem culture for sweet potato improvement?

Introduction / Context:
Meristem culture of Ipomoea batatas targets rapid recovery of clean, vigorous plantlets. Balanced auxin and cytokinin inputs are pivotal for initiating shoots from tiny meristems and for subsequent multiplication.

Given Data / Assumptions:

• Explants are very small meristem tips that require precise hormonal cues.
• Cytokinins drive shoot proliferation; auxins modulate root initiation and morphogenesis.
• Species-specific optimization is typical in protocols.

Concept / Approach:
Cytokinins (e.g., BAP, kinetin) are primary drivers for shoot induction and multiplication. Auxins (e.g., NAA, IAA, IBA) support morphogenesis and later rooting. Using both, in tuned ratios, speeds the culture cycle and improves plantlet quality.

Step-by-Step Solution:

Verification / Alternative check:
Comparative trials show higher shoot numbers and faster cycles when both hormone classes are used appropriately versus single-hormone or hormone-free media.

Why Other Options Are Wrong:

• Auxins alone or cytokinins alone often reduce efficiency or imbalance growth.
• Adenine can act as a cytokinin enhancer but is rarely sufficient by itself.
• Hormone-free media are generally inadequate for rapid meristem multiplication.

Common Pitfalls:
Overuse of cytokinins leading to hyperhydricity; insufficient auxin during rooting prolongs the cycle.

Final Answer:
Both (a) and (b)