Use of very high sugar concentrations (approximately 40–100 g/L) in plant tissue culture: In which situations are such elevated carbohydrate levels purposefully applied?

Introduction / Context:
Carbohydrate concentration in plant culture media affects osmotic potential, growth rate, morphogenesis, and metabolite pathways. While 20–30 g/L sucrose is common, some applications deliberately use higher concentrations for specific physiological and metabolic outcomes.

Given Data / Assumptions:

• Typical basal media use ~30 g/L sucrose.
• Higher levels (40–100 g/L) are exceptional and goal-driven.
• Two common goals: secondary metabolite enhancement and osmotic manipulation during regeneration or stress conditioning.

Concept / Approach:
Elevated sugars can impose osmotic stress that alters water relations and can direct morphogenesis or improve stress tolerance during critical transitions. High sugar also modifies carbon flux and may upregulate or stabilize pathways tied to secondary metabolite accumulation.

Step-by-Step Solution:

Verification / Alternative check:
Reports on somatic embryo maturation and metabolite-focused cultures document efficacy of higher sucrose concentrations for these aims.

Why Other Options Are Wrong:

• Routine maintenance: usually 20–30 g/L; higher levels are not standard.
• Single-purpose options omit legitimate uses.

Common Pitfalls:
Prolonged exposure to hyperosmotic conditions can reduce growth or cause stress responses; adjust duration and concentration carefully.

Final Answer:
Both (a) and (b)