Correct option is B
Answer: b) A – Phenols, B – Lignin, C – Cellulose, D – Sugars
Explanation
The graph represents the decomposition rates of different plant litter components over time, showing % weight remaining vs. years.
The curve with the slowest decomposition (A) indicates the most resistant or recalcitrant material, while the fastest decomposing (D) represents the most readily degradable compound.
Sugars (D): Decompose very rapidly (within a few months to a year).
Cellulose (C): Decomposes moderately fast—microbes can easily utilize it but slower than sugars.
Lignin (B): Highly resistant to microbial attack due to its complex aromatic structure—decomposes slowly.
Phenols (A): Most resistant, often inhibit microbial activity, causing them to persist the longest.
Thus, the decomposition order is:
Sugars > Cellulose > Lignin > Phenols
Information Booster
Lignin and phenolic compounds contribute to humus formation due to their resistance.
Cellulose and sugars are carbon sources that decompose quickly, fueling early microbial activity in litter decomposition.
Decomposition rate depends on chemical composition, climate, and microbial community.
