This is the process of lignin binding with cellulose and hemicellulose in the cell wall, thereby reducing their digestibility:

Correct option is B

The correct answer is (B) Lignification

Explanation:
• Lignification is the biological process in which lignin, a complex aromatic polymer, is deposited within plant cell walls and becomes tightly bound with cellulose and hemicellulose.
• This deposition strengthens the cell wall, increases rigidity, and provides mechanical support to plants, especially in woody tissues.
• When lignin binds to cellulose fibers, it forms a protective barrier that reduces enzymatic access, thereby lowering digestibility in herbivores and ruminants.
• In forage crops, higher lignification is associated with reduced nutritional value because digestive microbes cannot easily break down lignified tissues.
• The process is particularly significant during maturation of stems and vascular tissues, where secondary wall thickening occurs.

Information Booster:
• Lignin is mainly composed of phenolic compounds derived from coniferyl, sinapyl, and p-coumaryl alcohols.
• It provides resistance against pathogens and environmental stress.
• It is abundant in xylem vessels and sclerenchyma tissues.
• Paper and pulp industries remove lignin to obtain pure cellulose fibers.

Additional Knowledge:
• Esterification (Option A): Refers to the formation of esters from acids and alcohols and is unrelated to cell wall hardening.
• Magnification (Option C): An optical term describing enlargement of images, not a plant physiological process.
• Transpiration (Option D): Concerns water loss through stomata and does not involve binding of structural polymers.
• Therefore, only lignification directly explains the reduction in digestibility caused by lignin–carbohydrate complex formation. This concept is important in agriculture, fodder science, and plant physiology, as managing lignification levels influences crop quality, biomass utilization, and animal nutrition. Understanding this process helps breeders develop varieties with better digestibility while maintaining structural strength, making lignification a central concept in both botany and agronomy. The interplay between structural integrity and nutritional value makes lignification a key determinant of plant maturity and biomass usability in farming systems, thereby explaining why it is the correct and most scientifically accurate choice among the given options.