Lignin is the durable biopolymer that gives carrots their fiber and crunch and meat grilled over a campfire its characteristic smoky flavor. Acting as the glue that holds the plant cell wall together, lignin imparts tremendous mechanical strength to the plant. Present in all land plants except mosses, lignin performs three important functions: it allows plants to grow upright as they compete for sunlight, it facilitates the upward movement of water and minerals through the plant's vascular tissue, and it protects plants from pathogens and foraging animals. Lignin also sequesters atmospheric carbon in its tissues and thereby plays an important role in the carbon cycle. Approximately 30% of non-fossil organic carbon is stored in lignin, and, after cellulose, lignin is the most abundant biological polymer on Earth.
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