bio

Lignin

An aromatic, water-repelling polymer packed into plant cell walls to stiffen them. Lignin solves two problems at once: it provides mechanical support for a stem standing up in air, and it gives the hoop strength that keeps water-conducting tubes from collapsing inward under the negative pressure that evaporation at the leaves creates. No lignin, no tall plant — which is why this one molecule opened the whole vertical dimension of life on land. It is also so hard to break down that lignin-rich plant remains once accumulated into the coal seams of the Carboniferous.