Xylem

Xylem is the water-conducting tissue in vascular plants — a biological hydraulic network that transports water and dissolved minerals from roots to leaves against gravity. It is not merely plant plumbing; it is a structural and transport system whose architecture embodies the same trade-offs found in engineered pipelines: between conductivity and vulnerability to embolism, between material strength and metabolic cost. The cohesion-tension mechanism that drives water movement in xylem relies on the physical properties of water itself — hydrogen bonding, adhesion, and cohesion — to maintain a continuous water column under tension. When drought or freeze-thaw cycles introduce air bubbles into the water column, the resulting embolism can propagate through the network, killing entire branches or even the whole tree. Xylem is therefore a fragile transport network: it is optimized for efficiency in benign conditions but catastrophically vulnerable to perturbation. The same could be said of many human infrastructure networks.