The growth of land plants depends on the integrity of leaf vein networks that supply water to tissues engaged in photosynthesis. But drought endangers these networks, as drying soil increases water tension in xylem cells, resulting in air embolisms that disrupt water supply and cause leaf death.

To illuminate plant adaptations against catastrophic leaf network failure, researchers developed an optical technique that records rapid changes in light transmission through leaf veins to visualize the formation and spread of embolisms.

The authors severed the contact between branches and soil to simulate the onset of severe drought and used a microscope to record images of leaf networks every 30 seconds. Across different fern and angiosperm species, air bubbles originated in the largest veins and spread to smaller veins.

However, the pattern of vein failure varied across three types of network architecture. The findings reveal the role of vein size and network architecture in the spread of drought-induced embolism damage in leaves.

According to the authors, studying how leaf vein patterns prevent water transport failure could help improve the safety of a range of man-made networks. 

http://www.pnas.org/content/early/2016/04/06/1522569113