What are bordered pits?
Bordered pits are cavities in the lignified cell walls of water conduits (vessels and tracheids) that are essentially components in the water - transport system of higher plants.
The hydraulic function of xylem tissue in any plant organ, whether root, stem or leaf cannot be understood without taking into account the influence of bordered pit structure on the balance of safety and efficiency in vascular transport.
The pit membrane that lies in the centre of each pit allows water to pass between xylem conduits but limits the spread of embolism and vascular pathogens in the xylem. On an average pits account for more than 50% of total xylem hydraulic resistance, indicating that they are an important factor in the overall hydraulic efficiency of plants.