There are usually large intercellular gas spaces to permit gas exchange. Sometimes cells produce crystals or toxins as an herbivore defense. There may also be sclerenchyma cells for herbivore defense. Xylem The conductive cells of xylem are sclerenchyma. Tracheids have perforated end walls and vessels lack end walls.
Water is conducted from dead cell to dead cell in a passive way.
The xylem may also include fibers for additional structural support, and parenchyma for a range of biosynthetic biochemical functions. The overall function is to conduct water and minerals from the soil up through the rest of the plant. This process is called transpiration. The conductive cells of phloem are parenchyma. The sieve elements have perforated end walls and simple cytoplasm to allow conduction.