Ultrastructure of the Water-absorbing Trichomes of Pineapple (Ananas comosus, Bromeliaceae)

An ultrastructural study of dry and wet trichomes from the upper leaf surface of pineapple revealed that shield cells were normally dead and stalk cells were often living. In stalk cells of dry trichomes, polysaccharide material was present within vacuoles and a layered material was present between the plasma membrane and cell wall. In stalk cells of trichomes wet for 12 h vacuoles were enlarged and appeared to contain little material. Layered material between the plasma membrane and cell wall was also absent. In both wet and dry trichomes, numerous mitochondria were present and plasmodesmata were observed connecting stalk, foot, and adjacent epidermal and mesophyll cells. It is suggested that the large numbers of mitochondria, which indicate high metabolism, and the numerous plasmodesmata connecting the cells, provide indirect evidence for the function of the trichomes in uptake of dissolved nutrients.