Fig. 2.

Ultrastructural detail of the hydrolysed pit membrane typically observed between the metaxylem vessels and xylem parenchyma elements in small, intermediate, and large veins in leaf blades of Oryza sativa. (a) Pit membrane between a tracheary element (TE) and xylem parenchyma cell (XVP) which has a perforate, fenestrated appearance. Numerous mitochondria (M) are found in XVP cells. (b) Pit membrane of xylem parenchyma cell with adjacent mitochondrion (M), endoplasmic reticulum (ER), and dictyosome (D). (c–f) Details of the wall interface showing the vesicles at the membrane–wall interface. (c) Stalked vesicle attached to the plasma membrane. (d) Spherical vesicles (solid arrows) occur beneath the plasma membrane, attached to the outer face of the hydrolysed wall region by thin electron-dense stalks. The plasma membrane adjacent to the cell wall is elaborated with interspersed tubules (arrowheads). (e) The plasma membrane appears discontinuous, especially adjacent to vesicles (V) which appear to have a double membrane. (f) Detail of an elongate vesicle (V) attached to the plasma membrane (PL) attached to and in close association with the underlying hydrolysed pit membrane region of the cell wall (CW).