TEM images, showing details of vascular tissue in intermediate vascular bundles in leaf blades of

(a) Intermediate vein with metaxylem vessels (MX) and associated xylem vascular parenchyma (XVP). The phloem contains two thick-walled sieve tubes (arrowheads) and thin-walled sieve tubes (S), associated companion cells (CC), and parenchyma cells (VP) surrounded by a bundle sheath (BS). (b) A plasmodesmal field between a xylem vascular parenchyma cell (right) and a parenchyma cell (left). Note mitochondria (M). (c) Detail showing a thick-walled sieve tube (TST) with pore-plasmodesmata connections (arrowheads) to the vascular parenchyma cell above. The thin-walled sieve tube (ST) is associated with a CC and two adjacent xylem parenchyma cells. (d) A small intermediate vascular bundle showing hydrolysed cell wall (arrows) between the metaxylem vessel (MX) and associated xylem parenchyma (XVP) which has a loosely fibrillar appearance. The wall structure between the xylem vessel and the xylem parenchyma is highly modified, hydrolysed on the vessel side, and delimited by a plasma membrane on the parenchyma cell side.<p><b>Copyright information:</b></p><p>Taken from "A xylem sap retrieval pathway in rice leaf blades: evidence of a role for endocytosis?"</p><p></p><p>Journal of Experimental Botany 2008;59(11):2945-2954.</p><p>Published online 9 Jul 2008</p><p>PMCID:PMC2504346.</p><p>