Ultrastructure of bands of Igersheim.
TEM images of material postfixed in osmium tetroxide, embedded in SPI 812, and viewed in transverse section. Shown are the distal portion of two adjacent epidermal cells (ec-1 and ec-2), primary cell walls (cw), thickenings of Igersheim (ti) affecting tangential cell walls, and bands of Igersheim (bi). (A) Distal portion of two bordering epidermal cells showing a common band of Igersheim in transverse section. These bands develop in areas of primary wall rich in plasmodesmata, the remains of which persist as electron-dense transverse areas towards the centre (compare C). Transverse section through the distal portion of a band of Igersheim between two epidermal cells. Note faintly longitudinally-layered fibrillar structure of matrix and surrounding electron-transparent zone (compare Figure 7) between plasmalemma and band; labels as in A. (C) Enlarged central portion of a band of Igersheim (bi) between two epidermal cells showing electron-dense transverse zones reflecting the prior position of plasmodesmata in the common primary cell wall.