Anatomy, ultrastructure and lignin distribution in cell wall of Caragana Korshinskii

Anatomy and ultrastructure in cell wall of Caragana Korshinskii was examined by transmission electron microscopy (TEM). Lignin distribution was determined by using confocal laser scanning microscopy (CLSM) and transmission electron microscopy with energy dispersive X-ray analysis (TEM–EDXA). TEM images showed that cell wall of C. Korshinskii was typically divided into three layers including the primary wall (P), the middle lamellar (ML) and the secondary wall (S1, S2 and S3). Confocal images (530 nm) of C. Korshinskii showed that strongly lignified CCML, and weakly lignified ML and S2 layer. Weakly lignified fibres (F) and strongly ligninfied vessels (V) were also detected by using CLSM. TEM–EDXA was applied to determine the lignin concentration in the cell corner of middle lamellar (CCML), compound middle lamellae (CML) and S2 layer. Results obtained from confocal microscopy were further confirmed by using TEM–EDXA, indicating that the ratio of lignin concentration in CCML, ML and S2 is 1.5:1.2:1.