The changes in cell wall architecture during lignification of bamboo, Phyllostachys aurea Carr.

Abstract

The cell wall architecture of bamboo at various developmental stages of culm growth was investigated by rapid-freezing and deep-etching (RFDE) electron microscopy. The unlignified primary wall (ULP) was characterized by the narrow spacing between the cellulose microfibrils in fibres, but not in parenchyma cells. The unlignified secondary wall (ULS) largely consisted of dense cellulose microfibrils with narrow spacing or "slit-like" pores. However, such pores are difficult to observe in the lignified secondary wall (LS) of fibres. The cell wall architecture of the delignified secondary wall (DLS) in fibres showed porosity similar to that of ULS. Pores in the middle lamella and secondary walls of ULS in fibres were reduced considerably or disappeared immediately after lignification. However, the pores reappeared following delignification. These findings suggest that deposition of lignin in ULS immediately proceeds in the pores during maturation to LS. Based on RFDE electron microscopic images, the pore sizes of primary and secondary fibre walls were significantly smaller in bamboo than in either Eucalyptus or Pinus, suggesting a denser arrangement of cellulose microfibrils in bamboo fibre walls than in either tree species. The author hypothesizes that the narrow spacing between cellulose microfibrils in bamboo fibres may be one of the reasons for the deposition of less lignin in bamboo than in tree species. This is the first report on the three-dimensional architecture of unlignified and lignified walls in bamboo.

Tensile growth stress and lignin distribution in the cell walls of yellow poplar, Liriodendron tulipifera Linn.

“…Decreasing UV absorption reflects decreasing lignin content Goring 1970a, 1970b;Nakashima et al 1997;Donaldson et al 1999;Gindl et al 2000;Kleist and Bauch 2001;Sander and Koch 2001;Suzuki and Itoh 2001). With increasing tensile released strain, the UV absorption, and therefore the lignin content, of the secondary wall decreased (Table 2).…”

Cell wall structure and formation of maturing fibres of moso bamboo ( Phyllostachys pubescens ) increase buckling resistance

“…Fibre wall anatomy [5,6], and in particular cell wall thickening [4,9], lignification [10,11] and cell wall nanostructural changes [12] during development of bamboo culms have been intensively studied. Only a few studies have been performed on mechanical properties of fibres or fibre caps [13][14][15], and the underlying structureproperty relationships of bamboo fibres that establish the gradients across the fibre caps are not well understood yet.…”

Modification of cambial cell wall architecture during cambium periodicity in Populus tomentosa Carr.

“…Pore size of primary wall of Pinus tracheid is 8-28 nm, while secondary wall is 8-40 nm (Hafren et al 1999). In bamboo, the pore of both primary and secondary wall of fiber is about 4 nm, while the pore of primary wall of parenchyma cells is about 13.1 nm, much larger than secondary wall of parenchyma cells about 3.8 nm (Suzuki and Itoh 2001). Recently, the cell wall porosity is reported to be related to gelatinous fiber development in tension wood formation (Chang et al 2009).…”

“…Within a complex tissue, such as cambium and secondary xylem, chemical analysis in situ techniques, such as immuno-labeling and Fourier-transform infrared microspectroscopy (micro-FTIR), are required to determine the precise chemical composition of individual cells (Mellerowicz et al 2001). Rapid-freezing and deep-etching (RFDE) electron microscopy is useful for revealing the three-dimensional architecture of cell walls, and was successfully used to observe the changes in cell wall architecture during lignification in the trees Eucalyptus tereticornis and Pinus thunbergii (Fujino and Itoh 1998;Hafren et al 1999), and the bamboo Phyllostachys aurea (Suzuki and Itoh 2001). Considering the important functions of the cell wall in plant development (Somerville et al 2004), changes in the molecular architecture of the cambial cell wall and its role in cambium activity and cell differentiation need further investigation.…”