The positional distribution of cell death of ray parenchyma in a conifer, Abies sachalinensis

Abstract

We monitored the distribution of death of secondary xylem cells in a conifer, Abies sachalinensis. The cell death of tracheids, which are tracheary elements, occurred successively and was related to the distance from cambium. Thus, it resembled programmed cell death. By contrast, the death of long-lived ray parenchyma cells had the following features: (1) ray parenchyma cells remained alive for several years or more; (2) in many cases, no successive cell death occurred even within a given radial cell line of a ray; and (3) the timing of cell death differed among upper and lower radial cell lines and other lines of cells within a ray. These results indicate that the death of long-lived ray parenchyma cells involves a different process from the death of tracheids. The initiation of secondary wall formation and the lignification of ray parenchyma cells in the current year's annual ring were delayed in the upper and lower radial cell lines of a ray. In addition, the density of distribution and orientation of cortical microtubules in such cells were different from those in cells in other radial lines. Ray parenchyma cells in the previous year's annual ring within the upper and lower radial cell lines of a ray contained many starch grains. Our results indicate that positional information is an important factor in the control of the pattern of differentiation and, thus, of the functions of ray parenchyma cells that are derived from the same cambial ray cells.

Lignification of ray parenchyma cells (RPCs) in the xylem of Phellodendron amurense Rupr.: quantitative and structural investigation by TOF-SIMS and thioacidolysis of laser microdissection cuts of RPCs

“…UV absorbance of RPCs is higher in hW than in sW (Fujikawa and Ishida 1975;Nakaba et al 2006), which is the result of deposition of aromatic extracts and/or lignification. In analogy to our previous study on a softwood (Zheng et al 2014a,b) it can be presumed that RPCs of hardwoods are also more lignified in hW than in sW. Nakaba et al (2008Nakaba et al ( , 2012 reported that the number of dead RPCs in sW increased from the cambium side towards the pith in both softwood and hardwood.…”

“…The hW is the non-living part of the stem that has no apparent physiological function (Filippis and Magel 2012). The pattern of cell death and the function of RPCs are modified by the transformation from sW to hW, which is a complex biological process and an essential part of the secondary growth (Nakaba et al 2006;Song et al 2011).…”

“…Lignification and the structure of the cell wall in different types of RPCs in Populus maximowiczii Henry were compared by Murakami et al (1999) by means of the UV microscopy, POM, and TEM. The pattern of cell death, the process of lignification, and the function of RPCs in several species of both softwood and hardwood species were studied by Nakaba et al (2006Nakaba et al ( , 2008Nakaba et al ( , 2012 by means of microscopy.…”

Concentration and Distribution of Nuclei and Plastids in Xylem Cells in Cunninghamia lanceolata and Aquilaria sinensis

“…Some of ray parenchyma cells and axial parenchyma cells contained nuclei and plastids, because these cells survived longer when compared to other cells, such as fiber, tracheary elements, and vessels. (Abe et al 2011;Nakaba et al 2006;Nakaba et al 2008). Xylem was formed after PCD.…”

Continuous expression of genes for xylem cysteine peptidases in long-lived ray parenchyma cells in <i>Populus</i>

“…However, little analogous information is available about the programmed death of long-lived cells. Therefore, we have been investigating the programmed death of ray parenchyma cells as a model of the programmed death of long-lived xylem cells in situ (Nakaba et al 2006(Nakaba et al , 2008(Nakaba et al , 2012. We showed previously that death does not occur successively in ray parenchyma cells, even within the same radial cell lines of a ray.…”