Changes in composition of the outer epidermal cell wall of pea stems during auxin-induced growth

Abstract

The gross composition of the outer epidermal cell wall from third internodes of Pisum sativum L. cv. Alaska grown in dim red light, and the effect of auxin on that composition, was investigated using interference microscopy. Pea outer epidermal walls contain as much cellulose as typical secondary walls, but the proportion of pectin to hemicellulose resembles that found in primary walls. The pectin and hemicellulose fractions from epidermal peels, which are enriched for outer epidermal wall but contain internal tissue as well, are composed of a much higher percentage of glucose and glucose-related sugars than has been found previously for pea primary walls, similar to non-cellulosic carbohydrate fractions of secondary walls. The epidermal outer wall thus has a composition rather like that of secondary walls, while still being capable of elongation. Auxin induces a massive breakdown of hemicellulose in the outer epidermal wall; nearly half the hemicellulose present is lost during 4 h of growth in the absence of exogenous sugar. The percentage breakdown is much greater than has been seen previously for whole pea stems. It has been proposed that a breakdown of xyloglucan could be the basis for the mechanical loosening of the outer wall. This study provides the first evidence that such a breakdown could be occurring in the outer wall.

Total epidermal cell walls of pea stems respond differently to auxin than does the outer epidermal wall alone

“…Bret-Harte et al (1991) found that in the absence of exogenous sugar, IAA depresses deposition of material into the pea outer epidermal wall. The primary reason for the low deposition rate is that under these conditions IAA causes a massive loss of hemicellulose from the outer wall (Bret-Harte and Talbott 1993). The primary reason for the low deposition rate is that under these conditions IAA causes a massive loss of hemicellulose from the outer wall (Bret-Harte and Talbott 1993).…”

“…The primary reason for the low deposition rate is that under these conditions IAA causes a massive loss of hemicellulose from the outer wall (Bret-Harte and Talbott 1993). The gross composition of epidermal peels does not indicate a loss of hemicellulose from the cell walls with auxin treatment, and in fact the composition of epidermal peels is rather different than that reported for the outer wall (Bret-Harte and Talbott 1993). The gross composition of epidermal peels does not indicate a loss of hemicellulose from the cell walls with auxin treatment, and in fact the composition of epidermal peels is rather different than that reported for the outer wall (Bret-Harte and Talbott 1993).…”

“…However, the relative thickness of the inner walls of the epidermis seen here, which may also be seen in sun- Table 5. Data on outer-wall composition is from interferometric determinations on segments grown from peas of the same lot, and extracted under the same conditions (Bret-Harte and Talbott 1993; Table 4, as in these experiments the wax was not extracted separately, but would be removed mostly with the hemicellulose fraction flower hypocotyls (Kutschera 1992; Fig. Data on the composition of cell walls of internal tissue is from the analysis of whole pea stem segments extracted under the same conditions by Talbott and Ray (1992), which is assumed to represent mainly walls of internal tissue.…”

Ultrastructure of the Epidermal Cell Wall and Cuticle of Tomato Fruit (Solanum lycopersicum L.) during Development

“…Despite the significant number of studies on cell wall composition and analysis, isolation and further analysis of the OEW is not trivial. Microscopic analysis of the OEW of pea stems showed higher cellulose content than typical primary walls (Bret-Harte and Talbott, 1993). Isolation of the polysaccharide fraction of mature tomato fruit cuticles showed an equimolecular contribution of the three main components of cell wall: cellulose, hemicellulose, and pectin (López-Casado et al, 2007).…”

Characterization of the Leaf Epidermis of Barley (Hordeum vulgareL. 'Himalaya')

“…The epidermis is considered one of the factors affecting the rate of growth in plants by restraining expansion of the internal tissues (Taiz, 1984 ;Kutschera, 1992 ;Bret-Harte and Talbott, 1993).…”