Epidermal tissues

The study of skin irritation is probably still more complex than that of eye irritation. Surfactants interact with epidermal tissues, proteins, and enzymes causing local effects. Singer and Pittz [369], Cooper and Berner [370], and Schwuger and Bartnik [371] presented excellent explanations and reviews on these interactions. 

The most conspicuous concentrations of calciiun in the cell-walls of the flax hypocotyl were in the epidermal and subepidermal layers, especially at the tricellular junctions (figure 13 D), where these were filled with pectic polymers [67], Open tricellular jimctions with intercellular spaces had smaller areas of calcium accumulation where the walls of each pair of cells diverged. These sites were occupied by relatively linear pectic polymers with a low degree of esterification, which could be visualised with gold-kbeUed endopolygalacturonase [68] and were extractable by chelation of calcium with CDTA. Similar pectic polymers are located in the corresponding sites in other plant tissue, as established by susceptibility to polygalacturonase... 

Figure 2. Lanel 1) cv cannelino . Lane 2) cv pinto . Lane 3) cv blue lake . Lanes a) epidermal tissue. Lanes b) extract of whole, immature pod.

Endomycorrhizal hyphae adopt a variety of colonization patterns in their penetration of the host root cells. Glomalean fungi are highly dependent on their ho.st and cannot survive for long in its absence. Their hyphae form appressoria on the epidermal cells, penetrate the cortical tissue, and eventually form highly branched structures called arbuscules (Figs. 3-6) (10). 

Let us consider how the skin is structured to better understand how this tissue performs some of its vital functions. Consider the cross section of the skin sketched in Fig. 1. This illustration shows the readily distinguishable layers of the skin, from the outside of the skin inwards the 10 pm thin, fully differentiated, devitalized outer epidermal layer called the stratum corneum the 100 pm thin live, cellular epidermis and the 1000 pm thin (1 mm thin) dermis. Note that all the thicknesses specified here are representative only, for the actual thickness of each stratum varies severalfold from place to place on the body. Dispersed... 

The outermost layer of the skin appearing in the exploded epidermal sketch of Fig. 1(b) represents the stratum corneum (the horny layer). The principal barrier element of the skin, it is an essentially meta-bolically inactive tissue comprised of acutely flattened, stacked, hexagonal cell building blocks formed from once-living cells. These cellular building blocks are... 

The biosynthesis of Me3,Mel 1-29 H takes place in oenocyte cells, released into the hemolymph and transported by lipophorin to peripheral tissues (Fig. 7) [71, 231, 232]. Direct evidence for oenocytes biosynthesizing hydrocarbon has come recently with the dissociation of oenocytes from epidermal cells and in vitro incubation with labeled propionate [233]. Differential uptake of some hydrocarbons in different tissues has also been documented although the exact mechanism behind the differential placement of hydrocarbons is unknown [20,128,230,232,234]. Although the biosynthesis of hydrocarbons may not be under direct endocrine regulation supply of precursor hydrocarbon that is converted to the sex pheromone is a requirement. 

OCT images of plant tissue in the process of its saturation with water are shown in Fig. 3b-3i. It can be seen from this figure that the thickness of the epidermal and palisade layers increase linearly with the time of the plant being in water. The layers reach their maximum thickness as soon as 40 minutes after the plant has been placed in water (Fig. 3g). Correspondingly, during the same time an increase in the volume of cells of the upper epidermal layer situated closer to the surface is observed. Most significantly the cells and the epidermis increase within the first 5-25 minutes (Fig. 3b-3f)... 

---