Tannin cells

Fig. 1-2. Transverse section of xylem and phloem of red spruce (P/cea rubens). CZ, cambial zone DP, differentiating phloem MP, mature phloem with sieve cells (sc) and tannin cells (tc) DX, differentiating xylem with ray cells and tracheids (tr) MX, mature xylem, earlywood (EW) with resin canals (rc), lined with epithelial cells (ec) LW, latewood. Note that each ray continuous from the xylem, through the cambial zone, and into the phloem. Light micrograph by L. W. Rees. Courtesy of Dr. T. E. Timell.

Tannins located in the vacuoles, forming dense clnsters in the cells close to the epidermis and diffnse grannlations in the internal cells of the mesocarp. The concentration gradient is reversed the thick-walled external cells are known as tannin cells (Figure 6.37). 

The strongly astringent taste of persimmon fruits arises from soluble tannins that accumulate in large specialized cells called tannin cells. In this chapter, some chemical properties of persimmon tannins, an outline of simple and reliable methods for estimation of the degree of astringency and the amount of tannins, and some aspects of the physiological changes in the tannin contents of persimmon fruits will be described. 

The tannin-containing vacuole may become very large and has been observed to occupy over 90% of the volume of Picea glauca cells (18) and also of tannin-containing cells in Pinus strobus needles (75). Tannins do not appear to be present in chloroplast cells and, in the case of Douglas-fir callus cell suspension cultures, some sort of metabolic balance appears to be struck between the chloroplast and tannin-producing cells. Too rapid production of the latter leads to death of the culture (H. A. Stafford, personal communication). Such specialized tannin cells have also been observed in Vitis vinifera phloem tissue and Lotus pedunculatus leaf and root tissues. Such a pattern may be the norm in the plant kingdom. 

Zobel A M 1985 Ontogenesis of tannin coenocytes in Sambucus racemosa L. 1. Development of the coenocytes from mononucleate tannin cells. Ann Bot 55 765-773... 

The impressive range of secondary products to be found in plants contrasts with the paucity of such compounds in animals (the con-stitutents of the bile salts of vertebrates and the contents of the preening glands of birds are in some ways comparable). One factor here may be that animals excrete waste products of their metabolism to the exterior. This can only be achieved to a very limited extent by plants by the shedding of leaves, floral parts or roots. Hence plants may seal off such products in vacuoles, resin canals, tannin cells, heartwood and so on. 

A final are we should discuss is color removal. This is perhaps the most difficult impurity to remove from waters. In surface waters color is associated with dissolved or colloidal suspensions of decayed vegetation and other colloidal suspensions. The composition of this material is largely tannins and lignins, the components that hold together the cellulose cells in vegetation. In addition to their undesirable appearance in drinking water, these organics can cause serious problems in downstream water purification processes. For examples ... 

Plant cell walls are constructed from cellulose, hemicelluloses, and pectins with varying amounts of lignin, tannins, gums, proteins, minerals,... 

A high proportion of the aromatic compounds in coffee beans are phenolic and presumably they are derived from the lignin and tannin of the cell structure.2 Hydroquinone is present in coffee beverages, 0.3 ppm, either in the free form or as its p-D-glucopyranoside, arbutin.35... 

Condensed or catechin tannins (catechol tannins. Fig. 11.3) are the most common tannins in vascular plants, occurring in three quarters of gym-nosperms and over half of the angiosperms. They are unbranched, linear polymers of flavonoid compounds (flavan-3-ols), linked through acid-labile carbon-carbon bonds. Condensed tannins may protect plant cell walls against microbial attack and so may affect microbial fermentation of plant cell walls in herbivores. 

Very little information exists on the phenolic protein-conplexing resins, except for that on creosote bush and sane arctic plants. In contrast to condensed tannins and hydrolyzable tannins, these are typically ether-soluble compounds this may allow their entry into the body across cell membranes, and thios give them the potential for action outside the gut lumen. Reports for animals consuming seaweed indicate that astringent protein-precipitating substances (presumably phlorotannins), are potentially important in marine plant-herbivore interactions. 

This is based on the method by Van Soest and Wine (1967) which has been modified according to subsequent recommendations. It is the only fibre determination suitable for non-ruminants. The residue consists of the plant cell-wall constituents cellulose, hemicellulose, lignin, cutin, NDF-insoluble tannin and ash. See the article by Cherney (2000) for current modifications these include the use of amylase to aid in the removal of starch from forages containing grain (Van Soest et al., 1991), which has been adopted by MAFF... 

Decendit, A. et al., Anthocyanins, catechins, condensed tannins and piceid production in Vitis vinifera cell bioreactor cultures, Biotechnol. Lett., 18, 659, 1996. 

Porter, L.J., Condensed tannins, in Natural Products of Woody Plants 1 Chemicals Extraneous to the Lignocellulosic Cell Wall, Rowe, J.W., Ed., Springer Verlag, New York, 1989, chap. 7.7. 

N.A. Quassinoids, ailanthone, quassin, alkaloids, flavonols, tannins." Antimalarial, against cancerous cells, counter worms, excessive vaginal discharge, gonorrhea, malaria, antispasmodic, cardiac depressant. 

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