Plant cell structure

This chapter is an introduction to methods-oriented microscopy. Because the contributing authors present methods in relation to their researches, plant cell structure-function relationships as revealed by light and electron microscopies are reviewed. Much of this conceptual and terminological information is summarized in tables that are augmented with references to either photomicrographs or electron micrographs of cells and tissues. 

Currently, transmission and scanning electron see Chapter 13) microscopies have become the two workhorses for day in and day out electron microscopy in both research and clinical laboratories. Many of the other techniques discussed in this volume are more recent offshoots of these two widely employed electronmicroscopies. They have further enriched our appreciation of plant cell structure-function. 

The herbicidal activity of the bipyridyliums depends on their redox properties. Their abilities as one-electron acceptors of the right redox potential (-350 mV for diquat and -450 mV for paraquat) allow them to siphon electrons out of the photosynthetic electron-transport system, competing with the natural acceptors. The radical anion produced is then reoxidized by oxygen, generating the real toxicant, hydrogen peroxide, which damages plant cells. Structure-activity relationships in this series have been reviewed (60MI10701). 

The other carbohydrates in cane juice are the soluble polysaccharides vaguely classified under the terms "hemi-celluloses, soluble gums and pectins. It is possible that some of these polysaccharides may enter the juice during the milling of the cane as the plant cell structure is destroyed. A gummy product has been isolated from cane fiber by alkali extraction followed by alcohol precipitation. Acid hydrolysis of this substance yielded crystalline D-xylose and L-arabinose.10 Such gums in Trinidad cane juices were isolated by alcohol precipitation at suitable hydrogen ion concentration and assayed for pentose content by the Tollens 2-fural-dehyde assay the results showed an apparent pentosan content of 0.04-0.07%u of the Brix solids. 

Macrinite maceral that is distinguished by a reflectance higher than that of associated vitrinite, absence of recognizable plant cell structure, and a nonangular shape. 

ACF Chemiefarma NV. NL8700061 13-01-1987. Differentiated plant cell structures used for the production of alkaloids. 

J.L. Hall, T.J. Flowers, and R.M. Roberts, Plant Cell Structure Metabolism, 2nd Ed., Longman, London, 1982. 

Zeng M, Mosier NS, Huang CP, Sherman DM, Ladisch MR. (2007). Microscopic examination of changes of plant cell structure in corn stover due to hot water pretreatment and enz)miatic hydrolysis. Biotechnol Bioeng, 97, 265-278. 

Enzymes are obtained from plants, animals and micro-organisms by extraction with a suitable solvent, preferably after the cell structure has been destroyed by drying or grinding. They can be purified by precipitation and resolution and by fractional absorption and elution. Many enzymes have been obtained crystalline. 

The major classes of organic compounds common to living systems are lipids pro terns nucleic acids and carbohydrates Carbohydrates are very familiar to us— we call many of them sugars They make up a substantial portion of the food we eat and provide most of the energy that keeps the human engine running Carbohy drates are structural components of the walls of plant cells and the wood of trees Genetic information is stored and transferred by way of nucleic acids specialized derivatives of carbohydrates which we 11 examine m more detail m Chapter 28... 

Plant cell membranes are similar in overall structure and organization to animal cell membranes but differ in lipid and protein composition. 

Plant cells contain a unique family of organelles, the plastids, of which the chloroplast is the prominent example. Chloroplasts have a double membrane envelope, an inner volume called the stroma, and an internal membrane system rich in thylakoid membranes, which enclose a third compartment, the thylakoid lumen. Chloroplasts are significantly larger than mitochondria. Other plastids are found in specialized structures such as fruits, flower petals, and roots and have specialized roles. 

Figures 3 and 5 from Biochimie, vol 85, Perez S, Rodrigues-Carvajal MA, Doco T (2003) A complex plant cell wall polysaccharide rhamnogalactmonan 11. A structure in quest of a function. p 109-pl21...

As plant cells grow, they deposit new layers of cellulose external to the plasma membrane by exocytosis. The newest regions, which are laid down successively in three layers next to the plasma membrane, are termed the secondary cell wall. Because the latter varies in its chemical composition and structure at different locations around the cell, Golgi-derived vesicles must be guided by the cytoskeleton... 

Hardham, A.R. Gunning, B.E.S. (1978). Structure of cortical microtubule arrays in plant cells. J. Cell Biol. 77, 14-34. 

Carpita N. Tierney M. Campbell M. (2001) Molecular biology of the plant cell wall Searching for genes that define structure, architecture and dynamics // Plant Mol. Biol. V. 47. P. 1- 5. 

The perceived sensitivity of plant cells to the hydrodynamic stress associated with aeration and agitation conditions is typically attributed to the physical characteristics of the suspended cells, namely their size, the presence of a cell wall, the existence of a large vacuole, and their tendency to aggregate. Table 1 illustrates some of the differences between plant cells and other biological systems. Chalmers [19] attributed shear sensitivity in mammalian cultures at least in part to the fact that these cells occur naturally as part of a tissue, surrounded by other cells. The same is true for plant cells. The more robust microbial systems, on the other hand, exist in nature as single organisms or mycelial structures, very close to the forms they assume in submerged culture. 

Plant cell walls are made of bundles of cellulose chains laid down in a cross-hatched pattern that gives cellulose strength in all directions. Hydrogen bonding between the chains gives cellulose a sheetlike structure. 

Dietary fibre, which comprises all the non-digestible structural carbohydrates of plant cell walls and any associate lignin, provides a further example of a complex food-borne factor which cannot be classified as a nutrient, and which continues to generate debate over such issues as definition and analytical techniques. However, whatever the unresolved complexities, dietary fibre has a lengthy history and had proved itself eminently suitable as a component of functional food products long before the term was even coined. 

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