Cell membranes plant

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

Alteration of Electrical Potential (PD). Study of the Influence of allelochemicals on the electrical potentials across plant cell membranes has been restricted to phenolic acids. Glass and Dunlop (42) reported that at pH 7.2, 500 yM salicylic acid depolarized the electrical potential in epidermal cells of barley roots. The electrical potential changed from -150 mV to -10 mV within 12 min. Recovery of the PD was very slow over about 100 min when the salicylic acid was removed. As the concentration of the allelochemical was increased, the extent of depolarization increased, but the time required for depolarization and recovery were constant. 

Volume 148. Plant Cell Membranes Edited by Lester Packer and Roland Douce... 

Packer L, Douce R. Plant Cell Membranes, Academic Press, San Diego, CA, 1987. 

The major phytotoxic components of the photochemical oxidant system, discussed in Chapter 11, are ozone and peroxyacetylnitrate (PAN), but there is indirect evidence that other phytotoxicants are present. Con siderable effort has gone into controlled exposures to ozone and into field studies. Leaf stomata are the principal sites for ozone and PAN entry into plant tissue. Closed stomata will protect plants from these oxidants. Both ozone and PAN may interfere with various oxidative reactions within plant cells. Membrane sulfhydryl groups and unsaturated lipid components may be primary targets of oxidants. Young leaf tissue is more sensitive to PAN newly expanding and maturing tissue is most sensitive to ozone. Light is required before plant tissue will respond to PAN that is not the case with ozone. 

Ting, I. P., J. Perchorowicz, and L. Evans. Effects of ozone on plant cell membrane permeability, pp. 8-21. In M. Dugger, Ed. Air Pollution Effects on Plant Growth. ACS Symposium Series 3. Washington, D.C. American Chemical Society, 1974. 

Transporters, particularly those carrying nonlipophilic species across biomembranes or model membranes, can be regarded as vectorial catalysts (and are also called carriers, translocators, permeases, pumps, and ports [e.g., symports and antiports]). Many specialized approaches and techniques have been developed to characterize such systems. This is reflected by the fact that there are currently twenty-three volumes in the Methods in Enzymology series (vols. 21,22,52-56,81,88,96-98,125-127,156-157, 171-174, and 191-192) devoted to biomembranes and their constituent proteins. Chapters in each of these volumes will be of interest to those investigating transport kinetics. Other volumes are devoted to ion channels (207), membrane fusion techniques (220 and 221), lipids (14, 35, 71, and 72), plant cell membranes (148), and a volume on the reconstitution of intracellular transport (219). See Ion Pumps... 

The hydrophobic waxy cuticle of plants can inhibit the movement and accessibility of nutrients to bacterial cells. However, biosurfactants produced by the majority of epiphytic Pseudomonas spp. decreases the water tension, enabling relatively free movement across the leaf surface to nutrient sources and natural openings such as stomata. Pseudomonas are also known to release a toxin called syringomycin that can produce holes in the plant cell membrane allowing access to intracellular nutrients without necessarily resulting in disease symptoms (Cao et al.r 2005). 

Effect of Ozone on Plant Cell Membrane Permeability... 

Ozone changes plant cell membrane (17, 18) and chloroplast membrane permeability (19). Loss of membrane integrity is also caused by plant pathogens (20), drought (21), herbicides (22) and frost (21). 

Several groups have obtained data Indicating that changes In calcium flux from ellcitor-treated plant cells may serve as a second messenger in phytoalexin Initiation (77-80). The altered calcium flux may In turn be caused by rapid depolarizatlon/polarizatlon and redox perturbation of the plant cell membrane (56 81-85). For Instance, production of superoxide anion, hydrogen peroxide and hydroxyl radicals have been observed In plant tissues undergoing hypersensitive reactions (86-89). 

C. The plant sterols are always present as part of the plant cell membranes and are not free in solution like cholesterol. 

Linoleic acid and LNA and their long-chain derivatives arc important components of animal and plant cell membranes. When humans ingest fish or fish oil, the EPA and DHA from the diet partially replace the omega-6 fatty acids, especially AA, in the membranes of probably all cells, but especially in the membranes of platelets, erythrocytes, neutrophils, monocytes, and liver cells [reviewed in Simopoulos, 19911. A diet that has a high ratio of omega-6 omega-3 fatty acids has detrimental effects on eicosanoid metabolism and gene expression. 

Graziana, A. Fosset, M. Ranjeva, R. Hetherinton, A. Lazdunski, M. "Ca+ Channel Inhibitors that Bind to Plant Cell Membranes Block Ca+2 Entry into Protoplasts", Biochemistry, 1988,27, 764-768. 

Humidity-induced pressurization is the result of vapor pressure differential between the leaf and atmosphere separated by a porous partition (plant cell membrane) (Figure 7.16). The total pressure will be greater on the more humid side. Humidity-induced diffusion is more important than thermal transpiration because it can be increased with temperature and can function at a constant temperature, as well as across temperature gradient (Armstrong et al., 1991a, 1991b). 

Kinraide, T.B., Yermiyahu, U., Rytwo, G., 1998. Computation of surface electrical potentials of plant cell membranes. Correspondence to published zeta potentials from diverse plant sources. Plant Physiol. 118, 505-512. 

While the current state of knowledge does not permit much more than speculation concerning the molecular events at plant cell membranes in host-pathogen interactions, the application of the concepts derived from the mammalian membrane receptor-effector systems provides a unifying model which allows rationalisation of the available data and may suggest useful experimental approaches. 

The studies confirm that the close-packed region of the membrane forms the rate-limiting barrier for trans-membrane movement by simple diffusion. This situation may be physiologically relevant in that the leakiness of the cell membrane can clearly be affected by physiological control of the cholesterol content of the cell membrane. Bacterial and plant cell membranes which do not contain cholesterol and which are not particularly leaky must have other compositional pecuharities to provide well-sealed membranes. 

Some T. have major physiological significance. Thus, lanosterol is converted biosynthetically to cholesterol, the precursor of all steroid hormones, bile acids, and vitamin D3. In fungi, lanosterol is converted to er-gosterol (see sterols), an essential component of the fungal cell membrane. Plant cell membranes also incorporate steroids (phytosterols). In prokaryotes, the hopanoids take over the functions of steroids in the cell membranes. As a component of animal and plant waxes T. strengthen the structures. They protect the plant surface from desiccation and attack by microorganisms (e.g., betulin, lupeol, oleanolic acid, and ursolic acid). 

Xylan, one of the better known hemicelluloses, is a component of plant cell membranes. This pentosan occurs in association with cellulose. The structure of xylan was shown to be 1,4-polyxylose ... 

Amaranthus tricolor plant cells were entrapped with chitosan gel to determine the polycationic properties of chitosan on plant cell membrane permeability. On the fifth day, maximum tricolor cells were released from chitosan-immobilized cells (Knorr and Teutonico 1986). 

R357 M. E. Gonzalez and D. M. Barrett, Thermal, High Pressure, and Electric Field Processing Effects on Plant Cell Membrane Integrity and Relevance to Fruit and Vegetable Quality , J. Food ScL, 2010, 75, 121. 

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