Cell damage plant cells

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). 

Positive vital staining data are usually equated with life, implying a cellular capacity to grow and divide. Mammalian red blood cells and plant cells heavily irradiated with X-rays for use as nurse cultures are vital by such assays, yet they lack the ability to divide. Many vital stains, such as fluorescein diacetate and neutral red, measure the intactness of the cell membrane tetrazoliums measure mitochondrial reductive capacity. Respiration continues and membranes remain intact well after nuclear death. Some cells can be rescued after membrane damage and leakage. At best, lack of vital staining is indicative that cells are dying or are dead. Positive... 

C12H20O4. M.p. 165°C. A plant growth hormone, which is produced in damaged plant tissue, and on diffusing into adjacent intact tissue cells stimulates them to divide. Traumatic acid has been isolated from the pods of green beans. 

Plant Cell Culture. Air-lift bioreactors have been favored for plant cell systems since these cultures were first studied (4). However, they can give rise to problems resulting from flotation of the cells to form a meringue on the top. It is interesting to note that some reports indicate that stirred bioreactors do not damage such cells (4). 

Some mycehal fermentations exhibit early sporulation, breakup of mycehum, and low yields if the shear is excessive. A tip speed or 250 to 500 cm/s (8 to 16 ft/s) is considered permissible. Mixing time has been proposed as a scale-up consideration, but httle can be done to improve it in a large fermenter because gigantic motors would be required to get rapid mixing. Culturing cells from plants or animals is beset by mixing problems because these cell are easily damaged by shear. 

Fig. 8. Sustained damage in Daucus carota suspensions, as a function of total energy expended, under laminar flow conditions in a Couette viscometer. Redrawn from Dunlop et al. (1994) Effect of fluid shear forces on plant cell suspensions. Chem Eng Sci 49 2263 - 2276, with permission of Elsevier Science...

Enzymatic maceration, which is a softening of plant tissue by the use of enzymes, has some potential quality advantages over mechanical-thermal disintegration as maceration is obtained with less damage to the cell walls. The major part of the plant cells remains intact by enzymatic maceration [25], as the enzymes attack only the space between the cells, and with only rare injury to the cell membrane [26]. The intact cells protect nutritional components within the cells which minimise flavour changes and deterioration on storage [27,28]. 

When crops freeze, the ice crystals that form damage the cell walls of the plants, which ultimately destroys the cells. Explain how removal of INP from plant surfaces could help the plants. 

Kikuta Y, Ueda H, Nakayama K et al (2011) Specific regulation of pyrethrin biosynthesis in Chrysanthemum cinerariaefolium by a blend of volatiles emitted from artificially damaged conspecific plants. Plant Cell Physiol 52 588-596... 

All plant diseases result from the invasion of plant tissue by microscopic organisms. These can be fungi, bacteria, or viruses. Taking their nourishment from the plant tissue as parasites, they cause cell damage and death, and sometimes distortions of growth rather like tumors or cancers. 

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