Electron transport in plants

Mitochondrial electron transport in plants and fungi. Plant mitochondria resemble those of mammals in many ways, but they contain additional dehydrogenases and sometimes utilize alternative pathways of electron transport,68-73 as do fungi.74 Mitochondria are impermeable to NADH and NAD+. Animal mitochondria have shuttle systems (see Fig. 18-16) for bringing the reducing equivalents of NADH into mitochondria... 

Metribuzin is a member of the substituted as-triazinone group of herbicides. Activity is due to interference with photosystem II electron transport in plant chloroplasts (Dodge, 1983). The metabolism of metribuzin in plants has been the subject of many short-term and long-term studies dating back to the early 1970s. 

Providing Insight Into the Chemical Basis of Plant Processes. A wide variety of carbamates, triazines, amides, ureas, quinones and other herbicides are known to exert their action by inhibiting the plant s photosynthetic process (17). However, some of the same compounds have been used very effectively as probes into the pathways of photosynthesis and electron transport in plants. 

Fig. 6. Electron transport in plants and fimgi. Three complexes (7, II and IV) translocate protons to gradient across the mitochondrial membrane Complex 7NADH dehydrogenase complex II succinate dehydrogenase complex III cytochrom be, complex IV cytochrome c oxidase (Cox). Cyc Cytochrome c UbiQ ubiquinone Aox alternative oxidase SHAM salicylhy-droxamic acid AA antimycin A KCN potassimn cyanide. (From Vanlerberghe and McIntosh [137])...

Rotenone is a complex flavonoid found in the plant Derris ellyptica. It acts by inhibiting electron transport in the mitochondrion. Derris powder is an insecticidal preparation made from the plant, which is highly toxic to hsh. 

Rotenone A complex flavonoid produced by the plant Denis ellyptica. It has insecticidal activity due to its ability to inhibit electron transport in the mitochondrion. 

P. Askerlund and C. Larsson, Transmembrane electron transport in plasma membrane vesicles loaded with an NADH-generating system or ascorbate. Plant Phy-.i-iol. 96 1178 (1991). 

Benzoquinones, such as 2,6-dimethoxybenzoquinone (1.62), are present in root exudates of maize and stimulate parasitic plants to form haustoria (Matvienko et al., 2001). Ubiquinones, such as ubiquinonc(j) (1.63), where (3) indicates the number of isoprenoid sidechains, is also known as Coenzyme Q and has a role in electron transport in the mitochondria. 

Boydston, R., Paxton, J.D., Koeppe, D.E. Glyceollin a site-specific inhibitor of electron transport in isolated soyabean mitochondria. Plant Physiol 1983 72 151-155. 

Haehnel, W. 1984. Photosynthetic electron transport in higher plants. Annu. Rev. Plant Physiol. 

In green plants, vitamin K (phyUoquinone) functions as a secondary electron acceptor in photosystem I, and in bacteria a variety of menaquinones (which also have vitamin K activity) have a role in the plasma membrane in electron transport, where they serve the same role as ubiquinone (Section 14.6) in mitochondrial electron transport. There is no evidence that vitamin K has any role in electron transport in animals. 

D-10) Antimycin A, a fungal antibiotic, blocks oxidative phosphorylation at the step between cytochromes b and C. Rotenone, a toxic plant derivative used as a fish poison, and amytal, a baibituate sedative, both interrupt electron transport in the step between NADH and FMN. 

Lead is taken up and transported in plants (Cannon and Bowles 1962) and can decrease cell division at very low concentrations. Lead inhibits the electron transport in com mitochondria, especially when phosphate is present (Koeppe and Miller 1970). 

Once metals have been transported to their target tissue, they need to be distributed within the subcellular compartments where they are required, and need to be safely stored when they are in excess. Nearly 90% of Fe in plants is located in the chloroplasts, where it is required in the electron transfer chain, and in the synthesis of chlorophylls, haem, and Fe—S clusters. Fe, Cu, and Zn are also required in chloroplasts as cofactors for superoxide dismutases to protect against damage by reactive oxygen species during chloroplast development, and Cu is also required in other enzymes including the essential Cu protein plastocyanin. Pathways of intracellular metal transport in plant cells are illustrated in Fig. 8.10. Transport into the chloroplast is best characterised for Cu,... 

M Tsionsky, ZG Cardon, AJ Bard, RB Jackson. Photosynthetic electron transport in single guard cells as measured by scanning electrochemical microscopy. Plant Physiol 113 895-901, 1997. 

Badretdinov DZ, Baranova EA, Kukushkin AK. Study of temperature influence on electron transport in higher plants via delayed luminescence method experiment, theory. Bioelectrochem 2004 63 67-71. 

Blue copper proteins contain a minimum of one Type 1 Cu centre, and those in this class include plastocyanins and azurins. Plastocyanins are present in higher plants and blue-green algae, where they transport electrons between Photosystems I and II (see above). The protein chain in a plastocyanin comprises between 97 and 104 amino acid residues (most typically 99) and has 10 500. Azurins occur in some bacteria and are involved in electron transport in the conversion of [N03] to N2. Typically, the protein chain contains 128 or 129 amino acid residues (M 14600). 

---