The utilization of the photosynthesis product triose phosphate is strictly regulated

As shown in Figure 6.11, five of the six triose phosphate molecules generated in the Calvin cycle are required for the regeneration of the CO2 acceptor ribulose bisphosphate. Therefore, a maximum of one-sixth of the triose phosphate produced is available for export from the chloroplasts. In fact, due to photorespiration (Chapter 7), the portion of available triose phosphate is only about one-eighth of the triose phosphate synthesized in the chloroplasts. If more triose phosphate would be...

The glycolysis pathway plays a central role in the utilization of carbohydrates

The carbohydrates delivered by phloem transport to the sink cells are fuel for the energy metabolism and also a carbon source for the synthesis of the cell matter. The glycolysis pathway, which is present at least in part in almost all living organisms, has a fundamental role in the utilization of carbohydrates. The enzymes of this pathway not only occur in sink tissues but are also present in all plant cells. Each cell has two sets of glycolytic enzymes, one in the cytosol and one in the...

Genetic engineering is used to produce renewable resources for industry

Genetic engineering is a method with a great promise for the production of plants as renewable resources for industry. Transgenic plants which produce customized fats, with short chain fatty acids for the detergent and cosmetic industries, and with high erucic acid content for the production of synthetic materials, were discussed in section 15.5. Transgenic potatoes which contain only the branched starch amylopectine (section 9.1) (AMFLORA, BASF) are grown as raw material for industry, e.g.,...

Xenobiotics are detoxified by conjugation

Toxic compounds produced by the plant or which are taken up (xenobi-otics, including herbicides) are detoxified by reaction with glutathione. Catalyzed by glutathione- transferases, the reactive SH group of glutath-ione can form a thioether by reacting with electrophilic carbon double bonds, carbonyl groups, and other reactive groups. Glutathione conjugates (Fig. 12.6) synthesized in this way in the cytosol are transported into the vacuole by a specific glutathione translocator against a...

The cell wall gives the plant cell mechanical stability

Nanocellulose Fiber

The difference between plant cells and animal cells is that plant cells have a cell wall. This wall limits the volume of the plant cell. The water taken up into the cell by osmosis presses the plasma membrane against the inside of the cell wall, thus giving the cell mechanical stability. The cell walls are very complex structures in Arabidopsis about 1,000 genes were found to be involved in its synthesis. Cell walls also protect against infections. The cell wall consists mainly of carbohydrates...

Nitrate assimilation is strictly controlled

During photosynthesis, CO2 assimilation and nitrate assimilation have to be matched to each other. Nitrate assimilation can progress only when CO2 assimilation provides the carbon skeletons for the amino acids. Moreover, nitrate assimilation must be regulated in such a way that the production of amino acids does not exceed the demand. Finally, it is important that nitrate reduction does not proceed faster than nitrite reduction, to prevent the accumulation of toxic levels of nitrite section...