Immunolocalization of PEP carboxylase (PEPC, A–C), glutamine synthetase (GS, D), and NADP-malic enzyme (NADP-ME, E) in barley leaves before (A, D, E) and after 4 d (B) or 8 d (C) dark senescence. Of the 88 species, only three had low CO2 compensation points and had bundle sheath chloroplasts that were specialized for starch formation (both features indicating that they were likely to possess the C4 pathway). This is more efficient than the C3 pathway. Esau (1965) has suggested that bundle sheath extensions may be involved in conduction, particularly as there is an inverse correlation with vein frequency and distribution (see also Roth-Nebelsick et al., 2001). Differences in antioxidant metabolism also exist in the C4 plant, maize, and are indicated by the fact that glutathione reductase and dehydroascorbate reductase were almost exclusively localized in the leaf mesophyll tissue, whereas ascorbate, ascorbate peroxidase, and superoxide dismutase were largely absent from the mesophyll fraction. The ratio of oxygenation versus carboxylation by RubisCO increases with the temperature (section 6.2). Of course, the presence either of a Casparian strip or of extensive suberization in the bundle sheath would restrict apoplastic transport of solutes. For Permissions, please e-mail: journals.permissions@oxfordjournals.org. Although studies of the activities of single cells or groups of cells in plants are, to a large degree, still in their infancy, there is evidence for intercellular compartmentation of activities between the different types of cells of the vasculature. However, Lersten (1997) concludes that the Casparian strip in stems and leaves occurs unevenly among major taxa. Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK. 2009 Apr;50(4):756-72. doi: 10.1093/pcp/pcp033. Williams et al. Overall, the data suggest that the highest expression of PEP carboxylase, PEPCK, and NADP-ME does not occur in the same cells in C3 plants as in the leaves of C4 plants. J Cell Biol. CO2 molecules combine with Phosphoenolpyruvate (PEP) and form 4-carbon compound oxaloacetate, thus the process called C4 Pathway. Its role as an interface between the vasculature and the mesophyll is considered in relation to the movement of water and assimilates during leaf development, export of photosynthates, and senescence. In L-type bundle sheath cells, chloroplast volume and number per unit volume are similar to those of mesophyll cells. Although it is tempting to infer a role for the bundle sheath in the metabolism and exchange of solutes between the vasculature and the mesophyll, it must be remembered that we are equally ignorant about the degree of specialization of mesophyll cells at various distances from the bundle sheath and the vasculature (Walter et al., 2004). Crookston and Moss (1970) collected 88 dicotyledon species with chlorenchymatous vascular bundle sheaths, originating from 22 families. Cell-specific mechanisms and systemic signalling as emerging themes in light acclimation of C3 plants. C4 is an efficient biochemical modification of the C3 Plants. More sophisticated measurements in Arabidopsis have been used to measure changes in the quantum efficiency of photosynthetic electron transport, estimated from chlorophyll fluorescence parameters that can be imaged from individual chloroplasts, in the bundle sheath and mesophyll cells of an intact leaf (Fryer et al., 2002). Phosphoenolpyruvate carboxykinase in cucumber plants is increased both by ammonium and by acidification and is present in the phloem, A unique short-chain dehydrogenase/reductase in Arabidopsis glucose signaling and abscisic acid biosynthesis and functions, Generation of active pools of abscisic acid revealed by, The relation of carbon dioxide compensation and chlorenchymatous vascular bundle sheaths in leaves of dicots, Differentiation of bundle sheath, mesophyll, and distinctive cells in the C, Differential localization of antioxidants in maize leaves, Carbon dioxide compensation—its relation to photosynthetic carboxylation reactions, systematics of the Gramineae, and leaf anatomy, Enzymes of starch and sucrose metabolism in, Localization of starch biosynthetic and degradative enzymes in maize leaves, An immunohistochemical study of the compartmentation of metabolism during the development and ripening of grape berries, An unusual layer of cells in the mesophyll of the soybean leaf, The paraveinal mesophyll of soybean leaves in relation to assimilate transfer and compartmentation. Knowledge of the activities of the C3 bundle sheath is also important in relation to attempts to engineer C4 photosynthesis into C3 crops, which would result in large changes to the bundle sheath cells of the C3 target species. Plant Cell Physiol. Epub 2020 Aug 25. van Rooijen R, Schulze S, Petzsch P, Westhoff P. J Exp Bot. Roles of the bundle sheath cells in leaves of C3 plants. Fryer et al. Cytosolic ascorbate peroxidase (APX2) is expressed specifically in bundle sheath cells (Fryer et al., 2003), and the accumulation of H2O2 in the chloroplasts of the bundle sheath parallels the induction of APX2 expression (Fryer et al., 2003; Chang et al., 2004).