Localization of Heavy Metals in Cells and Tissues of Different Plant Organs

As shown in Fig. 2, general mechanisms for detoxification and accumulation of heavy metals in plants are the distribution of the metals to apoplastic compartments

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Fig. 2 Possible metal localization and presence of major metal-binding ligands in a model plant with a standard root, stem and shoot system. In each organ, tissues and cells are conventionally divided into apoplasic and symplastic sites. The former including xylem (sap) in the conductive tissues of each organ, and rizosphere connected to or surrounding the root system underground, and also in some cases vacuoles (apoplast but inside the protoplasm). The latter includes phloem (sap) and cytoplasm in each organ. The xylem and phloem systems support large parts of the stem and other tissues, and they play considerable roles in mineral/water transport from root to shoot and vice versa, with assimilatives as long-distance transports. Trichomes in shoot (leaf) also consist of apoplastic and symplastic sites but develop their special structure and functions for metal binding and accumulation. Mit mitochondria, Chl chloroplast, PC, phytochelatin, GSH glutathione, OA organic acid, NA nicotianamine, AA amino acid, -COOH carboxyl group, -NH amino- or imino- group, -SH sulfhydryl group

Fig. 2 Possible metal localization and presence of major metal-binding ligands in a model plant with a standard root, stem and shoot system. In each organ, tissues and cells are conventionally divided into apoplasic and symplastic sites. The former including xylem (sap) in the conductive tissues of each organ, and rizosphere connected to or surrounding the root system underground, and also in some cases vacuoles (apoplast but inside the protoplasm). The latter includes phloem (sap) and cytoplasm in each organ. The xylem and phloem systems support large parts of the stem and other tissues, and they play considerable roles in mineral/water transport from root to shoot and vice versa, with assimilatives as long-distance transports. Trichomes in shoot (leaf) also consist of apoplastic and symplastic sites but develop their special structure and functions for metal binding and accumulation. Mit mitochondria, Chl chloroplast, PC, phytochelatin, GSH glutathione, OA organic acid, NA nicotianamine, AA amino acid, -COOH carboxyl group, -NH amino- or imino- group, -SH sulfhydryl group like cell walls or trichome, and the chelation of the metals by a ligand in cytoplasm, followed by the sequestration of the metal—ligand complex into the vacuole, in the different organs such as roots, stems and leaves (Yang et al. 2005). Generally, the heavy metal contents in plant organs decrease in the following sequence; root > leaves > stems > inflorescence > seeds. However, this order sometimes varies with plant species, especially in hyperaccumulators, of which the shoots have the highest heavy metal content. Roots usually manifest the maximum content of heavy metals. Leaves vary with age in their ability to accumulate heavy metals, some heavy metals accumulate preferentially in the youngest leaves of plants, whereas in others, the maximum content is found in senescing leaves. Preventing Cd ions from entering the cytosol by the plant cell walls theoretically represents the best detoxification mechanism (Ma et al. 2005). Cd stress may be alleviated by sequestration of Cd in the cell wall or the vacuole in Cd-tolerant genotypes of barley, especially in short-term Cd-exposed experiments. Cell walls of the root can act as a first barrier against Cd stress in immobilizing excesses of Cd (Wu et al. 2005). Available evidence suggests that Cd binds to the secondary wall and middle lamellae in maize roots (Khan et al. 1984). On the other hand, in bush bean, Cd was mainly bound to pectic sites and hystidyl groups of the cell wall in roots and leaves (Leita et al. 1996). In white lupin, the cell wall was found to retain up to 47% of the absorbed Cd in leaves, 51% in stems, and 42% in the roots, although 20-40% of total Cd was associated with PCs (Vazquez et al. 2006), implying that this plant may use cell wall binding as a more effective mechanism of Cd detoxification than PCs. However, excess and non-specific metal binding to primary cell walls did not appear to be the tolerance mechanism in tomato suspension-cultured cells and roots of some dicotyledonous plants (Inouhe et al. 1991, 1994). In these cases, where the cells are actively growing, the cytoplasmic formation of PCs followed by metal binding and transport to vacuoles can be more effective mechanisms of Cd detoxification than wall bindings.

Body Detox Made Easy

Body Detox Made Easy

What exactly is a detox routine? Basically a detox routine is an all-natural method of cleansing yourbr body by giving it the time and conditions it needs to rebuild and heal from the damages of daily life and the foods you eat and other substances you intake. There are many different types of known detox routines.

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