Aquatic and Terrestrial Plants

Even though plants that live in water look dramatically different from terrestrial plants, the two groups have a lot in common. Both types of plants capture the Sun s energy and use it to make food from raw materials. In each case, the raw materials required include carbon dioxide, water, and minerals. The differences in these two types of plants are adaptations to their specific environments. 

Land plants are highly specialized for their lifestyles. They get their nutrients from two sources soil and air. It is the job of roots to absorb water and minerals from the soil, as well as hold the plant in place. 

Essential materials are transported to cells in leaves by a system of tubes called vascular tissue. Leaves are in charge of taking in carbon dioxide gas from the atmosphere for photosynthesis. Once photosynthesis is complete, a second set of vascular tissue carries the food made by the leaves to the rest of the plant. Land plants are also equipped with woody stems and branches that hold them upright so that they can receive plenty of light. 

Marine plants, called macroalgae or seaweeds, get their nutrients, water, and dissolved gases from seawater. Since water surrounds the entire marine plant, these dissolved nutrients simply diffuse into each cell. For this reason, marine plants do not have 

Ulva can be found on all the world s coasts. Known commonly as sea lettuce or green laver, the alga usually grows in dense colonies. Many species are used as ingredients in soups and salads, and as a substitute for nori, the popular seaweed in sushi. 

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Starch A polymeric substance of glucose molecules and a component of many terrestrial and aquatic plants used by some organisms as a means of energy storage starch is broken down by enzymes (amylases) to yield glucose, which can be used as a feedstock for chemical or energy production. 

Food Chain Bioaccumulation. Lead is bioaccumulated by terrestrial and aquatic plants and animals (Eisler 1988). However, lead is not biomagnified in terrestrial or aquatic food chains (Eisler 1988). No additional information is needed. 

Data are scarce on ecosystems treated with paraquat. It is clear, however, that both terrestrial and aquatic plants accumulate paraquat, and that the compound disappears rapidly from the water column and tends to concentrate in surface muds (Table 22.1). 

Photosynthesis of terrestrial and aquatic plants, from tall trees to microscopic phytoplanktons, has a significant influence on the global carbon cycle. The better utilization of this biological process is clearly one of the solutions to cope with the rise in atmospheric GO 2 concentration and the possible global warming. 

The term hyperaccumulators was first used by Brooks et al. [113] to describe the plants that take up and accumulate more than 1000 pmoles As/g dry weight. A report about an arsenic-hyperaccumulating fern species additionally discussed the ph)Poremediation potentials of such plants [114]. Recent investigation has shown that the arsenic compounds in terrestrial and aquatic plants, fimgi, and lichen species are also interesting natural products [115, 116]. 

Fig. 2 shows the different pathways in which chemical elements contained in rocks are released to the different environmental compartments. Five main processes are responsible for their dispersion into the different ecosystems (1) Weathering, either directly by rain water on rock outcrops, by soil percolation water or by root exsu-dates, which interact with rock fragments, contained in the soil cover (2) Down hill mechanical transport of weathered rock particles, such as creep and erosion and subsequent sedimentation as till material or alluvial river and lake sediments (3) Transport in dissolved or low size colloidal form by surface and groundwater (4) Terrestrial and aquatic plants growing in undisturbed natural situations will take up whatever chemical elements they need and which are available in the surface and shallow groundwater. Trace elements taken up from the soil will accumulate in the leaves and will possibly enrich the soil by litterfall (5) Diffuse atmospheric input by aerosols and rain rock particles from volcanic eruptions, desertic areas (Chester et al., 1996), seaspray and their reaction with rain water. A considerable part of this can be anthropogenic. 

Polyphenolic secondary metabolites are a large and diverse group of chemical compounds which exist both in terrestrial and aquatic plants. Polyphenols from terrestrial plants are derived from gallic and ellagic acids, whereas the algal pol)q>henols are derived from polymerized... 

Humic substances, which are biopolymers widely and abundantly present in natural waters and soils, also have a high complexing ability with various heavy metal ions. These compounds are formed by the random condensation of breakdown products of terrestrial and aquatic plants and extracellular metabolites of phytoplankton. Concentrations of metals in marine and fresh waters are often higher than predicted from the solubility products of corresponding hydroxide and carbonate compounds. The complexation of metal ions with dissolved humic substances is responsible for the apparent supersaturation of metals in natural waters [9-21], Water-soluble humic substances are usually divided into two fractions, humic acid (HA) and Mvic acid (FA). HA is defined in operational terms as the fraction of humic substance soluble in alkaline solutions and insoluble in acidic solutions, while FA is the fraction soluble in both alkaline and acidic solutions. A general method for the fractionation of humic substances is illustrated in Fig. 1. HA is easily obtained as a precipitate in acidic solution (pH < 1.5). Although HA appears to be an attractive adsorbent for the recovery of heavy metal ions, there is little information on its practical application as adsorbent. It is difficult to use humic acid as the adsorbent because of its high solubility in water. 

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