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Submerged Aquatic Vegetation: Seagrasses
Published in Yeqiao Wang, Coastal and Marine Environments, 2020
Alyssa B. Novak, Frederick T. Short
Seagrasses evolved 40–100 million years ago in the late Cretaceous Period. They arose from terrestrial monocotyledons that reinvaded the sea and developed into three separate lineages (Cymodoceaceae complex, Hydrocharitaceae, and Zosteraceae [14,15]. The colonization of the sea required seagrasses to grow and reproduce while enduring the osmotic effects of salt water, changes in the availability of dissolved CO2, changes in the intensity and quality of light, and the density and mechanical drag of water [16–18]. Seagrasses have a number of unique adaptations that allow for survival in these conditions, including a well-developed horizontal rhizome that anchors plants into the substrate and roots extending from the rhizome that assist in anchoring and nutrient uptake. Leaves are flexible and offer little resistance to wave action. They also function in nutrient uptake and as receptors of light, with the epidermis of blades serving as the main site for photosynthesis. Tissues (aerenchyma) extending through the roots, rhizomes, and leaves facilitate internal gas and solute transport while regularly arranged air spaces (lacunae) give plants buoyancy. Finally, all species of seagrasses exhibit hydrophilous pollination while completely submerged except for Enhalus acoroides and Ruppia spp., which pollinates at the water surface [16–20].
Adaptive Mechanisms of Plants Occurring in Wetland Gradients
Published in George Mulamoottil, Barry G. Warner, Edward A. McBean, Wetlands, 2017
C.W.P.M. Blom, H. M. van de Steeg, L. A. C. J. Voesenek
After flooding or soil waterlogging, first reactions occur in the soil. The oxygen available for plant roots and microorganisms rapidly decreases as the soil water level rises (Laan et al., 1989b). At least two changes can be observed in soils after flooding. First is the development of aerenchyma. Plants require oxygen for cell division and when the gas exchange between the atmosphere and the soil is hampered roots of many species are affected, at least during periods of growth involving cell division. As a response to these conditions, flood-resistant species are able to generate a new root system. These roots are characterized by aerenchyma formed either by cell differentiation and cell collapse — lysigenous aerenchyma — or by cell separation without collapse, defined as schizogenous aerenchyma (Jackson and Drew, 1984; Justin and Armstrong, 1987; Crawford, 1992). Well-developed aerenchyma — which is a charateristic feature of above-and below-ground parts of many wetland and aquatic species — provides large and continuous air spaces that facilitate the downward diffusion of oxygen from shoot to root (Armstrong and Armstrong, 1988; Laan et al., 1989a).
Seasonal Growth Patterns in Wetland Plants Growing in Landfill Leachate
Published in George Mulamoottil, Edward A. McBean, Frank Rovers, Constructed Wetlands for the Treatment of Landfill Leachates, 2018
An internal structural feature of these plants is that tissues contain large open spaces called aerenchyma. Plants such as Phragmites and cattails that grow typically in somewhat deep water typically have more aerenchyma than species such as Phalaris growing in more shallow water. Figure 14.2 illustrates aerenchyma tissue in T. angustifolia, a species found typically in deeper water sites (Grace and Wetzel, 1981; 1982). Both the leaves and roots have large air spaces while the rhizome has a more spongy consistency. This aerenchyma is important because it allows oxygen to diffuse from the atmosphere into stems and leaves, then into the belowgound roots and rhizomes (Brix and Schierup, 1990).
Heavy metals and nutrients removal in a batch-fed greywater treatment system planted with Canna indica and Oryza sativa L.
Published in Journal of Environmental Science and Health, Part A, 2023
Davids O. Raphael, Christopher O. Akinbile, Oluwaseyi M. Abioye, David A. Olasehinde, Muritala Ogunremi, Oluwayemisi M. Bolarin
The BOD5 removal value for C. indica was not significantly different from that of O. sativa L. as shown in Table 2. Zhang et al.[52] reported that the uptake and reduction of organic contaminants are based on their constituent and concentration. Low concentration will lead to more absorption and vice versa. The uptake in the study can be attributed to the process of food reserve build-up in rhizomatous C. indica than in O. sativa L. uptake which is based on the plants’ need per time, C. indica also needs more organics to support its broad leaves. Hence, more BOD5 removal was observed. Plants, like O. sativa L., can cope when submerged by adaptations found in their roots, stems and leaves. The gas-filled spaces (aerenchyma) found in aquatic and semi-aquatic plants facilitate gas exchange between aerial and submerged plant parts by reducing the diffusion resistance to gas exchange from cells.[53] This same feature can be said to be responsible for the reduction in BOD5 through the admittance of air into the CW substrate media.
Removal of nitrogen and phosphorus by aboveground biomass of Phragmites australis in Constructed Wetland System under the conditions of temperate continental climate
Published in International Journal of Phytoremediation, 2023
LJiljana Nikolić, Ivana Maksimović, Dejana Džigurski, Marina Putnik-Delić, Branka Ljevnaić-Mašić
Hydrophytes developed many morphological and anatomical particularities, i.e., hydromorphic structures, which give them the ability to live in aquatic and wetland environments, where the conditions of gas and light regime are specific. One of the important characteristics of the hydromorphic structure is the presence of a special tissue, aerenchyma, which is characterized by an extremely well-developed system of intercellular spaces that serve to store air. The presence of well-developed aerenchyma facilitates the exchange of gases between the plant and the external environment, but also improves the supply of plants with air, in which the water and wetland environment is generally poor (Engloner 2009). In addition to the above, an important characteristic of these plants is vegetative propagation (by rhizome), which allows these plants to spread very successfully (Packer et al. 2017; Čuda et al. 2021). The growth and development of certain macrophyte species depend on a number of factors. Thus, water depth, i.e., water regime, water chemical composition, pH and salinity are important factors influencing their abundance and biomass. Moreover, the composition and properties of sediments and substrates also significantly affect their growth and development (Packer et al. 2017; Čuda et al. 2021).
Field-scale baffled and biorack hybrid constructed wetland: effect of fluctuating loading rates and recirculation for domestic wastewater treatment
Published in International Journal of Phytoremediation, 2021
Mitil M. Koli, Guru R. Munavalli
An onsite treatment facility is a better option for developing countries particularly for isolated establishment/s (Sathe and Munavalli 2019). Decentralized wastewater treatment (DWT) systems are appropriate for communities with low population density, varying site conditions and more cost-effective than centralized practices (Jamshidi et al. 2014). DWT comprised of constructed wetland/s (CW) in its secondary stage is an appropriate system of low-cost wastewater management for such establishments due to availability of space. CW is a unit that consists of large tanks/artificial ponds with porous media beds planted with aquatic emergent macrophytes and other plants adapted to saturated conditions through which wastewater is passed either in horizontal or vertical mode. Wetland vegetation, supporting media, and associated microbial assemblages contribute to the natural processes of treatment in CWs. The vegetation (normally emergent type) in CW provides larger surface area through dense root matrix and shelter a great diversity of microbial communities on the root surface. The presence of aerenchyma (air-filled) tissue in many wetlands plants enables these plants to grow in anaerobic or anoxic soils and leak oxygen required for growth of many aerobic microbes on the root surface (Vymazal 2011). The root structure of these plants enhances hydraulic conductivity of the CW system as well as aid in velocity reduction, sedimentation and filtering effect (Shelef et al. 2013). Moreover, the plants add to the esthetic beauty at the site of installation of CWs (Haritash et al. 2015). Hence, these facilities are started to be used as a sustainable method of wastewater treatment for small communities and individual households (Gajewska et al. 2018).