Estimating the Water Requirements for Plants of Floodplain Wetlands

Figure 9. Aquatic growth-formsText gives a general description, with notes on adaptations and some examples. Diagrams are drawn to differentscales, (*) indicates an introduced species.EMERGENT MACROPHYTES – erect formsRooted in sediment, leaves growing through water, into air. Size ranges from tall >1 m, medium to small. C-3 and C-4species. Forms with leaf blades have high surface area, often very productive. Tall forms often dominant.Can grow in permanent water, but tolerant of periodic temporary dry conditions or deeper water. Rhizome and rhizosphereoxygenated from leaves.Tall and medium forms are mainly perennials. Most perennials have substantial underground carbohydrate storage, usuallyrhizomes but sometimes as corms or tubers.Monocots, mostly from Cyperaceae or Poaceae. Examples of species are Typha, Phragmites, Eleocharis, Cyperus, Baumea,Bolboschoenus, Juncus.EMERGENT MACROPHYTES – trailing formsRooted at channel edge or bank. Leaves on water or slightly rising above surface, from floating stems or stolons. Traildownstream in low-velocity current.Buoyancy mechanisms for stems not always evident but can include inflated hollow stems, spongy tissues. Stems flexible,not rigid, so move easily with small changes in water level or waves.Many species have rootlets at nodes, some species can establish from fragments with these.Examples: Ludwigia peploides, Rumex bidens (*), Nymphoides spp., also several grasses with prostrate-ascending stems,eg. Pseudoraphis spinescens.FLOATING-LEAFED MACROPHYTES – trailing formsRooted in sediment, leaves floating on water surface. Floating leaf typically rounded or oval, glossy above, and may becomemore erect when leaves are crowded. Some species have, initially, submerged leaves.Grow in or near permanent water, to 2 m sometimes 3 m, depth range defined by length of stem or petiole. Stems havelacunae, and/or aerenchyma, to facilitate internal movement of gases.Mainly perennials. Rhizome may be compact at stem base, or bulky and extensive.Species in the family Nymphaceae, also Ottelia ovalifolia, Brasenia schreberi, Potamogeton tricarinatus, Marsilea spp.,Villarsia reniformis, Nelumbo nucifera.SUBMERGED MACROPHYTERooted in sediment, and grow submerged in water,