The Structural Adaptation of Aerial Parts of Invasive Alternanthera philoxeroides to Water Regime

Abstract

Alternanthera philoxeroides has successfully invaded diverse habitats with considerably various water availability, threatening biological diversity in many parts of the world. Because its genetic variation is very low, phenotypic plasticity is believed to be the primary strategy for adapting to the diverse habitats. In the present paper, we investigated the plastic changes of anatomical traits of the aerial parts of A. philoxeroides from flooding to wet then to drought habitat; the results are as follows: A. philoxeroides could change anatomical structures sensitively to adapt to water regime. As a whole, effects of water regime on structures in stem were greater than those in leaf. Except for principal vein diameter and stoma density on leaf surfaces, all other structural traits were significantly affected by water regime. Among which, cuticular wax layer, collenchyma cell wall, phloem fiber cell wall, and hair density on both leaf surfaces thickened significantly with decrease of water availability, whereas, pith cavity and vessel lumen in stem lessened significantly; wet habitat is vital for the spread of A. philoxeroides from flooding to drought habitat and vice versa, because in this habitat, it had the greatest structural variations; when switching from flooding to wet then to drought habitat, the variations of cuticular wax layer, collenchyma cell wall, phloem fiber cell wall, pith cavity area ratio, diameter of vessel lumen, and hair density on both leaf surfaces, played the most important role. These responsive variables contribute most to the adaptation of A. philoxeroides to diverse habitats with considerably various water availability.

Morphology of the Invasive Amphiphyte Alternanthera Philoxeroides Under Different Water Levels and Nitrogen Concentrations

“…This might account for their similar responses to the water level/nitrogen treatments. Alternatively, it is known that the amphibious A. philoxeroides can grow in diverse habitats under different water conditions and that it has different anatomical structures enabling it to adapt to terrestrial and aquatic habitats (Tao et al, 2009). When environmental conditions change, its morphological structures can be altered accordingly.…”

“…In aquatic systems it often roots on the edge of water bodies and spreads from a terrestrial to an aquatic habitat (Sainty et al, 1998). Many studies have examined the growth, performance and clonal integration of A. philoxeroides under various conditions, including resource level Liu et al, 2008;Tao et al, 2009;Xu et al, 2010), disturbance (Schooler et al, 2007;Dong et al, 2010Dong et al, , 2012, water depth (Wang et al, 2009) and submergence Luo et al, 2011). Morphological and physiological acclimation to frequent fluctuation of water level is a crucial element of the successful establishment of this species in zones of water level fluctuation, such as riparian areas (Luo et al, 2009(Luo et al, , 2011.…”

Gene Expression Reaction Norms Unravel the Molecular and Cellular Processes Underpinning the Plastic Phenotypes of Alternanthera Philoxeroides in Contrasting Hydrological Conditions

“…Given that all of these genes are known to promote programmed cell death (Feys et al, 2001 ; Suarez et al, 2004 ; Olszak et al, 2006 ), their simultaneous up-regulation strongly implies that they all contributed to the formation of lysigenous aerenchyma during the extension of pith cavity in submerged A. philoxeroides shoots. The enlarged cavity may facilitate the efficient movement of gases (such as O 2 , CO 2 , and ethylene) within the plant, which is crucial for survival while submerged (Carr et al, 1995 ; Tao et al, 2009 ).…”

Peroxidase as a metric of stress tolerance and invasive potential of alligator weed (Alternanthera philoxeroides) growing in aquatic habitats

“…Once established, aquatic invasive plant species can have dramatic effects on the native ecosystem (Homans and Smith 2011). Alternanthera philoxeroides (Martius) Griseb (Amaranthaceae), alligator weed, an invasive perennial wetland herb originating from South America (Maddox 1968), has many attributes of a successful invasive weed such as rapid growth and vegetative propagation (Tao et al 2009;Wang et al 2009) as well as a broad ecological amplitude (Geng et al 2007). This amphibious clonal plant has invaded many ecosystems worldwide (Julien et al 1995), including riparian zones (Pan et al 2006) and agricultural lands (Spencer and Coulson 1976), and is regarded as one of the worst weeds of the world (http://www.waikatoregion.nz).…”