Responses to flooding intensity in Leontodon taraxacoides

Abstract

Natural flooding is one of the major factors affecting vegetation dynamics in many regions of the world. The Flooding Pampa Grasslands (Argentina) are frequently exposed to flooding events of diverse intensity and duration, some of which Leontodon taraxacoides, an exotic dicot. frequent in these grasslands, seems to survive. Its responses to four different water depths (0, 1, 7 and 13 cm) were studied. The results indicate that plants in conditions of total submergence (depth of 13 cm) did not survive. In less severe flood conditions, increases in the leaf insertion angle resulted in the maintenance of a large proportion of the total leaf area above the water. Differences in leaf length and a decrease in the width and the proportion of lobes per leaf were also found under partial submergence conditions (depth of 7 cm). Root and leaf aerenchyma, present in unflooded plants, showed a significant increase in flood conditions. In spite of the anatomical and morphological responses, total biomass and leaf area were severely affected by water depth. Control plants allocated more biomass to reproductive organs, while partly submerged plants allocated more to leaves and less to reproductive organs. Mature L. taraxacoides plants presented a wide range of plastic adjustment as a survival strategy in soil anaerobiosis, and appear to be able to survive short spring floods in a vegetative state ; in contrast, they might not tolerate total submergence conditions imposed by more intense and long-lasting floods.

Flooding tolerance: suites of plant traits in variable environments

“…Hyponastic growth in R. palustris occurs mainly in petioles of younger leaves, and results from differential cell elongation across the petiole base (Cox et al 2004). Hyponastic growth alone, is a trait of relevance as vertical re-orientation by itself can bring leaves above the water; an example is L. taraxacoides that does not display a shoot elongation response (Grimoldi et al 1999). Even if hyponastic growth occurs and leaves do not reach the water surface, potential benefits might still be improved access to light, shortening of the submergence period, and prevention of sediment/debris covering leaves.…”

“…(Grimoldi et al 1999), Paspalum dilatatum Poir. (Insausti et al 2001), and even Arabidopsis (Millenaar et al 2005).…”

“…P. australis, Armstrong et al 1992). Another shoot trait of relevance during soil waterlogging, possessed by several species with rosette-type shoots that inhabit flood-prone environments (Grimoldi et al 1999), is a capacity to change leaf orientation from rather prostrate to almost vertical (hyponastic growth). This acclimation prevents partial submergence when some water ponds on waterlogged soils.…”

The Roles of Ethylene, Auxin, Abscisic Acid, and Gibberellin in the Hyponastic Growth of Submerged Rumex palustris Petioles

“…These nastic responses (Palmer, 1985) can be divided into epinastic (downward) and hyponastic (upward) curvatures and are caused by differential growth, with, respectively, the adaxial (upper) or the abaxial (lower) side of the organ growing more rapidly (Kang, 1979). One of the environmental factors inducing hyponastic leaf movement is flooding (Ranunculus repens and Caltha palustris, Ridge, 1987; Leontodon taraxacoides, Grimoldi et al, 1999;Paspalum dilatatum, Insausti et al, 2001;Rumex palustris, Cox et al, 2003). In the semiaquatic species R. palustris, hyponastic growth upon complete submergence, together with stimulated petiole elongation, contributes to increased survival by enabling the leaves to reach the water surface so that gas exchange with the atmosphere is restored (for review, see Voesenek et al, 2003).…”

Responses of six Brachiaria spp. accessions to root zone flooding

“…Similarly, Rubio & Lavado (1999) Brachiaria spp. Also, a higher proportion of biomass allocated to leaves was observed in flooded Leontodon taraxacoides (Asteraceae) by Grimoldi et al (1999). In contrast, Mattos et al (2005) reported that flooding caused a lower LMR in Brachiaria spp.…”