poster f2

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Materials and methods TOF and TLA seeds were collected from various locations in Columbus and Wooster, OH. Seeds were germinated and grown in four environments: 2 light condition (full light vs. green shade)*2 soil moisture (wet vs. dry) 8 replicates; split-plot design with light condition as the main plot effect (n=2*2*2*8=64) Plants were maintained in greenhouse from Sep. to Dec. 2005, and were then harvested, separated into different parts, oven dried and weighted. Soil pH and electric conductivity (EC) was measured before harvest. Acknowledgments We thank Emilie Regnier and Maria Miriti for comments and suggestions, Steven St Martin and Bert Bishop for statistical advice, David Snodgrass and Jim Vent for greenhouse care. Introduction Exotic noxious plants, including invasive plants and exotic weeds, have caused huge economic loss and ecological damage around the world. In order to predict the noxious potential of proposed species and thus prevent further introductions of possible invasive species as crops or ornamental plants, identification of biological and ecological traits associated with invasiveness and weediness becomes extremely important. It was suggested that weeds were usually generalists that can survive and reproduce in a wide range of environments, i.e., they were quite plastic in response to different environments (Baker 1974). Following this idea, phenotypic plasticity has been recently proposed as an indicator and predictor for weeds and invasive plants (Sultan 2001). The objective of this study is to test the above hypothesis using two exotic dandelion species: Taraxacum officinale (TOF hereafter), a widespread weed, and T. laevigatum (TLA hereafter), which is only found in several locations. Both species were grown in four different environments. Phenotypic plasticity was then compared between TOF and TLA. Results Conclusions The results indicated that when grown in different environments, Taraxacum officinale was more plastic than T. laevigatum in traits related to morphology, allocation, and soil property. High phenotypic plasticity may allows T. officinale to search and capture resources (such as light and water) more efficiently when environment changes, and be able to survive, persist, and reproduce in a wider range of habitats. This is probably why T. officinale is a more successful exotic noxious plant than its close relative, T. laevigatum . This conclusion could be very useful when trying to evaluate the potential invasiveness and weediness of an exotic plant species of high horticulture value. Phenotypic plasticity as an indicator for exotic noxious plants Jing Luo¹, David Tay², John Cardina¹ ¹Department of Horticulture and Crop Science, ²Ornamental Plant Germplasm Center, The Ohio State University, Columbus, Ohio 43210 Literature cited Baker HG. 1974. The evolution of weeds. Annual Review of Ecology and Systematics 5:1-24 Sultan SE. 2001. Phenotypic plasticity for fitness components in Polygonum species of contrasting ecological breadth. Ecology 82(2):328-43 Fig. 2 Green filter (roscolux #4430, Rosco Laboratories Inc. Stamford, CT) , instead of neutral shade cloth, was used for shade treatment. Green filter is better than shade cloth because it simulates e light competition environment with other vegetation: reduced red light and increased infrared:red ratio. Fig. 3. This graph shows how CV (coefficient of variance) was calculated and compared between TOF and TLA. CV was used as an index of phenotypic plasticity – larger CV means more plastic, and vice versa. CV was first calculated on 4 plants grown in different environments for each species in each replicate, and then compared between species using type 3 t-test to see if one species is more plastic than the other. Future study Another study is being carried out including a third dandelion species with unknown weediness potential. Nutrient level is also included as another environmental factor. This study will be more concentrated on fitness components such as reproduction, seed germination, and seedling establishment. Fig. 1 Morphology, Ohio distribution, and seed color of Taraxacum officinale (TOF, weedy), and T. laevigatum (TLA, non-weedy). TOF and TLA are both native to Europe. The former usually has less indented leaves and produces brown-colored seeds. Leaves are more deeply-indented for the later one with red-colored seeds. Although very similar in morphology, TOF is a wide spread noxious weed found in all Ohio counties, while TLA has only limited distributions in Ohio. Fig. 4. Mean CV (+ 1 SE) of TOF and TLA for eight traits. Asterisk indicates significant difference between two species (P<0.05, type 3 t-test). Notice that TOF, the weedy species, had larger CVs for most traits than TLA, the non-weedy species. Fig. 5. Least square mean (+1 SE) of: (a) height, (b) shoot:root ratio, and (c) soil pH for both species in four different environments. CVs of these three traits were significantly different between TOF and TLA (see Fig. 4). Notice that TOF expanded in a wider range than TLA in these three trait, which indicates TOF is more plastic than TLA when grown in various environments. TOF and TLA were significantly different in many traits including height, leaf shape index, soil pH, and EC. However, there were not many significant interactions between species and environments except diameter and soil EC. (Table 1) CV (coefficient of variance) was calculated as an index of phenotypic plasticity (Fig. 3). TOF generally had larger CVs than TLA, and was significantly (P<0.05) more plastic in diameter, shoot:root ratio, and soil pH (Fig. 4) TOF expanded a wider range than TLA for the above three traits in different environments. For TOF, rosette diameter decreased when shaded, probably due to a more upward arrangement of leaves to capture light. Rosette diameter increased for TLA, accompanied by a less increase in height when shaded. Shoot:root ratio decreased in a larger extend for TOF in dry environment, which allowed it to search for more water by investing more biomass in root tissue (Fig. 5). Soil pH and EC was significantly different for the two species, probably due to different root exudates. Further study is needed to investigate if there is any allelopathic effect related to this pH differences. http://aoki2.si.gunma-u.ac.jp/