Exotic invasive aquatic weeds such as alligator weed (Alternanthera philoxeroides) threaten native ecosystems by interfering with native plant communities, disrupting hydrology, and diminishing water quality. Development of new tools to combat invaders is important for the well being of these sensitive areas. Integrated pest management offers managers an approach that combines multiple control methods for better control than any one method used exclusively. In a greenhouse and field study, we tested the effects of selective herbicide application frequency, native competitor plant introduction, and their integration on alligator weed. In the greenhouse study, alligator weed shoot, root, and total biomass were reduced with one herbicide application, and further reduced with two. Alligator weed cumulative stem length and shoot/root ratio was only reduced after two applications. In the greenhouse, introduction of competitors did not affect alligator weed biomass, but did affect shoot/root ratio. The interaction of competitor introduction and herbicide did not significantly influence alligator weed growth in the greenhouse study. In the field, alligator weed cover was reduced after one herbicide application, but not significantly more after a second. Introduction of competitor species had no effect on alligator weed cover, nor did the interaction of competitor species and herbicide application. This study demonstrates that triclopyr amine herbicide can reduce alligator weed biomass and cover, and that two applications are more effective than one. To integrate selective herbicides and native plant introduction successfully for alligator weed control, more research is needed on the influence competition can potentially have on alligator weed growth, and the timing of herbicide application and subsequent introduction of plants.

Made available in DSpace on 2014-08-20T13:59:15Z (GMT). No. of bitstreams: 1 tese_marcia_vaz_ribeiro.pdf: 713659 bytes, checksum: 2dc33e63ce136dffc6ae1dfd420cfab3 (MD5) Previous issue date: 2011-10-31 / The medicinal Alternanthera (Amaranthaceae) species, such as A. philoxeroides, present a great variety of bioactive compounds, among which are the betacyanins, nitrogen pigments that belong to the betalains class. These compounds are widely used as additives for food and drugs, due to their antioxidant action and lack of toxicity, which have already been proven. Techniques have been developed in order to improve productivity and performance of this pigment, one of those is the use of in vitro elicitors or in vivo stressing agents. Both have an important role in the transduction process of signals that regulate the defense genes in plants, acting as stimulators of production or degradation of several primary and secondary metabolites. This work aimed to assess, in A. philoxeroides plants, the growth and production characteristics of betacyanin in in vitro plants; the levels of photosynthetic pigments, betacyanins, lipid peroxidation and antioxidant enzymes activity in in vivo plants under salt stress, and also to quantify the level of betacyanin and the 5GT-DBs gene expression in the biosynthetic route of this compound in in vitro plants submitted to elicitation by NaCl and by tyrosine. For this, three trials were conducted. In the first one, A. philoxeroides explants were inoculated in MS medium with increasing NaCl concentrations (0, 50, 100, 150, 200 and 250 mM) for 35 days. In the second one, plants from in vitro cultures were acclimatized in greenhouses and irrigated with a sodium chloride solution (0, 200 and 400 mM) for 30 days. The third trial had two essays, one composed of in vitro A. philoxeroides plants in a liquid MS medium in vermiculite substrate for 35 days. After this period, a NaCl solution (400 mM) was added to the medium and the shoots were collected after 0, 12, 24, 36 and 48 hours of exposure. In the second one, nodal segments were inoculated in MS medium with and without tyrosine (0 e 75 µM), and its aerial parts were collected after 35 days. In the growth analysis, reduction of the averages was observed for the following variables: height, number of shoots, number of sprouts and root number and length; for the plants that have grown in the sodium chloride medium. The highest concentrations of betacyanins were found in the stalks of plants from MS medium, with 50 mM of NaCl. After 30 days of in vivo cultivation, the levels of chlorophyll a, chlorophyll b and carotenoids decreased as the salt concentration increased, while the reason of chlorophyll a/b in plants submitted to a higher salt concentration presented a difference in comparison to the control. Higher levels of betacyanin were observed on stalks, when compared to the leaves, in the highest salt concentrations. On the leaves, there was a significant increase of lipid peroxidation and superoxide dismutase activity. On the roots, there was an increase of enzymes catalase and ascorbate peroxidase. Regarding the analysis of differential expression (qRT-PCR), it was possible to observe that from 12 to 24 hours of salt stress, the 5-GT gene expression firstly increased, then there was a decrease in 36 hours and a new increase in 48 hours. The 5-GT gene also showed increased expression as a response to tyrosine. It was possible to conclude that A. philoxeroides elicited in vitro with sodium chloride present a decrease of the assessed morphological parameters, but in low concentrations betacyanin synthesis is stimulated. Salt stress causes greater degradation in the photosynthetic pigments, increment of betacyanin synthesis in stalks and damage to the cell membranes of the leaves. The increase of antioxidant enzymes activity stimulated the protective system against oxidative stress on in vivo A. philoxeroides plants. It is suggested that in this species, the enzyme bethanidine 5-Oglucosyltransferase reaches its highest expression in 48 hours of exposure to salt elicitation and also when grown in a medium containing tyrosine. / As espécies medicinais do gênero Alternanthera (Amaranthaceae) como A. philoxeroides apresentam uma variedade de compostos bioativos, entre eles as betacianinas, que são pigmentos nitrogenados pertencentes à classe das betalaínas. Esses compostos são amplamente utilizados como aditivos de produtos alimentícios e medicamentos devido à sua comprovada ação antioxidante e ausência de toxicidade. Técnicas têm sido desenvolvidas para aprimorar a produtividade e o rendimento deste pigmento, sendo uma delas o uso de elicitores in vitro ou agentes estressantes in vivo. Ambos apresentam um importante papel no processo de transdução de sinais que regulam os genes de defesa nas plantas, agindo como estimuladores para a produção e ou degradação de diversos metabólitos, tanto primários quanto secundários. Assim, o objetivo do presente trabalho foi avaliar em plantas de A. philoxeroides, as características de crescimento e produção de betacianina em plantas cultivadas in vitro; os teores dos pigmentos fotossintéticos, betacianinas, peroxidação lipídica e atividade de enzimas antioxidantes em plantas cultivadas in vivo, sob estresse salino, além de, quantificar o teor de betacianina e a expressão do gene 5GT-DBs envolvido na rota biossintética, deste composto, em plantas in vitro submetidas à elicitação por NaCl e pelo aminoácido tirosina. Para isso, foram conduzidos três experimentos. No primeiro, explantes de A. philoxeroides foram inoculados em meio MS, com concentrações crescentes de NaCl (0, 50, 100, 150, 200 e 250 mM), durante 35 dias. No segundo, plantas provenientes da cultura in vitro foram aclimatizadas em casa de vegetação e irrigadas com solução de cloreto de sódio (0, 200 e 400 mM), por 30 dias. O terceiro experimento contou com dois ensaios, sendo o primeiro composto de plantas de A. philoxeroides cultivadas in vitro, em meio MS líquido, no substrato vermiculita, durante 35 dias. Após esse período, foi adicionada ao meio, solução de NaCl (400 mM) e coletada a parte aérea das plantas após 0, 12, 24, 36 e 48 horas de exposição ao sal, Já o segundo, segmentos nodais foram inoculados em meio MS, na presença e ausência de tirosina (0 e 75 µM), tendo sua parte aérea coletada após 35 dias de cultivo. Nas análises de crescimento observou-se redução das médias para as variáveis altura, número de gemas, número de brotos e no número e comprimento de raiz, nas plantas crescidas nos meios contendo cloreto de sódio. As maiores concentrações de betacianinas foram encontradas nos caules de plantas cultivadas em meio MS com 50 mM de NaCl. Após 30 dias de cultivo in vivo os teores de clorofilas a, clorofila b, e carotenóides decresceram à medida que aumentou a concentração de sal, enquanto a razão clorofila a/b das plantas submetidas à maior concentração de sal apresentou