Revisão taxonômica das espécies de Paspalum L., grupo Parviflora (Poaceae, Paspaleae)

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Botânica, Programa de Pós-Graduação em Botânica, 2017.Poaceae é uma das maiores famílias botânicas em número de espécies e uma das mais importantes para a espécie humana, ecológica e economicamente. O gênero Paspalum L. possui mais de 350 espécies e é um dos mais diversos dentre as gramíneas (Poaceae). Nativo das Américas, possui poucas espécies fora do novo continente. Historicamente o gênero foi subdividido em grupos Informais, ou seja, grupos de espécies sem categoria taxonômica. O grupo Parviflora distingue-se por possuir touceiras com as folhas normalmente concentradas na base, espiguetas diminutas, com gluma superior e lema inferior geralmente delicados. Atualmente o grupo conta com sete espécies: P. clavuliferum C. Wright, P. crispatum Hack., P. hyalinum Nees ex Trin., P. minarum Hack., P. multicaule Poir., P. parviflorum Rhode ex Flüggé e P. scalare Trin. Todas possuem registro para o Brasil. Foram realizadas análises morfológicas e micromorfológicas das espécies do grupo Parviflora. As contribuições em Microscopia Eletrônica de Varredura são inéditas por utilizarem todas as peças das espiguetas, não só o antécio superior, e geraram caracteres importantes para a distinção das espécies do grupo. As espécies do grupo foram circunscritas; algumas espécies, como P. hyalinum e P. scalare necessitam de abordagens além da morfológica (exemplo: citogenética) para que possam ser melhor delimitadas intraespecificamente.Poaceae is one of the largest botanical families in number of species and one of the most important for the human species, ecologically and economically. Paspalum L. has more than 350 species and is one of the most diverse genera among the grasses. Native of the Americas, has few species outside of the new continent. Historically the genus was subdivided into Informal groups (groups of species without taxonomic category). The Parviflora group is distinguished by having culms with leaves normally concentrated in the base, tiny spikelets with upper glume and lower lemma usually delicate. Currently the group has seven species: P. clavuliferum C. Wright, P. crispatum Hack., P. hyalinum Nees ex Trin., P. minarum Hack., P. multicaule Poir., P. parviflorum Rhode ex Flüggé and P. scalare Trin. All are registered to Brazil. Morphological and micromorphological analyzes of the species of the Parviflora group were carried out. The contributions in Scanning Electron Microscopy are inedited, because were used all the parts of the spikelets, not only the upper anthecium, and they generated important characters for the distinction of the species of the group. The species of the Parviflora group were circumscribed; Some species such as P. hyalinum and P. scalare require approaches other than morphology (e.g. cytogenetics) to be better delimited intraspecifically

Nutrient enrichment changes water transport structures of savanna woody plants

Brazilian savanna is a seasonally dry biome, highly diverse and distributed mainly on nutrient-limited soils. Interactions between water stress and nutrient availability are important evolutionary filters in these environments. Previous evidence indicated that reducing the nutritional limitation increases growth rate, optimizes water transport and decreases stomatal conductance in woody plants. However, the anatomical mechanisms that explain such responses are not well-understood. We studied the effects of long-term (20 years) nutrient addition (N, NP and P) on soil chemistry and hydraulic morphological and anatomical traits in six dominant woody savanna species. Nutrient addition and decrease in soil moisture, probably related to changes in grass cover, influenced the plant hydraulic traits at the anatomical level, namely increasing the xylem vessels’ diameter. Consequently, the specific theoretical xylem conductivity (Ktx) increased in five species under NP and P addition. Additionally, the stomatal pore index (SPI) decreased with species-specific responses regarding the intrinsic water use efficiency (iWUE). Four species had higher vulnerability to cavitation (lvul) under NP and P addition. Using community-weighted mean and structural equation modeling approaches, we observed that nutrient enrichment at the community level did not affect iWUE, while the vulnerability to cavitation (lvul) strongly increased. The Ktx and SPI were positively and negatively affected by nutrient addition, respectively, but the effects were not as strong as expected due to contrasting species responses. These changes optimized water transport with a hydraulic safety cost and reduced water loss. In comparison with responses to N addition, the greater P-limitation in Cerrado vegetation explains the inter-specific convergence in the responses of P-fertilized individuals. We showed that long-term responses to increased nutrient availability in dystrophic soils include anatomical changes in savanna woody vegetation with relevant interactions with soil-plant–atmosphere water relations.Fil: Silva Costa, Lucas. Universidade do Brasília; BrasilFil: De Moura, Clapton Olimpio. Universidade do Brasília; BrasilFil: Bucci, Sandra Janet. Universidad Nacional de la Patagonia "San Juan Bosco". Instituto de Biociencias de la Patagonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biociencias de la Patagonia; ArgentinaFil: Sonsin-Oliveira, Julia. Universidade do Brasília; BrasilFil: Gomes, Sueli Maria. Universidade do Brasília; BrasilFil: Da Cunha Bustamante, Mercedes Maria. Universidade do Brasília; Brasi