Role of plant functional traits in the invasion success: analysis of nine species of Asteraceae.

Various attributes are hypothesized to facilitate the dominance of an invasive species in non-native geographical and ecological regimes. To explore the characteristic invasive attributes of the family Asteraceae, a comparative study was conducted among nine species of this family, co-occurring in the western Himalayan region. Based on their nativity and invasion status, the species were categorized as "Invasive", "Naturalized", and "Native". Fifteen plant functional traits, strongly linked with invasion, were examined in the test species. The analyses revealed a strong dissimilarity between all the plant functional traits (except leaf carbon [Leaf C]) represented by "Invasive" and "Native" categories and most of the traits (except leaf area [LA], leaf nitrogen [Leaf N], Leaf C, and leaf carbon-nitrogen ratio [C: N]) represented by the "Naturalized" and "Native" categories. Similarly, "Invasive" and "Naturalized" categories also varied significantly for most of the traits (except Leaf N, Leaf C, capitula per m² population [Cm²], seeds per capitula [Scapitula], and seed mass). Invasive species are characterized by high LA, specific leaf area [SLA] and germination, and low C:N and leaf construction costs [LCC]. Most of the traits represented by native species justify their non-invasive behavior; whereas the naturalized species, despite having better size metrics (plant height), resource investment strategy (aboveground non-reproductive biomass [BNR], and aboveground reproductive biomass [BR]), and reproductive output (capitula per individual plant [Cplant], and seeds per individual plant [Splant]) failed to invade, which implies that the role of these functional aspects in imparting invasion potential to a species is not consistent in all the ecosystems and/or phylogenetic groups. Results of PCA revealed that trait divergence plays a more imperative role in invasion success than naturalization in the species of the family Asteraceae. The present study is intended to refine the pre-generalized invasion concepts associated with family Asteraceae to ensure more accurate identification of the potential invaders and better management of the existing ones.

Toxic nonpreferred species accelerate the natural restoration of plant productivity and diversity in degraded grasslands.

Long-term overgrazing may lead to the degradation of grasslands which are often characterized by an increase in nonpreferred species, especially toxic plants. However, the impact of these toxic nonpreferred species on the restoration processes of degraded grasslands is not well understood, particularly their interactions with soil properties and other plant functional groups. To address this knowledge gap, we conducted an in situ grazing exclusion experiment in a temperate degraded grassland of Inner Mongolia, China. The objective of this study was to investigate how toxic nonpreferred plants influence the recovery of plant diversity and productivity in degraded grasslands and whether these effects can be explained by changes in soil properties. Our findings revealed that Stellera chamaejasme, a toxic nonpreferred species widely distributed in North China, directly altered plant community composition and improved species diversity in degraded grasslands dominated by Asteraceae plants. The presence of S. chamaejasme could inhibit Asteraceae abundance and increase soil copper content in this study area, because Asteraceae plants have a high copper accumulation capacity. Within the communities with S. chamaejasme, the alleviation of soil copper limitation to plants may subsequently enhance the abundance and aboveground productivity of Poaceae and Forbs. Our study demonstrated that the strong direct and indirect interactions of toxic nonpreferred species with other ecosystem components promoted competitive release in terms of biomass accumulation and species diversity. The change of soil limiting microelements content caused by toxic species exerts an important mediation function during the recovery process of degraded grasslands. Thus, these toxic nonpreferred species can act primarily as accelerators for the restoration of community structure and ecosystem function in degraded grasslands.

Isoprenoid emissions from Schima superba and Cunninghamia lanceolata: Their responses to elevated temperature by two warming facilities.

Isoprenoids (including isoprene (ISO) and monoterpenes (MTs)) are the majority of biogenic volatile organic compounds (BVOCs) which are important carbon-containing secondary metabolites biosynthesized by organisms, especially plant in terrestrial ecosystem. Results of the warming effects on isoprenoid emissions vary within species and warming facilities, and thus conclusions remain controversial. In this study, two typical subtropical tree species seedlings of Schima superba and Cunninghamia lanceolata were cultivated under three conditions, namely no warming (CK) and two warming facilities (with infrared radiators (IR) and heating wires (HW)) in open top chamber (OTC), and the isoprenoid emissions were measured with preconcentor-GC-MS system after warming for one, two and four months. The results showed that the isoprenoid emissions from S. superba and C. lanceolata exhibited uniformity in response to two warming facilities. IR and HW both stimulated isoprenoid emissions in two plants after one month of treatment, with increased ratios of 16.3 % and 72.5 % for S. superba, and 2.47 and 5.96 times for C. lanceolata. However, the emissions were suppressed after four months, with more pronounced effect for HW. The variation in isoprenoid emissions was primarily associated with the levels of Pn, Tr, monoterpene synthase (MTPS) activity. C. lanceolata predominantly released MTs (mainly α-pinene, α-terpene, γ-terpene, and limonene), with 39.7 % to 99.6 % of the total isoprenoid but ISO was only a very minor constituent. For S. superba, MTs constituted 24.7 % to 96.1 % of total isoprenoid. It is noteworthy that HW generated a greater disturbance to physiology activity in plants. Our study provided more comprehensive and more convincing support for integrating temperature-elevation experiments of different ecosystems and assessing response and adaptation of forest carbon cycle to global warming.

The hidden diversity of vascular patterns in flower heads.

Vascular systems are intimately related to the shape and spatial arrangement of the plant organs they support. We investigate the largely unexplored association between spiral phyllotaxis and the vascular system in Asteraceae flower heads. We imaged heads of eight species using synchrotron-based X-ray micro-computed tomography and applied original virtual reality and haptic software to explore head vasculature in three dimensions. We then constructed a computational model to infer a plausible patterning mechanism. The vascular system in the head of the model plant Gerbera hybrida is qualitatively different from those of Bellis perennis and Helianthus annuus, characterized previously. Cirsium vulgare, Craspedia globosa, Echinacea purpurea, Echinops bannaticus, and Tanacetum vulgare represent variants of the Bellis and Helianthus systems. In each species, the layout of the main strands is stereotypical, but details vary. The observed vascular patterns can be generated by a common computational model with different parameter values. In spite of the observed differences of vascular systems in heads, they may be produced by a conserved mechanism. The diversity and irregularities of vasculature stand in contrast with the relative uniformity and regularity of phyllotactic patterns, confirming that phyllotaxis in heads is not driven by the vasculature.

Physical quality of seeds of Moquiniastrum polymorphum / Qualidade física de sementes de Moquiniastrum polymorphum

Abstract This study aimed to analyze the physical properties of the seeds of Moquiniastrum polymorphum when processed by mini-SAS, X-ray and seed blower systems. The seeds were purchased from Seeds Caiçara, located in Penápolis-SP. After purchase, the seed lot was characterized by standard tests. In the X-ray test the seeds were classified according to their internal morphology as filled, unfilled or malformed. The seed blower was set at six opening settings, resulting in light and heavy fractions. The evaluations were performed by weighing the seeds that remained in the blower (heavy fraction) and by the amount of filled seeds indicated by the X-ray test. The germination tests were composed of four replicates of 50 seeds. The mini-SAS was used for external evaluation. It was concluded that the combined use of the seed blower and the X-ray test was efficient for the evaluation and determination of the physical quality of the seeds of M. polymorphum. The seed blower at opening settings 5 resulted in the best lot quality. The external parameters were not able to qualitatively evaluate the seeds of M. polymorphum.

Resumo O presente estudo objetivou analisar as propriedades físicas das sementes de Moquiniastrum polymorphum por meio dos equipamentos raios-X, mini-SAS e soprador de sementes. As sementes foram adquiridas da empresa Sementes Caiçara em matrizes localizadas no município de Penápolis-SP. Após adquirido e beneficiado, o lote de sementes foi caracterizado por meio de testes padrões. No teste de raios-X as sementes foram classificadas de acordo com sua morfologia interna como cheias, vazias ou mal formadas. O soprador de sementes foi ajustado em seis aberturas, resultando em frações leves e pesadas. As avaliações foram realizadas pesando-se as sementes que permaneceram no soprador (fração pesada) e pela quantidade de sementes cheias pela análise de raios-X. Posteriormente foram realizados testes de germinação compostos por quatro repetições de 50 sementes. Na avaliação externa das sementes utilizou-se o equipamento mini-SAS. Após análise dos dados, concluiu-se que a utilização em conjunto dos equipamentos soprador de sementes e raios-X foi eficiente para avaliação e determinação da qualidade física das sementes de M. polymorphum. O soprador de sementes na regulagem da abertura 5 resultou na melhor qualidade do lote. Os parâmetros externos não foram capazes de avaliar qualitativamente as sementes de M. polymorphum.

Can climate and soil conditions change the morpho-anatomy among individuals from different localities? A case study in Aldama grandiflora (Asteraceae) / Condições climáticas e de solo podem alterar a morfo-anatomia entre indivíduos de diferentes localidades? Um estudo de caso em Aldama grandiflora (Asteraceae)

Abstract Vegetative aerial organs are considerably more exposed to environmental conditions and can reflect the specific adaptations of plants to their local environment. Aldama grandiflora species are known to be widely distributed in Brazil; therefore, individuals from different populations of this species are thought to be exposed to different abiotic and biotic conditions. Several anatomical studies conducted on Brazilian Aldama species have mainly focused on the qualitative anatomical characters or traits of these species, but not on their quantitative traits. In this study, we evaluated whether climate and soil conditions can change the morphometry among individuals of A. grandiflora collected from six sites in the Goiás State, Brazil, by assessing their anatomical characters. Further, soil sampling was performed, and climate data were collected from all the six sites. The analysis indicated few statistical differences among the populations evaluated, showing that A. grandiflora presented consistent leaf and stem anatomical characteristics. The small morpho-anatomical differences found among individuals of the different populations evaluated, reflected the soil conditions in which these populations were grown. Therefore, environmental factors have a significant influence on the morpho-anatomy of Aldama grandiflora.

Resumo Os órgãos vegetativos aéreos estão consideravelmente mais expostos às condições ambientais e podem refletir as adaptações específicas das plantas ao seu habitat. A espécie Aldama grandiflora é amplamente distribuída no Brasil e, dessa forma, indivíduos de diferentes populações podem estar expostos a diferentes condições ambientais. Vários estudos anatômicos realizados com espécies brasileiras do gênero Aldama têm abordado, principalmente, as características anatômicas qualitativas dessas espécies, mas não em suas características quantitativas. Neste estudo avaliamos se as condições climáticas e do solo podem alterar a morfometria entre os indivíduos de A. grandiflora coletados em seis populações do Estado de Goiás. Foram avaliados os caracteres anatômicos foliares e caulinares, além da amostragem do solo e coleta de dados climáticos, para os seis locais. A análise indicou algumas diferenças estatísticas entre as populações avaliadas, mostrando que A. grandiflora apresentou características anatômicas foliares e caulinares bastante consistentes. As pequenas diferenças morfo-anatômicas encontradas entre indivíduos das diferentes populações avaliadas, refletiram as condições do solo nos quais essas populações se desenvolveram. Assim sendo, fatores ambientais relacionados ao clima e condições do solo têm uma influência significativa sobre a morfo-anatomia de Aldama grandiflora.

Pérdida de pubescencia foliar y sus efectos fisiológicos en Espeletia paipana(Asterales, Asteraceae), en el departamento de Boyacá-Colombia / Loss of leaf pubescence and its physiological effects on Espeletia paipana (Asterales, Asteraceae), in the Boyacá-Colombia department

Espeletia paipanaes una roseta caulescente gigante en peligro de extinción, endémica del departamento de Boyacá. Con el fin de establecer si una enfermedad en la planta, atribuida a la acción patogénica de microorganismos endófitos y caracterizada por la pérdida de pubescencia foliar (PPF), puede ser causante de la acelerada mortandad poblacional, se evaluó el desempeño fisiológico de la especie con y sin PPF. La incidencia (% de hojas afectadas por cada uno de los 27 individuos de la población actual) y severidad (% de área foliar afectada en 135 hojas) de la PPF fueron monitoreadas durante un periodo de nueve meses, en tres zonas topográficas a diferentes altitudes. Parámetros fisiológicos como conductancia estomática (Gs) y temperatura foliar (Tfol) e índice de contenido de clorofila (ICC) fueron medidos en hojas sanas y enfermas durante cuatro días consecutivos, tanto en la época seca como en la época húmeda. El estudio fue complementado con aislamientos y pruebas de patogenici-dad para identificar el agente causal de la PPF. En general, aunque la incidencia de la enfermedad en E. paipanafue constante a lo largo del tiempo, la severidad avanzó superando el 60 % del área foliar. El aumento de la severidad en el haz fue atribuido al efecto foto-oxidativo de las altas radiaciones entre las 11:00 y14:00 h. La reducción del área foliar funcional a causa de la PPF, llevó a una baja Gs con serias implicaciones en la fijación de carbono, y por tanto limitando el crecimiento y la renovación de biomasa. El efecto estacional en la Tfol varió de acuerdo con la zona topográfica, mientras que el ICC no presentó un patrón definido con relación a la PPF; sus valores bajos podrían estar relacionados con la producción de otros pigmentos. Finalmente, aunque no es posible asegurar que Botrytissp. es el causante de la pérdida de pubescencia foliar, se postula como el agente causal más probable debido a su alta representatividad en los aislamientos y su potencial de infección durante las pruebas de patogenicidad. En general, la reducción de biomasa foliar sana y disminución del rendimiento fisiológico sugieren que la PPF afecta negativamente la sobrevivencia de E. paipana,lo que significa que el uso de biocontroladores podría ser una estrategia para el rescate poblacional.

Espeletia paipanais an endangered giant caulescent rosette endemic to Boyacá department. In order to establish whether a plant disease, characterized by the loss of leaf pubescence (PPF) and attributed to the pathogenic action of endophytic microorganisms, is the cause of the increasing mortality of population, the physiological performance of the species was evaluated with and without PPF. The incidence (% leaves affected in each of the 27 individuals in the current population) and severity (% leaf area affected on 135 leaves) of the PPF were monitored over a period of nine months, in three topographic zones of different heights. During four consecutive days in both dry and wet season, physiological parameters as chlorophyll content index (ICC), stomatal conductance (Gs) and leaf temperature (Tfol) were measured in healthy and affected leaves. The study was complemented with isolations and pathogenicity tests to identify the causal agent of the PPF. Overall, although the disease incidence in E. paipanawas constant over time, the severity progressed surpassing 60 % of the leaf area. The increasing of severity in the upper side of leaves was attributed to the photo-oxidative effect of high radiation between 11:00 h and 14:00 h of the day. The reduction of functional leaf area because of the PPF, led to low Gs with serious implications for carbon fixation and thus limiting growth and biomass renewal. The effect of season in Tfol varied according to the topographic zone, while the ICC did not present a defined pattern with respect to the PPF; its low values could be associated with the production of other pigments. Finally, although it is not possible to ensure that Botrytissp. is the causative of the loss of leaf pubescence, it is postulated as the most probably causal agent due to its high representativeness in the isolates and its infectious potential during the pathogenicity tests. In general, the reduction of healthy leaf biomass and decrease of physiological performance suggest that PPF affect negatively the survival of E. paipana,which means that the use of biological controllers could be a strategy to mitigate its effect on the population.

Compostas ­ uma abordagem antroposófica / Composite family ­ an anthroposophic approach

As plantas da família Compositae (Asteraceae) estão distribuídas por todo o globo terrestre e são largamente utilizadas para fins medicinais, entre outras aplicações. Uma abordagem botânica ampliada pela antroposofia permite classificar as compostas em grupos de acordo com a dinâmica das forças vitais na planta, a qual se reflete nas suas indicações terapêuticas. Distinguem-se claramente três grupos de compostas, atuantes respectivamente sobre cada sistema orgânico do ser humano: neurossensorial, rítmico e metabólico. A seguir é apresentada uma lista das indicações terapêuticas das compostas mais importantes, com base nos compêndios antroposóficos oficialmente reconhecidos para fins de registro de medicamentos.(AU)

The plants of the Compositae (Asteraceae) family are spread all over the globe and they are widely used for medicinal purposes, among other applications. An anthroposophic extended botanic approach allows classifying Compositae in groups according to the vital forces dynamics in the plant, which is reflected in its therapeutic indications. Three groups of Compositae are clearly recognizable, with effects respectively on each organic system of the human being: neurosensory, rhythmic and metabolic systems. A list of the therapeutic indications of the most important Compositae is presented, based on the officially recognized compendia for medicines registration. (AU)

Morpho-anatomical features of underground systems in six Asteraceae species from the Brazilian Cerrado

In the Brazilian Cerrado (neotropical savanna), the development of bud-bearing underground systems as adaptive structures to fire and dry periods can comprise an important source of buds for this ecosystem, as already demonstrated in the Brazilian Campos grasslands and North American prairies. Asteraceae species from both woody and herbaceous strata have subterranean organs that accumulate carbohydrates, reinforcing the adaptive strategy of these plants to different environmental conditions. This study aims to analyse the morpho-anatomy of underground systems of six species of Asteraceae (Mikania cordifolia L.f. Willd., Mikania sessilifolia DC, Trixis nobilis (Vell.) Katinas, Pterocaulon alopecuroides (Lam.) DC., Vernonia elegans Gardner and Vernonia megapotamica Spreng.), to describe these structures and to verify the occurrence and origin of shoot buds, and to analyse the presence of reserve substances. Individuals sampled in Cerrado areas in São Paulo State showed thick underground bud-bearing organs, with adventitious or lateral roots and presence of fructans. Xylopodium was found in all studied species, except for Trixis nobilis, which had stem tuber. The presence of fructans as reserve, and the capacity of structures in the formation of buds indicate the potential of herbaceous species of Asteraceae in forming a viable bud bank for vegetation regeneration in the Brazilian Cerrado.

No Cerrado brasileiro (savana neotropical), o desenvolvimento de sistemas subterrâneos que produzem gemas, como estruturas adaptativas contra o fogo e períodos de seca, pode compreender um importante suprimento de gemas para esse ecossistema, como já demonstrado nos campos brasileiros e nas pradarias norte-americanas. Espécies de Asteraceae tanto do estrato lenhoso, quanto do herbáceo têm órgãos que acumulam carboidratos, reforçando a estratégia adaptativa dessas plantas a diferentes condições ambientais. Este estudo tem o objetivo de analisar a morfo-anatomia de sistemas subterrâneos de seis espécies de Asteraceae (Mikania cordifolia L.f. Willd., Mikania sessilifolia DC, Trixis nobilis (Vell.) Katinas, Pterocaulon alopecuroides (Lam.) DC., Vernonia elegans Gardner e Vernonia megapotamica Spreng.), para descrever essas estruturas e verificar a ocorrência e origem de gemas caulinares, e analisar a presença de substâncias de reserva. Indivíduos amostrados em áreas de Cerrado no Estado de São Paulo apresentaram órgãos subterrâneos espessados produtores de gemas, com raízes adventícias ou laterais e presença de frutanos. Em todas as espécies estudadas foi constatada a presença de xilopódio, com exceção de Trixis nobilis, a qual apresentou caule tuberoso. A presença de frutanos como reserva e a capacidade de estruturas na formação de gemas indicam o potencial de espécies herbáceas de Asteraceae em formar um banco de gemas viável para regeneração da vegetação no Cerrado brasileiro.

Tetranychus urticae (Acari: Tetranychidae) on Gerbera jamesonii Bolus and Hook (Asteraceae) / Biologia de Tetranychus urticae (Acari: Tetranychidae) em Gerbera jamesonii Bolus and Hook (Asteraceae)

Gerbera (Gerbera jamesonii Bolus and Hook,) is an ornamental Asteraceae of great commercial value, and pests can affect adversely its cultivation. More than 20 species of arthropods cause economic damage on gerbera, among them the two spotted mite, Tetranychus urticae Koch, 1836 (Acari: Tetranychidae), considered a key pest for this and other ornamental plants. In this work, some life-cycle aspects of T. urticae on gerbera, considered important for the knowledge of its population dynamics and for pest management programs, were studied. Mites were reared on 3-cm diameter arenas of gerbera leaf discs maintained on distilled water in Petri dishes, under laboratory conditions of 25 ºC, 70 ± 10 percent RU and 14-hour photophase, with only one egg left per arena, in a total of 262 arenas. Egg viability was 96.5 percent and 97.1 percent for unmated and mated females, respectively. Unmated females originated larvae which lived for 3.2 days and the stages of protonymph and deutonymph, 1.9 and 1.6 days, respectively; those from mated females lived 3.5 days and for protonymphs and deutonymphs, 2.0 and 1.6 days, respectively. Except for the duration of one generation (T), with similar values, 18.6 and 19.7 days, respectively for unmated and mated females, the net reproductive rate of increase (Rº), the innate capacity to increase in number (r m) and the finite rate of growth (λ) were different for mated and unmated females, respectively 11.5 and 24.6 for R0; 0.12 and 0.17 for r m and 1.13 and 1.19 for λ.

A gérbera, Gerbera jamesonii Bolus and Hook, é uma planta ornamental pertencente à família Asteraceae de grande valor comercial. Dentre os vários fatores que podem afetar adversamente o seu cultivo se encontram as pragas. Mais de 20 espécies de artrópodes causam danos econômicos em gérbera, entre elas encontra-se o ácaro-rajado, Tetranychus urticae Koch, 1836 (Acari: Tetranychidae), considerado praga-chave dessa e de outras plantas ornamentais. O presente trabalho teve por objetivo estudar alguns aspectos do ciclo biológico de T. urticae em gérbera considerados importantes para o conhecimento da dinâmica populacional da espécie e para os programas de manejo de pragas. Os ácaros foram criados em arenas constituídas de discos de folhas de gérbera de 3 cm de diâmetro, sobre água destilada, colocados em placas de Petri, em condições de laboratório, a 25 ºC, 70 ± 10 por cento de U.R. e 14 horas de fotofase, deixando-se um ovo por arena, perfazendo um total de 262 arenas. A viabilidade dos ovos foi de 96,5 e 97,1 por cento para fêmeas não acasaladas e acasaladas, respectivamente. As larvas provenientes de fêmeas não acasaladas tiveram duração de 3,2 dias e os estágios de protoninfa e deutoninfa foram de 1,9 e 1,6 dias, respectivamente. Já para fêmeas acasaladas a fase de larva teve uma duração de 3,5 dias, a de protoninfa e deutoninfa 2,0 e 1,6 dias, respectivamente. À exceção da duração de uma geração (T) que tiveram valores próximos, 18,6 e 19,7, respectivamente para fêmeas não acasaladas e acasaladas, a taxa líquida de reprodução (Rº), capacidade inata de aumentar em número (r m) e razão finita de crescimento (λ) foram diferentes para fêmeas acasaladas e não, sendo respectivamente 11,5 e 24,6 para R0; 0,12 e 0,17 para r m e 1,13 e 1,19 para λ.

Fotosíntesis en tres poblaciones altitudinales de la planta andina Espeletia schultzii (Compositae) / Photosynthesis in three altitudinal populations of the Andean plant Espeletia schultzii (Compositae)

Photosynthesis was compared in three altitudinal populations of Espeletia schultzii: 3,100, 3,550 and 4,200 masl. The measured parameters were Rubisco activity (EC 4.1.139), chlorophyll, soluble protein and soluble sugars contents, and specific leaf area (SLA). The 4,200 m population had a higher Rubisco activity (at 4 degrees C) followed by those at 3,550 m and 3,100 m. There were no significant differences between populations at 3,100 m and 3,550 m (ANOVA), but their activities were different from those of the 4,200 m population. Chlorophyll a content decreased slightly with elevation, while chlorophyll b was constant; therefore, the Ra/b ratio decreased with elevation, but not significantly. The leaf soluble sugars content increased along the altitudinal gradient. Leaf protein content did not differ. The SLA decreased with altitude. The increase in Rubisco activity might reflect higher enzyme activation and not higher enzyme protein. The increase in soluble sugars is probably associated to Rubisco activity. Three out of the five measured parameters revealed differences with altitude, suggesting a compromise between a higher metabolic activity and a smaller cellular volume.

Se establece una comparación de algunos parámetros fotosintéticos: actividad Rubisco (Ribulosa 1, 5-bis-fosfato carboxilasa EC 4.1.1.39) contenidos de clorofilas, azúcares solubles totales y proteínas solubles totales y área foliar específica (AFE), en tres poblaciones altitudinales de Espeletia schultzii ubicadas a 3 100, 3 550 y 4 200 msnm. De acuerdo con el análisis de varianza la población a 4 200 m presentó una actividad Rubisco significativamente mayor que las otras dos, en cuyos casos los valores no fueron diferentes. Los contenidos de clorofila a presentan una leve tendencia a la disminución con la altura; mientras que la clorofila b se mantiene constante, razón por la cual la relación a/b (R a/b) disminuye con la elevación, aunque, las diferencias no son significativas. El contenido de azúcares en cada una de las poblaciones estudiadas (gm-2), aumenta con la elevación; las diferencias entre las poblaciones son significativas. Con relación al contenido de proteínas, no existen diferencias entre las poblaciones estudiadas. El área foliar específica (AFE) disminuye significativamente con la altura. Es probable que el incremento en la actividad Rubisco sea producido por una mayor activación de la enzima y no por el mayor contenido de proteína. Los azúcares solubles presentan incremento significativo, este hecho es probable que se encuentre asociado con la actividad Rubisco. De los cinco parámetros fotosintéticos medidos, tres presentan diferencias significativas asociadas con la altitud. Esto representa un compromiso entre una mayor actividad metabólica mantenida en un menor volumen celular.

Effects of hydroclimatic anomalies on bacteriological quality of the Middle Paraná River (Santa Fe, Argentina) / Efecto de anomalías hidroclimáticas sobre la calidad bacteriológica del río Paraná Medio (Santa Fe, Argentina)

Lenitic and lotic aquatic environments were studied in the Middle Paraná River basin, one of the largest rivers of the world (basin: 1,510,000 km2, length: 2,570 km). The Paraná River (S 31° 42’ 04"; W 60° 29’ 39"), during El Niño-Southern Oscillation (ENSO) (1997-1998), registered maximum flows of 29,962 m3 s-1(more than twice the mean flow) and also positive pluvial anomalies (A) (from +120 mm to +161 mm). However, concentrations of Escherichia coli remained low, with values similar to the mean (p > 0.05) (1.3802 log10 cfu/100 ml). Only a maximum peak (1.903 log10 cfu/100 ml), significantly higher than the mean (p < 0.0001), was detected during the ascending phase of the flood pulse. During La Niña (September 1999 - March 2000; Q =11,255 m3 s-1; A = -78 mm to -84 mm), concentrations of E. coli were significantly lower than the mean (p< 0.0001). During the post-Niña period, with normal flows (Q = 14,900 m3 s-1) but with strong positive pluvial anomalies (A= +118 mm to +377 mm), the fecal indicator density reached maximum values (up to 2.699 log10 cfu /100 ml, p< 0.0001). The multiple regression model used with all the results obtained in the Paraná River showed that variations in concentrations of E. coli are mainly explained by pluvial precipitations and hydrometric level (p = 0.001). Temporal patterns of concentrations of E. coli in a small, secondary course (Q = 101 m3 s-1) followed those of the Paraná River, but concentrations and peaks of E. coli produced by exceptional rains showed a higher magnitude (maximum: 3.325 log10 cfu /100 ml). In the floodplain lakes, away from urban centers, concentrations of E. coli were not associated to hydroclimatic anomalies, but directly to vegetable cover: maximum concentrations were always registered during periods that lakes remained covered by floating macrophytes (mainly Eichhornia crassipes); on the contrary, minimum concentrations were registered during periods without vegetable cover.

Se estudiaron ambientes acuáticos leníticos y lóticos en la cuenca del río Paraná Medio, uno de los ríos más grandes del mundo (cuenca: 1.510.000 km2, longitud: 2.570 km). El río Paraná (31° 42’ 04"S; 60° 29’39"W), durante El Niño Oscilación Sur (ENOS) (1997-1998), registró caudales máximos de 29.962 m3 s-1(más del doble del caudal medio) y también anomalías pluviales (A) positivas (desde +120mm a +161mm). Sin embargo, la concentración de Escherichia coli se mantuvo baja, con valores similares (p > 0,05) a la media (1,3802 log10ufc/100ml). Solamente se detectó un pico máximo (1,903 log10ufc/100ml) significativamente mayor a la media (p < 0,0001) durante la fase ascendente del pulso de la creciente. Durante La Niña (sept. 1999 - marzo 2000; Q =11.255 m3 s-1 ;A = -78mm a -84mm), las concentraciones de E. coli resultaron inferiores a la media (p<0,0001). Durante el período post-Niña, con caudales normales (Q = 14.900 m3 s-1) pero con fuertes anomalías pluviales positivas (A= +118 mm a +377mm), la densidad del indicador fecal alcanzó valores máximos (hasta 2,699 log10ufc /100ml, p< 0,0001).La aplicación de un modelo de regresión múltiple al conjunto de los resultados obtenidos en el río Paraná, muestra que las variaciones en la concentración de E. coli son principalmente explicadas por las precipitaciones pluviales y el nivel hidrométrico (p = 0,001). Los patrones temporales de las concentraciones de E. coli en un pequeño cauce secundario (Q = 101 m3s-1) siguieron a las del río Paraná, pero las concentraciones y los picos de E. coli producidos por lluvias excepcionales fueron de mayor magnitud (máximo: 3,325 log10ufc /100ml). Enlas lagunas de la llanura de inundación, lejos de centros urbanos, la concentración de E. coli no estuvo asociada con anomalías hidroclimáticas, sino directamente con la cobertura vegetal: las concentraciones máximas se registraron siempre durante los períodos que permanecían cubiertas con macrófitas flotantes (principalmente Eichhornia crassipes). Durante los períodos sin cobertura vegetal, por el contrario, se registraron las concentraciones mínimas de E. coli.