Microhabitat and plant structure of Characeae (Chlorophyta) populations in streams from São Paulo State, southeastern Brazil

Microhabitat distribution was investigated in five populations of Characeae (two of Chara guairensis, two of Nitella subglomerata and one of Nitella sp.) to determine the distributional patterns, the morphometric and reproductive adaptations to varying environmental conditions and niche width on a scale of few centimeters. Variations in physical variables revealed some general trends of microhabitat distribution for the Characeae populations studied, with occurrence under the following conditions: slow and narrow current velocities; substrata predominantly composed of small particle size (sand-clay); variable and generally low depths. In terms of morphological adaptations, we found some general patterns: plants with longer whorl branchlets also had longer internodes in all populations studied, whereas longer plants had also thicker axis. The former were generally associated with higher biomass (percent cover). Few correlations of morphological characters were observed with environmental variables (e.g. plant length with irradiance: negative in two populations and positive in one population). Despite the general patterns of occurrence mentioned above, our results also indicated that each population differed in its responses to environmental variables and had particular morphological and reproductive adaptations. The Characean populations occurred under a narrower range of microhabitat conditions than other macroalgae from lotic habitats, particularly lower current velocity (6.7-9.8 cm s(-1)) and a more specific substratum type (sand-clay). Niche width values (0.60-0.99) of the Characeae populations studied indicate a high degree of habitat specialization and are among the highest yet found in lotic macroalgae. The relatively narrow variations in microhabitat conditions and high niche widths here reported for Characean populations, suggest a lower tolerance to variations in current velocity, depth, irradiance and substratum type. These characteristics probably explain the relatively restricted distribution of Characeae species in streams of S (a) over tildeo Paulo State with low frequency of records in most regions.

Nitrogen redistribution to sorghum grains as affected by plant competition

An experiment was conducted to study nitrogen absorption and translocation in grain sorghum plants during their reproductive growth. Sorghum was grown in four row spacings: 50 and 70 cm in single rows, 80 and 120 cm in double rows 20 cm apart. Plant populations were 71000, 142000 and 213000 plants/ha. After flowering, samples were taken at 12 day intervals, and the plants were divided into grains and stover, where N was analyzed. There was an increase in N concentration in lower plant populations and in wider row spacings. However, total nitrogen accumulation (in kg/ha) increased as the number of plants was increased. In the vegetative parts of the plants there were higher N concentrations in lower populations showing that there was a higher N absorption and a lower translocation to the grains. When grain sorghum was grown in 50 cm rows, there was a high N accumulation, a high N translocation to the grains and the highest yield. This row spacing led to the highest N use efficiency.

Microhabitat and plant structure of Compsopogon coeruleus (Compsopogonaceae, Rhodophyta) populations in streams from São Paulo State, southeastern Brazil

Microhabitat distribution was investigated in three populations of C. coeruleus to determine the distributional patterns and their controlling factors, as well as morphometric adaptations to varying conditions on a scale of a few centimetres. Morphometric variations and their relations with physical variables (current velocity, irradiance, depth and type of substratum) revealed some particular characteristics for each population and indicate particular adaptations. However, some trends were clear: 1) larger plants (length and/or diameter) produced a higher quantity of monosporangia in the three populations; 2) plant length and diameter were positively correlated in two populations; 3) plant diameter was positively correlated with current velocity in two populations; 4) higher percent cover was associated with substrata composed of macrophytes in two populations. C. coeruleus occurred under relatively wide microhabitat conditions and had high niche width values, suggesting a tolerance to considerable variation in physical variables. These characteristics contribute to the species' wide distribution in Brazilian streams, both spatial (at distinct scales) and seasonal. (C) ADAC / Elsevier, Paris.

Colonization pattern of Cecropia by Azteca ants: Influence of plant ontogeny, environment and host plant choice by queens

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nitrous oxide production and potential denitrification in soils from riparian buffer strips: Influence of earthworms and plant litter

Vegetated riparian buffer strips have been established in Southern Quebec (Canada) in order to intercept nutrients such as nitrate (NO(3)(-)) and protect water quality near agricultural fields. Buffer strips may also favour denitrification through a combination of high soil moisture, NO(3)(-) and carbon supply, which could lead to the production of nitrous oxide (N(2)O), a greenhouse gas. Denitrification could be further amplified by the presence of earthworms, or by plant species that promote earthworm and bacterial activity in soils. Soils from four farms, comprising maize fields and adjacent buffer strips, were sampled in the fall of 2008. A total of six earthworm species were found, but average earthworm biomass did not differ between buffer strips and maize agroecoecosystems. Nitrate concentrations and net nitrification rates were higher in the maize fields than in the buffer strips: there was no difference in N(2)O production in soils collected from the two sampling locations. Potential denitrification, measured by acetylene inhibition, varied by two orders of magnitude, depending on experimental conditions: when amended with H(2)O or with H(2)O + NO3-, potential denitrification was higher (P < 0.05) in soils from buffer strips than from maize fields. Potential denitrification was highest in soils amended with H(2)O+glucose, or with H(2)O+ NO(3)(-) + glucose. Using microcosms, we tested the effect of litter-soil mixtures on earthworm growth, and the effect of earthworm-litter-soil mixtures on potential denitrification. Based on four categories of chemical assays, litters of woody species (oak, apple, Rhododendron) were generally of lower nutritional quality than litter from agronomic species (alfalfa, switchgrass, corn stover). Alfalfa litter had the most positive effect, whereas apple litter had the most negative effect, on earthworm growth. Potential denitrification was 2-4 times higher in earthworm-litter-soil mixtures than in plain soil. Litter treatments that included corn stover had lower potential denitrification than those that included alfalfa or switchgrass, whereas litter treatments that included oak had lower potential denitrification than those that included apple or Rhododendron. Results suggest that potential N(2)O emissions may be higher in riparian buffer strips than in adjacent maize fields, that N(2)O emissions in buffer strips may be amplified by comminuting earthworms, and that plant litters that reduce earthworm growth may not be best at mitigating N(2)O emissions. (c) 2010 Elsevier B.V. All rights reserved.

Microhabitat and plant structure of Batrachospermum (Batrachospermales, Rhodophyta) populations in four streams of São Paulo State, southeastern Brazil

Microhabitat and plant structure of seven Batrachospermum populations (four of Batrachospermum delicatulum (= Sirodotia delicatula), one of Batrachospermum macrosporum and two of the 'Chantransia' stage), including the influence of physical variables (current velocity, depth, irradiance and substratum), were investigated in four streams of São Paulo State, southeastern Brazil. The populations of B. delicatulum and the 'Chantransia' stage occurred under very diverse microhabitat conditions, which probably contributes to their wide spatial and seasonal distribution in Brazilian streams. Results suggest branch reconfiguration as a probable mechanism of adaptation to current velocity based on the occurrence of: (i) B. macrosporum (a large mucilaginous form with presumably little ability for branch reconfiguration) under lower current velocity than B. delicatulum; (ii) only dense plants in populations with high current velocities (> 60 cm s-1), whereas 53-77% of dense plants were seen in populations exposed to lower currents (< 40 cm s-1); (iii) positive correlations of plant length with internode length in populations under low current velocities and negative correlation in a population with high velocity (132 cm s-1); and (iv) negative correlations of current velocity with plant diameter and internode length in a population under high flow. This study, involving mainly dioecious populations, revealed that B. delicatulum displayed higher fertilization rates than B. macrosporum. A complementary explanation for a dioecious species to increase fertilization success was proposed consisting of outcrossing among intermingled male and female adjacent plants within an algal spot.

Cotton growth and boron distribution in the plant as affected by a temporary deficiency of boron

The knowledge of nutrient mobility is an important tool to define the best fertilizer management and diagnosis techniques. Patterns of boron (B) mobility in plants have been reviewed, but there is very little information on B distribution and mobility in cotton. An experiment was conducted to study plant growth and B distribution in cotton when the nutrient was applied in the nutrient solution or to the leaves, and when a temporary deficiency was imposed. Cotton (Gossypium hirsutum, Latifolia, cv. IAC 22) was grown in nutrient solutions where B was omitted or not for 15 days. Boron was applied to young or mature cotton leaves in some of the minus B treatments. Root growth decreased when the plants were transferred to B solutions, but there was a full recovery when B was replaced in the nutrient medium. Boron deficiency, even when temporary, reduced cotton shoot dry matter yields, plant height and flower and fruit set, and these could not be prevented by foliar application of B. Because of decreased dry matter production, leaves of deficient cotton plants actually showed higher B concentrations than non deficient leaves. This would be misleading when a mature leaf is sampled for diagnosis. If there is any B mobility in cotton phloem, it is very low.

Genotoxicity of the medicinal plant Maytenus robusta in mammalian cells in vivo.

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The role of multiple partners in a digestive mutualism with a protocarnivorous plant

Background and aimsThe protocarnivorous plant Paepalanthus bromelioides (Eriocaulaceae) is similar to bromeliads in that this plant has a rosette-like structure that allows rainwater to accumulate in leaf axils (i.e. phytotelmata). Although the rosettes of P. bromelioides are commonly inhabited by predators (e.g. spiders), their roots are wrapped by a cylindrical termite mound that grows beneath the rosette. In this study it is predicted that these plants can derive nutrients from recycling processes carried out by termites and from predation events that take place inside the rosette. It is also predicted that bacteria living in phytotelmata can accelerate nutrient cycling derived from predators.MethodsThe predictions were tested by surveying plants and animals, and also by performing field experiments in rocky fields from Serra do Cipó, Brazil, using natural abundance and enriched isotopes of 15N. Laboratory bioassays were also conducted to test proteolytic activities of bacteria from P. bromelioides rosettes.Key ResultsAnalyses of 15N in natural nitrogen abundances showed that the isotopic signature of P. bromelioides is similar to that of carnivorous plants and higher than that of non-carnivorous plants in the study area. Linear mixing models showed that predatory activities on the rosettes (i.e. spider faeces and prey carcass) resulted in overall nitrogen contributions of 26·5 % (a top-down flux). Although nitrogen flux was not detected from termites to plants via decomposition of labelled cardboard, the data on 15N in natural nitrogen abundance indicated that 67 % of nitrogen from P. bromelioides is derived from termites (a bottom-up flux). Bacteria did not affect nutrient cycling or nitrogen uptake from prey carcasses and spider faeces.ConclusionsThe results suggest that P. bromelioides derive nitrogen from associated predators and termites, despite differences in nitrogen cycling velocities, which seem to have been higher in nitrogen derived from predators (leaves) than from termites (roots). This is the first study that demonstrates partitioning effects from multiple partners in a digestion-based mutualism. Despite most of the nitrogen being absorbed through their roots (via termites), P. bromelioides has all the attributes necessary to be considered as a carnivorous plant in the context of digestive mutualism. © 2012 The Author. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.

Effects of plant cover on the macrofauna of Spartina marshes in northern Brazil

Dados sobre a densidade e diversidade da macrofauna em relação à altura e densidade de Spartina brasiliensis foram obtidos em bancos de marismas em um estuário tropical no norte do Brasil. A amostragem foi realizada quatro vezes durante um ano, nas estações chuvosa, seca e nos períodos de transição entre estas. A amostragem foi realizada em marismas de três classes de tamanho: pequeno, médio e grande. As variáveis foram analisadas em relação às estações do ano e das classes de tamanho das marismas. Um total de 46 táxons foram encontrados, com os poliquetos, isopodos e o gastropódo Neritina virginea dominando a fauna, resultados similares a estudos realizados em marismas no sul do Brasil. A densidade e a diversidade da macrofauna foram correlacionadas positivamente com a densidade de colmos da vegetação, indicando um possível papel da vegetação em proteção contra predação. Todas as três variáveis foram maiores durante os períodos transicionais entre as estações chuvosa e seca e mudanças sazonais em precipitação, salinidade e disponibilidade de luz possam influenciar mortalidade, disponibilidade de alimento e assentamento da macrofauna. Não houve um efeito de tamanho da marisma sobre a macrofauna ou a vegetação. O efeito beneficial da vegetação sobre a macrofauna é apoiado por outros estudos de marismas brasileiras.

Physiological indexese macro- and micronutrients in plant tissue and essential oil of Mentha piperita L. grown in nutrient solution with variation in N, P, K and Mg levels

Mentha piperita L. is an aromatic and medicinal species of the family Lamiaceae, known as mint or peppermint, and its leaves and branches produce essential oil rich in menthol. This study aimed to evaluate physiological indexes, macro- and micronutrients inthe shootsand essential oil of Mentha piperita L. grown in nutrient solution number 2 of Hoagland and Arnon (1950) with different N, P, K and Mg levels. Shoot length, dry mass of the different organs, total dry mass, leaf area, essential oil yield and composition, and macronutrient (N, P, K, Mg, Ca, S) and micronutrient (Mn, Cu, Fe, Zn) contents in the shoot were evaluated. Plants treated with 65%N/50%P/25%K/100%Mg had a tendency towards longer shoot, greaterroot and leaf blade dry masses, higher essential oil yield, higher menthol levels and lower menthone levels. The results showed that Mentha can be grown in nutrient solution by reducing 65% N, 50% P, 25% K and 100% Mg. This solution had better development compared to the other tested treatments. Therefore,we recommendMentha piperita L. to be grown with such nutrient levels.

Peanut mechanized digging regarding to plant population and soil water level

The largest losses in mechanical harvesting of peanuts occur during the stage of digging, and its assessment is still incipient in Brazil. Therefore, the aim of this study was to evaluate the quantitative losses and the performance of the tractor-digger-inverter, according to soil water content and plant populations. The experiment was conducted in a completely randomized block design with a factorial scheme 2 x 3, in which the treatments consisted of two soil, water content (19.3 and 24.8%) and three populations of plants (86,111, 127,603 and 141,144 plants ha-1), with four replications. The quantitative digging losses and the set mechanized performance were evaluated. The largest amount of visible and total losses was found in the population of 141.144 plants ha-1 for the 19.3% soil water content. The harvested material flow and the tractor-digger-inverter performance were not influenced by soil water content and plant population. The water content in the pods was higher in 24.8% soil water content only for the population of 86,111 plants ha-1; the yield was higher in the populations of 141.144 and 127.603 plants ha-1, in the 19.3 e 24.8% soil water content, respectively.

Candidatus Liberibacter asiaticus Titers in Citrus and Acquisition Rates by Diaphorina citri Are Decreased by Higher Temperature

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Changes in plant species composition and functional traits along the successional trajectory of a restored patch of Atlantic Forest

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Plant growth promoting bacteria in Brachiaria brizantha

Brachiaria brizantha is considered one of the preferred fodders among farmers for having high forage yield and large production of root mass. The association of beneficial bacteria with these grasses can be very valuable in the recovery of the pasture areas with nutritional deficiency. With the aim of studying this possibility, we carried out the sampling of soil and roots of B. brizantha in three areas (Nova Odessa-SP, So Carlos-SP and Campo Verde-MT, Brazil). Seventy-two bacterial strains were isolated and used in tests to evaluate their biotechnological potential. Almost all isolates presented at least one positive feature. Sixty-eight isolates produced analogues of indole-3-acetic acid, ten showed nitrogenase activity when subjected to the method of increasing the concentration of total nitrogen (total N) in the culture medium and sixty-five isolates showed nitrogenase activity when subjected to acetylene reduction technique. The partial sequencing of 16S rRNA of these isolates allowed the identification of seven main groups, with the prevalence of those affiliated to the genus Stenotrophomonas (69 %). At the end, this work elected the strains C4 (Pseudomonadaceae) and C7 (Rhodospirillaceae) as promising organisms for the development of inoculants due to their higher nitrogenase activity.