Evolution of the eye-end design of a composite leaf spring for heavy axle loads

This paper presents the design evolution process of a composite leaf spring for freight rail applications. Three designs of eye-end attachment for composite leaf springs are described. The material used is glass fibre reinforced polyester. Static testing and finite element analysis have been carried out to obtain the characteristics of the spring. Load-deflection curves and strain measurement as a function of load for the three designs tested have been plotted for comparison with FEA predicted values. The main concern associated with the first design is the delamination failure at the interface of the fibres that have passed around the eye and the spring body, even though the design can withstand 150 kN static proof load and one million cycles fatigue load. FEA results confirmed that there is a high interlaminar shear stress concentration in that region. The second design feature is an additional transverse bandage around the region prone to delamination. Delamination was contained but not completely prevented. The third design overcomes the problem by ending the fibres at the end of the eye section.

Long-term acclimation of leaf production, development, longevity and quality following 3 yr exposure to free-air CO2 enrichment during canopy closure in Populus

The effects of elevated CO2 on leaf development in three genotypes of Populus were investigated during canopy closure, following exposure to elevated CO2 over 3 yr using free-air enrichment.• Leaf quality was altered such that nitrogen concentration per unit d. wt (Nmass) declined on average by 22 and 13% for sun and shade leaves, respectively, in elevated CO2. There was little evidence that this was the result of ‘dilution’ following accumulation of nonstructural carbohydrates. Most likely, this was the result of increased leaf thickness. Specific leaf area declined in elevated CO2 on average by 29 and 5% for sun and shade leaves, respectively.• Autumnal senescence was delayed in elevated CO2 with a 10% increase in the number of days at which 50% leaf loss occurred in elevated as compared with ambient CO2.• These data suggest that changes in leaf quality may be predicted following long-term acclimation of fast-growing forest trees to elevated CO2, and that canopy longevity may increase, with important implications for forest productivity.

Effects of fully open-air CO2 elevation on leaf ultrastructure, photosynthesis and yield of two soybean cultivars.

The objective of this study was to investigate the effect of elevated (550 ± 17 μmol mol−1) CO2 concentration ([CO2]) on leaf ultrastructure, leaf photosynthesis and seed yield of two soybean cultivars [Glycine max (L.) Merr. cv. Zhonghuang 13 and cv. Zhonghuang 35] at the Free-Air Carbon dioxide Enrichment (FACE) experimental facility in North China. Photosynthetic acclimation occurred in soybean plants exposed to long-term elevated [CO2] and varied with cultivars and developmental stages. Photosynthetic acclimation occurred at the beginning bloom (R1) stage for both cultivars, but at the beginning seed (R5) stage only for Zhonghuang 13. No photosynthetic acclimation occurred at the beginning pod (R3) stage for either cultivar. Elevated [CO2] increased the number and size of starch grains in chloroplasts of the two cultivars. Soybean leaf senescence was accelerated under elevated [CO2], determined by unclear chloroplast membrane and blurred grana layer at the beginning bloom (R1) stage. The different photosynthesis response to elevated [CO2] between cultivars at the beginning seed (R5) contributed to the yield difference under elevated [CO2]. Elevated [CO2] significantly increased the yield of Zhonghuang 35 by 26% with the increased pod number of 31%, but not for Zhonghuang 13 without changes of pod number. We conclude that the occurrence of photosynthetic acclimation at the beginning seed (R5) stage for Zhonghuang 13 restricted the development of extra C sink under elevated [CO2], thereby limiting the response to elevated [CO2] for the seed yield of this cultivar.

Genotypic variation in photosynthetic and leaf traits in cocoa

The photosynthetic characteristics of eight contrasting cocoa genotypes were studied with the aim of examining genotypic variation in maximum (light-saturated) photosynthetic rates, light-response curve parameters and water use efficiency. Photosynthetic traits were derived from single leaf gas exchange measurements using a portable infra-red gas analyser. All measurements were conducted in a common greenhouse environment. Significant variation was observed in light-saturated photosynthesis ranging from 3.4 to 5.7 µmol CO2 m-2 s-1 for the clones IMC 47 and SCA 6, respectively. Furthermore, analyses of photosynthetic light response curves indicated genotypic differences in light saturation point and quantum efficiency (i.e. the efficiency of light use). Stomatal conductance was a significant factor underlying genotypic differences in assimilation. Genotypic variation was also observed in a number of leaf traits, including specific leaf area (the ratio of leaf area to leaf weight), chlorophyll concentration and nitrogen content. There was a positive correlation between leaf nitrogen per unit area and light-saturated photosynthesis. Water use efficiency, defined as the ratio of photosynthetic rate to transpiration rate, also varied significantly between clones (ranging from 3.1 mmol mol-1 H2O for the clone IMC 47 to 4.2 mmol mol-1 H2O for the clone ICS 1). Water use efficiency was a negative function of specific leaf area, suggesting that low specific leaf area might be a useful criterion for selection for increased water use efficiency. It is concluded that both variation in water use efficiency and the photosynthetic response to light have the potential to be exploited in breeding programmes.

Evidence of a universal scaling relationship for leaf CO2 drawdown along an aridity gradient

The leaf carbon isotope ratio (δ13C) of C3 plants is inversely related to the drawdown of CO2 concentration during photosynthesis, which increases towards drier environments. We aimed to discriminate between the hypothesis of universal scaling, which predicts between-species responses of δ13C to aridity similar to within-species responses, and biotic homoeostasis, which predicts offsets in the δ13C of species occupying adjacent ranges. The Northeast China Transect spans 130–900 mm annual precipitation within a narrow latitude and temperature range. Leaves of 171 species were sampled at 33 sites along the transect (18 at ≥ 5 sites) for dry matter, carbon (C) and nitrogen (N) content, specific leaf area (SLA) and δ13C. The δ13C of species generally followed a common relationship with the climatic moisture index (MI). Offsets between adjacent species were not observed. Trees and forbs diverged slightly at high MI. In C3 plants, δ13C predicted N per unit leaf area (Narea) better than MI. The δ13C of C4 plants was invariant with MI. SLA declined and Narea increased towards low MI in both C3 and C4 plants. The data are consistent with optimal stomatal regulation with respect to atmospheric dryness. They provide evidence for universal scaling of CO2 drawdown with aridity in C3 plants.

Relative effect of litter quality, forest type and their interaction on leaf decomposition in south-east Brazilian forests

Decomposition was studied in a reciprocal litter transplant experiment to examine the effects of forest type, litter quality and their interaction on leaf decomposition in four tropical forests in south-east Brazil. Litterbags were used to measure decomposition of leaves of one tree species from each forest type: Calophyllum brasiliense from restinga forest; Guapira opposita from Atlantic forest; Esenbeckia leiocarpa from semi-deciduous forest; and Copaifera langsdorffii from cerradao. Decomposition rates in rain forests (Atlantic and restinga) were twice as fast as those in seasonal forests (semi-deciduous and cerradao), suggesting that intensity and distribution of precipitation are important predictors of decomposition rates at regional scales. Decomposition rates varied by species, in the following order: E. leiocarpa > C. langsdorffii > G. opposita > C. brasiliense. However, there was no correlation between decomposition rates and chemical litter quality parameters: C:N, C:P, lignin concentration and lignin:N. The interaction between forest type and litter quality was positive mainly because C. langsdorffii decomposed faster than expected in its native forest. This is a potential indication of a decomposer`s adaptation to specific substrates in a tropical forest. These findings suggest that besides climate, interactions between decomposers and plants might play an essential role in decomposition processes and it must be better understood.

Synthetic amides toxic to the leaf-cutting ant Atta sexdens rubropilosa L. and its symbiotic fungus

1 Nine synthetic amides similar to natural N-piperidine-3-(4,5-methylenedioxyphenyl)-2-(E)-propenainide and N-pyrrolidine-3-(4,5-methylenedyoxiphenyl)2-(E)-propenamide were synthesized and identified by their spectroscopic data.2 the toxicity of these synthetic amides to the Atta sexdens rubropilosa workers and the antifungal activity against Leticoagaricus gongylophorus, the symbiotic fungus of the leaf-cutting ants, were determined.3 Workers ants that were fed daily on an artificial diet to which these compounds were added had a higher mortality rate than the controls for N-pyrrolidine-3(3',4'-methylenedioxyphenyl)-2-(E)-propenamide and N-benzyl-3-(3',4'-methylenedioxyphenyl)-2-(E)-propenamide at a concentration of 100 mu g/mL.4 the completely inhibition (100%) of the fungal growth was observed with N-piperldine-3-(3',4'-methylenedioxyphenyl)-2-(E)-propenamide and N,N-diethyl-3-(3',4'-methylenedioxyphenyl)-2-(E)-propenamide at concentrations of 50 and 100 mu g/mL and N-pirrolidine-3-(3',4'-methylenedioxyphenyl)-2-(E)-propenamide at a concentration of 100 mu g/mL.5 the possibility of controlling these insects in the future using synthetic piperamides that can simultaneously target both organisms is discussed.

Activity of sesame leaf extracts to the leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera : Formicidae)

Crude extracts of new and old sesame leaves (Sesamum indicum, Linaeus) obtained by a sequential process of extraction were tested through contact experiments to investigate their toxicity to Atta sexdens rubropilosa (Forel) workers. Methanol extract of old leaves was toxic to leaf-cutting ants at the lower tested concentration (20mg.ml(-1)). This extract was fractioned and their fractions were tested showing a toxic effect of the methanol fraction. The methanol fraction was fractioned again and the sub fraction responsible for worker's toxicity is composed of some sugars.

Preliminary studies on the effects of d-limonene to workers of the leaf-cutting ant Atta sexdens rubropilosa and its implications for control

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects of Silicon and Drought Stress on Tuber Yield and Leaf Biochemical Characteristics in Potato

Silicon has beneficial effects on many crops, mainly under biotic and abiotic stresses. Silicon can affect biochemical, physiological, and photosynthetic processes and, consequently, alleviates drought stress. However, the effects of Si on potato (Solanum tuberosum L.) plants under drought stress are still unknown. The objective of this study was to evaluate the effect of Si supply on some biochemical characteristics and yield of potato tubers, either exposed or not exposed to drought stress. The experiment was conducted in pots containing 50 dm(3) of a Typic Acrortox soil (33% clay, 4% silt, and 63% sand). The treatments consisted of the absence or presence of Si application (0 and 284.4 mg dm(-3)), through soil amelioration with dolomitic lime and Ca and Mg silicate, and in the absence or presence of water deficit (-0.020 MPa and -0.050 MPa soil water potential, respectively), with eight replications. Silicon application and water deficit resulted in the greatest Si concentration in potato leaves. Proline concentrations increased under lower water availability and higher Si availability in the soil, which indicates that Si may be associated with plant osmotic adjustment. Water deficit and Si application decreased total sugars and soluble proteins concentrations in the leaves. Silicon application reduced stalk lodging and increased mean tuber weight and, consequently, tuber yield, especially in the absence of water stress.

Changes in leaf proline and fruit production induced by potassium stress in eggplant

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Seasonal effects on the relationship between photosynthesis and leaf carbohydrates in orange trees

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

Changes in leaf physiology caused by Calacarus heveae (Acari, Eriophyidae) on rubber tree

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Amino acid, Antioxidant and Ion Profiles of Carpolobia lutea Leaf (Polygalaceae)

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

Yield performance and leaf nutrient levels of coffee cultivars under different plant densities

Cultivares de cafeeiro (Coffea Arabica L.) adaptadas às regiões de cultivo, com população de plantas otimizada e adequado estado nutricional são premissas para a obtenção de produções elevadas de café. Estudou-se a produção trienal de café e o teor foliar de macronutrientes de cultivares de cafeeiro em função das densidades de plantio. Foram utilizados os cultivares Catuaí Amarelo (IAC 47), Obatã (IAC 1669-20), Acaiá (IAC 474-19) e Icatu Amarelo (IAC 2944) nas populações de 2.500 plantas ha-1 com duas plantas por cova; e, 5.000, 7.519 e 10.000 plantas ha-1 com uma planta por cova. As plantas foram adubadas de modo homogêneo, porém, sem calagem. À medida que a população de cafeeiros aumentou, a produtividade trienal de café aumentou, a produção de frutos por planta diminuiu e os teores foliares de fósforo (P), potássio (K) e enxofre (S) aumentaram. Nos cafeeiros sob adensamento encontrou-se igual ou maior teor de macronutrientes do que naqueles sob espaçamento convencional, sendo que os maiores teores foram observados nas cultivares de porte alto, e os menores, na cultivar Obatã, de porte baixo. Nos cafeeiros das covas com uma planta observou-se maior produção de café e menores concentrações de P, Ca e S do que naqueles das covas com duas plantas. No geral, os cultivares e as populações de cafeeiros estavam com teores de N e S acima dos limites de referência citados na literatura, mas com teores dos demais macronutrientes dentro da faixa adequada.