New diprenylated dihyrochalcones from leaves of Artocarpus elasticus

Two new diprenylated dihydrochalcones, elastichalcone A 1 and elastichalcone B 2 and three known compounds were isolated from the leaves of Artocarpus elasticus. Their structures were determined by various spectroscopic techniques (UV, IR, MS, 1D-NMR and 2D-NMR). Elastichalcone B 2 and a known compound exhibited good free radical scavenging activity with IC₅₀ values of 11.30 and 11.89 μg/ml, respectively.     

Mode of high temperature injury to wheat during grain development

High temperature stress adversely affects wheat growth in many important production regions, but the mode of injury is unclear. Wheat ( Triticum aestivum L. cv. Newton) was grown under controlled conditions to determine the relative magnitude and sequences of responses of source and sink processes to high temperature stress during grain development. Regimes of 25°C day/15°C night, 30°C day/20°C night, and 35°C day/25°C night from 5 days after anthesis to maturity differentially affected source and sink processes. High temperatures accelerated the normal decline in viable leaf blade area and photosynthetic activities per unit leaf area. Electron transport, as measured by Hill reaction activity, declined earlier and faster than other photosynthetic processes at the optimum temperature of 25/15 °C and at elevated temperatures. Changes in RUBP carboxylase activities were similar in direction but smaller in magnitude than changes in photosynthesic rate. Increased protease activity during senscence was markedly accentuated by high temperature stress. Specific protease activity increased 4-fold at 25/15 °C and 28-fold at 35/25 °C from 0 to 21 days after initiation of temperature treatments. Grain-filling rate decreased from the lowest to the highest temperature, but the change was smaller than the decrease in grain-filling duration at the same temperatures. We concluded that a major effect of high temperature is acceleration of senescence, including cessation of vegetative and reproductive growth, deterioration of photosynthetic activities, and degradation of proteinaceous constituents.     

Metallic Core-Shell Photonic Crystals for Surface-Enhanced Raman Scattering (SERS)

Plasmonics - Metallic core-shell substrate is specially used to serve ultrasensitive molecular detection down to concentration of micromolar level based on surface-enhanced Raman spectroscopy...     

Decelerating growth in tropical forest trees

The impacts of global change on tropical forests remain poorly understood. We examined changes in tree growth rates over the past two decades for all species occurring in large (50-ha) forest dynamics plots in Panama and Malaysia. Stem growth rates declined significantly at both forests regardless of initial size or organizational level (species, community or stand). Decreasing growth rates were widespread, occurring in 24–71% of species at Barro Colorado Island, Panama (BCI) and in 58–95% of species at Pasoh, Malaysia (depending on the sizes of stems included). Changes in growth were not consistently associated with initial growth rate, adult stature, or wood density. Changes in growth were significantly associated with regional climate changes: at both sites growth was negatively correlated with annual mean daily minimum temperatures, and at BCI growth was positively correlated with annual precipitation and number of rainfree days (a measure of relative insolation). While the underlying cause(s) of decelerating growth is still unresolved, these patterns strongly contradict the hypothesized pantropical increase in tree growth rates caused by carbon fertilization. Decelerating tree growth will have important economic and environmental implications.     

The Peoples of the Middle Niger: The Island of Gold

The Peoples of the Middle Niger: The Island of Gold. Roderick J. Mclntosh. Williston, VT: Blackwell, 1998. 346 pp.     

Quantitative observations on the pulmonary anatomy of the domestic Muscovy duck (Cairina moschata)

The lungs of five female domestic Muscovy ducks, mean body weight 1.627 kg, total lung volume 48.07 cm³, were analysed by standard morphometric methods. Principal results obtained are: lung volume per unit body weight, 30.17 cm³/g; volume densities of exchange tissue relative to lung volume, 49.24%, blood capillaries relative to exchange tissue, 29.63%, tissue of the blood gas (tissue) barrier relative to exchange tissue, 5.88%; surface area of the blood-gas (tissue) barrier per unit body weight, 30.04 cm²/g; ratios of the surface area of the blood-gas (tissue) barrier per unit volume of the lung and per unit volume of exchange area, 979 cm²/cm³ and 200.06 mm²/mm³, respectively; harmonic and arithmetic mean thicknesses of the tissue barrier, 0.199 μm and 0.303 μm, respectively. The anatomical diffusing capacity of the tissue barrier for oxygen ( DtO₂ ) and the total pulmonary diffusing capacity ( DLO₂ ), 49.58 ml O₂/min/mmHg/kg and 4.55 ml O₂/min/mm Hg/kg, respectively. The lungs of the domestic Muscovy duck appear to be about as well adapted anatomically for gas exchange as the lungs of wild anatid species, and there is no clear evidence that domestication has been associated with any deterioration in the anatomical capacity for oxygen uptake. The weight-specific anatomical diffusing capacity of the lung for oxygen ( DLO₂/W ) was about 3.6 times greater than the weight-specific physiological value, a factor which falls within the expected range.     

The role of gap phase processes in the biomass dynamics of tropical forests

The responses of tropical forests to global anthropogenic disturbances remain poorly understood. Above-ground woody biomass in some tropical forest plots has increased over the past several decades, potentially reflecting a widespread response to increased resource availability, for example, due to elevated atmospheric CO2 and/or nutrient deposition. However, previous studies of biomass dynamics have not accounted for natural patterns of disturbance and gap phase regeneration, making it difficult to quantify the importance of environmental changes. Using spatially explicit census data from large (50 ha) inventory plots, we investigated the influence of gap phase processes on the biomass dynamics of four 'old-growth' tropical forests (Barro Colorado Island (BCI), Panama; Pasoh and Lambir, Malaysia; and Huai Kha Khaeng (HKK), Thailand). We show that biomass increases were gradual and concentrated in earlier-phase forest patches, while biomass losses were generally of greater magnitude but concentrated in rarer later-phase patches. We then estimate the rate of biomass change at each site independent of gap phase dynamics using reduced major axis regressions and ANCOVA tests. Above-ground woody biomass increased significantly at Pasoh (+0.72% yr(-1)) and decreased at HKK (-0.56% yr(-1)) independent of changes in gap phase but remained stable at both BCI and Lambir. We conclude that gap phase processes play an important role in the biomass dynamics of tropical forests, and that quantifying the role of gap phase processes will help improve our understanding of the factors driving changes in forest biomass as well as their place in the global carbon budget.