Detrimental effects of latex and cardiac glycosides on survival and growth of first-instar monarch butterfly larvae Danaus plexippus feeding on the sandhill milkweed Asclepias humistrata

1. A novel experimental method was developed to study negative physical and chemical effects of latex and cardiac glycosides on first-instar monarch butterfly larvae in their natural environment in north central Florida. Forceps were used to nibble through the petioles of leaves of the sandhill milkweed Asclepias humistrata, mimicking the behaviour of mature monarch larvae. This notching cut off the supply-of latex to the leaves without significantly reducing either their cardiac glycoside concentration or water content. 2. The mean cardiac glycoside concentration in larvae that fed on intact leaves was nearly two: and a half times greater than in larvae that fed on notched leaves. This was probably because more latex is present in the gut of the larvae that fed on the intact leaves. Supporting this is the fact that the mean concentration of cardiac glycosides in the latex was 34-47 times that in the leaves. 3. Wet weights, dry weights, and growth rates of first-instar larvae that fed on intact leaves over a 72-h period were less than half those of larvae that fed on notched leaves. 4. Mortality due to miring in the latex was 27% on the intact leaves compared with 2% on the notched leaves. 5. Latex, cardiac glycosides, and other as yet undetermined plant factors all have a negative effect on:first-instar larval survival. 6. Video-analyses indicated that ingestion of latex caused the larvae to become cataleptic and increased their chances of being mired on the leaf by the setting latex glue. Dysfunction resulting from latex ingestion may lead to the larvae falling off the plant and being killed by invertebrate predators. 7. The difficulty of neonate monarch larvae surviving on A. humistrata - one of the principal milkweed species fed on each spring as monarchs remigrate from Mexico into the southern U.S.A. - is evidence that a co-evolutionary arms race is operating in this plant-herbivore system.

Natural abundance of stable carbon and nitrogen isotopes in Cannabis sativa reflects growth conditions

Stable carbon and nitrogen isotope signatures (delta C-13 and delta N-15) of Cannabis sativa were assessed for their usefulness to trace seized Cannabis leaves to the country of origin and to source crops by determining how isotope signatures relate to plant growth conditions. The isotopic composition of Cannabis examined here covered nearly the entire range of values reported for terrestrial C-3 plants. The delta C-13 values of Cannabis from Australia, Papua New Guinea and Thailand ranged from -36 to -25 parts per thousand, and delta N-15 values ranged from -1.0 to 15.8 parts per thousand. The stable isotope content did not allow differentiation between Cannabis originating from the three countries, but delta C-13 values of plantation-grown Cannabis differed between well-watered plants (average delta C-13 of -30.0 parts per thousand) and plants that had received little irrigation (average delta C-13 of -26.4 parts per thousand). Cannabis grown under controlled conditions had delta C-13 values of -32.6 and -30.6 parts per thousand with high and low water supply, respectively. These results indicate that water availability determines leaf C-13 in plants grown under similar conditions of light, temperature and air humidity. The delta C-13 values also distinguished between indoor- and outdoor-grown Cannabis; indoor- grown plants had overall more negative delta C-13 values (average -31.8 parts per thousand) than outdoor-grown plants (average -27.9 parts per thousand). Contributing to the strong C-13-depletion of indoor- grown plants may be high relative humidity, poor ventilation and recycling of C-13-depleted respired CO2. Mineral fertilizers had mostly lower delta N-15 values (-0.2 to 2.2 parts per thousand) than manure-based fertilizers (7.6 to 22.7 parts per thousand). It was possible to link delta N-15 values of fertilizers associated with a crop site to soil and plant delta N-15 values. The strong relationship between soil, fertilizer, and plant delta N-15 suggests that Cannabis delta N-15 is determined by the isotopic composition of the nitrogen source. The distinct delta N-15 values measured in Cannabis crops make delta N-15 an excellent tool for matching seized Cannabis with a source crop. A case study is presented that demonstrates how delta C-13 and delta N-15 values can be used as a forensic tool.

Eutectic growth mode in strontium, antimony and phosphorus modified hypoeutectic Al-Si foundry alloys

The effect of strontium (Sr), antimony (Sb) and phosphorus (P) on nucleation and growth mode of the eutectic in hypoeutectic Al-10 mass%Si alloys has been investigated by electron back-scattering diffraction (EBSD) mapping. Specimens were prepared from a hypoeutectic Al-10 mass%Si base alloy, adding different levels of strontium, antimony and phosphorus for modification of eutectic silicon. By comparing the orientation of the aluminium in the eutectic to that of the surrounding primary aluminium dendrites, the solidification mode of the eutectic could be determined. The results of these studies show that the eutectic nucleation mode, and subsequent growth mode, is strongly dependent on additive elements. The EBSD mapping results indicate that the eutectic grew from the primary phase in unmodified and phosphorus-containing alloys. When the eutectic was modified by strontium or antimony, eutectic grains nucleated and grew separately from the primary dendrites.

Latitudinal variability in symbiont specificity within the widespread scleractinian coral Plesiastrea versipora

We examined the genetic diversity of symbiotic dinoflagellates (Symbiodinium sp.) in the widespread hermatypic coral Plesiastrea versipora from tropical/subtropical (north-eastern Australia) and temperate waters (south-eastern Australia) using restriction fragment length polymorphisms of partial 18S ribosomal DNA (rDNA), together with sequence analysis of partial 28S rDNA. This study revealed that P. versipora associates with at least two distinct genotypes of symbiotic dinoflagellates and that the presence of these genotypes varies with latitude. P. versipora colonies from subtropical and tropical waters contained symbionts belonging to Symbiodinium clade C, while P. versipora colonies at high-latitude sites contained clade B. Variability within the two groups of symbionts (clades H and C) was minimal, suggesting possible host fidelity. The geographically distinct varieties of symbionts within the tissue of this hermatypic coral are likely to be associated with algal physiological differences, which in turn may relate to changing selective pressures as a function of latitude along the eastern Australian seaboard.

Growth regime map for liquid-bound granules: further development and experimental validation

An attempt was made to quantify the boundaries and validate the granule growth regime map for liquid-bound granules recently proposed by Iveson and Litster (AlChE J. 44 (1998) 1510). This regime map postulates that the type of granule growth behaviour is a function of only two dimensionless groups: the amount of granule deformation during collision (characterised by a Stokes deformation number, St(def)) and the maximum granule pore saturation, s(max). The results of experiments performed with a range of materials (glass ballotini, iron ore fines, copper chalcopyrite powder and a sodium sulphate and cellulose mixture) using both drum and high shear mixer granulators were examined. The drum granulation results gave good agreement with the proposed regime map. The boundary between crumb and steady growth occurs at St(def) of order 0.1 and the boundary between steady and induction growth occurs at St(def) of order 0.001. The nucleation only boundary occurs at pore saturations that increase from 70% to 80% with decreasing St(def). However, the high shear mixer results all had St(def) numbers which were too large. This is most likely to be because the chopper tip-speed is an over-estimate of the average impact velocity granules experience and possibly also due to the dynamic yield strength of the materials being significantly greater than the yield strengths measured at low strain rates. Hence, the map is only a useful tool for comparing the granulation behaviour of different materials in the same device. Until we have a better understanding of the flow patterns and impact velocities in granulators, it cannot be used to compare different types of equipment. Theoretical considerations also revealed that several of the regime boundaries are also functions of additional parameters not explicitly contained on the map, such as binder viscosity. (C) 2001 Elsevier Science B.V. All rights reserved.

Nucleation, growth and breakage phenomena in agitated wet granulation processes: a review

Wet agglomeration processes have traditionally been considered an empirical art, with great difficulties in predicting and explaining observed behaviour. Industry has faced a range of problems including large recycle ratios, poor product quality control, surging and even the total failure of scale up from laboratory to full scale production. However, in recent years there has been a rapid advancement in our understanding of the fundamental processes that control granulation behaviour and product properties. This review critically evaluates the current understanding of the three key areas of wet granulation processes: wetting and nucleation, consolidation and growth, and breakage and attrition. Particular emphasis is placed on the fact that there now exist theoretical models which predict or explain the majority of experimentally observed behaviour. Provided that the correct material properties and operating parameters are known, it is now possible to make useful predictions about how a material will granulate. The challenge that now faces us is to transfer these theoretical developments into industrial practice. Standard, reliable methods need to be developed to measure the formulation properties that control granulation behaviour, such as contact angle and dynamic yield strength. There also needs to be a better understanding of the flow patterns, mixing behaviour and impact velocities in different types of granulation equipment. (C) 2001 Elsevier Science B.V. All rights reserved.

Genetic variability of the symbiotic dinoflagellates from the wide ranging coral species Seriatopora hystrix and Acropora longicyathus in the Indo-West Pacific

The scleractinian coral species, Seriatopora hystrix and Acropora longicyathus, are widely distributed throughout the latitudinal range of the tropical west Pacific. These 2 coral species live in a mutually beneficial relation with symbiotic dinoflagellates (zooxanthellae), which are passed to their progeny by vertical transmission (zooxanthellate eggs or larvae) and horizontal transmission (eggs or larvae that acquire symbionts from the environment), respectively. For S. hystrix, vertical transmission might create biogeographically isolated and genetically differentiated symbiont populations because the extent of its larval migration is known to be limited. On the other hand, horizontal transmission in corals such as A. longicyathus may result in genetically connected symbiont populations, especially if its zooxanthellae taxa are widely distributed. To examine these hypotheses, symbionts were collected from colonies of S. hystrix and A. longicyathus living in the Great Barrier Reef (Australia), South China Sea (Malaysia) and East China Sea (Ryukyus Archipelago, Japan), and were examined using restriction fragment length polymorphism and sequence analysis of large and small subunit rRNA genes. Phylogenetic analysis assigned the symbionts to 1 of 3 taxonomically distinct groups, known as clades. Symbionts from Australian and Japanese S. hystrix were placed in Clade C, and Malaysian S. hystrix symbionts in the newly described Clade D. Seven of 11 Australian and all Japanese and Malaysian colonies of A. longicyathus had symbiotic dinoflagellates that also grouped with Clade C, but symbionts from the remaining Australian colonies of A. longicyathus grouped with Clade A. Analysis of molecular variance of Clade C symbionts found significant genetic variation in 1 or more geographic groups (69.8%) and to a lesser extent among populations within geographic regions (13.6%). All populations of Clade C symbionts from S. hystrix were genetically differentiated according to geographic region. Although Clade C symbionts of A. longicyathus from Japan resolved into a distinct geographic group, those from Australia and Malaysia did not and were genetically connected. We propose that these patterns of genetic connectivity correlate with differences in the dispersal range of the coral or symbiont propagules and are associated with their respective modes of symbiont transmission.

Diurnal changes in the photochemical efficiency of the symbiotic dinoflagellates (Dinophyceae) of corals: photoprotection, photoinactivation and the relationship to coral bleaching

The photochemical efficiency of symbiotic dinoflagellates within the tissues of two reef-building corals in response to normal and excess irradiance at wafer temperatures < 30 C were investigated using pulse amplitude modulated (PAM) chlorophyll fluorescence techniques, Dark-adapted F-v/F-m showed clear diurnal changes, decreasing to a low at solar noon and increasing in the afternoon. However, F-v/F-m also drifted downwards at night or in prolonged darkness, and increased rapidly during the early morning twilight. This parameter also increased when the oxygen concentration of the wafer holding the corals was increased. Such changes have not been described previously, and most probably reflect state transition's associated with PQ pool reduction via chlororespiration. These unusual characteristics may be a feature of an endosymbiotic environment, reflective of the well-documented night-time tissue hypoxia that occurs in corals. F-v/F-m decreased to 0.25 in response to full sunlight in shade-acclimated (shade) colonies of Stylophora pistillata, which is considerably lower than in light-acclimated (sun) colonies. In sun colonies, the reversible decrease in F-v/F-m was caused by a lowering of F-m and F-o suggesting photoprotection and no lasting damage. The decrease in F-v/F-m, however, was caused by a decrease in F-m and an increase in F-o in shade colonies suggesting photoinactivation and long-term cumulative photoinhibition. Shade colonies rapidly lost their symbiotic algae (bleached) during exposure to full sunlight. This study is consistent with the hypothesis that excess light leads to chronic damage of symbiotic dinoflagellates and their eventual removal from reef-building corals. It is significant that this can occur with high light conditions alone.

Rate and timing of vegetative growth, flowering and fruit development of Persoonia virgata (Proteaceae)

Persoonia virgata R. Br. is harvested from the wild in both its vegetative and flowering stages. There has been no systematic study published on the annual growth cycle and anecdotal reports are conflicting. The growth pattern, flowering and fruit development of P. virgata in its natural habitat was recorded monthly for two consecutive years. The main growth period occurred in late spring-mid-autumn (November-May) when the shrubs were producing little or no fruit. Very few open flowers were observed at the site over the 2 years, with only 6.7 and 12.7% of stems bearing open flowers in January and February 1996, respectively. A second study of flowering on container-grown shrubs showed that individual flowers were open for only 2-5 days, with individual stems taking 3-8.5 weeks to complete flowering. The main fruit growth period occurred from May to September, and in June and July 1996 the total fruit set per stem was 41.6 and 36.1%, respectively. The fruit took at least 6 months to develop during which vegetative growth was minimal. The harvesting of plants in the flowering or fruiting stages removes the annual seed crop, which may reduce regeneration of this obligate seed regenerator and threaten its survival after fire.

Canopy carbon and oxygen isotope composition of 9-year-old hoop pine families in relation to seedling carbon isotope composition, growth, field growth performance, and canopy nitrogen concentration

Carbon isotope composition (delta C-13), oxygen isotope composition (delta O-18), and nitrogen concentration (N-mass) of branchlet tissue at two canopy positions were assessed for glasshouse seedlings and 9-year-old hoop pine (Araucaria cunninghamii Ait. ex D. Don) trees from 22 open-pollinated families grown in 5 blocks of a progeny test at a water-limited and nitrogen-deficient site in southeastern Queensland, Australia. Significant variations in canopy delta C-13, delta O-18, and N-mass existed among the 9-year-old hoop pine families, with a heritability estimate of 0.72 for branchlet delta C-13 from the upper inner canopy position. There was significant variation in canopy delta C-13 of glasshouse seedlings between canopy positions and among the families, with a heritability estimate of 0.66. The canopy delta C-13 was positively related to canopy N-mass only for the upper outer crown in the field (R = 0.62, p < 0.001). Phenotypic correlations existed between tree height and canopy delta C-13 (R = 0.37-0.41, p < 0.001). Strong correlations were found between family canopy delta C-13 at this site and those at a wetter site and between field canopy delta C-13 and glasshouse seedling delta C-13. The mechanisms of the variation in canopy delta C-13 are discussed in relation to canopy photosynthetic capacity as reflected in the N-mass and stomatal conductance as indexed by canopy delta O-18.