Analysis of picogram quantities of indole-3-acetic acid by gas chromatography with fused silica column and flameless nitrogen selective detector

Use of a gas chromatograph equipped with a fused silica capillary column and a nitrogen-phosphorus detector permits selective detection of indole-3-acetic acid and other indoles at the low picogram level. The applicability of the method is demonstrated by the analysis of endogenous indole-3-acetic acid from shoots of Salix pentandra L.     

Genetics of breeding characters with possible effects on biomass production in Salix viminalis (L.)

 Genetic variation in number of sylleptic shoots, wood density, dry matter content, flower production, budbreak, growth cessation, insect susceptibility and rust susceptibility and the relationships of these characters with other growth characters were studied. Forty of sixty-four families in an 8×8 factorial crossing with Salix viminalis were used. Fourteen plants from each family were planted in the framework of a nutrient experiment with optimal and suboptimal nutrient availability and in a sandy soil. The analyses showed high additive genetic variances for all characters studied. Characters measured in both nutrient environments did not show any genotype×environment interaction. Both in the nutrient and in the sand environment insect susceptibility was negatively correlated to different growth characters. This was also the case for rust susceptibility in the sand environment. The highest negative correlation was found between number of days to budburst and weight, indicating the importance of early budburst for production. Ideas on important characteristics for an Salix ideotype are discussed. Received: 2 March 1998 / Accepted: 13 August 1998     

Manipulation of host plant development by the gall-midge Rhabdophaga strobiloides

Abstract. 1. The gall-midge Rhabdophaga strobiloides (O.S.) forms a gall in the apical bud of actively growing willow twigs.
2. Galls were not randomly distributed among twigs. Twigs that arose towards the distal end of the branch were much more likely to be galled. Distally located twigs also grew to greater girth than more proximally located twigs.
3. Comparisons of galled twigs with normal twigs in similar locations along their branch showed that the gall causes even greater growth in twig girth than when no gall is present.
4. The hypothesis that galled twigs draw photosynthate produced elsewhere in the plant was tested in an experiment that measured the growth of galled and normal twigs. with their leaves intact, to galled and normal twigs that were manually defoliated. Defoliation caused reduced growth in normal twigs, but galled twigs grew equally well with or without their leaves. Leaf removal had no effect on gall growth.
5. Twig diameter was positively correlated with gall diameter. Call diameter was positively correlated with larval biomass.
6. Patterns of twig and gall growth suggest that the gall-midge manipulates host plant growth and development to provide resources for growth and survival. Manipulation of the host may be an important phenomenon in the evolution of parasitic organisms.     

Host‐plant genotype mediates supply and demand of animal food in an omnivorous insect

1. Omnivorous predators can protect plants from herbivores, but may also consume plant material themselves. Omnivores and their purely herbivorous prey have previously been thought to respond similarly to host‐plant quality. However, different responses of omnivores and herbivores to their shared host plants may influence the fitness, trophic identity, and population dynamics of the omnivores. 2. The aim of the present study was to show that an omnivorous heteropteran (Anthocoris nemorum L.) and two strictly herbivorous prey species respond differently to different genotypes of their shared host plant, Salix. Some plant genotypes were sub‐optimal for the omnivore, although suitable for the herbivores, and vice versa. 3. The contrasting patterns of plant suitability for the omnivore and the herbivores highlight an interaction between plant genotype and omnivores' access to animal food. Plant genotypes that were sub‐optimal for the omnivore when herbivores were experimentally excluded became the best host plants when herbivores were present, as in the latter situation additional prey became available. By contrast, the quality of plant genotypes that were intrinsically suitable for omnivores, did not improve when herbivores were present as these plant genotypes were intrinsically sub‐optimal for herbivores, thus providing omnivores with almost no additional animal food. 4. The differential responses of omnivores and their prey to the same host‐plant genotypes should allow omnivores to colonise sub‐optimal host plants in their capacity as predators, and to colonise more suitable host plants in their capacity as herbivores. It may thus be difficult for Salix to escape herbivory entirely, as it will rarely be unsuitable for both omnivores and pure herbivores at the same time.     

Weight Changes of Dunlins on the Dee Estuary in May

In an attempt to increase the number of breeding pairs of Long-eared Owls at Woodwalton Fen National Nature Reserve, wicker baskets of varying design were placed throughout the reserve. Between 1981 and 1996, owls used the baskets on 77 occasions. Of 71 nests followed from incubation, 59.2% hatched young and 50.7% fledged one or more chicks. In only two nests were the complete clutches hatched and fledged. Early nesters laid larger clutches and raised more broods than those nesting later in the season. It is suggested that the level of the water table and the management regime necessary for the restoration of open fen communities affect the number of breeding owls.     

The Effect of Mycorrhizal Fungi on the Fate of Aldrin: Phytoremediation Potential

The objective of this study was to investigate the phytoremediation potential of mycorrhizal systems for the remediation of aldrin-contaminated soils. Feltleaf willow (Salix alaxensis) and balsam poplar (Populus balsamifera) were grown in soil spiked with 0.8 mg/kg aldrin- (1,2,3,4,10-¹⁴C). Daconil₂₇₈₇® was employed to suppress indigenous mycorrhizal infection. After 100 days of greenhouse incubation, mycorrhizal infection in the fungicide-amended willows was found to be 2.5 fold lower than in controls. Mycorrhizal infection in the poplar systems was unaffected by fungicide addition. Mycorrhizae were correlated with radiolabel uptake in the willow systems (r = 0.79), and not as strongly in the poplar systems (r = 0.58). Most of the radiolabel in the root material was bound product regardless of mycorrhizal infection, but 12 to 21% was found to be extractable dieldrin. Aldrin was not detected in any vegetative matrix. Dieldrin constituted less than 1% of the radiolabel in the willow leaf material, accumulating to approximately 5 μg/kg. Dieldrin was not detected in the poplar leaves (MDL ≈ 1 μg/kg), although the poplars took up approximately the same amount of radiolabel as the willows. Water-soluble transformation products were formed in the vegetated soils (6 to 12%) and nonvegetated controls (1 to 2%).     

Structure of two macrolepidopteran assemblages on Salix nigra (Marsh) and Acer negundo L.: abundance,diversity, richness,and persistence of scarce species

1. Most insect species occur at low abundance but a greater research effort has been devoted to so‐called outbreak species and little research is available on scarce (low abundance) species that are typical of most insect species. 2. Larval free‐feeding macrolepidoptera of two riparian trees Salix nigra (Marsh) (black willow) and Acer negundo L. (box elder) were sampled and sorted by species and abundance. 3. Data collected established that the majority of species in the assemblages in each tree species occurred at low abundance in each of the 5 years when larvae were sampled. 4. Species in the Noctuidae and Geometridae dominated both assemblages. 5. On both trees, assemblages were dominated numerically by relatively few species, a pattern that has been observed for insect assemblages on plants in managed and unmanaged habitats.     

Spatial correlations of Diceroprocta apache and its host plants: evidence for a negative impact from Tamarix invasion

Abstract 1. The hypothesis that the habitat‐scale spatial distribution of the Apache cicada Diceroprocta apache Davis is unaffected by the presence of the invasive exotic saltcedar Tamarix ramosissima was tested using data from 205 1‐m² quadrats placed within the flood‐plain of the Bill Williams River, Arizona, U.S.A. Spatial dependencies within and between cicada density and habitat variables were estimated using Moran's I and its bivariate analogue to discern patterns and associations at spatial scales from 1 to 30 m. 2. Apache cicadas were spatially aggregated in high‐density clusters averaging 3 m in diameter. A positive association between cicada density, estimated by exuvial density, and the per cent canopy cover of a native tree, Goodding's willow Salix gooddingii, was detected in a non‐spatial correlation analysis. No non‐spatial association between cicada density and saltcedar canopy cover was detected. 3. Tests for spatial cross‐correlation using the bivariate I_YZ indicated the presence of a broad‐scale negative association between cicada density and saltcedar canopy cover. This result suggests that large continuous stands of saltcedar are associated with reduced cicada density. In contrast, positive associations detected at spatial scales larger than individual quadrats suggested a spill‐over of high cicada density from areas featuring Goodding's willow canopy into surrounding saltcedar monoculture. 4. Taken together and considered in light of the Apache cicada's polyphagous habits, the observed spatial patterns suggest that broad‐scale factors such as canopy heterogeneity affect cicada habitat use more than host plant selection. This has implications for management of lower Colorado River riparian woodlands to promote cicada presence and density through maintenance or creation of stands of native trees as well as manipulation of the characteristically dense and homogeneous saltcedar canopies.