Long term lily scale bulblet storage: effects of temperature and storage in polyethylene bags

Collections of lily genotypes are usually maintained by yearly planting, harvesting and storage of the bulbs. To facilitate this maintenance, a storage method has been developed for a collection of lily genotypes, including Asiatic hybrids, Oriental hybrids, Lilium longiflorum and L. henryi. Scale bulblets were stored either dry, sealed air-tight in polyethylene bags, or in moist vermiculite in open polyethylene bags for a period of 2 yr. The decrease in mass, sprouting proportion and ion leakage or sprouting proportion alone were determined for treatments carried out at -2°C, °C and 17°C. Sealing scale bulblets in polyethylene bags at -2°C resulted in the smallest decrease in mass, the least ion leakage and the highest sprouting proportion after 2 yr of storage.     

No overlap in song repertoire size between yearling and older Starlings Sturnus vulgaris

We recorded the song of 25 male Starlings Sturnus vulgaris to investigate differences in song characteristics between yearling and older males. Older males had significantly larger repertoire sizes and sang significantly longer average song bouts than yearling males. Since older males had almost twice as large a repertoire size as yearling males and since there was no overlap in repertoire size between yearling and older males, our data indicate that the repertoire size of Starlings increases after the first year of life. The largest difference between yearling and older males occurred in the 'variable song types' which are the song types containing most of the heterospecific imitations sung in a song bout.     

Major morphological changes in a Lake Victoria cichlid fish within two decades

During the upsurge of the introduced predatory Nile perch in Lake Victoria in the 1980s, the zooplanktivorous Haplochromis ( Yssichromis ) pyrrhocephalus nearly vanished. The species recovered coincident with the intense fishing of Nile perch in the 1990s, when water clarity and dissolved oxygen levels had decreased dramatically due to increased eutrophication. In response to the hypoxic conditions, total gill surface in resurgent H. pyrrhocephalus increased by 64%. Remarkably, head length, eye length, and head volume decreased in size, whereas cheek depth increased. Reductions in eye size and depth of the rostral part of the musculus sternohyoideus, and reallocation of space between the opercular and suspensorial compartments of the head may have permitted accommodation of larger gills in a smaller head. By contrast, the musculus levator posterior, located dorsal to the gills, increased in depth. This probably reflects an adaptive response to the larger and tougher prey types in the diet of resurgent H. pyrrhocephalus . These striking morphological changes over a time span of only two decades could be the combined result of phenotypic plasticity and genetic change and may have fostered recovery of this species.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 41–52.     

Substitution of top predators: effects of pike invasion in a subarctic lake

1. Invasions of top predators may have strong cascading effects in ecosystems affecting both prey species abundance and lower trophic levels. A recently discussed factor that may enhance species invasion is climate change and in this context, we studied the effects of an invasion of northern pike into a subarctic lake ecosystem formerly inhabited by the native top predator Arctic char and its prey fish, ninespined stickleback. 2. Our study demonstrated a strong change in fish community composition from a system with Arctic char as top predator and high densities of sticklebacks to a system with northern pike as top predator and very low densities of sticklebacks. A combination of both predation and competition from pike is the likely cause of the extinction of char. 3. The change in top predator species also cascaded down to primary consumers as both zooplankton and predator‐sensitive macroinvertebrates increased in abundance. 4. Although the pike invasion coincided with increasing summer temperatures in the study area we have no conclusive evidence that the temperature increase is the causal mechanism behind the pike invasion. But still, our study provides possible effects of future pike invasions in mountain lakes related to climate change. We suggest that future pike invasions will have strong effects in lake ecosystems, both by replacing native top consumers and through cascading effects on lower trophic levels.     

Photopic adaptations to a changing environment in two Lake Victoria cichlids

During the past 30 years, Lake Victoria cichlid fishes have encountered severe environmental and ecological changes including an introduced predator and new prey types. Furthermore, increased eutrophication has led to reduced water transparency and shifted the spectral composition of underwater light to longer wavelengths. In the present study, collections of two cichlid species, Haplochromis pyrrhocephalus and Haplochromis tanaos, from before and after the environmental changes, were compared with respect to their photopic resolution and sensitivity. Eyes of both species were dissected and retinal features were measured from tangential sections. In both species, the eyes became smaller, independently of body size. This decrease possibly occurred to make space for other structures that increased in size. In H. pyrrhocephalus, a significantly lower resolution was found. However, the size, and thus photon‐catching ability of the double cones, remained unchanged, despite the smaller eyes. In the modern populations of H. tanaos, the double cone size increased in relation to eye size, so that the photon‐catching ability of the smaller fish remained the same. However, no significant decrease in resolution was found. Shortwave sensitivity was found to be lower in both modern populations because of a reduction or the complete absence of single cones. The results obtained in the present study imply that these resurgent zooplanktivores are capable of adapting their eye morphology to the changed environmental conditions without losing crucial aspects used for survival and reproduction. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 328–341.     

Role of Rostellum Desiccation in Emasculation-Induced Phenomena in Orchid Flowers

The effects of relative humidity (RH) and of treatment of therostellum with aminoethoxyvinylglycine (AVG), 1-aminocyclopropane-1-carboxylicacid (ACC) and water-insoluble vacuum grease on emasculation-inducedphenomena in Cymbidium and Phalaenopsis flowers were investigated.Under conditions of high RH and after treatment of the rostellumwith water-insoluble grease, the normal response to emasculation(i.e. increased ethylene production, lip coloration and wilting)was absent. However, under conditions of high RH this responsecould be restored by the addition of 2.0 nmol ACC on to therostellar surface. Under conditions of low RH the response wasinhibited by AVG; this inhibition was partially reversed byaddition of 2.0 nmol ACC. The data provide evidence that desiccation of the rostellumis responsible for post-emasculation phenomena in orchid flowers. Key words: Emasculation, ethylene, orchids, senescence     

IMPROVED PERFORMANCE OF THE AROMASCAN A32S ELECTRONIC NOSE AND ITS POTENTIAL FOR DETECTING AROMA DIFFERENCES IN DAIRY PRODUCTS

The Aromascan A32S, an "electronic nose", was evaluated for its performance under conditions of total humidity control. Initially, it was shown that the very high concentration of water vapor in the headspace above a variety of food products used for this study, in comparison with the concentration of their aroma compounds, completely determined the response of the instrument's sensors. Differentiation between the food aromas was impossible. Only when the concentration of a nonaqueous analyte was increased to approximately the water vapor concentration was perfect distinction achieved between air samples with and without analyte. It was obvious that the instrument in its original form would not be capable of distinguishing subtle aroma differences as are encountered within one type of product in quality assurance, storage trials, taint studies etc. However, significant modification of the original version of the instrument and of the sample presentation procedure improved its performance. Now it was possible to distinguish in certain cases, not only between water vapor and food aromas, but also between different samples of the same types of dairy products. These tests were complemented by sensory evaluation by untrained panels. In this form, the Aromascan A32S offers a new vista for successful and reliable application in the food area.     

Analysis of the occurrence and distribution of tobacco rattle virus in field soil and disease in a subsequent tulip crop

The occurrence and distribution of tobacco rattle virus (TRV) in field plots was determined by soil bait-testing and disease incidence in tulips subsequently grown on these plots was studied. The virus occurred in patches, calculated as 1.5 m × 3.6 m. The presence of virus was not correlated with numbers of potential vector trichodorid nematodes. Of three trichodorid nematode species present, only Paratrichodorus teres transmitted TRV which, as with virus isolates obtained in bait-tests and from infected tulips, reacted in serological tests with an antiserum prepared against a Dutch isolate of pea-early browning virus (PEBV). Virus prevalence in a subsequent tulip crop was 0.8% and in a sample of tulip plants, virus was recovered only from plants showing virus symptoms. Plots from which TRV was recovered in bait-tests yielded significantly more virus diseased tulips than plots which tested negative for virus. Growing bait-plants in field-plots, as compared with greenhouse tests using soil collected as a series of sub-samples, resulted in an underestimate of the occurrence of TRV.