The Formation and Development of Adventitious Buds on Potato Sprouts

Potato tubers were pre-sprouted in trays at 10 C for 28 d.The scale leaves at the base of the sprouts were marked andtubers then planted in field soil. Twenty-eight days after plantingan average of three adventitious buds were present per sproutcompared with an average of six below-ground axillary buds.Ten per cent of adventitious buds formed stolons compared withalmost 100 per cent of axillary buds. Similar responses wereseen with tubers pre-sprouted either in the light or dark.     

Relationship between the bovine major histocompatibility complex (BoLA), erythrocyte markers and susceptibility to mastitis in Icelandic cattle

Summary. Milk and blood samples were obtained from three Icelandic dairy herds. The herds were monitored regularly for mastitis incidence. Cell counts, adenosine triphosphate (ATP) and antitrypsin levels of the milk samples were recorded. In addition, red cell and BoLA typing were performed on the blood. Although cell counts and ATP levels showed significant associations with mastitis, antitrypsin levels did not. Red blood cell antigens N'₂ and S₁ and the lymphocyte antigen detected by the monoclonal antibody M7 were associated with low cell counts, whilst BoLA w6 and w6.1 were associated with high cell counts. BoLA w6.2 and w11 showed significant association with high antitrypsin levels. Only ED116 showed a significant association with mastitis.     

Ecological sensitivity of Australian rainforests to selective logging

To assess the ecological consequences of selective logging in the major rainforest areas in Australia, past studies are reviewed with respect to the following: recovery of stand structure; regeneration capacity; individual tree growth and species composition of stands; hydrologie impact; floristics; wildlife; soil nutrient levels; fire susceptibility; and incursion of weeds and diseases. Although rainforest logging has become a sensitive issue in the community and its effects are of concern to ecologists, relatively few scientific studies of selective logging have been published. Thus, the full nature and extent of ecological changes to Australian rainforests due to this form of disturbance cannot yet be determined. However, some cautious interpretation of the studies that have been completed is possible. Following a single selective logging, the changes indicated by individual studies often appeared to be relatively minor. It is suggested that many of these effects are not extensive or irreversible and might not persist beyond structural recovery of the rainforest. However, two changes were identified as likely to persist beyond structural recovery. These are: a post-logging difference in the proportional representation of major overstorey tree species and a reduction in the numbers of large-diameter trees. Further, results indicate that more extensive and longer-lasting changes may result from multiple selective loggings, especially if the time between successive loggings is short. Even with light logging intensities, a conservative interval of at least 60 years between selective loggings, to allow canopy and below-canopy conditions to be restored, is indicated. Apart from disturbance frequency, the studies reviewed raise questions as to whether long-term natural disturbance effects per se are distinguishable from long-term selective logging effects. A need for further work is highlighted. Overall, there appears to be a distinction between the recovery capability of the more northerly mainland rainforests and those of Tasmania. Slower growth in the more southerly rainforests, compounded by a geographical susceptibility to summer drought, increases the possibility of fire damage following selective logging.     

Comparative behavioural responses of silvereyes (Zosterops lateralis) and European blackbirds (Turdus merula) to secondary metabolites in grapes

Secondary metabolites in fruit are compounds that are not directly associated with plant growth; some are directly related to plant reproductive processes, specifically seed protection and dispersion. There is a complex and species‐specific interaction between these plant compounds and their avian seed dispersers. To determine whether two important secondary metabolites in wine grapes – tannins and colour pigments – might be important cues to two of the avian species that forage on wine grapes, and how species‐specific this interaction might be, comparative field experiments were run with Australasian silvereyes (Zosterops lateralis) and European blackbirds (Turdus merula). Both species were offered a glucose/fructose artificial nectar with increasing concentrations of grape tannins. In a second experiment, they were offered both green and purple artificial grapes where only the colour differed. Both species showed aversion to tannins; silvereyes appeared to have greater tolerance than blackbirds of tannin concentrations above 5%. In summer no preference was shown between green and purple coloured artificial grapes, but in late autumn blackbirds took only purple grapes whereas silvereyes pecked mostly at green. Links between tannin for seed protection and colour signals to birds are discussed. Colour may cue the two species to different species‐specific aspects of fruit nutritive value.     

Evidence for rodent pollination in Erica hanekomii (Ericaceae)

Pollination by rodents, originally discovered in Cape Proteaceae, is known from a handful of plant lineages and may be more widespread than current data suggest. Here, we demonstrate the occurrence of this mode of pollination in Erica, the largest plant genus in the Cape flora of South Africa. The localized endemic Erica hanekomii appears to be adapted for pollination by rodents, on account of its low, mat‐forming habit with many dull‐coloured, pendulous flower heads, large volumes (up to c. 30 µL per inflorescence) of sucrose‐dominated nectar, hook‐shaped styles and late winter flowering phenology. Rodents trapped in the vicinity of E. hanekomii plants had many thousands of Erica tetrads in their droppings. Nocturnal laboratory observation showed that Acomys subspinosus (Cape spiny mouse) is adept at manipulating E. hanekomii inflorescences and lapping nectar without destroying gynoecia. During terrarium experiments, pollen was deposited mainly on the rostrum, but also on the chest area and forelegs of A. subspinosus. No birds or insects were seen to visit E. hanekomii in the field. Whereas natural fruit set was 73%, inflorescences from which rodents, but not insects, were excluded using mesh cages, had fruit set of just 3.3%. Exclusion of all visitors resulted in zero seed production. Broken anther rings (a sign of flower visitation in Erica) were observed in 90.1% of flowers in the field and 92% of flowers exposed to rodents in the laboratory, but in virtually none of the flowers from which rodents were selectively excluded. This first record of a non‐flying mammal pollination syndrome in Ericaceae raises interesting new questions about the origins of the rodent pollination system and the selective factors that lead to its evolution. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 166 , 163–170.     

Urban catchment hydrology overwhelms reach scale effects of riparian vegetation on organic matter dynamics

1. Urbanisation severely affects stream hydrology, biotic integrity and water quality, but relatively little is known about effects on organic matter dynamics. Coarse particulate organic matter (CPOM) is a source of energy and nutrients in aquatic systems, and its availability has implications for ecosystem productivity and aquatic communities. In undisturbed environments, allochthonous inputs from riparian zones provide critical energy subsidies, but the extent to which this occurs in urbanised streams is poorly understood. 2. We investigated CPOM inputs, standing stocks, retention rates and retention mechanisms in urban and peri‐urban streams in Melbourne, Australia. Six streams were chosen along a gradient of catchment urbanisation, with the presence of reach scale riparian canopy cover as a second factor. CPOM retention was assessed at baseflow via replicate releases of marked Eucalyptus leaves where the retention distance and mechanism were recorded. CPOM and small wood (>1 cm diameter) storage were measured via cores and direct counts, respectively, while lateral and horizontal CPOM inputs were assessed using riparian litter traps. Stream discharge, velocity, depth and width were also measured. 3. CPOM inputs were not correlated with urbanisation, but were significantly higher in ‘closed’ canopy reaches. Urbanisation and riparian cover altered CPOM retention mechanisms, but not retention distances. Urban streams showed greater retention by rocks; while in less urban streams, retention by small wood was considerably higher. CPOM and small wood storage were significantly lower in more urban streams, but we found only a weak effect of riparian cover. 4. These findings suggest that while riparian vegetation increases CPOM inputs and has modest/weak effects on storage, catchment scale urbanisation decreases organic matter availability. Using an organic matter budget approach, it appears likely that the increased frequency and magnitude of high flows associated with catchment urbanisation exerts an overriding influence on organic matter availability. 5. We conclude that to maintain both organic matter inputs and storage, the restoration and protection of streams in urban or rapidly urbanising environments relies on the management of both riparian vegetation and catchment hydrology.     

Effects of lipid environment on the conformational changes of an ABC importer

In order to shuttle substrates across the lipid bilayer, membrane proteins undergo a series of conformation changes that are influenced by protein structure, ligands, and the lipid environment. To test the effect of lipid on conformation change of the ABC transporter MolBC, EPR studies were conducted in lipids and detergents of variable composition. In both a detergent and lipid environment, MolBC underwent the same general conformation changes as detected by site-directed EPR spectroscopy. However, differences in activity and the details of the EPR analysis indicate conformational rigidity that is dependent on the lipid environment. From these observations, we conclude that native-like lipid mixtures provide the transporter with greater activity and conformational flexibility as well as technical advantages such as reconstitution efficiency and protein stability.