Composition and Distribution of Free Amino Acids in Flatpea (Lathyrus sylvestris L.) as Influenced by Water Deficit and Plant Age

Drought-stressed flatpea (Lathyrus sylvestris L.) plants from8 to 22 weeks old were analysed for nitrogen, soluble proteinand free amino acids. An increase in nitrogen and free aminoacid concentrations and a decrease in soluble protein levelwere observed in roots of plants up to 16 weeks old. The cumulativeconcentration of free amino acids increased with drought stress.Tissue concentrations of 2, 4-diaminobutyric acid (1.6–2.6%of the dry weight) were highest in leaves. Levels increasedsteadily, nearly doubling, in leaves and stems between weeks10 and 16. Levels in drought-stressed leaves were, on average,11.9% higher than those of controls. Estimated concentrationsof a mixture of 4-aminobutyric acid and an unknown amino acidwere highest in stems, increased in this tissue with age andtended to increase in stems and leaves and decrease in rootsin response to water deficit. Levels of the mixture of homoserineand another unidentified amino acid were not influenced by ageor water status of the plants. Root concentrations of asparagine,arginine, glutamine, aspartate, and another prominent, unidentifiedamino acid increased with plant age and reached a peak at thetime of flowering (14 to 18 weeks). Only the concentration ofthe unknown compound was elevated following drought stress.Concentrations of valine, isoleucine, leucine, phenylalanine,and methionine also increased during this period and were elevatedin drought-stressed plants. Proline levels increased with plantage and drought stress, but proline accounted for only about10% of the total free amino acids in the drought-stressed plants. Key words: 2, 4-Diaminobutyric acid, drought, flatpea     

Electrophoretic detection of the internal parasite, Aphidius matricariae in Myzus persicae

The presence of the internal parasite (Aphidius matricariae) of the aphid Myzus persicae can be identified by electrophoresis, and staining of several enzyme systems, of which malate dehydrogenase is recommended as the most reliable. It is suggested that the technique could be extended to other small insects, and that pest populations can be screened for percentage parasitism as an adjunct to insecticide and integrated control field trials.     

Effects of Patch-Burn Management on Dickcissel Nest Success in a Tallgrass Prairie

Abstract Grassland birds have declined more than any other North American habitat-associated bird community. Because most species of grassland birds evolved within heterogeneous landscapes created by the interaction of fire and grazing, traditional rangeland management that promotes homogeneity, including annual dormant-season burning combined with early-intensive grazing, might be partly responsible for these declines, especially in some regions of the Great Plains, USA. Recently, an alternative grassland management practice known as patch-burning has been promoted as a means of restoring heterogeneity to grasslands by mimicking the grazing-fire interaction that once occurred on the prairie before European settlement. From 2003 to 2004, we examined effects of patch-burning and traditional management (annual burning followed by early-intensive grazing) on the reproductive success of dickcissels (Spiza americana) in tallgrass prairie in Oklahoma. We monitored 296 dickcissel nests and found that dickcissel nesting phenology differed between traditional and patch-burned pastures. Specifically, dickcissels tended to initiate their nests later in the traditional pasture. Mean number of eggs laid and fledglings produced were similar between the treatments, but nest densities were higher in traditional pastures. Predation was the predominant cause of nest failure and was higher in traditional pastures than in patch-burned pastures. Brown-headed cowbird (Molothrus ater) parasitism was higher in traditional pastures than in patch-burned pastures. Overall, dickcissel nest success was higher in patch-burned pastures than in traditional pastures. The positive response of dickcissel nest success to patch-burn management provides further evidence that this practice can be a useful tool for grassland bird conservation. By creating a mosaic of different stature vegetation, patch-burn management enhances productivity of grassland bird species by providing a refuge area in the unburned patches that affords dickcissels and other nesting grassland birds some protection from the direct (e.g., trampling) and indirect (e.g., cowbird parasitism and predation) effects of grazing, which are not available under traditional management. Patch-burn management should be encouraged as a conservation strategy for grassland birds throughout the Great Plains.     

Hugo de Vries and the Development of Seed Aging Theory

Although work published in 1901 by de Vries has helped shapeour current understanding of the relationship between seed agingand genetic mutation, it has been fundamentally misinterpreted.Upon sowing 5 year-old Oenothera erythrosepala seed, de Vriesobtained an emergence of about 1 per cent. A relatively highproportion of the seedlings (about 40 per cent) displayed mutantphenotypes, mostly albida or lata. De Vries concluded that thesephenotypes, which were already present to a minor extent (about1 per cent) in unaged seed lots, were more resistant to agingthan the erythrosepala norm. Later opinion has dismissed DeVries' hypothesis, contending instead that the mutant phenotypesarose as a consequence of seed aging. A reconsideration of thesedata suggests that the De Vries' explanation remains more convincing;paradoxically, his work on seed aging has been influential becauseit has been consistently misunderstood. Mutation, Oenothera, seed aging     

Rates of seed removal by ants at heath and woodland sites in southeastern Australia

Ants often appear to be important post-dispersal seed predators, particularly in Australia where they are exceptionally abundant and apparently can remove large quantities of seeds from the ground. Rates of seed removal by ants usually are measured by recording removal from artificial seed baits, but the reliability of this approach has not been tested, nor have there been many attempts to integrate the results with the activity of seed-eating ants. This paper describes the rates of seed removal, estimated using a baiting technique that is tested for its reliability, by the seed-eating ants in adjacent heath and woodland sites at Wilson's Promontory, Victoria. Ants removed up to 100% of seeds, but rates varied according to seed species, size of seed clumps, season, time of exposure, and other aspects of the baiting technique. Methodological guidelines are provided to make baiting conditions approximately those likely to occur in nature. Seed-eating ants, particularly species of Rhytidoponera, Chelaner and Pheidole, were by far the most important post-dispersal seed predators, and patterns of seed removal were directly related to their composition, abundance and foraging behaviour. Lygaeid bugs were also observed eating seeds, but there was no evidence of seed predation by rodents or birds. The results suggest that seed predation by ants can substantially deplete seed reserves: however, its actual effect on seedling recruitment is likely to depend on many factors including seed size, crop size, weather, timing and location of seed fall, availability of alternative food sources, patterns of seedling mortality, and fire, none of which have been adequately investigated.     

Microsatellite markers for the whelk Buccinum undatum

Five microsatellite loci are described for the commercially exploited marine gastropod, Buccinum undatum. Levels of polymorphism were variable with three to 19 alleles per locus and expected heterozygosities of 0.26–0.94 in 60 individuals of the population from which the loci were isolated. Homozygote excess at two of the loci might be attributable to null alleles, and these loci should not be used in, for example, parentage analysis. Nevertheless, because null allele frequencies can be estimated and their effects partitioned, all are useful markers for studies of population differentiation.