Effects of triazole growth retardants on oilseed rape; photosynthesis of single leaves

Rates of CO₂ exchange were measured for single leaves on oilseed rape plants after application of triapenthenol and BAS111. For leaves which expanded after treatment, there was no detectable change in the rate of photosynthesis per unit leaf area compared with the control for either chemical about 3 wk after application. For fully expanded leaves at the time of application a reduction in the rate of photosynthesis per unit leaf area occurred and was sustained for at least 2 wk. The reduction in the rate of photosynthesis is explained by decreased stomatal conductance.     

Gynandromorphs of the pycnogonid Anoplodactylus portus

A large sample of the pycriogonid Anoplodactylus portus , collected from the Pacific side of the Panama Canal Zone, contains a high percentage of gynandromorphs. The literature on aquatic arthropod gynandromorphs is outlined. The nature and variations of the sexual mosaic population are described and discussed. The several morphological differences between normal and mosaic members of the population are illustrated, and the possible origin of these gynandromorphs is discussed.     

Stomatal responses to light and CO2 are dependent on KCI concentration

Abstract. The responses of stomata on detached epidermis of Commelina communis to light and CO₂ have been shown to be strongly dependent on the concentration of KCI in the incubation medium. There was a high sensitivity to the two stimuli in 50 mM KCI, but there were much reduced responses at lower and higher concentrations. It is considered that an appropriate choice of medium is essential if useful physiological studies of stomata are to be made using epidermal strips. At lower KCI concentrations, the ability of the stomata to open is thought to be limited by the availability of K⁺ ions, and at higher concentrations their ability to close may be affected because of an inhibition of the net efflux of K⁺. The production of malate was related to KCI concentration, and was largest in the medium containing zero KCI which supported poor stomatal responses to light and CO₂It is concluded that malate metabolism is unlikely to play a central part in the changes in guard cell turgor that are brought about by light and CO₂.     

Isolation and characterization of tetranucleotide microsatellite markers in a mouth‐brooding haplochromine cichlid fish (Pseudocrenilabrus multicolor victoriae) from Uganda

Eight tetranucleotide microsatellite loci were isolated from the haplochromine cichlid fish, Pseudocrenilabrus multicolor victoriae, an important model species for studies in respiratory ecology, conservation, and evolution. We surveyed variation at these loci in 23 individuals from western Uganda, finding four to 19 alleles per locus and an average expected heterozygosity of 0.8575. These microsatellite loci will be used to examine gene flow and population structure in Ugandan P. m. victoriae.     

Microsatellite markers isolated from polyploid wood‐sorrel Oxalis alpina (Oxalidaceae)

Twelve polymorphic microsatellite loci were isolated from polyploid alpine wood‐sorrel, Oxalis alpina (Oxalidaceae), and optimized for future studies of its breeding system. The loci were screened for variability among 72 individuals from Pinos Altos, New Mexico. The primers amplified loci with allele number ranging from two to 17 per locus and with estimates of Nei's genetic diversity varying from 0.10 to 0.99. These primers provide an opportunity to use polymorphic DNA markers to study the causes of breeding system variability in this species.     

Microsatellite markers isolated from barn swallows (Hirundo rustica)

Fifteen polymorphic microsatellite DNA loci were isolated from barn swallow (Hirundo rustica) and optimized for future studies of radiation‐induced mutations in populations from Ukraine. The loci were screened for variability among 25 individuals from two populations. The primers amplified loci with relatively high numbers of alleles ranging from five to 32 alleles per locus and polymorphic information content from 0.481 to 0.951. Observed heterozygosity varied from 0.458 to 0.960. None of the loci showed deviations from Hardy–Weinberg equilibrium in either population.     

Adaptive differences in plant physiology and ecosystem paradoxes: insights from metabolic scaling theory

The link between variation in species‐specific plant traits, larger scale patterns of productivity, and other ecosystem processes is an important focus for global change research. Understanding such linkages requires synthesis of evolutionary, biogeograpahic, and biogeochemical approaches to ecological research. Recent observations reveal several apparently paradoxical patterns across ecosystems. When compared with warmer low latitudes, ecosystems from cold northerly latitudes are described by (1) a greater temperature normalized instantaneous flux of CO₂ and energy; and (2) similar annual values of gross primary production (GPP), and possibly net primary production. Recently, several authors attributed constancy in GPP to historical and abiotic factors. Here, we show that metabolic scaling theory can be used to provide an alternative ‘biotically driven’ hypothesis. The model provides a baseline for understanding how potentially adaptive variation in plant size and traits associated with metabolism and biomass production in differing biomes can influence whole‐ecosystem processes. The implication is that one cannot extrapolate leaf/lab/forest level functional responses to the globe without considering evolutionary and geographic variation in traits associated with metabolism. We test one key implication of this model – that directional and adaptive changes in metabolic and stoichiometric traits of autotrophs may mediate patterns of plant growth across broad temperature gradients. In support of our model, on average, mass‐corrected whole‐plant growth rates are not related to differences in growing season temperature or latitude. Further, we show how these changes in autotrophic physiology and nutrient content across gradients may have important implications for understanding: (i) the origin of paradoxical ecosystem behavior; (ii) the potential efficiency of whole‐ecosystem carbon dynamics as measured by the quotient of system capacities for respiration, R, and assimilation, A; and (iii) the origin of several ‘ecosystem constants’– attributes of ecological systems that apparently do not vary with temperature (and thus with latitude). Together, these results highlight the potential critical importance of community ecology and functional evolutionary/physiological ecology for understanding the role of the biosphere within the integrated earth system.     

Ecohydrological impacts of woody-plant encroachment: seasonal patterns of water and carbon dioxide exchange within a semiarid riparian environment

Across many dryland regions, historically grass‐dominated ecosystems have been encroached upon by woody‐plant species. In this paper, we compare ecosystem water and carbon dioxide (CO₂) fluxes over a grassland, a grassland–shrubland mosaic, and a fully developed woodland to evaluate potential consequences of woody‐plant encroachment on important ecosystem processes. All three sites were located in the riparian corridor of a river in the southwest US. As such, plants in these ecosystems may have access to moisture at the capillary fringe of the near‐surface water table. Using fluxes measured by eddy covariance in 2003 we found that ecosystem evapotranspiration (ET) and net ecosystem exchange of carbon dioxide (NEE) increased with increasing woody‐plant dominance. Growing season ET totals were 407, 450, and 639 mm in the grassland, shrubland, and woodland, respectively, and in excess of precipitation by 227, 265, and 473 mm. This excess was derived from groundwater, especially during the extremely dry premonsoon period when this was the only source of moisture available to plants. Access to groundwater by the deep‐rooted woody plants apparently decouples ecosystem ET from gross ecosystem production (GEP) with respect to precipitation. Compared with grasses, the woody plants were better able to use the stable groundwater source and had an increased net CO₂ gain during the dry periods. This enhanced plant activity resulted in substantial accumulation of leaf litter on the soil surface that, during rainy periods, may lead to high microbial respiration rates that offset these photosynthetic fluxes. March–December (primary growing season) totals of NEE were ?63, ?212, and ?233 g C m^?2 in the grassland, shrubland, and woodland, respectively. Thus, there was a greater disparity between ecosystem water use and the strength of the CO₂ sink as woody plants increased across the encroachment gradient. Despite a higher density of woody plants and a greater plant productivity in the woodland than in the shrubland, the woodland produced a larger respiration response to rainfall that largely offset its higher photosynthetic potential. These data suggest that the capacity for woody plants to exploit water resources in riparian areas results in enhanced carbon sequestration at the expense of increased groundwater use under current climate conditions, but the potential does not scale specifically as a function of woody‐plant abundance. These results highlight the important roles of water sources and ecosystem structure on the control of water and carbon balances in dryland areas.