Inhibition of the growth of apple pollen tubes by EDTA, surfactants and fungicides

The effects of EDTA (ethylene diamine tetraacetic acid), Kresoxim‐methyl, Wettable Sulphur 80 WP and the surfactants Triton X‐100, Triton X‐114, Dehydol TA 5 and Dehydol TA 29 on pollen tube growth of Malus domestica, Borkh. cvs ‘Golden Delicious’ and ‘Mondial Gala’ were determined by image analysis. The ED₅₀ ‐ and ED₉₀ ‐ values (effective doses giving 50% and 90% reduction of growth) of the chemicals, except for the surfactants, were determined. The selected test substances showed an inhibiting effect on pollen tube growth, with Kresoxim‐methyl being the most active. Surfactants are components of pesticides and they also caused inhibition of pollen tube growth but only at application rates more then 10‐fold higher than typically recommended. Pollen of both apple cultivars were almost equally sensitive to the chemicals.     

Projected changes in mineral soil carbon of European croplands and grasslands, 1990–2080

We present the most comprehensive pan‐European assessment of future changes in cropland and grassland soil organic carbon (SOC) stocks to date, using a dedicated process‐based SOC model and state‐of‐the‐art databases of soil, climate change, land‐use change and technology change. Soil carbon change was calculated using the Rothamsted carbon model on a European 10 × 10′ grid using climate data from four global climate models implementing four Intergovernmental Panel on Climate Change (IPCC) emissions scenarios (SRES). Changes in net primary production (NPP) were calculated by the Lund–Potsdam–Jena model. Land‐use change scenarios, interpreted from the narratives of the IPCC SRES story lines, were used to project changes in cropland and grassland areas. Projections for 1990–2080 are presented for mineral soil only. Climate effects (soil temperature and moisture) will tend to speed decomposition and cause soil carbon stocks to decrease, whereas increases in carbon input because of increasing NPP will slow the loss. Technological improvement may further increase carbon inputs to the soil. Changes in cropland and grassland areas will further affect the total soil carbon stock of European croplands and grasslands. While climate change will be a key driver of change in soil carbon over the 21st Century, changes in technology and land‐use change are estimated to have very significant effects. When incorporating all factors, cropland and grassland soils show a small increase in soil carbon on a per area basis under future climate (1–7 t C ha^?1 for cropland and 3–6 t C ha^?1 for grassland), but when the greatly decreasing area of cropland and grassland are accounted for, total European cropland stocks decline in all scenarios, and grassland stocks decline in all but one scenario. Different trends are seen in different regions. For Europe (the EU25 plus Norway and Switzerland), the cropland SOC stock decreases from 11 Pg in 1990 by 4–6 Pg (39–54%) by 2080, and the grassland SOC stock increases from 6 Pg in 1990 to 1.5 Pg (25%) under the B1 scenario, but decreases to 1–3 Pg (20–44%) under the other scenarios. Uncertainty associated with the land‐use and technology scenarios remains unquantified, but worst‐case quantified uncertainties are 22.5% for croplands and 16% for grasslands, equivalent to potential errors of 2.5 and 1 Pg SOC, respectively. This is equivalent to 42–63% of the predicted SOC stock change for croplands and 33–100% of the predicted SOC stock change for grasslands. Implications for accounting for SOC changes under the Kyoto Protocol are discussed.     

Morphometric Analysis of the Growth of Phsp70-ipt Transgenic Tobacco Plants

The effect of introducing a supplementary ipt-gene into thegenome of Nicotiona tabacum L. cv. Petit Havana SR 1 is studiedon the morphological plant development. The ipt-gene, accountingfor the biosynthesis of cytokinins, was coupled to the heat-induciblehsp70- promoter from Drosophila melanogaster. Besides the influenceof the hormonal changes involved, the effects of the experimentalconditions are examined, namely the in vitro growth conditionsfor selecting transformed plants and the heat treatment to induceipt-gene expression. The phenotype of the plants is determined by the tissue sensitivityto three factors: (1) heat treatment reduces stem elongationand diameter growth; (2) in vitro pre-cultivation also reducesstem elongation; and (3) expression of the ipt-gene stimulatesdiameter growth, induces debudding of the axillary shoots andinhibits root development. In addition, axillary bud developmentindicates that in vitro cultivation affects ipt-gene expression. Key words: Cytokinin, heat treatment, in vitro cultivation, ipt-gene, morphology     

Observations on the zooplankton and littoral macroinvertebrates of Nyumba ya Mungu reservoir, Tanzania

Eight species of Crustacea and 28 species of Rotifera were identified in zooplankton samples from Nyumba ya Mungu reservoir. In all localities the dominant organism was the copepod Thermocyclops hyalinus. Cladocerans and rotifers made a variable contribution. Insects, among which the Chironomidae were pre-eminent, formed the major component of littoral macroinvertebrate communities. Oligochaetes, crustaceans and gastropods, including vectors of Schistosomiasis, were rare or restricted in distribution. In contrast to the deep end of the lake, where submerged trees were the poorest substrate, those at the shallow end supported a high biomass of invertebrates, since prolonged exposure had accelerated rotting and facilitated colonisation by the burrowing nymphs of Povilla. The variety of invertebrates on stony and muddy shores was increased when rooted emergent plants were present. The richest benthic community was found in submerged beds of Ceratophyltum. It is suggested that drawdown and the restricted development and movement of floating vegetation, have limited the spread of gastropods in the lake. Zooplankton, chironomid larvae and pupae, and ephemeropteran nymphs were shown to be important in the diet of small carnivorous and omnivorous fish species.     

THE ULTRASONIC SONG OF THE MOTH AMYNA NATALIS (LEPIDOPTERA: NOCTUIDAE: ACONTIINAE)

ABSTRACT

In Malaysia, males of the noctuid moth Amyna natalis were observed producing a continuous ultrasonic song of high intensity (about 102 dB SPL measured at a distance of 10 cm). The frequency spectrum of the sound impulses had its peak between 60 and 80 kHz. During song production the animals were perching on plants and moving their wings up and down quickly. Simultaneously, by twisting the wings it seems likely that a male-specific “bubble” in the forewing functions as a tymbal, resulting in sound production.     

Comparative functional morphology of the wings of Diptera

Wings of representative species of the order Diptera were compared with a simple model structure in which corrugated spars diverge from a V-shaped leading edge spar. Both develop torsion and camber when subjected to aerodynamic loads, forming a propeller shape. Both the leading edge and the cubitus of flies' wings twist basally, allowing camber to be set up as the media hinges up or down at the arculus. Three different wing types were identified: stiff wings possessing two or three main spars; and wings capable of ventral flexion. In wings possessing only two spars, found mainly in the Nematocera, control of camber is achieved largely by the use of cross veins. Wing control and flight are generally imprecise. The third spar, found in most Brachycera, in the Syrphidae and in the Conopidae controls camber and helps support a broader wing. Finer control of camber is exerted by marginal cross veins, and these insects generally have precise, darting flight. Ventral flexion mechanisms are found in the Simuliidae, the Stratiomyiidae, and widely in the Schizophora. Control of ventral flexion, which occurs at the end of the downstroke, allows fast, unpredictable manoeuvres. Functional similarities indicate either phylogenetic relationship or convergence.     

Hydrologic effects on riparian vegetation in a boreal river: an experiment testing climate change predictions

Climate change is expected to alter the magnitude and variation of flow in streams and rivers, hence providing new conditions for riverine communities. We evaluated plant ecological responses to climate change by transplanting turfs of riparian vegetation to new elevations in the riparian zone, thus simulating expected changes in water‐level variation, and monitored the results over 6 years. Turfs moved to higher elevations decreased in biomass and increased in species richness, whereas turfs transplanted to lower elevations gained biomass but lost species. Transplanted plant communities responded slowly to the new hydrologic conditions. After 6 years, biomass of transplanted turfs was statistically indistinguishable from target level controls, but species richness and species composition of transplants were intermediate between original and target levels. By using projections of future stream flow according to IPCC climate change scenarios, we predict likely changes to riparian vegetation in boreal rivers. Climate‐driven hydrologic changes are predicted to result in narrower riparian zones along the studied Vindel River in northern Sweden towards the end of the 21st century. Present riparian plant communities are projected to be replaced by terrestrial communities at high elevations as a result of lower‐magnitude spring floods, and by amphibious or aquatic communities at low elevations as a result of higher autumn and winter flows. Changes to riparian vegetation may be larger in other boreal climate regions: snow melt fed spring floods are predicted to disappear in southern parts of the boreal zone, which would result in considerable loss of riparian habitat. Our study emphasizes the importance of long‐term ecological field experiments given that plant communities often respond slowly and in a nonlinear fashion to external pressures.