Transpiration in seven plant species colonizing a fishpond shore

In 7 species (Eleocharis palustris R. Br.,Juncus bufonius L.,Gypsophila muralis L.,Trifolium repens L.,Agrostis stolonifera L.,Potentilla anserina L. andAchillea millefolium L.) growing in a gradient of habitats from aquatic to terrestrial, on a sandy fishpond shore in Southern Bohemia, Czechoslovakia, the daily course of transpiration rate and water content was assessed gravimetrically in their cut-off transpiring parts on two typical summer days. Transpiration rate was largely controlled by microclimate but depressions occurred inJuncus and in some species growing in the drier habitats. The highest instantaneous transpiration rate and total daily transpiration per unit dry weight, about 100 mg g^?1 min^?1 and 50 g g^?1 d^?1, respectively, were recorded inAchillea andTrifolium. The water turnover rate ranged from 16.1 g g^?1 (H₂O) d^?1 inJuncus to 10.7 inGypsophila. The estimated daily maximum water saturation deficit was highest inEleocharis (45.7%) and lowest inAchillea (15.0%). The adaptational significance of the observed phenomena is discussed.     

Response ofPhragmites australis,Glyceria maxima,andTypha latifolia to additions of piggery sewage in a flooded sand culture

One-year-old clones ofPhragmites australis, Glyceria maxima, andTypha latifolia were subjected to different doses of piggery sewage added in flooded sand cultures for one growing season.Phragmites responded to increasing sewage doses by an increase in the shoot biomass and a decrease in root porosity and carbohydrate levels in rhizomes;Glyceria responded by a decrease in the biomass and depth penetration of the root system, and carbohydrate levels in rhizomes. In contrast,Typha increased both root porosity and carbohydrate levels in rhizomes. These findings are discussed in relationship to plant performance in sewage-polluted wetlands.     

Cry9Ca1 Toxin, a Bacillus thuringiensis Insecticidal Crystal Protein with High Activity against the Spruce Budworm (Choristoneura fumiferana)

The Cry9Ca1 toxin from Bacillus thuringiensis was significantly more toxic to spruce budworm (Choristoneura fumiferana) than the Cry1Ab6, Cry1Ba1, Cry1Ca2, Cry1Da1, Cry1Ea1, and Cry1Fa2 toxins. It displayed high activity against silkworm (Bombyx mori) but was not toxic to black army cutworm (Actebia fennica) or gypsy moth (Lymantria dispar). The Cry9Ca1 is the most effective spruce budworm toxin known to date and may offer promise for control and resistance management of that species.     

Autoradiographic study of the effect of 5-aminouracil on the S phase and mitosis of barley root meristems

The effect of 5-aminouracil on the S phase and mitosis in root meristems of barley embryos cultivated in the liquid nutrient solution was followed. Embryos were cultivated in different concentrations of 5-aminouracil (200 ppm, 400 ppm and 750 ppm) for 48 h. The drug postponed the onset of mitosis. In the lowest concentration used, synchronization was observed even in the presence of 5-aminouracil. In higher concentrations, mitosis was suppressed irregularly with increasing concentration. 5-aminouracil slowed down the rate of DNA synthesis during S phase and prolonged the S phase, as measured by the utilization of [³H] thymidine. The drug does not influence considerably the entry of cells into the S phase. The transition from G₂ to mitosis is delayed in the presence of 5-aminouracil, especially in higher concentrations. After prolonged treatment with 5-aminouracil, all the effects of the drug on the mitotic cycle decrease continuously.     

Utilization of the label from bacterial [3H] DNA by isolated barley roots and embryos under different conditions

[³H] DNA fromEscherichia coli and [³H] thymidine were applied, in sterile conditions, on isolated barley embryos and on roots excised from these embryos, both cultivated in the liquid medium and on halves of barley seeds, through the endosperm bridge. In embryos and roots, the labelled compounds were applied in 1.5% sucrose + 0.2 SSC alone, or together with either unlabelled thymidine or DEAE-dextran. Similar labelling indices were found after [³H] thymidine and [³H] DNA treatment which shows that the activity of [³H] DNA is utilized during the S phase. After application of [³H] thymidine, only cell nuclei in S phase were labelled. After the application of [³H] DNA an extranuclear label, in addition to the labelling of nuclei in the S phase, was observed in some experimental variants. The density of label above labelled nuclei after [³H] DNA treatment sharply decreased when unlabelled thymidine or DEAE-dextran was added, while the density of label above nuclei labelled by [³H] thymidine decreased when unlabelled thymidine but not DEAE-dextran was added. The labelling of nuclei with the label from [³H] DNA is the result of degradation of exogenous DNA reutilization of low molecular weight products. Extranuclear labelling is most probably due to the polymerous or partly degraded DNA.     

Response of Lymantria dispar L. (Lepidoptera: Lymantriidae) to Bacillus thuringiensis subsp. kurstaki at different ingested doses and temperatures

We examined mortality and feeding inhibition response of Lymantria dispar L. (Lepidoptera: Lymantriidae) larvae to ingested doses of Bacillus thuringiensis subsp. kurstaki as a function of dose, instar and temperature. We developed generalized (logistic) linear mixed models and a mixture survival model, commonly used in medical statistics, to analyze the complex data set. We conducted bioassays of Foray 48B with larvae from the NJSS laboratory stock, using droplet imbibing or force-feeding to ensure dose ingestion. The dose causing mortality in 50% of the test population (LD₅₀) under standard test conditions (22 °C) ranged from 0.019 International Units (IU)/larva for first instar larvae (L₁) to 1.6 IU/larva for L₄. Temperature affected larval mortality in two ways. Mortality occurred sooner and progressed more rapidly with increasing temperature (13-25 °C) at each dose level and instar, while the maximum level of mortality attained by each instar decreased with increasing rearing temperature. The mechanisms underlying this effect are being investigated. Larvae that survived exposure to B. thuringiensis resumed feeding after a period that was dependent on instar, dose, and temperature. The equations describing observed mortality and feeding recovery responses were used to construct a simulation model, which was able to predict both processes, and which forms the basis for a process-oriented model that can be used as a decision support tool in aerial sprays.     

Performance of Sparganium emersum Rehm. shoots in response to sediment quality

Biomass, dry matter production, nutrient (N, P, K, Ca, Mg) contents and accumulation were studied in Sparganium emersum Rehm. in Southern Bohemia, Czech Republic. The aim was to determine the species' relationship to sediment quality and water flow and to estimate its nutrient uptake from sediments. The plants were sampled from six field sites, and one cultivation experiment was carried out. In the field, dry weight, shoot length and leaf number related to one another, while probably responding to nutrient supply both from water and sediment, while leaf width seemed to be correlated with other environmental factors. In the experiment, all measured growth parameters, except for the number of leaves, reflected sediment quality. The standing stocks of N, P and K reflected best the sediment nutrient contents in the field, both in running and standing water, but the stocks were generally higher in running water. In the experiment, all the measured growth parameters were correlated with sediment nutrient contents, and for N and P they were also with these nutrient contents in the plants. Nutrient removal from the rooting media was substantial for nitrogen. S. emersum was found to grow well in sediments rich both in mineral nutrients and organic matter.