Growth efficiency ofDaphinia magna. I. The effect of food concentration

Summary In 24 hour experiments in a flow-through set-up the growth efficiency ofDaphnia magna fed withChlorella vulgaris was determined at different food concentrations. All parameters were measured simultaneously. Food uptake was measured with the Coulter Counter and in each experiment the conversion factor for cell volumes to joules was determined. Growth was measured directly in joules by burningDaphnia at the end of the experiment in a calorimeter and a parallel group ofDaphnia at the start of the experiment. No effect of food concentration on growth efficiency was found.     

Coding of chemosensory information by the nervous system ofDaphnia magna andEnchytraeus albidus under conditions of action of high environmental temperature

Chemical stimuli (glutamate, glycine, cAMP, and AMP) cause slow and pronounced changes in thermostability of the organisms ofDaphnia magna andEnchytraeus albidus, which can be explained by functioning of not adapted or partially adapted chemoreceptive cells. In experiments with action of purines on the thermostability, the presence inE. albidus of two different chemoreceptors, specific accordingly to cAMP and non-cyclic purines, is shown. A complex extremal stimulus—reaction function, with several optimal values of intensity of the chemical stimulus, at its action on theD. magna andE. albidus thermostability, shows that the elements (neurons or their systems) with the extremal input-output function take part in coding the chemosensory information by the nervous system of these animals.     

The effect of temperature on maturation threshold body-length in Daphnia magna

Aquatic invertebrates are usually larger at maturity when water temperatures are lower. For the freshwater cladoceran Daphnia, it has been suggested that a threshold size must be attained to initiate maturation, which results two instars later in the deposition of eggs into the brood chamber. This threshold size is believed to temperature on maturation threshold body-length in Daphnia magna. Daphnids were raised from birth to maturity under three constant-temperature regimes (12°C, 16°C, 22°C), and two food-level conditions. Animals were measured daily, and a body-length based maturation threshold determined for each individual. We demonstrate that mean maturation threshold length is negatively correlated with ambient water temperature. Further, daphnids with a larger threshold length tended to be larger at maturity. A maturation threshold linked to body length suggests that reduced variation in size at maturity is adaptive, even at the cost of additional variation in instar number or age at maturity.     

The quantum efficiency of photosystem II and its relation to non-photochemical quenching of chlorophyll fluorescence; the effect of measuring-and growth temperature

The relation between the quantum yield of oxygen evolution of open photosystem II reactions centers (_p), calculated according to Weis and Berry (1987), and non-photochemical quenching of chlorophyll fluorescence of plants grown at 19°C and 7°C was measured at 19°C and 7°C. The relation was linear when measured at 19°C, but when measured at 7°C a deviation from linearity was observed at high values of non-photochemical quenching. In plants grown at 7°C this deviation occurred at higher values of non-photochemical quenching than in plants grown at 19°C. The deviations at high light intensity and low temperature are ascribed to an increase in an inhibition-related, non-photochemical quenching component (q_I).The relation between the quantum yield of excitation capture of open photosystem II reaction centers (_exe), calculated according to Genty et al. (1989), and non-photochemical quenching of chlorophyll fluorescence was found to be non-linear and was neither influenced by growth temperature nor by measuring temperature.At high PFD the efficiency of overall steady state electron transport measured by oxygen-evolution, correlated well with the product of q _N and the efficiency of excitation capture (_exe) but it deviated at low PFD. The deviations at low light intensity are attributed to the different populations of chloroplasts measured by gas exchange and chlorophyll fluorescence and to the light gradient within the leaf.Abbreviations F₀ basic fluorescence - F₀ basic fluorescence, thylakoid in energized state - F_m maximal fluorescence - F_m maximum fluorescence in energized state - F_s steady state fluorescence - F_v maximal variable fluorescence - PFD photon flux density - PS II_rc Photosystem II reaction center - q_F0 quenching of basic fluorescence - q_E energy related quenching - q_N non-photochemical quenching:-q_f-total quenching - q_I inhibition-related quenching - q_p photochemical quenching - q_r quenching due to state transition - R_d dark respiration - _p PS II efficiency of excitation capture of open PS II_rc - _pe extrapolated minimal value of _p - _p0 extrapolated maximal value of _p - _si quantum efficiency of linear electron transport, calculated from gas exchange measurements based on incident light - _sf quantum efficiency of linear electron transport, calculated from fluorescence measurements, based on incident measuring light     

Effects of type II pyrethroids on Daphnia magna: dose and temperature dependences.

Environmental contamination with various insecticides remains an actual problem. In this connection, investigation of toxicologic hazard of insecticides is essential. In this work, effects of the type II pyrethroids (fenvalerate, cypermethrin and deltamethrin) on Daphnia magna were determined. It was found for the first time that not only low doses (up to 10(-12) M) of the above-mentioned chemicals but also extremely low doses (up to 10(-29) M) showed toxicological action on the invertebrates both at optimal (23 +/- 0.5 degrees C) and increased (28 +/- 0.5 degrees C) temperature. At higher temperature, toxic effects were more pronounced.     

The ultrastructure of the so-called olfactory setae on the antennula ofDaphnia magna Straus (Crustacea,Cladocera)

A group of nine sensory setae is found on the tip of the antennula ofDaphnia magna in both sexes. Inside a seta four dendrites are situated, each with one receptor cilium. The receptor cilia extend through a liquor space into the exterior part of the seta. The exterior part of the liquor space is divided from the interior part by a knob-like thickening of the innermost layer of the epicuticle, the basal bead. The basal bead narrows the liquor space and the receptor cilia. The interior part of the liquor space is surrounded by five sheath cells, the exterior part by a thin cuticle. In the exterior part the receptor cilia branch partly and reach a terminal pellet on the tip of the seta. The terminal pellet is a thickened part of the epicuticle. It is permeable to several dissolved substances. It is the exterior part of the receptor that projects over the tip of the antennula and seems to be the entire seta. During the premoult the fifth sheath cell builds up the articulation of the seta, the fourth the basal bead, and the third the shaft of the seta. The first sheath cell forms the cuticular sheath. The organ seems to be a chemoreceptor, but the adequate stimulus is as yet unknown.     

Energetics of Bacillus stearothermophilus growth: molar growth yield and temperature effects on growth efficiency.

The major growth yield of a prototrophic strain of Bacillus stearothermophilus under aerobic conditions on salts medium containing ammonium nitrate as the nitrogen source and glucose or succinate as the carbon source was maximal at the lowest growth temperature employed and decreased steadily as the temperature was raised. The temperature optima for growth yield and for growth rate were thus different. The molar growth yield values of the thermophile, especially at the lower growth temperatures, were similar to those reported for aerobically grown mesophilic bacteria, both on glucose and on succinate. At the higher growth temperatures, a lower proportion of glucose carbon was incorporated into cells and a correspondingly greater proportion was left incompletely utilized in the medium, mostly as acetate. This suggests a greater inefficiency in the coordination of the nonoxidative and oxidative phases of glucose metabolism at the gigher temperatures. Another factor causing a decreased cell yield at higher temperatures was possibly an uncoupling of energy production from respiration. The rates of respiration by intact cells of the thermophile on glucose and on succinate followed the Arrhenius relationship from 55 C to 20 C, which is some 20 C below the minimal growth temperature of the organism. The Arrhenius constant was 17.1 kcal/mol for glucose oxidation and 13.5 kcal/mol for succinate oxidation. These results are comparable to those reported for some mesophiles, and they suggest that the inability of the thermophile to grow at temperatures below about 41 C is not due to an abnormally high temperature coefficient for the uptake and oxidation of the carbon source.     

The effect of root temperature on growth of curled parsley

Summary Curled parsley was grown at root-zone temperature (RZT) of 18, 21, 24, 27 and 36°C at air temperature (AT) of 18 and 21°C. Maximum growth was obtained at 18°C AT and 24°C RZT, but there were no significant differences between 18 and 27°C RZT. Shoot and root growth were severely inhibited at 36°C constant RZT. The growth was also retarded when RZT rose to 36°C for 30 minutes per day, even when compared to a RZT of constant 27°C. This indicates that a short exposure to RZT above 30°C retards growth. A relatively low daily average RZT did not compensate for the damage caused by a short daily high temperature exposure. Optimum temperature for curled parsley seems to be about 21°C. Report No. 316.     

The development of dormancy in bulblets of Lilium speciosum generated in vitro. II. The effect of temperature

Upon harvest, lily ( Lilium speciosum Thunb. cv. Rubrum) bulblets generated in vitro under standard conditions (11 weeks at 20°C) were dormant and needed a cold treatment prior to planting. During culture in vitro at 20°C, the bulblets proceeded through three phases: (1) at first they were non–viable and non-dormant (up to 5 weeks), (2) then viable and non-dormant (5–9 weeks) and (3) finally viable and dormant (from 9 weeks onwards). At 15°C, the bulblets became viable but did not develop dormancy, even after protracted culture. The results suggest that the development of dormancy depends upon an accumulation of'heat units'occurring at temperatures higher than 15°0. At 25°C, the succession of the three phases occurred more rapidly than at 20°C and heat units were accumulated more rapidly. During the third period, the chilling requirement increased showing that heat units continued to be accumulated during this period.
Dormancy connotes an arrest of growth. In lily bulblets, however, the number of scales continued to increase after the induction of dormancy at 20 or 25°C. Many of the scales initiated before the onset of dormancy were formed by swelling of a petiole, whereas, after the onset of dormancy, all scales were formed directly from a primordium. We conclude that the development of dormancy corresponds to a switch in the development of the primordium. Thus, after the induction of dormancy the primordium lost the ability to become a leaf and always developed into a scale.     

The effect of temperature on the growth of A. niger in solid state fermentation

A kinetic model of solid state fermentation with temperature deactivation of microorganisms is presented. The experimental results of cultivation of Aspergillus niger on a mixture of wheat bran and beet pulp in temperature range from 26 °C to 40 °C were used to estimate the parameters of the model. The activation energies of growth, thermal deactivation and maintenance have been calculated.List of Symbols C _CX mol/g proportionality coefficient - E _d J/mol energy of activation for thermal deactivation - E _g J/mol energy of activation for growth - J _CO2 mol/gh carbon dioxide evolution rate - k _d h^–1 thermal deactivation constant - k _g h^–1 growth kinetic constant - k _x h^–1 net growth constant - m h^–1 maintenance coefficient - N _CO2 mol amount of carbon dioxide - N _{m, CO2} mol maximum amount of carbon dioxide generated by growth - t h time - X g dry biomass weight - X _m g maximum biomass weight - X dimensionless biomass weight - X _0,r g real mass of inoculum - X _0,a g apparent mass of inoculum - X ₀ dimensionless apparent mass of inoculum - dimensionless maintenance coefficient This work was supported by the Committee of Scientific Research under grant No 3 3401 91 02.     

Control of polytenic replication in dipteran larvae. II. Effect of growth temperature

A comparison has been made, by Feulgen photometry, of the polytene nuclei of the salivary glands of a wild-type strain of Drosophila melanogaster grown at 17°C and 25°C, respectively. Despite the fact that the time period of the larval stage was more than doubled at the lower temperature, the DNA values were the same in magnitude and similar in distribution of replication classes at each of the stages studied. The data have been interpreted as indicating that, so long as the larval state prevails, initiation of polytenic replication occurs upon completion of the previous cycle.     

Description of the individual growth of Daphnia magna (Crustacea: Cladocera) through the von Bertalanffy growth equation. Effect of photoperiod and temperature

Daphnia magna is a cladoceran used as a model organism in aquatic ecology and ecotoxicology studies. Because growth is a critical parameter to study the effect of environmental conditions on the development of zooplankters, the somatic growth of D. magna was measured here and described by the von Bertalanffy growth equation (VBGE), a mathematical model widely used in fisheries management. For this purpose, the effect of two temperatures (20 and 25°C) and two photoperiod conditions (12:12 and 16:8, light:dark) was assayed. Experiments began with neonate females and were finished when parthenogenetic females reached the age of 41 days; they were fed the microalga Ankistrodesmus falcatus (400,000 cell ml⁻¹, 12 mg l⁻¹, dry weight). According to the VBGE, maximal length (L _max) was inversely correlated with the growth rate (K). The highest L _max (6.45 mm) was for the females grown at 20°C with the 12:12 photoperiod, whereas the maximum growth rate (K = 0.182 ± 0.010) was for individuals grown at 25°C with the 12:12 photoperiod. The number of clutches during the studied period was significantly higher for females grown at 25°C, 12:12. Temperature affected the growth rate and the maximum size in D. magna; interaction of temperature with photoperiod was also noteworthy. The VBGE was a nifty way to assess the effects of the tested environmental factors.     

The effect of nitrogen supply on growth and water-use efficiency of xylem-tapping mistletoes

Xylem-tapping mistletoes are known to have normally a higher rate of transpiration and lower water-use efficiency than their hosts. The relationships between water relations, nutrients and growth were investigated for Phoradendron juniperinum growing on Juniperus osteosperma (a non-nitrogen-fixing tree) and for Phoradendron californicum growing on Acacia greggii (a nitrogen-fixing tree). Xylem sap nitrogen contents were approximately 3.5 times higher in the nitrogen-fixing host than in the non-nitrogen-fixing host. The results of the present study show that mistletoe growth rates were sevenfold greater on a nitrogen-fixing host. At the same time, however, the differences in water-use efficiency between mistletoes and their hosts, which were observed on the non-nitrogen-fixing host did not exist when mistletoes were grown on hosts with higher nitrogen contents in their xylem sap. Growth rates and the accumulation of N, P, K, and Ca as well as values for carbon-isotope ratios of mistletoe tissues support the hypothesis that the higher transpiration rates of mistletoes represent a nitrogen-gathering mechanism.Abbreviation ¹³C carbon-isotope ratio Dedicated to Professor Dr. Hubert Ziegler on the occasion of his 60th birthday     

The temperature sensitivity of mutations in species of the virilis group of Drosophila. II. The effect of temperature on the maternal effect on the puffed marker following hybridization

The influence of temperature (17 and 31 degrees) on the maternal effect of mutation Puffed (Pu) in Drosophila hybrids has been studied. In the hybrids female D. littoralis +/+ x male D. virilis Pu/Pu, the stage of formation of black ring on anterior spiracles in the 3rd larval instar is sensitive to 31 degrees. In the hybrids female D. virilis Pu/Pu x male D. littoralis +/+, the expression of Pu gene manifests the maternal effect and as a result, two temperature-sensitive stages are found. The first one--onset of embryogenesis (2 to 4 hrs). At the temperature 17 degrees, the penetrance of Pu increases. The second stage is sensitive to 31 degrees and coincides with the period of black rings formation on anterior spiracles in the 3rd laval instar. It has been shown that at least two genetic systems take part in the formation of this feature. One group of genes controls the maternal effect and is sensitive to low temperature in the early embryogenesis of the hybrids female D. virilis x male D. littoralis. The second one--Pu gene and its modifiers--is active during the 2nd half of the 3rd larval instar and is heat-sensitive.