Additional evidence for separable responses to auxin in soybean hypocotyl

Additional evidence for two separable responses to auxin is presented. The average of 24 control experiments indicated lag times of 12.4 and 35.4 min, and maximum rates of 0.57 and 0.54 mm hr⁻¹, for the first and second response, respectively. The auxin analog 4-azido-2-chlorophenoxyacetic acid increased the lag time of the second response (but not the first), resulting in the temporal separation of the two responses. Plots of elongation rates against time, taken from the literature, allowed the characterization of the two responses in monocotyls and dicotyls. Study of published rate-time elongation curves showed that the maximum rate of the first response is frequently greater than the maximum rate of the second response; however, the maximum rate of the second response has not yet been shown to exceed the maximum rate of the first response.     

Small‐scale genetic structure and mating patterns in an extensive sessile oak forest (Quercus petraea (Matt.) Liebl.)

Oaks (Quercus) are major components of temperate forest ecosystems in the Northern Hemisphere where they form intermediate or climax communities. Sessile oak (Quercus petraea) forests represent the climax vegetation in eastern Germany and western Poland. Here, sessile oak forms pure stands or occurs intermixed with Scots Pine (Pinus sylvestris). A large body of research is available on gene flow, reproduction dynamics, and genetic structure in fragmented landscapes and mixed populations. At the same time, our knowledge regarding large, contiguous, and monospecific populations is considerably less well developed. Our study is an attempt to further develop our understanding of the reproduction ecology of sessile oak as an ecologically and economically important forest tree by analyzing mating patterns and genetic structure within adult trees and seedlings originating from one or two reproduction events in an extensive, naturally regenerating sessile oak forest. We detected positive spatial genetic structure up to 30 meters between adult trees and up to 40 meters between seedlings. Seed dispersal distances averaged 8.4 meters. Pollen dispersal distances averaged 22.6 meters. In both cases, the largest proportion of the dispersal occurred over short distances. Dispersal over longer distances was more common for pollen but also appeared regularly for seeds. The reproductive success of individual trees was highly skewed. Only 41 percent of all adult trees produced any offspring while the majority did not participate in reproduction. Among those trees that contributed to the analyzed seedling sample, 80 percent contributed 1–3 gametes. Only 20 percent of all parent trees contributed four or more gametes. However, these relatively few most fertile trees contributed 51 percent of all gametes within the seedling sample. Vitality and growth differed significantly between reproducing and nonreproducing adult trees with reproducing trees being more vital and vigorous than nonreproducing individuals. Our study demonstrates that extensive, apparently homogenous oak forests are far from uniform on the genetic level. On the contrary, they form highly complex mosaics of remarkably small local neighborhoods. This counterbalances the levelling effect of long‐distance dispersal and may increase the species’ adaptive potential. Incorporating these dynamics in the management, conservation, and restoration of oak forests can support the conservation of forest genetic diversity and assist those forests in coping with environmental change.     

Compensation of large motion sensor displacements during long recordings of limb movements

In motion capture applications using electromagnetic tracking systems the process of anatomical calibration associates the technical frames of sensors attached to the skin with the human anatomy. Joint centers and axes are determined relative to these frames. A change of orientation of the sensor relative to the skin renders this calibration faulty. This sensitivity regarding sensor displacement can turn out to be a serious problem with movement recordings of several minutes duration. We propose the “dislocation distance” as a novel method to quantify sensor displacement and to detect gradual and sudden changes of sensor orientation. Furthermore a method to define a so called fixed technical frame is proposed as a robust reference frame which can adapt to a new sensor orientation on the skin. The proposed methods are applied to quantify the effects of sensor displacement of 120 upper and lower limb movement recordings of newborns revealing the need for a method to compensate for sensor displacement. The reliability of the fixed technical frame is quantified and it is shown that trend and dispersion of the dislocation distance can be significantly reduced. A working example illustrates the consequences of sensor displacement on derived angle time series and how they are avoided using the fixed technical frame.     

Soil and root nutrient chemistry structure root-associated fungal assemblages in temperate forests

Root-associated fungi (RAF) link nutrient fluxes between soil and roots and thus play important roles in ecosystem functioning. To enhance our understanding of the factors that control RAF, we fitted statistical models to explain variation in RAF community structure using data from 150 temperate forest sites covering a broad range of environmental conditions and chemical root traits. We found that variation in RAF communities was related to both root traits (e.g., cations, carbohydrates, NO₃⁻) and soil properties (pH, cations, moisture, C/N). The identified drivers were the combined result of distinct response patterns of fungal taxa (determined at the rank of orders) to biotic and abiotic factors. Our results support that RAF community variation is related to evolutionary adaptedness of fungal lineages and consequently, drivers of RAF communities are context-dependent.     

How Prof. Burnstock’s enthusiasm supported P2 receptor research in Germany

Purinergic Signalling -     

Species- and clone-specific responses to environmental stimuli in the cladocerans Bosmina cornuta and B. pellucida - a comparison with Daphnia

We studied the variation of small-scale swimming behaviour in eight Bosmina cornuta and ten B. pellucida clones in response to key environmental factors to test whether swimming behaviour and genotypes are linked in non-Daphnia cladocerans. We quantified (1) the short-term responses to changes in temperature, light intensity and pH, (2) the response to long-term temperature acclimation, and (3) the pH-related survival rates. Vertical swimming activity S was quantified in cuvette experiments as crossings of a line at 2 cm height per individual an hour. S differed significantly among species and conspecific clones. At any temperature, light intensity and pH tested, B. cornuta (clone variation: 40-58 crossings/ind.- h) showed a higher vertical swimming activity than B. pellucida (clone variation: 25-48 crossings/ind.- h). A short-term change of water temperature (range tested: 10-25C) only affected S of B. cornuta, whereas that of B. pellucida remained unaltered. In contrast, S increased with rising temperature following long-term temperature acclimation (range tested: 10-20C) in both species. Swimming activity was inversely related to the light intensity (range tested: 60-60,000 lux), but decrease of activity was stronger in B. pellucida (44′ 12 crossings/ind - h) than in B. cornuta (50′ 40 crossings/ind.- h). Short-term changes of pH (range tested: 4-6) did not influence swimming activity in any species, although a prolonged exposure (24 h) to pH 4 was lethal. Thus, Bosmina showed behavioural responses which permit to distinguish between the species and which are related to their seasonal succession and distribution pattern.     

Reverse Action of Ribonuclease T1 Variants In ICE

Abstract

Synthesis of guanylyl(3′→5′)cytidine catalysed by RNase T1 variants (Tyr42Trp, Tyr24Trp and GluSSAla) was studied in frozen aqueous systems at-10°C and in solution at 0°C. Freezing the reaction mixture resulted in significantly enhanced dinucleoside monophosphate yields independently of the effect of mutation on substrate binding and catalytic mechanism. We assume that the protonation state of the catalytic residues is influenced by freezing, possibly due to conformational changes of the enzyme proteins.