Seasonal occurrence of Aphis glycines and physiological responses of soybean plants to its feeding

The soybean aphid Aphis glycines Matsumura （Hemiptera： Aphididae） is an important pest of soybean in China. To monitor and manage this pest effectively it is neces-sary to understand its population dynamics and demographics, as well as the physiological responses of soybean plants to its feeding. In this study, using field surveying and suction-trap monitoring, we investigated the population dynamics of the soybean aphid in Xiuyan County, Liaoning Province in northeastern China during 2009-2012. The results indicatedthat the population dynamics of the soybean aphid followed a unimodal curve distribution, with the insect generally colonizing soybean fields from the middle of June to early Julyand the population reaching a peak between early July and early August. On the whole, soybean aphids occurred in suction-traps at least 2 weeks earlier than they were foundin field surveys. A total of 72 alates were collected by suction-trapping over the 4 years, with the earliest alate captures occurring on 28 May in 2009, 2011, 2012 and 4 June in 2010. The life table parameters clearly showed that this aphid had a short doubling time （4.73 ± 0.21 days）, and 7.36± 0.98 nymphs were produced by a soybean aphid adult during its lifetime （13.57 ± 0.30 days）. Finally, biochemical assays indicated that the amount of malondialdehyde and the activities of four defense-related enzymes in soybean leavessignificantly changed between 0 day and 7 days of aphid infestation. Polyphenol oxidase （PPO） and catalase （CAT） activities increased more dramatically after 1 day of aphid feed-ing. In addition, significantly higher levels of superoxide dismutase and CAT were found after aphid feeding for 7 days, whereas there was no significant change in the activitiesof peroxidase and PPO. Consequently, this study will be beneficial in determining the seasonal occurrence of the soybean aphid and selecting insect-resistant soybean varieties,and thus in developing a theoretical framework for appropriate management strategies.     

Photosynthetic metabolism of an antarctic diatom and its physiological responses to fluctuations in light

Summary The short-term incorporation of NaH¹⁴CO₃ (10 to 60 s) into photosynthetic products has been studied in the antarctic diatom Nitzschia turgiduloides. It appears that there are two pathways of inorganic carbon assimilation: the C₃ pathway (Calvin cycle) principally, on which are superimposed -carboxylation reactions. Photorespiration, which contributes to decrease the net photosynthesis rate, has also been reported. With regard to these results the antarctic diatom was not different from the temperate one. However, the antarctic diatom presents some distinctive features. -carboxylation reactions which are probably favoured in Antarctic waters because of the high nitrate or ammonium concentrations, and also because they are more economical in terms of energy, are enhanced at the expense of the Calvin cycle reactions. On the other hand, the photorespiration rate is lower than that observed in temperate species, leading to an enhancement of net photosynthesis rate; this seems to occur principally by the more advantageous tartronic semialdehyde pathway. These two features are more pronounced for cells grown under light: dark cycles, particularly a 2:2 hour regime, as compared to continuous light. By contrast to the temperate species Skeletonema costatum, changes in the light regime modifies not only the relative amount of inorganic carbon assimilated by the C₃ or the -carboxylation pathways, but also the total amount of CO₂ incorporated per g Chl a. The productivity is highest in 2:2 regime, which simulates conditions of vertical mixing encountered in Antarctic Ocean more than does a 12:12 regime. This finding corroborates the view that the antarctic diatom is well adapted to its environment, although its production is not optimal compared to that of the temperate species grown under the same conditions of irradiance and temperature. Whether this is a genetic adaptation needs to be examined.     

Deep-water aquatic plant communities in an oligotrophic lake: physiological responses to variable light

1. Oligotrophic Lake Waikaremoana, New Zealand, is used for hydroelectric power generation and the lake levels are manipulated within an operating range of 3 m. There was concern that rapidly changing water levels adversely affected the littoral zone by decreasing light availability in two ways: local turbidity caused by shoreline erosion at low water levels; and decreased light penetration to the deep littoral zone caused by high water levels in summer. 2. The littoral zone was dominated by native aquatic plants with vascular species to 6 m and a characean meadow below this to 16 m. The biomass and heights of the communities in the depth zone 0–6 m were reduced at a site exposed to wave action relative to those at a sheltered site. However, the community structure below 6 m was similar at exposed and sheltered sites. The lower boundary of the littoral zone was sharply delimited at 16 m and this bottom boundary remained constant throughout the year despite large seasonal changes in solar radiation and the 3 m variation in lake level. 3. There was evidence that the deep-water community consisting of Chara corallina had adapted physiologically to low-light conditions. Net light saturated photosynthesis (CO₂ exchange) per unit chlorophyll a (Chl a) was reduced to 1.7 μg C (μg Chl a)^?1 h^?1 at the lower boundary, half of that recorded at 5 m. The concentration of Chi a per gram of biomass (dry weight), was considerably greater at the lower boundary than higher in the profile [c. 7 mg Chl a (g dry wt)^?1 at 16 m vs. 4 mg Chl a (g dry wt)^?1 at 5 m]. Chl b also increased with depth and there was no change in the ratio of Chl a and Chl b with increasing depth. The saturation light intensity (I_k) of the community at the lower boundary was only 78 μmol photons m^?2 s^?1. Photosynthetic parameters (I_k and α) as well as the Chl a content remained relatively constant throughout the seasonal and short-term changes in radiation. 4. The photosynthetic characteristics of the littoral community were therefore not greatly affected by the lake level change caused by the present hydroelectric operations. However, the sharpness of the lower boundary and its extreme shade characteristics imply that the deep-water community would be sensitive to any further changes in underwater light availability.     

Mutations in the gene for the red/far-red light receptor phytochrome B alter cell elongation and physiological responses throughout Arabidopsis development.

Phytochromes are a family of plant photoreceptors that mediate physiological and developmental responses to changes in red and far-red light conditions. In Arabidopsis, there are genes for at least five phytochrome proteins. These photoreceptors control such responses as germination, stem elongation, flowering, gene expression, and chloroplast and leaf development. However, it is not known which red light responses are controlled by which phytochrome species, or whether the different phytochromes have overlapping functions. We report here that previously described hy3 mutants have mutations in the gene coding for phytochrome B (PhyB). These are the first mutations shown to lie in a plant photoreceptor gene. A number of tissues are abnormally elongated in the hy3(phyB) mutants, including hypocotyls, stems, petioles, and root hairs. In addition, the mutants flower earlier than the wild type, and they accumulate less chlorophyll. PhyB thus controls Arabidopsis development at numerous stages and in multiple tissues.     

Early developmental responses to seedling environment modulate later plasticity to light spectral quality

Correlations between developmentally plastic traits may constrain the joint evolution of traits. In plants, both seedling de-etiolation and shade avoidance elongation responses to crowding and foliage shade are mediated by partially overlapping developmental pathways, suggesting the possibility of pleiotropic constraints. To test for such constraints, we exposed inbred lines of Impatiens capensis to factorial combinations of leaf litter (which affects de-etiolation) and simulated foliage shade (which affects phytochrome-mediated shade avoidance). Increased elongation of hypocotyls caused by leaf litter phenotypically enhanced subsequent elongation of the first internode in response to low red:far red (R:FR). Trait expression was correlated across litter and shade conditions, suggesting that phenotypic effects of early plasticity on later plasticity may affect variation in elongation traits available to selection in different light environments.     

Comparing symbiotic performance and physiological responses of two soybean cultivars to arbuscular mycorrhizal fungi under salt stress

The presented experiments evaluated the symbiotic performance of soybean genotypes with contrasting salt stress tolerance to arbuscular mycorrhizal fungi (AMF) inoculation. In addition, the physiological stress tolerance mechanisms in plants derived from mutualistic interactions between AMF and the host plants were evaluated. Plant growth, nodulation, nitrogenase activity and levels of endogenous growth hormones, such as indole acetic acid and indole butyric acid, of salt-tolerant and salt-sensitive soybean genotypes significantly decreased at 200 mM NaCl. The inoculation of soybean with AMF improved the symbiotic performance of both soybean genotypes by improving nodule formation, leghemoglobin content, nitrogenase activity and auxin synthesis. AMF colonization also protected soybean genotypes from salt-induced membrane damage and reduced the production of hydrogen peroxide, subsequently reducing the production of TBARS and reducing lipid peroxidation. In conclusion, the results of the present investigation indicate that AMF improve the symbiotic performance of soybean genotypes regardless of their salt stress tolerance ability by mitigating the negative effect of salt stress and stimulating endogenous level of auxins that contribute to an improved root system and nutrient acquisition under salt stress.     

Adaptive thermoregulation in endotherms may alter responses to climate change

Climate change is one of the major issues facing natural populations and thus a focus of recent research has been to predict the responses of organisms to these changes. Models are becoming more complex and now commonly include physiological traits of the organisms of interest. However, endothermic species have received less attention than have ectotherms in these mechanistic models. Further, it is not clear whether responses of endotherms to climate change are modified by variation in thermoregulatory characteristics associated with phenotypic plasticity and/or adaptation to past selective pressures. Here, we review the empirical data on thermal adaptation and acclimatization in endotherms and discuss how those factors may be important in models of responses to climate change. We begin with a discussion of why thermoregulation and thermal sensitivity at high body temperatures should be co-adapted. Importantly, we show that there is, in fact, considerable variation in the ability of endotherms to tolerate high body temperatures and/or high environmental temperatures, but a better understanding of this variation will likely be critical for predicting responses to future climatic scenarios. Next, we discuss why variation in thermoregulatory characteristics should be considered when modeling the effects of climate change on heterothermic endotherms. Finally, we review some biophysical and biochemical factors that will limit adaptation and acclimation in endotherms. We consider both long-term, directional climate change and short-term (but increasingly common) anomalies in climate such as extreme heat waves and we suggest areas of important future research relating to both our basic understanding of endothermic thermoregulation and the responses of endotherms to climate change.     

Changes in temperature and light alter the flight speed of hornets (Vespa crabro L.)

Although the principal mechanisms of insect flight are well understood, knowledge about the influence of environmental factors on flight performance is scarce. We show that ambient temperature (TA) and illuminance have an influence on the flight performance of hornets. Moreover, the regulation of flight speed at different environmental conditions is sex specific. In roundabout experiments with tethered hornets, the flight speed of workers was independent of TA, while that of drones was negatively correlated with TA. We hypothesize that the reasons for these differences may lie in sex-specific cooling mechanisms; workers might regulate their body temperature through forced heat loss, whereas drones might reduce their heat production rates. At low illuminance, workers reduced their flight speed, whereas drones did not. Reduced flight speed at low illuminances is probably a behavioral mechanism of compensation for disadvantages caused by changing neuronal processes in the sensory neurons in darkness.     

Changes in morphological, photosynthetic and physiological responses of Mono Maple seedlings to enhanced UV-B and to nitrogen addition

In the southeast of the Qinghai-Tibetan Plateau of China, Mono Maple is a common species in reforestation processes. The paper mainly investigated the changes in morphological, photosynthetic and physiological responses of Mono Maple seedlings to UV-B radiation, nitrogen supply and their combination. The experimental design included two levels of UV-B treatments (ambient UV-B, 11.02 KJ m⁻² day⁻¹; enhanced UV-B, 14.33 KJ m⁻² day⁻¹) and two nitrogen levels (0; 20 g N m⁻² a⁻¹)—to determine whether the adverse effects of UV-B on plants are eased by nitrogen supply. Enhanced UV-B caused a marked decline in growth parameters, net photosynthetic rate, and photosynthetic pigments, whereas it induced an increase in reaction oxygen species (hydrogen peroxide accumulation and the rate of superoxide radical production) and malondialdehyde content. Enhance UV-B also induced an increase in antioxidant compounds of Mono Maple, such as UV-B absorbing compounds, proline content, and activities of antioxidant enzymes (peroxidase, superoxide dimutase and catalase). On the other hand, nitrogen supply caused an increase in some growth parameters, net photosynthetic rate, photosynthetic pigments and antioxidant compounds (peroxidase, proline content and UV-B absorbing compounds), and reduced the content of reaction oxygen species (H₂O₂ accumulation, the rate of O₂⁻ production) and malondialdehyde content under ambient UV-B. However, under enhanced UV-B, nitrogen supply inhibited some growth parameters, and increased H₂O₂ accumulation, the rate of O₂⁻ production and MDA content, though proline content, UV-B absorbing compounds and activities of POD and SOD increased. These results implied that enhanced UV-B brought harmful effects on Mono Maple seedlings and nitrogen supply made plants more sensitive to enhanced UV-B, though increased some antioxidant activity.     

Comparative physiological responses to stressors in animals.

1. The species-specific experimental response to stressors (SSERTS) analysis has been applied to a number of species under varied short and long term conditions. 2. The measure provides quantitative data relating to the physiological responses of animals when exposed to stressors and results are presented comparing these for different methods of immobilization, euthanasia, etc. at intra- and inter-species level. 3. It is suggested that the SSERTS measure is of greater value for measuring the responses of animals to stressors than is the measurement of the concentration of single blood variables.     

Proteins involved in biophoton emission and flooding-stress responses in soybean under light and dark conditions

To know the molecular systems basically flooding conditions in soybean, biophoton emission measurements and proteomic analyses were carried out for flooding-stressed roots under light and dark conditions. Photon emission was analyzed using a photon counter. Gel-free quantitative proteomics were performed to identify significant changes proteins using the nano LC–MS along with SIEVE software. Biophoton emissions were significantly increased in both light and dark conditions after flooding stress, but gradually decreased with continued flooding exposure compared to the control plants. Among the 120 significantly identified proteins in the roots of soybean plants, 73 and 19 proteins were decreased and increased in the light condition, respectively, and 4 and 24 proteins were increased and decreased, respectively, in the dark condition. The proteins were mainly functionally grouped into cell organization, protein degradation/synthesis, and glycolysis. The highly abundant lactate/malate dehydrogenase proteins were decreased in flooding-stressed roots exposed to light, whereas the lysine ketoglutarate reductase/saccharopine dehydrogenase bifunctional enzyme was increased in both light and dark conditions. Notably, however, specific enzyme assays revealed that the activities of these enzymes and biophoton emission were sharply increased after 3 days of flooding stress. This finding suggests that the source of biophoton emission in roots might involve the chemical excitation of electron or proton through enzymatic or non-enzymatic oxidation and reduction reactions. Moreover, the lysine ketoglutarate reductase/saccharopine dehydrogenase bifunctional enzyme may play important roles in responses in flooding stress of soybean under the light condition and as a contributing factor to biophoton emission.     

Species interactions alter evolutionary responses to a novel environment

Studies of evolutionary responses to novel environments typically consider single species or perhaps pairs of interacting species. However, all organisms co-occur with many other species, resulting in evolutionary dynamics that might not match those predicted using single species approaches. Recent theories predict that species interactions in diverse systems can influence how component species evolve in response to environmental change. In turn, evolution might have consequences for ecosystem functioning. We used experimental communities of five bacterial species to show that species interactions have a major impact on adaptation to a novel environment in the laboratory. Species in communities diverged in their use of resources compared with the same species in monocultures and evolved to use waste products generated by other species. This generally led to a trade-off between adaptation to the abiotic and biotic components of the environment, such that species evolving in communities had lower growth rates when assayed in the absence of other species. Based on growth assays and on nuclear magnetic resonance (NMR) spectroscopy of resource use, all species evolved more in communities than they did in monocultures. The evolutionary changes had significant repercussions for the functioning of these experimental ecosystems: communities reassembled from isolates that had evolved in polyculture were more productive than those reassembled from isolates that had evolved in monoculture. Our results show that the way in which species adapt to new environments depends critically on the biotic environment of co-occurring species. Moreover, predicting how functioning of complex ecosystems will respond to an environmental change requires knowing how species interactions will evolve.     

Biochemical and physiological comparison of heavy metal-triggered defense responses in the monocot maize and dicot soybean roots

Defense responses against cadmium, arsenic and lead were compared in two crop plants such as the monocotyledonous maize (Zea mays cv. Quintal) and dicotyledonous soybean (Glycine max cv. Korada). The applied metals caused root growth retardation, membrane damage and subsequent loss of cell viability, while enhanced H₂O₂ generation, lipid peroxidation and lignification were detected with respect to corresponding controls. The measured data suggest that soybean was in general more tolerant to tested doses of metals and showed more pronounced defense responses than maize. Concurrently, the total activity of β-1,3-glucanases, a subgroup of so called pathogenesis-related defense proteins, was comparable in root extracts of both plant types. Though in a view of previous comparative genome approaches the β-1,3-glucanases do not mirror the differences in the cell wall structure and architecture between the monocots and dicots, we show that in both plant types they clearly respond to metal stress. Accumulation patterns of different glucanase isoforms upon exposure to tested metals indicate that they do contribute to plant defense mechanisms during exposure to heavy metals and their biological role is more complex than expected.     

传统大豆发酵食品中大豆异黄酮的生理保健机能的研究进展

大豆异黄酮属于黄酮类化合物,是一类具有重要生物活性的化合物,在大豆和传统大豆发酵食品中含量丰富。近年来研究发现大豆异黄酮在预防癌症、骨质疏松症、心血管疾病和改善妇女更年期综合症等方面具有广泛的生理活性,因此引起了国内外学者的广泛关注。大豆异黄酮的研究,不仅为功能性大豆制品的开发提供理论基础,也为人们合理的膳食提供参考。综述近年来国内外对大豆异黄酮生理保健机能的研究进展。