Changes in parameters of the plasmalemma ATPase during cold acclimation of apple (Mains domestica) tree bark tissues

A plasmalemma fraction was isolated from homogenized apple tree (Mains domestica Borkh 'Golden Delicious') hark tissues using aqueous phase partitioning and ultra-centrifugation. Results of marker enzyme assays indicated that a membrane preparation highly enriched in plasma membranes was obtained. ATPase activity in this preparation possessed a high specificity for ATP as substrate, was inhibited by vanadate, diethylstilbcsterol and dicyclohexylcarbocHimide, and was insensitive to inhibitors of mitochondria! and tonoplasl ATPases. Specific activity of the plasma-lemma ATPase increased during cold acclimation prior to the attainment of vegetative maturity. Kinetic parameters (Km, Vln) determined from assays performed at different temperatures (10, 30°C) indicated a differential effect of cold acclimation on enzyme activity. Vm increased during cold acclimation, whereas Km increased when determined at 30°C but declined at 10°C. Acclimation treatments during April and May resulted in alteration of ATPase kinetics in the absence of any increase in bark frost hardiness. Changes in ATPase kinetics may be related more to enhanced low temperature metabolism than to frost hardiness per se.     

猫肾离体保存中亚细胞水平上Ca^2＋浓度的X—射线微区分析

应用定量Ｘ－射线微区分析技术结合细胞化学技术,分析测定用单纯冷冻法保存离体猫肾脏过程中肾脏细胞的胞浆、线粒体、内质网、细胞核等细胞器内的Ｃａ２＋浓度变化,并探索钙通道阻滞剂对这种变化的影响。保存３６小时及７２小时后,线粒体与胞浆中Ｃａ２＋的峰背比极显著地提高,内质网、细胞核中钙颗粒减少。添加Ｖｅｒａｐａｍｉｌ后,保存过程中细胞器内Ｃａ２＋无显著变化。线粒体中的Ｃａ２＋峰背比与胞浆中的呈强的正相关,ｒ＝０９９０。实验结果显示：保存过程中,Ｃａ２＋由钙库（内质网等）进入胞浆中,线粒体在胞浆Ｃａ２＋浓度高时摄取Ｃａ２＋,而钙通道阻滞剂可抑制该过程。     

The persistence of short‐term cold acclimation in Drosophila melanogaster (Diptera: Drosophilidae)

Daily and seasonal fluctuations in temperature present significant challenges for the survival of many ectothermic species that can be tempered via thermal acclimation. In the present study, we use multiple naturally derived genotypes of Drosophila melanogaster to determine the persistence of beneficial short‐term thermal acclimation on subsequent survival after cold shock. We found that the benefit of short‐term acclimation persisted for 2 h in most genotypes after a rapid cold hardening treatment. Genotype did not directly influence the persistence of short‐term acclimation benefits, indicating that environmental variation may be more important for the persistence of acclimation benefits rather than genetic capacity for acclimation. The present study extends the current understanding of the limits and importance of short‐term acclimation events, providing greater detail on the timing of the loss of short‐term acclimation benefits in a genetically variable natural population.     

Spatial co‐localisation of extreme weather events: a clear and present danger

Extreme weather events have become a dominant feature of the narrative surrounding changes in global climate with large impacts on ecosystem stability, functioning and resilience; however, understanding of their risk of co‐occurrence at the regional scale is lacking. Based on the UK Met Office’s long‐term temperature and rainfall records, we present the first evidence demonstrating significant increases in the magnitude, direction of change and spatial co‐localisation of extreme weather events since 1961. Combining this new understanding with land‐use data sets allowed us to assess the likely consequences on future agricultural production and conservation priority areas. All land‐uses are impacted by the increasing risk of at least one extreme event and conservation areas were identified as the hotspots of risk for the co‐occurrence of multiple event types. Our findings provide a basis to regionally guide land‐use optimisation, land management practices and regulatory actions preserving ecosystem services against multiple climate threats.     

Seed reproductive biology of the rare aquatic carnivorous plant Aldrovanda vesiculosa (Droseraceae)

Despite the unprecedented global decline in extant populations of Aldrovanda vesiculosa in the last century, little is known about the reproductive biology of this iconic aquatic carnivorous plant. This study aimed to investigate the role of seed‐based reproduction in the ecology of A. vesiculosa, with particular focus on the interplay between the regulation of seed dormancy by temperature cues and the efficacy of exogenous ethylene gas to act as a germination stimulant, the desiccation capacity and long‐term storage potential of seeds for conservation purposes. Sexual reproduction appears to be extremely limited in both natural and naturalized populations across three continents, with high variability in the success of flowering and seed set between sites and between seasons. Overall, flowering yielded few fertile fruit (6–19% of flowers producing fertile fruit) and seed viability was variable but generally low (29–88%). Fecundity appears to be influenced by seasonal climatic conditions and microhabitat characteristics. Aldrovanda vesiculosa possesses physiologically dormant seeds, with germination stimulated by exposure to ethylene gas (>90% germination) at 25 °C. Seeds appear sensitive to desiccation and sub‐zero temperature storage, with no germination and markedly reduced embryo growth after storage of seeds for >1 month at 15 °C and 15% relative humidity or after short‐term (24 h) storage at ?18 °C. In the absence of significant conservation and restoration initiatives, the continuing decline of dystrophic freshwater wetland habitats globally leaves A. vesiculosa facing extinction. As the successful long‐term storage of seeds appears unfeasible based on the approaches described in this study, other alternatives for germplasm conservation such as cryostorage of vegetative tissues or zygotic embryos must be considered for establishing long‐term ex situ collections of critical germplasm.     

Habitat temperature and the temporal scaling of cold hardening in the high Arctic collembolan, Hypogastrura tullbergi (Schäffer)

Abstract.  1. Cold tolerance is a fundamental adaptation of insects to high latitudes. Flexibility in the cold hardening process, in turn, provides a useful indicator of the extent to which polar insects can respond to spatial and temporal variability in habitat temperature.
2. A scaling approach was adopted to investigate flexibility in the cold tolerance of the high Arctic collembolan, Hypogastrura tullbergi , over different time-scales. The cold hardiness of animals was compared from diurnal warming and cooling phases in the field, and controlled acclimation and cooling treatments in the laboratory. Plasticity in acclimation responses was examined using three parameters: low temperature survival, cold shock survival, and supercooling points (SCPs).
3. Over time-scales of 24–48 h, both field animals from warm diurnal phases and laboratory cultures from a 'warm' acclimation regime (18 °C) consistently showed greater or equivalent cold hardiness to animals from cool diurnal phases and acclimation regimes (3 °C).
4. No significant evidence was found of low temperature acclimation after either hours or days of low temperature exposure. The cold hardiness of H. tullbergi remained 'seasonal' in character and mortality throughout was indicative of the summer state of acclimatization.
5. These data suggest that H. tullbergi employs an 'all or nothing' cryoprotective strategy, cold hardening at seasonal but not diel-temporal scales.
6. It is hypothesised that rapid cold hardening offers little advantage to these high Arctic arthropods because sub-zero habitat temperatures during the summer on West Spitsbergen are rare and behavioural migration into soil profiles offers sufficient buffering against low summer temperatures.     

Specific and unspecific responses of plants to cold and drought stress

Different environmental stresses to a plant may result in similar responses at the cellular and molecular level. This is due to the fact that the impacts of the stressors trigger similar strains and downstream signal transduction chains. A good example for an unspecific response is the reaction to stressors which induce water deficiency e.g. drought, salinity and cold, especially frost. The stabilizing effect of liquid water on the membrane bilayer can be supported by compatible solutes and special proteins. At the metabolic level, osmotic adjustment by synthesis of low-molecular osmolytes (carbohydrates, betains, proline) can counteract cellular dehydration and turgor loss. Taking the example of Pinus sylvestris, changes at the level of membrane composition, and concomitantly of photosynthetic capacity during frost hardening is shown. Additionally the effect of photoperiod as measured via the phytochrome system and the effect of subfreezing temperatures on the incidence of frost hardening is discussed. Extremely hydrophilic proteins such as dehydrins are common products protecting not only the biomembranes in ripening seeds (late embryogenesis abundant proteins) but accumulate also in the shoots and roots during cold adaptation, especially in drought tolerant plants. Dehydrins are characterized by conserved amino acid motifs, called the K-, Y-or S-segments. Accumulation of dehydrins can be induced not only by drought, but also by cold, salinity, treatment with abscisic acid and methyl jasmonate. Positive effects of the overexpression of a wild chickpea (Cicer pinnatifidum) dehydrin in tobacco plants on the dehydration tolerance is shown. The presentation discusses the perception of cold and drought, the subsequent signal transduction and expression of genes and their products. Differences and similarities between the plant responses to both stressors are also discussed.     

冷型小麦旗叶衰老和活性氧代谢特性研究

以典型的冷型小麦和暖型小麦为试验材料,研究了同一环境背景下不同温度型小麦开花后的旗叶衰老和活性氧代谢特性。结果表明,与暖型小麦相比,冷型小麦籽料灌浆期旗叶叶绿素和可溶性蛋白质含量下降缓慢、含量高,整个业粒形成和灌浆期ＭＤＡ积累速度慢、含量低,籽粒灌浆期防御活性氧伤害的关键性保护酶（ＳＯＤ、ＣＡＴ和ＰＯＤ）活性下隆幅度小,灌浆中后期活性水平高。由此认为,小麦旗叶衰老和活性氧代谢特性与其温度型的归属关     

Seed germination response to cold stratification period and thermal regime in Phacelia secunda (Hydrophyllaceae) – Altitudinal variation in the mediterranean Andes of central Chile

The ability to germinate under a variety of environmental conditions is essential for plant species inhabiting a wide range of altitudes and latitudes. Phacelia secunda J. F. Gmel. (Hydrophyllaceae) is a perennial herb with wide latitudinal and altitudinal distributional ranges. In the central Chilean Andes (33 °S) P. secunda can be found from 1600 m sealevel up to the vegetation limit at 3400 m. It has been suggested that seeds from populations encountering long periods with snow cover and adverse winter conditions would require longer periods of cold stratification for germination than those from populations exposed to milder winters. Given that the snow-free period decreases with elevation, seeds from high elevation populations could require longer period of cold stratification to germinate. Moreover, it has been shown that seeds from arctic and higher elevations environments are adapted to germinate better under high temperature conditions. Germination response with increasing periods of cold stratification (0–6 mo.) and under two contrasting thermoperiods (20 °/1O °C; 10 °/5 °C; 12 h day/night), were studied for 4 populations of P. secunda located at 1600, 2100, 2900 and 3400 m a.s.l. Initiation of germination required increasingly longer periods of stratification with elevation, and proportionately fewer seeds germinated for any one stratification treatment at the higher elevations. Seeds from higher elevations germinated to a higher percentage under the high than the low temperature thermoperiods. These results illustrates a significant variation in germination characteristics over a spatially short environmental gradient.     

冷型小麦对干旱和阴雨的双重适应性

通过 10余年的研究 ,发现冠层温度持续偏低的冷型小麦具有广幅生态适应性 ,即在正常天气条件下 ,它的活力较好、代谢功能较强、具有较好的抗早衰能力 ,优于其它类型小麦 ;而在气象要素反差很大的干旱和连阴雨天气下 ,冷型小麦和暖型小麦、中间型小麦相比 ,不但冠层温度依然持续偏低 ,且在叶片功能期、叶绿素含量、可溶性蛋白质含量、过氧化氢酶活性、净光合速率和籽粒饱满指数等一系列重要内、外性状上仍能继续保持优势。这种对干旱和阴雨条件的双重适应性是冷型小麦一种宝贵的生物学品质 ,它有可能为小麦在多种气象生态条件下的高产、稳产打下较为坚实的生态生理基础 ,并能为优良品种的选育提出一个把冷温特征作为重要内容的较为新鲜的育种目标。