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"Long, Stephen"
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Slow induction of photosynthesis on shade to sun transitions in wheat may cost at least 21% of productivity
Wheat is the second most important direct source of food calories in the world. After considerable improvement during the Green Revolution, increase in genetic yield potential appears to have stalled. Improvement of photosynthetic efficiency now appears a major opportunity in addressing the sustainable yield increases needed to meet future food demand. Effort, however, has focused on increasing efficiency under steady-state conditions. In the field, the light environment at the level of individual leaves is constantly changing. The speed of adjustment of photosynthetic efficiency can have a profound effect on crop carbon gain and yield. Flag leaves of wheat are the major photosynthetic organs supplying the grain of wheat, and will be intermittently shaded throughout a typical day. Here, the speed of adjustment to a shade to sun transition in these leaves was analysed. On transfer to sun conditions, the leaf required about 15 min to regain maximum photosynthetic efficiency. In vivo analysis based on the responses of leaf CO2 assimilation (A) to intercellular CO2 concentration (ci) implied that the major limitation throughout this induction was activation of the primary carboxylase of C3 photosynthesis, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). This was followed in importance by stomata, which accounted for about 20% of the limitation. Except during the first few seconds, photosynthetic electron transport and regeneration of the CO2 acceptor molecule, ribulose-1,5-bisphosphate (RubP), did not affect the speed of induction. The measured kinetics of Rubisco activation in the sun and de-activation in the shade were predicted from the measurements. These were combined with a canopy ray tracing model that predicted intermittent shading of flag leaves over the course of a June day. This indicated that the slow adjustment in shade to sun transitions could cost 21% of potential assimilation.
This article is part of the themed issue ‘Enhancing photosynthesis in crop plants: targets for improvement’.
Journal Article
المسيرة الطويلة
بين يدينا النسخة العربية من رواية «المسيرة الطويلة The Long Walk» للروائي الأميركي \"ستيفن كينغ\"، وترجمة أوليغ عوكي. تقول الحكاية، كل سنة، في اليوم الأول من شهر مايو، يلتقي مئة فتى مراهق للمشاركة في حدث معروف في كل أنحاء الدولة تحت اسم \"المسيرة الطويلة\"، وقد بينت النتيجة المختارة لهذه السنة \"راي غازاتي\" البالغ السادسة عشرة من عمره، إنه يعرف قواعد اللعبة: أن التحذيرات تصدر إذا أبطأ تحت السرعة المسموحة، إذا تعثر، إذا جلس، وأنه بعد ثلاث تحذيرات... يحصل على بطاقة. وما يجري عندها يخدم كتذكير مروع إلى أنه لا يمكن أن يكون هناك سوى فائز واحد في المسيرة–الشخص الذي يصمد إلى النهاية. وفي هذه المنافسة المطلقة فقط الموت يستطيع أن يمنعه من الوصول إلى خط النهاية!! المنطلق الأولي للحكاية يقوم على ظهور نوع من ألعاب الموت، يشترك فيه مائة شاب كل سنة ويمثل كل واحد منهم مدينة من المدن الأميركية، وبتشجيع جمهور عريض، ونقل المسابقة إلى شاشات التلفزيون.ولعبة الموت هذه تتطلب من الشباب المائة الذين دخلوها طوعا، السير دون انقطاع في الطرق الأميركية، وكلما انتهوا من طريق انتقلوا للطريق الذي يتصل به، ويكون على الجيش مواكبتهم بعربات مدرعة، ومن تقل سرعته عن أربعة كيلومترات في الساعة يتلقى إنذارا، يليه إنذارا آخر بعد دقائق.. إن لم يستطع زيادة سرعته، وهكذا إلى أن تتراكم الإنذارات ؛ ولكي يسقط عن اللاعب إنذار ما عليه سوى الاستمرار في السير بسرعة لا تقل عن أربع كيلومترات في الساعة لمدة ساعتين، ومن يقع عليه أربعة إنذارات يتم قتله فورا بإطلاق النار عليه من قبل الجيش.. سوف يتساقط اللاعبون قتلى واحدا تلو الآخر، ولن يبقى سوى لاعب واحد هو بطل الحكاية.
BOOK
Structure and insights into the function of a Ca(2+)-activated Cl(-) channel
Bestrophin calcium-activated chloride channels (CaCCs) regulate the flow of chloride and other monovalent anions across cellular membranes in response to intracellular calcium (Ca(2+)) levels. Mutations in bestrophin 1 (BEST1) cause certain eye diseases. Here we present X-ray structures of chicken BEST1-Fab complexes, at 2.85 Å resolution, with permeant anions and Ca(2+). Representing, to our knowledge, the first structure of a CaCC, the eukaryotic BEST1 channel, which recapitulates CaCC function in liposomes, is formed from a pentameric assembly of subunits. Ca(2+) binds to the channel's large cytosolic region. A single ion pore, approximately 95 Å in length, is located along the central axis and contains at least 15 binding sites for anions. A hydrophobic neck within the pore probably forms the gate. Phenylalanine residues within it may coordinate permeating anions via anion-π interactions. Conformational changes observed near the 'Ca(2+) clasp' hint at the mechanism of Ca(2+)-dependent gating. Disease-causing mutations are prevalent within the gating apparatus.
Journal Article
Concrete economics : the Hamilton approach to economic growth and policy
\"Brilliantly written and argued, Concrete Economics shows exactly how the US government has shaped and directed the economy since the very inception of the country. This book does not rehash the sturdy and well-known arguments that to thrive, an entrepreneurial economy needs a social and policy environment characterized by a broad range of freedoms. Nor does it buy into the myth of the absolutely free market. Instead, Cohen and DeLong focus on the forgotten role played by the US government in initiating and enabling a redesign of the US economy. The government not only sets the ground rules for entrepreneurial activity but directs the surges of energy that mark a vibrant economy. It is as true for present-day Silicon Valley as it was for New England manufacturing at the dawn of the nineteenth century. This is not an argument based on abstract truths, complex correlations, or arcane discoveries, but rather on the facts of how the US economy succeeded so brilliantly. And that provides a blueprint for how the government, established companies, and new ventures can partner to yet again successfully reshape the economy. \"-- Provided by publisher.
Book
Short-term impacts and value of a periodic no take zone (NTZ) in a community-managed small-scale lobster fishery, Madagascar
The small-scale lobster fisheries of Madagascar's impoverished southeast coast account for the majority of national catch and export, making a significant contribution to the regional economy. Data suggests catches have declined, likely due to over-exploitation. In response, the community of Sainte Luce has established a locally managed marine area (LMMA) to manage their lobster fishery, including a 13 km2 periodic no take zone (NTZ). Participatory monitoring data were used to assess compliance, identify changes in catch per unit effort (CPUE) associated with the NTZ and consider the short-term value of the NTZ. Compliance is low for measures dictated by national legislation (minimum landing size (MLS), national closed season, prohibition on landing berried females), but may be higher for those designed by the community (NTZ). Upon NTZ opening in July 2015, an estimated 435% increase in catch was observed compared with the mean for the preceding five months, a product of increased effort and significantly higher CPUE. Zero Altered Negative Binomial modelling showed CPUE was significantly higher during the NTZ opening in 2015 and in 2016 when the opening period had been moved. Whilst it is unlikely that tangible ecological benefits have accrued from NTZ operation, there have been important socio-economic effects. Specifically, there was a 33% increase in the price fishers received, a significant effect at the bottom of the value chain. Temporary increases in catch and income acted as a catalyst, engaging neighbouring communities in fishery management, resulting in two additional NTZs. Attention is drawn to the fact that current national legislation may be sub-optimal and should be reviewed. Successful management of the regional fishery will require the state and industry to support communities in adopting community-based management. The NTZ measure considered here may be an effective tool to achieve this.
Journal Article
حرب واشنطن الطويلة على سورية
يقدم هذا الكتاب قراءة للحرب الإرهابية التي شنت على سورية في الفترة الممتدة ما بين (2011- 2016م)، والتي ما زالت مستمرة. يدرس مراحل تشكلها، ويبحث في القوى الثلاث التي تصارعت على الدولة السورية، ليس فقط من عام 2011م، بل من نهاية الحرب العالمية الثانية، وهذه القوى هي : القوى القومية العربية العلمانية، والإسلام السياسي الممثل بالإخوان المسلمين وأشباههم، والإمبريالية الأمريكية. يعطي المؤلف إهتماماً خاصاً لفكرة أن الذين تحاربهم الإدارة الأمريكية من العرب هم أولئك الذين يتبعون سياسات تلبي مصالحهم الوطنية، ويديرون سياسات اقتصادية تستجيب لاحتياجات شعوبهم، وتحرم سوق المال، والشركات الأمريكية من إستغلال ثرواتهم، ويرفضون هيمنة الولايات المتحدة وإملاءاتها.
Book
One crop breeding cycle from starvation? How engineering crop photosynthesis for rising CO2 and temperature could be one important route to alleviation
Global climate change is likely to severely impact human food production. This comes at a time when predicted demand for primary foodstuffs by a growing human population and changing global diets is already outpacing a stagnating annual rate of increase in crop productivity. Additionally, the time required by crop breeding and bioengineering to release improved varieties to farmers is substantial, meaning that any crop improvements needed to mitigate food shortages in the 2040s would need to start now. In this perspective, the rationale for improvements in photosynthetic efficiency as a breeding objective for higher yields is outlined. Subsequently, using simple simulation models it is shown how predicted changes in temperature and atmospheric [CO2] affect leaf photosynthetic rates. The chloroplast accounts for the majority of leaf nitrogen in crops. Within the chloroplast about 25% of nitrogen is invested in the carboxylase, Rubisco, which catalyses the first step of CO2 assimilation. Most of the remaining nitrogen is invested in the apparatus to drive carbohydrate synthesis and regenerate ribulose-1:5-bisphosphate (RuBP), the CO2-acceptor molecule at Rubisco. At preindustrial [CO2], investment in these two aspects may have been balanced resulting in co-limitation. At today's [CO2], there appears to be over-investment in Rubisco, and despite the counter-active effects of rising temperature and [CO2], this imbalance is predicted to worsen with global climate change. By breeding or engineering restored optimality under future conditions increased productivity could be achieved in both tropical and temperate environments without additional nitrogen fertilizer. Given the magnitude of the potential shortfall, better storage conditions, improved crop management and better crop varieties will all be needed. With the short time-scale at which food demand is expected to outpace supplies, all available technologies to improve crop varieties, from classical crop breeding to crop genetic engineering should be employed. This will require vastly increased public and private investment to support translation of first discovery in laboratories to replicated field trials, and an urgent re-evaluation of regulation of crop genetic engineering.
Journal Article
Improving photosynthesis and crop productivity by accelerating recovery from photoprotection
Crop leaves in full sunlight dissipate damaging excess absorbed light energy as heat. When sunlit leaves are shaded by clouds or other leaves, this protective dissipation continues for many minutes and reduces photosynthesis. Calculations have shown that this could cost field crops up to 20% of their potential yield. Here, we describe the bioengineering of an accelerated response to natural shading events in Nicotiana (tobacco), resulting in increased leaf carbon dioxide uptake and plant dry matter productivity by about 15% in fluctuating light. Because the photoprotective mechanism that has been altered is common to all flowering plants and crops, the findings provide proof of concept for a route to obtaining a sustainable increase in productivity for food crops and a much-needed yield jump.
Journal Article
Can the Cyanobacterial Carbon-Concentrating Mechanism Increase Photosynthesis in Crop Species? A Theoretical Analysis
Experimental elevation of [CO₂] around C₃ crops in the field has been shown to increase yields by suppressing the Rubisco oxygenase reaction and, in turn, photorespiration. Bioengineering a cyanobacterial carbon-concentrating mechanism (CCM) into C₃ crop species provides a potential means of elevating [CO₂] at Rubisco, thereby decreasing photorespiration and increasing photosynthetic efficiency and yield. The cyanobacterial CCM is an attractive alternative relative to other CCMs, because its features do not require anatomical changes to leaf tissue. However, the potential benefits of engineering the entire CCM into a C₃ leaf are unexamined. Here, a CO₂ and HCO₃⁻ diffusion-reaction model is developed to examine how components of the cyanobacterial CCM affect leaf light-saturated CO₂ uptake (Asat) and to determine whether a different Rubisco isoform would perform better in a leaf with a cyanobacterial CCM. The results show that the addition of carboxysomes without other CCM components substantially decreases Asat and that the best first step is the addition of HCO₃⁻ transporters, as a single HCO₃⁻ transporter increased modeled Asat by 9%. Addition of all major CCM components increased Asat from 24 to 38 µmol m⁻² s⁻¹. Several Rubisco isoforms were compared in the model, and increasing ribulose bisphosphate regeneration rate will allow for further improvements by using a Rubisco isoform adapted to high [CO₂]. Results from field studies that artificially raise [CO₂] suggest that this 60% increase in Asat could result in a 36% to 60% increase in yield.
Journal Article