Photon requirement for O2-Revolution in red (λ= 680 nm) light for some C3 and C4 plants and a C3–C4 intermediate species*

Photon requirements for O₂-evolution in red (λ=680nm) light (Ф_r) were measured for six C₃ species, one C₃-like, C₃–C₄ intermediate species, and three C₄ species, including examples of NADP-malic enzyme and PEP-carboxykinase C₄ sub-groups. Variation in Ф_r within the C₃ species was small with a mean value of 7.96 ±0.12 mol photon mol⁻¹ O₂, whereas the mean value for the C₄ species was 12.27± 1.53 mol photon mol⁻¹ O₂, with the lowest value, 9.24 ±0.13 mol photon mol⁻¹ O₂, for the PEP-carboxykinase C₄ species Spartina townsendii. The C₃–C₄ intermediate species Panicum milioides had a value of 9.05 ±0.29 mol photon mol⁻¹ O₂, approximately 1 mol photon mol⁻¹ O₂ greater than the C₃ species. The possibility that this extra cost is due to PEP-carboxylase-dependent recycling of CO₂ is discussed. No correlation was found between Ф_r and chlorophyll content or leaf absorptance. Based on white (Ф_W) and red light measurements of the photon requirement, values in red light were approximately 20% higher than white-light estimates. These results are discussed with reference to accepted mechanisms of energy transduction in thylakoid membranes (Z-scheme), expected inefficiencies and losses during light-harvesting and electron transport reactions, and the influence of respiratory processes.     

Molecular evolution of mammalian aquaporin-2: further evidence that elephant shrew and aardvark join the paenungulate clade

A 328-bp sequence from exon 1 of the gene for aquaporin-2 (AQP2) was compared in 12 mammalian species, representing as many eutherian orders. This sequence encodes the N-terminal half of this kidney- specific water channel protein. Most amino acid replacements, as well as an insertion, have occurred in extracellular loops connecting the transmembrane helices, in agreement with a lower functional importance of these loops. Phylogenetic analyses were performed with parsimony, distance, and maximum-likelihood methods. The AQP2 data set, alone as well as in combination with previously published alpha A-crystallin protein sequences, strongly supports a clade consisting of elephant, hyrax, aardvark, and elephant shrew, reaching bootstrap values of 99%. This finding fully agrees with the only other presently available sequence data sets that include these taxa, those of von Willebrand factor and interphotoreceptor retinoid-binding protein, and suggests that this extended paenungulate clade is one of the most conspicuous superordinal groupings in eutherian phylogeny. Some support was obtained for an artiodactyl/perissodactyl clade, while the grouping of pholidotes with edentates was contradicted.      

Exo-glycosidases Activities in Artemisia sphaerocephalaMucilaginous Achene Germination Process

白沙蒿粘液瘦果萌发中聚糖内切水解酶的活动特性 黄振英4* Daphne J.OSBORNE ²      

Invertebrate diet of the Houbara Bustard Chlamydotis [undulata] macqueenii in Abu Dhabi from calibrated faecal analysis

The ecology of the Houbara Bustard Chlamydotis [undulata] macqueenii is poorly known and populations are declining due to hunting and habitat loss. As wintering populations in Abu Dhabi may be limited by habitat and food, we studied the diet using calibrated faecal analysis. Prey were categorized into 16 groups and fed to captive birds under controlled conditions. We calculated the recovery rates of prey following digestion and identified consistent fragments for each group. Wild Houbara Bustard faeces were collected and examined for key fragments, and initial prey intake was calibrated. Plant remains were identified and their contribution was estimated. Fewer than 28% faeces contained >50% plant material by volume and only 12% contained 95% or more. Numerically, the most important prey were: ants (64%), large nocturnal tenebrionids (14.5%), small climbing tenebrionids (12%) and diurnal tenebrionids. However, the Tenebrionidae contributed 97% of the animal biomass. The relative proportions of prey in the diet were similar to relative abundance as assessed by pitfall trapping. Estimates of the energetic value of the prey suggested that on average Houbara Bustards must consume around 670 desert invertebrates/day to meet energy needs. The effort required to catch these prey may vary at least ten-fold seasonally. On average plants could provide a further 6.4–14% energy but more work is needed on this. Whether Houbara Bustards wintering in Abu Dhabi are prey-limited depends on prey densities and renewal rates which remain unknown.     

The representation of root processes in models addressing the responses of vegetation to global change

The representation of root activity in models is here confined to considerations of applications assessing the impacts of changes in climate or atmospheric [CO₂]. Approaches to modelling roots can be classified into four major types: models in which roots are not considered, models in which there is an interplay between only selected above-ground and below-ground processes, models in which growth allocation to all parts of the plants depends on the availability and matching of the capture of external resources, and models with explicit treatments of root growth, architecture and resource capture. All models seem effective in describing the major root activities of water and nutrient uptake, because these processes are highly correlated, particularly at large scales and with slow or equilibrium dynamics. Allocation models can be effective in providing a deeper, perhaps contrary, understanding of the dynamic underpinning to observations made only above ground. The complex and explicit treatment of roots can be achieved only in small-scale highly studied systems because of the requirements for many initialized variables to run the models.     

Response of wild C4 crop progenitors to subambient CO2 highlights a possible role in the origin of agriculture

The synchronous origin of agriculture in at least four independent climatic regions at the end of the last glacial period (c10 kyr bp ) points to a global limitation for crop domestication. One hypothesis proposes that a rapid carbon dioxide (CO₂) increase from 18 Pa to ～27 Pa during deglaciation caused significant increases in the growth rates of wild crop progenitors, thereby removing a productivity barrier to their successful domestication. However, early C₄ crops present a challenge to this hypothesis, because they were among the first domesticates, but have a carbon‐concentrating mechanism that offsets the limitation of photosynthesis by CO₂. We investigated the CO₂‐limitation hypothesis using the wild progenitors of five C₄ founder crops from four independent centres of domestication. Plants were grown in controlled environment chambers at glacial (18 Pa), postglacial (28 Pa) and current ambient (38 Pa) CO₂ levels, and photosynthesis, transpiration and biomass were measured. An increase in CO₂ from glacial to postglacial levels caused a significant gain in vegetative biomass of up to 40%, but the equivalent rise in CO₂ from postglacial to modern levels generally had no effect on biomass. Investigation into the underlying mechanisms showed C₄ photosynthesis to be limited more by glacial than postglacial CO₂ levels, matching theoretical expectations. Moreover, the increase in CO₂ from glacial to postglacial levels caused a reduction in the transpiration rate via decreases in stomatal conductance of ～35%. In combination, these physiological changes conferred a large improvement in water‐use efficiency at the postglacial CO₂ partial pressure compared with the glacial level. Our data, therefore, provide experimental support for the CO₂‐limitation hypothesis, suggesting that these key physiological changes could have greatly enhanced the productivity of wild crop progenitors after deglaciation.     

正常人左心室功能指标的参考值及其预计公式的初步研究报告*

目的: 当前评估左心室容量和功能仍常用正常值范围,个体化分析也仅使用体表面积进行校正。尚缺少个体化因素相关的大样本参考值和预计公式。方法: 本研究纳入美国加州洛杉矶县南湾地区1200名健康志愿者,其中男807女393,年龄20岁-94岁,心脏CT造影（CTA）,经过高精度三维成像技术处理,计算左心室容积在收缩和舒张过程中的连续动态变化,测定左心室（LV）容量和功能指标：舒张末期容积（EDV)、收缩末期容积(ESV)、每搏输出量(SV)、射血分数(EF)和心输出量(CO)。将以上指标与一般特征指标进行多因素相关分析,以探索正常人预计值计算公式。结果: 男性除LVEF小于女性外（P<0.001）,其余各指标均大于女性（P<0.001）。多元线性回归分析提示, 性别、年龄、身高和体质量均为EDV、ESV、SV的独立影响因子(P<0.001); 而CO仅受年龄、性别、体质量显著影响(P<0.001),但与身高无关(P>0.05)。CO的预测公式CO (L·min^-1)= 6.963+0.446(Male) -0.037×年龄(yr)+0.013×体质量(kg)。结论: 性别、年龄、身高、体质量均影响左心室容量和功能,建立预测值计算公式,对心血管疾病的无创评估和个体化精准医疗具有重要参考价值。     

Increased Tolerance to Mn Deficiency in Transgenic Tobacco Overproducing Superoxide Dismutase

The effect of Mn deficiency on plant growth and activities ofsuperoxide dismutase (SOD) was studied in hydroponically-grownseedlings of transgenic tobacco (Nicotiana tabacum L.) engineeredto overexpress FeSOD in chloroplasts or MnSOD in chloroplastsor mitochondria. In comparison to the non-transgenic parentalline, the activity of MnSOD in the lines overproducing MnSODwas 1.6-fold greater, and the activity of FeSOD in the FeSOD-overproducinglines was 3.2-fold greater, regardless of the Mn treatment (deficientor sufficient). The MnSOD activities decreased due to Mn deficiency,while activities of FeSOD and Cu/ZnSOD remained unaffected 25d after transplanting (DAT). With an increased duration of theMn deficiency stress (45 DAT), FeSOD activity decreased, andthat of MnSOD continued to decrease, while Cu/ZnSOD activitysimultaneously increased. Under Mn sufficiency, non-transgenicparental plants had greater shoot biomass than the transgenics;however, when subjected to Mn deficiency stress, non-transgenicparents suffered a proportionally greater growth reduction thantransgenic lines. Thus, overproduction of MnSOD in chloroplastsmay provide protection from oxidative stress caused by Mn deficiency.Copyright 1999 Annals of Botany Company Manganese deficiency, Nicotiana tabacum, superoxide dismutase (SOD), transgenic tobacco.