Decreased eggshell strength caused by impairment of uterine calcium transport coincide with higher bone minerals and quality in aged laying hens

Background Deteriorations in eggshell and bone quality are major challenges in aged laying hens.This study compared the differences of eggshell quality,bone parameters and their correlations as well as uterine physiologi-cal characteristics and the bone remodeling processes of hens laying eggs of different eggshell breaking strength to explore the mechanism of eggshell and bone quality reduction and their interaction.A total of 24074-week-old Hy-line Brown laying hens were selected and allocated to a high(HBS,44.83±1.31 N)or low(LBS,24.43±0.57 N)eggshell breaking strength group.Results A decreased thickness,weight and weight ratio of eggshells were observed in the LBS,accompanied with ultrastructural deterioration and total Ca reduction.Bone quality was negatively correlated with eggshell quality,marked with enhanced structures and increased components in the LBS.In the LBS,the mammillary knobs and effective layer grew slowly.At the initiation stage of eggshell calcification,a total of 130 differentially expressed genes(DEGs,122 upregulated and 8 downregulated)were identified in the uterus of hens in the LBS relative to those in the HBS.These DEGs were relevant to apoptosis due to the cellular Ca overload.Higher values of p62 protein level,caspase-8 activity,Bax protein expression and lower values of Bcl protein expression and Bcl/Bax ratio were seen in the LBS.TUNEL assay and hematoxylin-eosin staining showed a significant increase in TUNEL-positive cells and tissue damages in the uterus of the LBS.Although few DEGs were identified at the growth stage,similar uterine tissue damages were also observed in the LBS.The expressions of runt-related transcription factor 2 and osteocal-cin were upregulated in humeri of the LBS.Enlarged diameter and more structural damages of endocortical bones and decreased ash were observed in femurs of the HBS.Conclusion The lower eggshell breaking strength may be attributed to a declined Ca transport due to uterine tissue damages,which could affect eggshell calcification and lead to a weak ultrastructure.Impaired uterine Ca transport may result in reduced femoral bone resorption and increased humeral bone formation to maintain a higher mineral and bone quality in the LBS.

Transcriptome-based insights into the calcium transport mechanism of chick chorioallantoic membrane

Chorioallantoic membrane(CAM)is responsible for respiratory gas exchange,eggshell calcium transport,embryonic acid-base equilibrium,allantoic ion,and water reabsorption during avian embryonic development.To further understand the timing of CAM gene expression during chick embryonic development,especially the calcium absorption mechanism,transcriptome quantitative comparative analysis was conducted on chick CAM during the embryonic period(E)of 9,13,17,and 20 days.A total of 6378 differentially expressed genes(DEGs)were identified.Functional enrichment analysis of DEGs showed that CAM DEGs were mainly involved in biological processes such as"ion transport regulation","immune response"and"cell cycle".Time series analysis of the differential genes showed that the functional cells of CAM began to proliferate and differentiate at E9 and the calcium content of egg embryo increased significantly at E13.Simultaneously,the observation of the ultrastructure of the eggshell showed that the interstice of the fiber layer was enlarged at E13,and the mastoid layer was partly exposed.Therefore,it is preliminarily inferred that CAM calcium transport starts at E13,and genes such as TRPV6,S100 A10,and RANKL cooperate to regulate calcium release and transport.

1,25-Dihydroxyvitamin D_3 modulates calcium transport in goat mammary epithelial cells in a dose- and energydependent manner

Background： Calcium is a vital mineral and an indispensable component of milk for ruminants. The regulation of transcellular calcium transport by 1,25-dihydroxyvitamin D3 （1,25-（OH）2D3, the active form of vitamin D） has been confirmed in humans and rodents, and regulators, including vitamin D receptor （VDR）, calcium binding protein Dgk （calbindin-Dgk）, plasma membrane Ca2＋-ATPase ] b （PMCAlb）, PMAC2b and Oral1, are involved in this process. However, it is still unclear whether 1,25-（OH）2D3 could stimulate calcium transport in the ruminant mammary gland. The present trials were conducted to study the effect of 1,25-（OH）2D3 supplementation and energy availability on the expression of genes and proteins related to calcium secretion in goat mammary epithelial cells. Methods： An in vitro culture method for goat secreting mammary epithelial cells was successfully established. The cells were treated with different doses of 1,25-（OH）2D3 （0, 0.1, 1.0, 10.0 and 100.0 nmol/L） for calcium transport research, followed by a 3-bromopyruvate （3-BrPA, an inhibitor of glucose metabolism） treatment to determine its dependence on glucose availability. Cell proliferation ratios, glucose consumption and enzyme activities were measured with commercial kits, and real-time quantitative polymerase chain reaction （RT-qPCR）, and western blots were used to determine the expression of genes and proteins associated with mammary calcium transport in dairy goats, respectively. Results： 1,25-（OH）2D3 promoted cell proliferation and the expression of genes involved in calcium transport in a dose-dependent manner when the concentration did not exceed 10.0 nmol/L. In addition, 100.0 nmol/L 1,25-（OH） 2D3 inhibited cell proliferation and the expression of associated genes compared with the 10.0 nmol/L treatment. The inhibition of hexokinase 2 （HK2）, a rate-limiting enzyme in glucose metabolism, decreased the expression of PMCA1 b and PMCA2b at the mRNA and protein levels as well as the transcription of Oral1, indicating that glucose avaitability was required for goat mammary calcium transport. The optimal concentration of 1,25-（OH）2D3 that facilitated calcium transport in this study was 10.0 nmol/L. Conclusions： Supplementation with 1,25-（OH）2D3 influenced cell proliferation and regulated the expression of calcium transport modulators in a dose- and energy-dependent manner, thereby highlighting the role of 1,25-（OH）2D3 as an efficacious regulatory agent that produces calcium-enriched milk in ruminants when a suitable energy status was guaranteed.

Mechanisms of calcium transport across the placenta: Review

Studies of calcium transfer across the placenta have been reviewed because of the physiological and nutritional importance of this mineral during pregnancy, especially in order to better understand its contribution to development of the fetal skeleton. The placental transfer of maternal calcium to the fetus represents a vital mechanism for fetal development and breast-milk production, yet little meaningful information is currently available regarding the biochemical mechanisms involved in this process. Once again, the use of different animal models as rodents, rabbit, sheep and bovine have demonstrate different mechanisms of calcium transport across the placenta and contribute to better understand its effects in both fetus and mother during the gestation. In relation to the transfer of calcium from the mother to fetus data suggest it occur via an active mechanism;thus calcium concentration is higher in fetus than in maternal blood. Despite conflicting reports, several investigators agreed that calcium concentration in the fetal blood is mainly regulated by fetal parathyroid hormone and plasma concentration of vitamin D3, a metabolite that plays a key role in calcium transport through the syncytial cells.

Genome-Wide Comparative in silico Analysis of Calcium Transporters of Rice and Sorghum

The mechanism of calcium uptake, translocation and accumulation in Poaceae has not yet been fully understood. To address this issue, we conducted genome-wide comparative in silico analysis of the calcium （Ca2＋） transporter gene family of two crop species, rice and sorghum. Gene annotation, identification of upstream cis-acting ele- ments, phylogenetic tree construction and syntenic mapping of the gene family were performed using several bio- informatics tools. A total of 31 Ca2＋ transporters, distributed on 9 out of 12 chromosomes, were predicted from rice genome, while 28 Ca2＋ transporters predicted from sorghum are distributed on all the chromosomes except chromosome 10 （Chr 10）. Interestingly, most of the genes on Chr 1 and Chr 3 show an inverse syntenic relation- ship between rice and sorghum. Multiple sequence alignment and motif analysis of these transporter proteins re- vealed high conservation between the two species. Phylogenetic tree could very well identify the subclasses of channels, ATPases and exchangers among the gene family. The in silico c/s-regulatory element analysis suggested diverse functions associated with light, stress and hormone responsiveness as well as endosperm- and meris- tem-specific gene expression. Further experiments are warranted to validate the in silico analysis of the predicted transporter gene family and elucidate the functions of Ca2＋ transporters in various biological processes.

Abnormal calcium transport ofmyocardial mitochondria during the early stage of combined radiation－burn injury in rats

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Calcium Hydroxide Removal in Curved Root Canals with Apical Transportation In Vitro

Calcium hydroxide（CH） is applied to improve disinfection of root canals in most root canal retreatment. This study aimed to analyze the CH removal efficacy using 7 different root preparing files（K file, pre-curved K file, EndoActivator, Ultrasonic file, pre-curved ultrasonic file, F file and needle irrigation alone） with apical transportation. Standardized models of curved canal with such apical transportation or not were set up before applying CH to root canal for 7 days. Seven techniques described above were used for its removal. Then the roots were disassembled and digital photos were taken. The ratio of residual CH in the overall canal surface was calculated using the image analyzer image pro plus 6.0. The data were analyzed using one-way ANOVA with post hoc Tukey test. Results revealed that CH was effectively removed（P〈0.05） by using all 6 mechanical methods except irrigation alone. In curved root canals with apical transportation, EndoActivator, pre-curved ultrasonic file and F file were found to be more effective in removing CH than the other four file（P〈0.001）, while there was no significant difference among EndoActivator, pre-curved ultrasonic file and F file groups（P〉0.05）. The percentage of residual CH in the canal with apical transportation was higher than that in the canal without apical transportation（P〈0.05）. In conclusion, CH can be hardly removed completely. Canal with apical transportation will result in insufficient CH removal. EndoActivator, pre-curved ultrasonic file and F file are more effective in the curved root canal with apical transportation.

钙在作物生长发育中的功能及应用

钙是作物必需的中量元素之一,广泛存在于根、茎、叶、花、果实、种子中,对作物的生长发育具有重要意义。钙属于再利用难的元素,其吸收、转运受制于蒸腾作用,因此农作物常发生生理性缺钙,从而导致抗逆性减弱,产量和品质降低。作物体内的钙具有双重功能,既参与细胞壁与细胞膜的构成,还可作为细胞内第二信使参与多种环境刺激和内部生长发育信号的响应。细胞中钙的吸收和转运对于维持细胞内钙离子稳态和钙信号精准传导至关重要。近年来,钙在作物生长与发育中的功能和在作物生产中的应用得到了广泛研究。本文阐述了作物体内钙元素的分布、吸收转运和需求状况,介绍了作物缺钙症状和原因,并综述了钙的营养结构功能和第二信使功能及钙信号产生、传导和解码机制,总结了钙在作物生长发育中的作用,包括对产量、品质和抗逆性等方面的影响,同时对其未来研究方向提出了展望。

鮰鱼骨胶原蛋白肽-钙螯合物促进钙转运和成骨细胞分化作用

以实验室前期制备的鮰鱼骨胶原蛋白肽-钙螯合物(F3-Ca螯合物)为原料,采用Caco-2细胞模型评价其对钙转运和吸收的影响,再分析其对hFoB1.19成骨细胞碱性磷酸酶(alkaline phosphatase,ALP)活性以及分化关键基因和蛋白表达的影响。结果发现F3-Ca螯合物能使Caco-2细胞的钙转运量提高到0.31 mg/mL,并促进成骨细胞的矿化。当F3-Ca螯合物的质量浓度为100μg/mL时,成骨细胞ALP的活性提高了53.68%。反转录聚合酶链式反应和蛋白质免疫印迹分析表明F3-Ca螯合物能提高成骨细胞中骨保护素(osteoprotegerin,OPG)、骨钙素和Runt相关转录因子2的基因和蛋白表达水平,降低核因子受体激活因子-κB配体(receptor activator for nuclear factor-κB ligand,RANKL)的基因和蛋白表达水平,增大OPG/RANKL的比值,从而激活OPG/RANKL/核因子受体激活因子-κB信号通路,促进成骨细胞的增殖、分化和矿化,达到加强钙吸收和抗骨质疏松的作用。本研究可为鮰鱼骨的高值化利用和新型钙补充剂的开发提供科学依据。

白细胞介素17对大鼠高血压心力衰竭的影响及其机制分析

目的 基于核转录因子-κB(Nuclear factorκB,NF-κB)/肌浆网钙三磷酸腺苷酶2(sarco-endoplasmic reticulum adenosine triphosphatease 2S,SERCA2)信号通路探讨白细胞介素(interleukin, IL)17对大鼠高血压心力衰竭的影响及机制。方法 选择6~8周的SPF级雄性自发性高血压大鼠30只,分为对照组、模型组、磷酸缓冲盐(phosphate buffer salt, PBS)溶液注射组(PBS组)、IL-17蛋白注射组(IL-17组)和抗体IL-17注射组(IL-17+IgG组),每组6只,PBS组、IL-17组和IL-17+IgG组大鼠建立高血压心力衰竭模型,分别腹腔注射PBS、IL-17和特异性抗体(IL-17、IgG),检测IL-17、NF-κB、SERCA2水平。结果 与对照组比较,模型组和PBS组大鼠血清N末端B型钠尿肽前体(N-terminal pro-brain natriuretic peptide, NT-proBNP)、IL-17和心脏组织IL-17 mRNA、NF-κB蛋白水平明显升高,血管内皮生长因子(vascularendothlialgrowthfactor, VEGF),SERCA2蛋白明显降低(P<0.01)。与模型组比较,IL-17组血清NT-proBNP、IL-17和心脏组织IL-17 mRNA、NF-κB蛋白水平明显升高,VEGF,SERCA2蛋白水平明显降低(P<0.01)。IL-17+IgG组血清IL-17和心脏组织NF-κB蛋白水平明显低于模型组,差异有统计学意义(8.98±1.20 vs 11.19±1.22,0.88±0.03 vs 0.93±0.03,P<0.01)。IL-17+IgG组血清NT-proBNP,IL-17和心脏组织IL-17 mRNA、NF-κB蛋白水平明显低于IL-17组,VEGF、SERCA2蛋白水平明显高于IL-17组,差异有统计学意义(P<0.01)。IL-17+IgG组大鼠心率、收缩压、舒张末期室间隔厚度、左心室舒张末期后壁厚度、左心室舒张末期内径、左心室收缩末期内径明显低于模型组和IL-17组,左心室短轴缩短率明显高于模型组和IL-17组(P<0.01)。IL-17+IgG组大鼠左心室射血分数明显高于IL-17组[(70.81±6.50)%vs(62.77±5.43)%,P<0.01]。结论 IL-17、NF-κB、SERCA2信号通路参与调节高血压心力衰竭后的炎性反应,且抑制IL-17后可有效改善高血压心力衰竭造成的心功能损伤。

MCU在神经系统中的研究进展

钙离子(Ca^(2+))在细胞的生理活动调控中起到重要作用,包括神经元细胞的能量代谢和细胞死亡方式。线粒体作为细胞的动力工厂,为细胞的一系列生理活动提供能量,线粒体钙对腺嘌呤核苷三磷酸(adenosine triphosphate,ATP)的产生至关重要,线粒体内Ca^(2+)失衡会严重影响神经细胞的生理活动。线粒体钙单向转运体(mitochondrial calcium uniporter,MCU)复合体是位于线粒体内膜上的一种Ca^(2+)选择性通道,在维持线粒体内Ca^(2+)的稳态中发挥重要作用,从而影响神经元的正常功能。在神经元树突中,细胞线粒体内Ca^(2+)的改变决定信号分子的释放和传入、神经元的兴奋性和突触可塑性的维持。神经系统疾病包括脑血管疾病、发作性疾病、运动障碍性疾病以及神经系统变性等都和线粒体钙有密不可分的关系。本文主要对MCU复合体的结构、功能、作用以及部分疾病治疗前景的关系进行归纳总结,探讨MCU复合体在神经系统中的作用机制。

产蛋鸡子宫部钙离子转运及调控的研究进展

鸡蛋蛋壳品质下降会造成经济效益损失和食品安全风险。产蛋鸡子宫部无机钙离子(Ca^(2+))的转运涉及不同的跨膜途径、离子稳态、相关转运基因和载体的表达,是蛋壳矿化及调控的重要环节。本文综述了子宫部Ca^(2+)转运途径、Ca^(2+)转运对蛋壳矿化和蛋壳品质的影响、营养因素对Ca^(2+)转运的调控作用,旨在为通过调节蛋壳矿化,改善鸡蛋蛋壳品质提供参考。

化痰祛瘀法对冠心病稳定型心绞痛患者外周血线粒体钙转运与动脉粥样硬化指数的影响

目的探讨化痰祛瘀法对冠心病稳定型心绞痛患者外周血线粒体钙转运与动脉粥样硬化指数(AI)的影响。方法选取冠心病稳定型心绞痛患者100例,按随机数表法均分为对照组和观察组,对照组采用西医常规治疗,治疗组在西医常规治疗基础上+化痰祛瘀方治疗,连续治疗8周;分别于治疗前及治疗结束时,采用西雅图心绞痛量表(SAQ评分)评估两组患者的心绞痛程度,双试剂酶法检测两组患者甘油三酯(TG)、总胆固醇(TC)及低密度脂蛋白胆固醇水平(LDL-C),全自动血流变检测仪测定血液流变学指标,电化学发光法测定血清线粒体钙离子单向转运蛋白(MCU)水平,颈动脉超声检测两组患者AI,并比较两组患者的临床疗效。结果治疗结束后,两组患者躯体受限程度、心绞痛稳定状态、心绞痛发作情况、治疗满意程度及疾病认识程度等SAQ评分均较治疗前上升,且观察组均高于对照组(P<0.05);两组患者TG、TC、LDL-C治疗后水平均较治疗前下降,且观察组低于对照组(P<0.05);两组全血高切黏度、全血低切黏度、血浆黏度及纤维蛋白原治疗后水平均较治疗前下降,且观察组均低于对照组(P<0.05);两组患者治疗后MCU水平较治疗前上升、AI较治疗前下降,且治疗后观察组MCU水平高于对照组、AI水平低于对照组(P<0.05);治疗后,观察组临床总疗效高于对照组,差异有统计学意义(P<0.05)。结论化痰祛瘀法对冠心病稳定型心绞痛患者有较好疗效,其机制可能与改善外周血线粒体钙转运功能及AI有关。

Ketamine effect on intracellular and mitochondrial calcium mobilization

The suppressive effects of ketamine on intracellular calcium has been reported in a variety of cells although the mechanisms involved are not well understood.The aim of this work was to evaluate the ketamine effect on the mitochondrial Ca^(2+)accumulation and the cellular Ca^(2+)mobilization using FLUO4-AM and flow cytometry.The results showed that mitochondria from ketamine injected animals presented a lower ability to retain calcium at concentrations higher than 20μM,as compared with controls(saline injected animals).In ad-dition,ketamine showed a significant decreased KCl-induced intracellular calcium concentration.KCl increased calcium influx through cellular depolarization.According to the data presented herein,ketamine presents a clear inhibitory effect on cytosolic Ca2+transport mechanisms,independently from their action on the calcium channel associated NMDA receptor.

高寒草甸圆穗蓼叶解剖结构与草酸钙含量对生境干旱化的响应

为揭示高寒草甸生境干旱化过程中侵入种圆穗蓼(Bistorta macrophylla)的生境适应能力,在滇西北白马雪山高寒草甸选择湿润、半湿润和干旱生境设置样方、采集实验材料。利用单因素方差分析、主成分分析等方法,分析叶片解剖结构和草酸钙含量与土壤水分之间的关系。结果表明:叶片栅栏组织紧密排列为2层,主脉中5~9个维管束呈环形排列,且木质部朝中心方向分布。叶片、上表皮及角质层、下表皮、栅栏组织与海绵组织、主脉与维管束、木质部与韧皮部等结构的厚度以及叶草酸钙含量在生境间差异显著(P<0.01),且干旱生境中数值最大,其中叶片草酸钙含量对植株耐旱能力贡献最大。下表皮角质层厚度、栅海比在生境间的差异不显著。圆穗蓼通过增加保水结构(表皮与角质层)厚度以减少水分蒸发,增加输水结构(维管束、木质部)厚度提高输水效率,增加草酸钙含量增强贮水能力。即采取增强保水和输水结构功能、提高解剖结构与草酸钙含量协同响应等策略抵御生境干旱化。

Calcium Signaling is Involved in Negative Phototropism of Rice Seminal Roots

Calcium ions （Ca2＋） act as an intracellular second messenger and affect nearly all aspects of cellular life. They are functioned by interacting with polar auxin transport, and the negative phototropism of plant roots is caused by the transport of auxin from the irradiated side to the shaded side of the roots. To clarify the role of calcium signaling in the modulation of rice root negative phototropism, as well as the relationship between polar auxin transport and calcium signaling, calcium signaling reagents were used to treat rice seminal roots which were cultivated in hydroculture and unilaterally illuminated at an intensity of 100-200 pmol/（m2.s） for 24 h. Negative phototropism curvature and growth rate of rice roots were both promoted by exogenous CaCI2 lower than 100 pmol/L, but inhibited by calcium channel blockers （verapamil and LaCI3）, calcineurin inhibitor （chlorpromazine, CPZ）, and polar auxin transport inhibitor （N-l-naphthylphthalamic acid, NPA）. Roots stopped growing and negative phototropism disappeared when the concentrations increased to 100 pmol/L verapamil, 12.500 ~Jmol/L LaCI3, 60 pmol/L CPZ, and 6 pmol/L NPA. Moreover, 100 pmol/L CaCI2 could relieve the inhibition of LaCI3, verapamil and NPA. The enhanced negative phototropism curvature was caused by the transportation of more auxin from the irradiated side to the shaded side in the presence of exogenous Ca2＋. Calcium signaling plays a key role as a second messenger in the process of light signal regulation of rice root growth and negative phototropism.

Emanuel Strehler’s work on calcium pumps and calcium signaling

Cells are equipped with mechanisms to control tightly the influx, efflux and resting level of free calcium (Ca 2+ ). Inappropriate Ca 2+ signaling and abnormal Ca 2+ levels are involved in many clinical disorders including heart disease, Alzheimer's disease and stroke. Ca 2+ also plays a major role in cell growth, differentiation and motility; disturbances in these processes underlie cell transformation and the progression of cancer. Accordingly, research in the Strehler laboratory is focused on a better understanding of the molecular "toolkit" needed to ensure proper Ca 2+ homeostasis in the cell, as well as on the mechanisms of localized Ca 2+ signaling. A longterm focus has been on the plasma membrane calcium pumps (PMCAs), which are linked to multiple disorders including hearing loss, neurodegeneration, and heart disease. Our work over the past 20 years or more has revealed a surprising complexity of PMCA isoforms with different functional characteristics, regulation, and cellular localization. Emerging evidence shows how specific PMCAs contribute not only to setting basal intracellular Ca 2+ levels, but also to local Ca 2+ signaling and vectorial Ca 2+ transport. A second major research arearevolves around the calcium sensor protein calmodulin and an enigmatic calmodulin-like protein (CALML3) that is linked to epithelial differentiation. One of the cellular targets of CALML3 is the unconventional motor protein myosin-10, which raises new questions about the role of CALML3 and myosin-10 in cell adhesion and migration in normal cell differentiation and cancer.

CaCo_1-xRu_xO_y: Role of Ru/Co Ratio on Its Transport Properties

Calcium cobaltites, especially Ca3Co4O9 with a misfit layered structure, are promising thermoelectric materials due to their suitability for high temperature applications and low densities. The existence of low spin-state electronic configurations for both and species is one of the key parameter to explain the large thermopower values. Ruthenium oxide, with a layered structure, exhibits strong electron-electron correlation and the extended nature of their 4d electrons enhances orbital overlapping which is expected to influence the transport characteristics of CaCo1-xRuxOy (CCR) samples, by affecting the spin state of the 3d Co ions. The effect on thermopower and electrical resistivity due to partial substitution of Co by Ru ions, up to 0.33 moles, from 300 to 600 K was investigated. A sharp decline in resistivity and in thermopower was observed until a transition ion ratio (TIR), (Ru/(Ru + Co)), of 0.5 is reached, beyond which both the properties became less sensitive to TIR. These variations in the transport properties are explained by the presence of 4d Ru in close proximity to the Co, which could influence the spin and oxidation state of Co ions. The Co rich and Ru rich samples exhibit very distinct microstructures and phase assemblages.

Improving Photosynthetic Responses during Recovery from Heat Treatments with Brassinosteroid and Calcium Chloride in Indian Bread Wheat Cultivars

Climate change is expected to unleash severe and frequent heat waves in future, adversely affecting crop productivity. The aim of this study was to examine the effect of two separate episodes of heat stress, mimicking heat wave conditions on the physiology of four Indian bread wheat cultivars and to study the ameliorating effects of epibrassinolide (BR) and calcium chloride on the recovery of these cultivars. The two thermo-tolerant cultivars C306 and K7903 suffered less inhibition of photosystem II efficiency as compared to the two thermo-susceptible cultivars HD2329 and PBW343. Application of BR and calcium chloride resulted in faster recovery in all the four cultivars. Measurement of the minimum fluorescence (Fo) versus temperature curves revealed a higher inflection temperature of Fo (Ti) for the two tolerant cultivars as compared to the susceptible cultivars, emphasizing greater thermo stability of the photosynthetic apparatus. The two thermo-tolerant cultivars showed higher photochemistry (ΦPSII) relative to the two susceptible cultivars. An increase in the steady state fluorescence was observed in both the susceptible cultivars as compared to the tolerant cultivars. Expression analysis revealed faster recovery of the transcripts involved in photosynthesis in tolerant cultivars as compared to susceptible cultivars. Exogenous application of the ameliorating compounds resulted in faster recovery of transcripts in all the cultivars. The result suggested that under severe stress conditions tolerant cultivars showed faster recovery and a better thermo-stability of its photosynthetic apparatus as compared to susceptible cultivars and application of epibrassinolide and calcium chloride could ameliorate the damaging effect of severe temperature stress to a considerable level in all the four cultivars under study.

河流泥沙输移过程中矿物风化的碳汇效应初探——以长江干流为例

本文首先提出了河流泥沙输移过程中泥沙中的钙镁矿物溶蚀消耗水体中的CO_(2)并具有碳汇功能的观点。基于前人长江干流从源头到入海口和支流2003~2007年期间4次河流悬移质泥沙的化学元素组成和矿物组成资料,分析悬移质中CaO、MgO含量和方解石、白云石含量变化特征,定量计算了这些取样点悬移质泥沙的CO_(2)总碳汇能力和非永久性、永久性碳汇能力,分析了不同碳汇能力沿程变化规律及其原因。碳汇计算结果表明:寸滩—大通河段1956~2000年期间泥沙输移过程中钙镁矿物溶蚀产生的总碳汇量、非永久性和永久性碳汇量分别为2572万t/a、1700万t/a和872万t/a。由于输沙量减少,寸滩站—大通站河段的总碳汇量、非永久性和永久性碳汇量2006~2019年期间较1956~2000年期间相应分别减少了1852万t、1224万t和872万t。三峡水库年均淤积量1.145亿t,损失总碳汇量675.6万t,相当于三峡电站减排二氧化碳8580万t的7.9%。全球河流入海年输沙量126.1亿t,以寸滩-吴淞口河段碳汇功能0.060 t/t计,总碳汇量7.57亿t相当于全球岩石风化碳汇总量10.56亿t CO_(2)的71.6%。河流泥沙输移过程中钙镁矿物溶蚀的碳汇量具有重要的作用,其溶蚀速率大于原地风化。