葡萄休眠的自然诱导因子及其对休眠诱导期冬芽呼吸代谢的调控

以高需冷量葡萄品种‘夏黑’为试材,研究短日照、长日照和自然光照3个条件下,葡萄冬芽休眠的自然诱导因子及其对休眠诱导期冬芽呼吸代谢的调控机制.结果表明: 自然低温、短日照2个环境因素单独或共同作用均能诱导葡萄冬芽进行自然休眠.短日照在诱导葡萄冬芽进入自然休眠的过程中起主导作用,自然低温起辅助作用;温度相同条件下,日照时间越短对葡萄冬芽自然休眠的诱导作用越强.总呼吸速率达到峰值是葡萄冬芽休眠诱导期结束的标志.在自然休眠诱导期间,葡萄冬芽磷酸戊糖途径运行活性和容量占总呼吸的比例迅速上升,其中自然条件的葡萄冬芽分别由16.0%和20.1%上升至22.3%和26.0%.自然低温是诱导葡萄冬芽底物氧化水平上呼吸途径发生变化的主导因素,短日照起促进作用.在葡萄冬芽自然休眠诱导期间,交替途径运行活性和容量占总呼吸的比例迅速上升,其中自然条件葡萄冬芽分别由19.4%和27.3%上升至38.2%和46.8%.自然低温和短日照均可诱导葡萄冬芽电子传递链水平上呼吸途径发生变化.     

桃叶片抗冷性对光周期诱导休眠的响应

以6年生“春捷”桃树为试材,以自然生长的桃树为对照,研究了长日照和短日照的休眠诱导效应和休眠诱导进程中叶片抗冷性对光周期的响应.结果表明: 在逐渐降低的自然环境温度下,长日照和短日照处理树体均能进入休眠诱导期,其中长日照处理延后1周而短日照处理提前1周进入.随着休眠程度的加深,各处理叶片的总含水量、自由水含量降低,束缚水含量、束缚水/自由水比值升高.超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性在休眠诱导期内均呈单峰曲线,高峰值出现在休眠诱导期的后期,过氧化物酶(POD)活性进入休眠诱导期后迅速下降,后期回升形成小高峰.休眠诱导期内可溶性蛋白含量稳步下降,脯氨酸和丙二醛(MDA)含量持续升高,伤害率逐渐增大.长日照可显著提高SOD、CAT活性及脯氨酸含量,减缓POD活性和可溶性蛋白含量的降幅,降低MDA和伤害率的增幅.这表明长日照处理叶片受伤害程度更轻,而短日照处理相应指标的变化则不同,尤其诱导期后期叶片的伤害率显著高于对照,表现出较低的抗冷性.如果环境温度允许,实际生产中可以适当延长光照时间来提高叶片的抗冷性.     

拟南芥保卫细胞微丝骨架的解聚可能参与了细胞外钙调素诱导的气孔关闭

细胞外钙调素(CaM)在植物的许多生理活动中都执行着重要功能, 但它对气孔运动的作用及其调控机制, 人们了解的很少. 以模式植物拟南芥为材料, 研究了细胞外CaM在保卫细胞壁上的存在及其对气孔运动的调控机制. 结果表明, 拟南芥保卫细胞壁中存在有分子量为17 kD的CaM, 并应用W7-琼脂糖和CaM抗血清初步证明了保卫细胞壁中存在的CaM可能具有促进气孔关闭和抑制气孔开放的作用. 在应用外源CaM诱导气孔关闭的实验中, 保卫细胞微丝骨架由长而呈辐射状分布的聚合态逐步解聚, 气孔开度也随着降低. 药理学实验结果表明, 保卫细胞微丝骨架的解聚能明显地促进外源CaM诱导的气孔关闭, 而微丝骨架的聚合则抑制这一过程. 研究结果还表明, 外源CaM能诱导保卫细胞[Ca²⁺]_cyt升高; 当使用Ca²⁺螯合剂EGTA时, 外源CaM诱导的[Ca²⁺]_cyt升高和气孔关闭运动均受到抑制. 为此推测细胞外CaM可能是通过诱导保卫细胞[Ca²⁺]_cyt升高, 导致微丝骨架的解聚, 进而促进气孔的关闭运动.     

盐胁迫下构树幼苗各器官中K+、Ca2+、Na+和Cl-含量分布及吸收特征

将当年生构树幼苗置于含有不同浓度（04、1、2、3、4 g·kg^-1）NaCl的土壤中,研究其生物量积累、叶片细胞质膜透性和K⁺、Ca²⁺、Na⁺、Cl^-等离子的吸收、分布及运输,并观察盐害症状.结果表明：构树幼苗的叶片质膜透性随着NaCl浓度的增加和胁迫时间的延长而升高,根冠比随NaCl浓度的升高而增加,大于3 g·kg^-1的土壤盐胁迫对构树叶片的质膜透性及植株的生物量积累影响显著.构树幼苗各器官中Na⁺和Cl^-含量随土壤NaCl浓度升高而显著增加,K⁺和Ca²⁺则随之降低,叶片各离子含量均明显高于根和茎.说明盐胁迫影响根系对K⁺和Ca²⁺的吸收,并抑制了它们向地上部分的选择性运输,使叶和茎的K⁺和Ca²⁺含量下降.构树通过吸收积累Na⁺和Cl^-抵御土壤盐分带来的渗透胁迫,但过量的Na⁺和Cl^-积累会造成单盐毒害.作为抗盐性较高的非盐生植物,构树地上部分的拒盐作用不显著.     

高温胁迫对花生幼苗光合速率、叶绿素含量、叶绿体Ca2+-ATPase、Mg2+-ATPase及Ca2+分布的影响

将水培后盆栽的花生幼苗,置于培养箱42℃高温培养,定时测定幼苗叶光合速率、叶绿素含量和叶绿体Ca²⁺-ATPase、Mg²⁺-ATPase的相对活性,并观察幼叶细胞内Ca²⁺分布的变化。试验结果表明：高温胁迫过程中,光合速率及叶绿素含量都随处理时间的延伸而下降,并呈显著正相关;叶绿体Ca²⁺-ATPase和Mg²⁺-ATPase高温胁迫过程中相对活性呈先升后降趋势,Ca²⁺-ATPase热敏性高于Mg²⁺-ATPase;高温胁迫过程中,Ca²⁺具有从胞外转运到胞质内和叶绿体中的趋势,Ca²⁺能够稳定高温胁迫下叶肉细胞膜和叶绿体的超微结构。     

外源钙离子对东南景天生长及锌积累的影响

采用水培试验,研究了外源添加不同浓度钙离子（Ca²⁺）对两种生态型东南景天生物量、根系形态及体内锌、钙、硫含量的影响.结果表明：随着外源Ca²⁺浓度的上升,两种生态型东南景天的干物质量均增加,且超积累生态型地上部增加显著(P<0.05);超积累生态型根长和根表面积增加,而非超积累生态型降低;超积累生态型根、茎、叶锌含量随着外源Ca²⁺浓度的增加而上升,但各处理间差异不显著(P>0.05),非超积累生态型地上部锌含量显著降低(P<0.05).非超积累生态型根、茎、叶钙含量与外源Ca²⁺浓度呈显著正相关(P<0.05),超积累生态型根系硫含量与外源Ca²⁺浓度呈极显著正相关(P<0.01).外源Ca²⁺对超积累生态型东南景天锌吸收及积累有促进作用,而Ca²⁺浓度的升高抑制了非超积累生态型东南景天对锌的吸收.适当增加外源Ca²⁺可促进超积累生态型东南景天生长,改善其锌积累能力.     

氯化钠胁迫对不同品种南瓜幼苗阳离子含量的影响

选择19个不同类型南瓜品种,研究了300 mmol·L^-1 NaCl胁迫条件下,幼苗地上部和根系Na⁺、K⁺、Ca²⁺含量、Na⁺/K⁺、Na⁺/Ca²⁺、钠-钾和钠-钙运输选择性系数(S_Na⁺,K⁺和S_Na⁺,Ca²⁺值)的变化.结果表明：NaCl胁迫处理8 d后,不同品种南瓜幼苗Na⁺含量均明显增加,而K⁺含量下降,离子平衡被打破.青栗（Q₁）南瓜幼苗根系Na⁺含量、地上部Na⁺/K⁺、Na⁺/Ca²⁺、S_Na⁺,K⁺和S_Na⁺,Ca²⁺值均明显高于黑蜜南瓜（H₂）和黑籽南瓜（H₃）.不同品种南瓜幼苗体内Na⁺含量、地上部Na⁺/K⁺和Na⁺/Ca²⁺、S_Na⁺,K⁺和S_Na⁺,Ca²⁺值变化趋势与NaCI胁迫下不同品种南瓜幼苗盐害指数的结果基本一致,进一步验证了Q₁耐盐性强与NaCl胁迫下地上部Na⁺/K⁺、Na⁺/Ca²⁺、S_Na⁺,K⁺和S_Na⁺,Ca²⁺值较低以及K⁺、Ca²⁺含量较高有关;而H₂和H₃对盐敏感与NaCl胁迫下地上部Na⁺/K⁺、Na⁺/Ca²⁺、S_Na⁺,K⁺和S_Na⁺,Ca²⁺值较高,以及K⁺、Ca²⁺含量较低有关.     

L型Ca2+通道自发激活对静息心肌细胞钙火花的影响

钙火花是心肌细胞肌浆网Ca²⁺释放的基本单位. 为了研究L型Ca²⁺通道自发开放对心肌细胞钙火花的影响, 实验使用激光共聚焦扫描显微镜和Ca²⁺荧光探针Fluo-4, 在大鼠心肌细胞上观察局部钙火花的发放. 结果表明, 0.2 mmol/L CdCl₂通过阻断L型Ca²⁺通道, 使自发性钙火花的发放频率从给药前的4.20下降到给药后的2.04个/(100 μm&#8729;s), 但不影响火花的时空特性. 对Cd²⁺敏感的钙火花进行分析, 推测在静息膜电位下(&#8722;80 mV), L型Ca²⁺通道的开放概率约为10^&#8722;5. 因此, 在静息心肌细胞中, L型Ca²⁺通道低频随机开放对自发性钙火花的产生及细胞钙稳态调节有重要影响.     

模拟氮沉降下南方针叶林红壤的养分淋溶和酸化

以中国科学院红壤生态实验站林草生态试验区针叶林红壤为研究对象,在恒温(20 ℃)条件下,通过大土柱（直径10 cm、高60 cm）,8个月间隙性淋溶试验模拟研究了不同氮输入量（0、7.8、26和52 mg N/月/柱）对针叶林红壤NO₃^-、NH₄⁺、H⁺和土壤盐基离子(Ca²⁺、Mg²⁺、K⁺、Na⁺⁾淋溶以及土壤酸化的影响.结果表明,土壤交换态盐基总量、Ca²⁺和Mg²⁺淋溶量随氮输入量的增加而增加,土壤交换态Na⁺和K⁺则无明显影响.4种N输入处理的土壤交换态盐基总量净淋溶（淋溶出的盐基与淋洗液累计输入的盐基之差）分别占土壤交换性盐基总量的13.9%、18.6%、31.8% 和57.9％,土壤交换态Ca²⁺净淋溶分别占土壤交换性Ca²⁺总量的19.6%、25.8%、45.3%和84.8%,土壤交换态Mg²⁺净淋溶分别占土壤交换性Mg²⁺总量的4.4%、6.1%、10.9%和17.1%.随氮输入量增加,表层土壤pH值逐渐下降,4种N输入处理的表层土壤pH（KCl）分别为3.85、3.84、3.80和3.75;随氮输入量增加,淋溶液中无机氮、NO₃^-和H⁺逐渐增加.氮沉降可促进针叶林红壤的有机氮矿化,加速养分淋失和土壤酸化.     

光周期对休眠诱导期桃树光合及PSⅡ光系统性能的影响

人工设置长日照和短日照2种光周期(以自然条件为对照),测定6年生春捷桃树叶片光合参数和叶绿素荧光快速诱导动力学参数,研究诱导休眠期间光周期对北方落叶果树光合性能的影响.结果表明： 短日照条件下树体可提前进入休眠诱导期,长日照条件下则延后进入.休眠诱导期间,桃树叶片净光合速率(P_n)、气孔导度(g_s)降低,胞间CO₂浓度(C_i)升高,表明P_n降低的原因是非气孔限制;PSⅡ的最大光化学效率φ_Po(或F_v/F_m)、潜在活性（F_v/F_o）、PSⅡ反应中心捕获的光能用于Q_A^-下游的电子传递的能量比例(ψ_o)和光合性能指数(PI_ABS)均降低,表明光合电子传递链的电子传递能力受到抑制,其原因可能是PSⅡ反应中心受体侧Q_A^-下游的电子传递链受到了伤害.长日照有利于提高休眠诱导期的光合速率,减小PI_ABS下降幅度,减轻光系统的受害程度,短日照则明显加深、加速光合机构的损坏.光周期的诱导效应与休眠进程相关.
     

Alterations in ultrastructure and subcellular localization of Ca2+ in poplar apical bud cells during the induction of dormancy

In poplar (Populus deltoides Bartr. ex Marsh), bud dormancyand freezing tolerance were concomitantly induced by short-day(SD) photoperiods. Ultrastructural changes and the alterationin subcellular localization of calcium in apical bud cells associatedwith dormancy development were investigated. During the developmentof dormancy, the thickness of cell walls increased significantly,the number of starch granules increased, and there was a significantaccumulation of storage proteins in the vacuoles of the apicalbud cells. The most striking change was the constriction andblockage of the plasmodesmata. It was demonstrated that antimonate precipitation is a reliabletechnique for studying subcellular localization of calcium inpoplar apical bud cells. Under the long day (LD) photoperiod,electron-dense calcium antimonate precipitates were mainly localizedin vacuoles, intercellular spaces and plastids. Some antimonateprecipitates were also found in the cell walls and at the entranceof the plasmodesmata. However, there were few Ca²⁺ depositsfound in the cytosol and nucleus. After 20 d of SD exposure,when development of bud dormancy was initiated, calcium depositsin intercellular spaces were decreased, whereas some depositswere found in the cytosol and nuclei. From 28–49 d ofSD exposure, while dormancy was developing, a large number ofCa²⁺ precipitates were found in the cytosol and nuclei. Whendeep dormancy was reached after 77 d of SD exposure, Ca²⁺ depositsbecame fewer in both cytosol and nuclei, whereas numerous depositswere again observed in the cell walls and in the intercellularspaces. These results suggest that under the influence of SDphotoperiods, there are alterations in subcellular Ca²⁺ localization,and changes in ultrastructure of apical bud cells during thedevelopment of dormancy. The constriction and blockage of plasmodesmatamay cause the cessation of symplastic transport, limit cellularcommunication and signal transduction between adjacent cells,which in turn may lead to events associated with growth cessationand dormancy development in buds. Key words: Poplar, apical bud cells, Ca²⁺ subcellular localization, dormancy     

Identification of genes associated with growth cessation and bud dormancy entrance using a dormancy-incapable tree mutant

Background  

In many tree species the perception of short days (SD) can trigger growth cessation, dormancy entrance, and the establishment of a chilling requirement for bud break. The molecular mechanisms connecting photoperiod perception, growth cessation and dormancy entrance in perennials are not clearly understood. The peach [Prunus persica (L.) Batsch] evergrowing (evg) mutant fails to cease growth and therefore cannot enter dormancy under SD. We used the evg mutant to filter gene expression associated with growth cessation after exposure to SD. Wild-type and evg plants were grown under controlled conditions of long days (16 h/8 h) followed by transfer to SD (8 h/16 h) for eight weeks. Apical tissues were sampled at zero, one, two, four, and eight weeks of SD and suppression subtractive hybridization was performed between genotypes at the same time points.     

低温胁迫下拟南芥CBF1 超表达突变体胞质中Ca2+ 浓度的变化

低温严重影响植物的生长, 低温刺激可引起植物细胞中Ca²⁺浓度迅速升高。以拟南芥(Arabidopsis thaliana) CBF1 超表达突变体为材料, 研究了低温处理时CBF1基因的表达情况及胞质Ca²⁺的浓度变化。结果表明, CBF1本身可受低温诱导。同时将水母发光蛋白基因转入该拟南芥突变体中并检测Ca²⁺的浓度变化, 发现低温刺激时突变体细胞质中Ca²⁺的浓度变化幅度明显高于野生型, 但液泡的胞质面两侧Ca²⁺的浓度变化相似。用EGTA和LaCl₃处理拟南芥后, 胞质Ca²⁺的浓度升高被抑制, 并且CBF1突变体及对照胞质中的Ca²⁺浓度下降到同一水平。上述结果表明, Ca²⁺参与了CBF1应答低温信号的转导过程, 并且CBF1超表达突变体可能是通过提高胞质Ca²⁺浓度来提高植物的抗低温胁迫能力。     

Phylogenetic analysis and molecular evolution of the dormancy associated MADS-box genes from peach

Background  

Dormancy associated MADS-box (DAM) genes are candidates for the regulation of growth cessation and terminal bud formation in peach. These genes are not expressed in the peach mutant evergrowing, which fails to cease growth and enter dormancy under dormancy-inducing conditions. We analyzed the phylogenetic relationships among and the rates and patterns of molecular evolution within DAM genes in the phylogenetic context of the MADS-box gene family.     

Temperature-driven plasticity in growth cessation and dormancy development in deciduous woody plants: a working hypothesis suggesting how molecular and cellular function is affected by temperature during dormancy induction

The role of temperature during dormancy development is being reconsidered as more research emerges demonstrating that temperature can significantly influence growth cessation and dormancy development in woody plants. However, there are seemingly contradictory responses to warm and low temperature in the literature. This research/review paper aims to address this contradiction. The impact of temperature was examined in four poplar clones and two dogwood ecotypes with contrasting dormancy induction patterns. Under short day (SD) conditions, warm night temperature (WT) strongly accelerated timing of growth cessation leading to greater dormancy development and cold hardiness in poplar hybrids. In contrast, under long day (LD) conditions, low night temperature (LT) can completely bypass the short photoperiod requirement in northern but not southern dogwood ecotypes. These findings are in fact consistent with the literature in which both coniferous and deciduous woody plant species’ growth cessation, bud set or dormancy induction are accelerated by temperature. The contradictions are addressed when photoperiod and ecotypes are taken into account in which the combination of either SD/WT (northern and southern ecotypes) or LD/LT (northern ecotypes only) are separated. Photoperiod insensitive types are driven to growth cessation by LT. Also consistent is the importance of night temperature in regulating these warm and cool temperature responses. However, the physiological basis for these temperature effects remain unclear. Changes in water content, binding and mobility are factors known to be associated with dormancy induction in woody plants. These were measured using non-destructive magnetic resonance micro-imaging (MRMI) in specific regions within lateral buds of poplar under SD/WT dormancing inducing conditions. Under SD/WT, dormancy was associated with restrictions in inter- or intracellular water movement between plant cells that reduces water mobility during dormancy development. Northern ecotypes of dogwood may be more tolerant to photoinhibition under the dormancy inducing LD/LT conditions compared to southern ecotypes. In this paper, we propose the existence of two separate, but temporally connected processes that contribute to dormancy development in some deciduous woody plant: one driven by photoperiod and influenced by moderate temperatures; the other driven by abiotic stresses, such as low temperature in combination with long photoperiods. The molecular changes corresponding to these two related but distinct responses to temperature during dormancy development in woody plants remains an investigative challenge.     

Identification of QTLs controlling seed dormancy in peach (Prunus persica)

Dormancy is a condition that delays or inhibits growth in seed, vegetative buds, and floral buds. In peach, seed germination occurs when seed accumulate sufficient stratification and growing degree hours to break dormancy and begin growing. Correlations have been reported between mean seed stratification requirements and mean bud chilling requirements among Prunus families, but an individual seed’s germination date and subsequent vegetative and floral bud break date are not correlated. Prior to this study, the genetic factors involved in regulating seed dormancy and their location on the peach genomic map were unknown. Segregating F₂ seed were collected from a high?×?low chill F₁ peach hybrid in 2005, 2006, and 2008. Germination date and growth habit was measured after the stratification requirement of the 2005 seed was fully met. The seed collected in 2006 and 2008 received varying amounts of stratification, which enabled data on stratification requirement, heat requirement, and growth habit to be collected. Genomic DNA was extracted from seedling leaf tissue and screened with SSR markers selected from the Prunus reference map at an average resolution of 20 cM. Seed dormancy quantitative trait loci (QTLs) were detected on G1, G4, G6/8, and G7. The QTLs detected on G6/8 and G7 were discovered in the same region as QTLs associated with floral bud chilling requirement and bloom time in peach.     

Effects of Ca2+ and Cd2+ on the Carbohydrate Metabolism in Sugar Beet (Beta vulgaris)

Sugar beet (Beta vulgaris L. cv. Monohill) were cultivated ina nutrient solution with different combinations of Ca²⁺ (36,180, 720 or 3560µM) and Cd²⁺ (0, 1, 5 or 20µM).The dry and fresh weights, the content of Ca²⁺ and Cd²⁺ , sucrose,fructose, glucose and starch in 5-week-old plants was analysedas well as the rate of [¹⁴C]-sucrose uptake in discs from 3-month-oldstorage roots. The carbohydrate metabolism was indirectly affectedby the presence of calcium or cadmium. Cadmium caused a diminisheddry weight and carbohydrate concentration. The dry weight wasunaffected by the Ca²⁺ level but the carbohydrate distributionbetween storage and growth processes was affected; at low Ca²⁺in the tissue, the growth was retarded and the level of storagecarbohydrate increased, while at high Ca²⁺ the opposite wasfound. The [¹⁴C]-sucrose uptake decreased in tap roots cultivatedat low Ca²⁺ . Long term exposure to Cd²⁺ also decreased thesucrose uptake in tap roots. Direct Cd²⁺ addition to the assaymedium, however, increased the sucrose uptake, probably at thetonoplast, while Ca²⁺ had no transient effect on the uptake.Cadmium increased the Ca²⁺ concentration in the plant, but Ca²⁺did not affect the net-uptake of Cd²⁺. Key words: Sugar beet, cadmium uptake, calcium uptake, carbohydrate formation, growth     

Ecotype-dependent control of growth,dormancy and freezing tolerance under seasonal changes in <Emphasis Type="Italic">Betula pendula</Emphasis> Roth

Woody plants in the temperate and boreal zone undergo annual cycle of growth and dormancy under seasonal changes. Growth cessation and dormancy induction in autumn are prerequisites for the development of substantial cold hardiness in winter. During evolution, woody plants have developed different ecotypes that are closely adapted to the local climatic conditions. In this study, we employed distinct photoperiodic ecotypes of silver birch (Betula pendula Roth) to elucidate differences in these adaptive responses under seasonal changes. In all ecotypes, short day photoperiod (SD) initiated growth cessation and dormancy development, and induced cold acclimation. Subsequent low temperature (LT) exposure significantly enhanced freezing tolerance but removed bud dormancy. Our results suggested that dormancy and freezing tolerance might partially overlap under SD, but these two processes were regulated by different mechanisms and pathways under LT. Endogenous abscisic acid (ABA) levels were also altered under seasonal changes; the ABA level was low during the growing season, then increased in autumn, and decreased in winter. Compared with the southern ecotype, the northern ecotype was more responsive to seasonal changes, resulting in earlier growth cessation, cold acclimation and dormancy development in autumn, higher freezing tolerance and faster dormancy release in winter, and earlier bud flush and growth initiation in spring. In addition, although there was no significant ecotypic difference in ABA level during growing season, the rates and degrees of ABA alterations were different between the ecotypes in autumn and winter, and could be related to ecotypic differences in dormancy and freezing tolerance.