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1.
氮素形态对杉木幼苗侧根生长和叶片光合特性的影响   总被引:3,自引:0,他引:3  
以3月龄的杉木实生苗为试验材料,分析了不同氮素形态——硝态氮(NO3- N)、铵态氮(NH4+ N)和硝酸铵(NH4NO3)(氮素浓度均为3 mmol·L-1)对杉木幼苗侧根生长、叶片光合气体交换参数和叶绿素荧光参数的影响,以揭示杉木幼苗对不同形态氮的偏好性,以及不同形态氮肥下杉木幼苗侧根生长和光合生理的响应特征,为杉木苗期氮肥管理提供理论依据。结果显示:(1)不同氮素形态对杉木幼苗地上部和侧根生物量具有显著影响,其中NH4+ N处理下幼苗地上部和侧根生物量最大,NO3- N处理次之,而NH4NO3处理最小。(2)NH4+ N和NO3- N处理下杉木幼苗总根长、根系总表面积和根系总体积均显著高于NH4NO3处理(P<0.05),且NH4+ N处理又显著高于NO3- N处理,但不同氮形态处理间侧根数量差异不显著。(3)NH4+ N处理下杉木幼苗叶片净光合速率、气孔导度和蒸腾速率明显高于NO3- N和NH4NO3处理,但NO3- N和NH4NO3处理之间无明显差异。(4)NH4+ N处理下杉木叶片初始荧光强度低于NO3- N处理,而最大荧光强度、可变荧光强度和PSⅡ潜在活性却高于全硝氮和硝铵氮处理。上述结果表明,NH4+ N处理不仅有利于杉木幼苗侧根生长发育,且其叶片具有较强的光合能力,较高的PSⅡ中心稳定性、光化学活性以及电子传递效率,从而更有利于植株生长。因此,从根系生长和光合特性来看,杉木幼苗对铵态氮具有偏好性。  相似文献   

2.
高寒冰川区氮素沉降量的变化会对区域生态系统产生显著影响,定量评估冰川区的氮沉降状况可以为修正相关模型提供重要的原始数据。通过2004年1月至2006年12月在天山乌鲁木齐河源1号冰川连续采样,分析了中国西北典型冰川区大气氮素的沉降特征,并估算了该区域的年均氮素沉降量。研究结果表明,1号冰川湿沉降中的硝态氮 (NO3--N)、铵态氮 (NH4+-N) 与总无机氮 (TIN) 存在着明显的季节变化特征:夏季沉降量最大,冬季最少,且与降水量表现出较好的对应关系。1号冰川氮素湿沉降的硝铵比 (NO3--N / NH4+-N) 月平均值在0.3-1间波动。1号冰川TIN湿沉降量年平均值为1.51 kg/hm2 (其中NH4+-N沉降量占总量的69%,而NO3--N沉降量仅占31%),干湿沉降总量年均值为1.56 kg/hm2,总氮 (TN) 的干湿沉降总量年均值为3.85 kg/hm2。得到的冰川区氮素沉降量符合中国西部高寒区的一般水平,代表了该区域的本底值。  相似文献   

3.
研究了盐氮处理条件下盐地碱蓬种子成熟过程中的离子积累以及种子萌发特性,以理解盐地碱蓬在种子发育及萌发过程中对高盐低氮生境的适应性。结果表明,种子成熟过程中,不同浓度盐氮处理下(0.5和5 mmol/L NO3--N;1和500 mmol/L NaCl),与果皮和果枝相比, 胚中Na+、K+、Cl- 和NO3-离子含量几乎没有变化。所有盐氮处理下Na+ 和Cl-都是果皮和果枝中高于胚中,尤其是在高盐处理下。高盐处理下,K+ 和NO3-含量呈现相反的趋势。高氮时无论高盐还是低盐,果皮中NO3-离子含量高于胚中,而果枝中NO3-离子含量低于胚中。而低氮时果皮及果枝中NO3-离子含量均显著低于胚中。与高氮环境下收获的种子相比,低氮环境下收获的种子萌发率,萌发指数,活力指数都要明显高。上述结果说明,盐地碱蓬种子成熟过程中存在完善的离子调控机制,保护胚免受Na+ 和Cl-等有害离子的伤害并且促进K+ 和NO3-等营养离子的积累。低NO3--N下收获的种子对外界的NO3-含量比较敏感,施以较高浓度的NO3-能够促进种子萌发,提高萌发指数和活力指数,可能与盐地碱蓬长期适应高盐低氮生境有关。  相似文献   

4.
康希睿  张涵丹  王小明  陈光才 《生态学报》2020,40(19):6958-6968
森林群落在净化空气、截留沉降污染物、改善地表水质等方面具有重要作用。本研究以北亚热带地区3种典型森林群落(毛竹林、杉木林、青冈阔叶林)为研究对象,通过分析沉降污染物(NH4+-N、NO3--N、NO2--N、TP和SO42-)在大气降水、林内穿透雨、树干茎流、枯透水和地表径流中的浓度和通量变化特征,探讨不同森林群落对氮、磷、硫的截留净化作用和分配特征。结果表明,该区域大气降水中NH4+-N、NO3--N、NO2--N、TP和SO42-年均浓度分别为1.06、0.61、0.04、0.07、1.84 mg/L,其年均pH为5.88;各森林群落林冠层能够调升降雨的pH且全年稳定,对TP和NH4+-N均有吸附作用,截留率分别为79.09%-84.68%和30.88%-69.36%;而枯落物层则是林下氮、磷、硫的主要释放源,对NH4+-N、NO3--N、TP和SO42-均具有淋溶作用;此外,由地表径流(输出)与大气降水(输入)的对比分析可知,各林地对沉降污染物中氮、磷、硫的截留率均超过98%;3种森林群落对沉降污染物中氮、磷、硫的截留能力依次为:青冈阔叶林 > 毛竹林 > 杉木林,阔叶林对沉降污染物的净化能力要高于毛竹林及针叶的杉木林。  相似文献   

5.
以大兴安岭多年冻土区泥炭地为研究对象,通过室内模拟增温实验,研究温度升高对不同深度(0-150 cm)土壤氮循环功能基因丰度的影响。同时针对0-20 cm和20-40 cm土壤设置两个水分处理,分别为土壤原始含水量和淹水状态,研究水分变化对表层土壤氮循环功能基因丰度的影响。结果表明温度升高显著提高了活动层(0-60 cm)、过渡层(60-80 cm)、永冻层(80-100 cm)中nifH、nirK基因丰度,温度升高显著提高了活动层(0-40 cm)和过渡层(60-80 cm)中nirS基因丰度。温度升高显著提高了过渡层(60-80 cm)NH4+-N和较深永冻层(140-150 cm)NO3--N的含量,但降低了过渡层(60-80 cm)NO3--N和较深永冻层(120-150 cm)NH4+-N的含量,相关性分析表明,NH4+-N含量与nifH和nirS基因丰度呈显著正相关,NO3--N含量与nirK基因丰度呈显著正相关,说明温度升高能够通过改变微生物丰度促进过渡层固氮作用和反硝化作用。在增温条件下,淹水处理使表层土壤nirS和nirK基因丰度及NH4+-N含量降低,但提高了NO3--N含量,说明淹水造成了过度还原的条件使反硝化底物浓度降低,降低反硝化微生物活性进而抑制了土壤反硝化作用。该结果对于明确未来气候变化影响下冻土区泥炭地土壤氮循环过程具有重要意义。  相似文献   

6.
为了解丛枝菌根真菌(AMF)和不同形态氮对杉木(Cunninghamia lanceolata)生长和养分吸收的影响,以1 a生杉木幼苗接种摩西球囊霉(Glomus mosseae)和添加不同形态氮(NH4+-N和NO3-N),对其养分元素和生长状况的变化进行研究。结果表明,AMF显著提高了杉木的苗高和生物量,促进了杉木对N、P、K、Ca、Mg、Fe和Na的吸收,AMF对微量元素Fe、Na的促进作用总体上要强于大量元素K、Ca。与NO3-N相比,AMF显著提高了NH4+-N处理杉木的生物量、总C和N、Ca、Mg、Mn含量,而且这种显著性在叶中普遍高于根和茎。接种AMF可以促进杉木幼苗的生长和对养分元素的吸收,且添加NH4+-N处理的促进作用要强于NO3-N。  相似文献   

7.
在无分子氧环境中,同时存在NH4+和NO2-时,NH4+作为反硝化的无机电子供体,NO2-作为电子受体,生成氮气,这一过程称为厌氧氨氧化。目前已经发现了3种厌氧氨氧化菌(Brocadia anamm oxidans,Kuenenia stuttgartiensis,Scalindua sorokinii);对厌氧氨氧化  相似文献   

8.
对不同畜禽粪便在堆肥过程中各种含氮化合物的动态变化进行了研究,结合综合性腐熟度评价指标——种子发芽指数(GI),探讨了畜禽粪便堆肥过程中与氮有关的腐熟度评价指标.结果表明:随着堆肥的进行,除奶牛粪外,其它畜禽粪便的全氮(TN)含量均呈先下降而后平稳变化趋势,奶牛粪则呈先增加而后平稳变化趋势;各种畜禽粪便中,碱解性氮(HN)含量先增后降;NH4+-N含量先下降而后保持平稳;NO3- -N含量则持续增加;NH4+ -N/NO3- -N迅速降低.堆肥腐熟度指标中,除综合性评价指标GI值外,HN/TN和NH4+ -N/TN也可作为评价畜禽粪便腐熟程度的优选指标,而NO3- -N/TN只能作为一般性评价指标.根据综合性评价指标GI值达到腐熟要求的标准(GI>0.50),除仔猪粪外,其它畜禽粪便在HN/TN<20.77%、NH4+ -N/TN<10.06%及NO3- -N/TN>0.38%时基本达到腐熟要求.  相似文献   

9.
滇西北高原纳帕海湿地土壤氮矿化特征   总被引:8,自引:4,他引:4  
解成杰  郭雪莲  余磊朝  许静 《生态学报》2013,33(24):7782-7787
采用树脂芯原位培育法,研究了纳帕海沼泽、沼泽化草甸和草甸土壤氮的矿化特征。结果表明,铵态氮(NH4+-N)为沼泽、沼泽化草甸土壤中无机氮的主要存在形式,分别占无机氮含量的96.76%和75.24%,而硝态氮(NO3--N)为草甸土壤中无机氮的主要存在形式,占无机氮含量的58.77%。植物生长期内,纳帕海湿地土壤的净氮矿化速率表现为沼泽化草甸 > 草甸 > 沼泽,表明干湿交替的土壤环境更利于土壤氮矿化作用的进行,土壤中氮素有效性和维持植物可利用氮素的能力更强。整个生长季,沼泽和草甸土壤氮矿化为硝化作用,而沼泽化草甸土壤氮矿化为氨化作用。土壤硝态氮含量、有机质含量、碳氮比和含水量均对纳帕海沼泽、沼泽化草甸和草甸土壤的氮矿化产生显著影响。  相似文献   

10.
以重庆市近郊中梁山槽谷为研究区,利用气象站和沉降仪获取2017年5月-2018年4月的大气无机氮、硫沉降数据和降水δ15N-NO3-、δ18O-NO3-和δ34S-SO42-、δ18O-SO42-数据,通过离子浓度比值、同位素值和气团后向轨迹探讨了研究区大气中氮、硫沉降变化特征及其来源。结果表明:(1)大气DIN总沉降量为19.99 kg/hm2,干、湿沉降量分别占11%和89%;大气S总沉降量为32.62 kg/hm2,干、湿沉降量分别占13%和87%。大气氮、硫湿沉降量与降水量均呈正相关(n=12,P < 0.01),氮、硫干湿沉降量具有明显的季节差异。(2)降水NH4+-N/NO3--N比值介于0.45-2.2之间,雨季(5-10月)NH4+-N/NO3--N>1,旱季(11-次年4月)NH4+-N/NO3--N<1,表明雨季氮主要来源于农业源,旱季来源于工业和交通源;降水NO3-/SO42-比值介于0.1-1.25之间,平均值为0.63,表明硫来源以固定污染源(燃煤)为主。(3)大气降水δ15N-NO3-、δ18O-NO3-值分别为-3.8‰-3.9‰(平均值为0.4‰±2.6‰)和58.7‰-98.7‰(平均值为76.1‰±14.3‰),夏季偏负,冬季偏正;降水δ34S-SO42-和δ18O-SO42-变化范围分别为1.3‰-3.2‰(平均值为2.3‰±1‰)和5.3‰-8.5‰(平均值为7.1‰±1.6‰),大气降水中NO3-和SO42-主要来源于当地的化石燃料燃烧,同时受到周边污染物的远距离传输影响。(4)气团后向轨迹表明影响研究区氮、硫干湿沉降来源的主要因素是东亚季风,北东-南西走向的川东平行岭谷大地貌格局加剧了季风的影响。  相似文献   

11.
Komárek has recently reviewed the various species assigned to the green algal genusNeochloris Starr (Chlorococcales, Chlorococcaceae) and removed those with uninucleate vegetative cells to a new genus,Ettlia. Watanabe & Floyd, unaware ofKomárek's work, also reviewed the species ofNeochloris and distributed them among three genera—Neochloris, Chlorococcopsis gen. nov., andParietochloris gen. nov.—on the basis of details of the covering of the zoospore and the arrangement of the basal bodies of the flagellar apparatus. This paper reconciles these two treatments and makes additional recommendations at the ranks of genus, family, order, and class.  相似文献   

12.
Systematic significance of mature embryo of bamboos   总被引:1,自引:0,他引:1  
The mature embryo of seven species belonging to five genera of Indian bamboos is described. In all these the basic pattern of embryo organisation is same: the scutellar and coleoptilar bundles are not separated by an internode, the epiblast is absent, the lower portion of the scutellum and the coleorhiza are separated by a cleft and the margins of embryonic leaves overlap. The features unique to fleshy fruited bamboos are: presence of a massive scutellum, the juxtaposition of plumule and radicle and the occurrence of a bud in the axil of the coleoptile. The fleshy fruit bearing bamboos should be classified into one group, the tribeMelocanneae. Evidence is provided to recognise additional groups in the subfamilyBambusoideae.  相似文献   

13.
The cardinalfishes (Apogonidae) are a diverse clade of small, mostly reef-dwelling fishes, for which a variety of morphological data have not yielded a consistent phylogeny. We use DNA sequence to hypothesize phylogenetic relationships within Apogonidae and among apogonids and other acanthomorph families, to examine patterns of evolution including the distribution of a visceral bioluminescence system. In conformance with previous studies, Apogonidae is placed in a clade with Pempheridae, Kurtidae, Leiognathidae, and Gobioidei. The apogonid genus Pseudamia is recovered outside the remainder of the family, not as sister to the superficially similar genus Gymnapogon. Species sampled from the Caribbean and Western Atlantic (Phaeoptyx, Astrapogon, and some Apogon species) form a clade, as do the larger-bodied Glossamia and Cheilodipterus. Incidence of visceral bioluminescence is found scattered throughout the phylogeny, independently for each group in which it is present. Examination of the fine structure of the visceral bioluminescence system through histology shows that light organs exhibit a range of morphologies, with some composed of complex masses of tubules (Siphamia, Pempheris, Parapriacanthus) and others lacking tubules but containing chambers formed by folds of the visceral epithelium (Acropoma, Archamia, Jaydia, and Rhabdamia). Light organs in Siphamia, Acropoma, Pempheris and Parapriacanthus are distinct from but connected to the gut; those in Archamia, Jaydia, and Rhabdamia are simply portions of the intestinal tract, and are little differentiated from the surrounding tissues. The presence or absence of symbiotic luminescent bacteria does not correlate with light organ structure; the tubular light organs of Siphamia and chambered tubes of Acropoma house bacteria, those in Pempheridae and the other Apogonidae do not.  相似文献   

14.
Intracellular cysteine aspartate-specific proteases (caspases) play both signaling and effector roles in realizing the program of cell death. Caspases function as proteolytic cascades unique for each cell type and signal triggering apoptosis. All parts of the proteolytic cascades are duplicated and controlled by feedback signals. Amplification cycles between pairs of caspases (the third and the sixth, the ninth and the third, the twelfth and the sixth, and others) help multiply the initial apoptotic signal. The presence of physiological inhibitors of apoptosis that directly interact with caspases creates a multilevel regulatory network of apoptosis in cell. The caspase proteolytic cascades are also regulated by sphingolipid secondary messengers, among them ceramide, sphingosine, and their phosphates. Moreover, an association of the caspase signaling with ubiquitin-dependent proteolysis is shown in cells. In particular, the use of extracellular activators and inhibitors of caspases allows irreversible activation of apoptosis in tumor cells or the prevention of apoptosis in cortical neurons under neurodegenerative diseases.  相似文献   

15.
Twenty three species in 11 genera were examined in the field to determine hosts. OnlyStriga asiatica andSeymeria cassioides have a narrow host range being restricted to grasses and pines, respectively. These are the only species which cause pronounced and sometimes serious host damage. The other species attach to a great diversity of hosts.  相似文献   

16.
Sixteen new species are proposed in the generaAckermania, Dressleria, Epidendrum, Maxillaria, Oncidium, Rodriguezia, Sigmatostalix, andTrigonidium. All new species are illustrated.Maxillaria vittariifolia L. O. Williams is newly recorded for Peru. A key is provided forTrigonidium of Peru.Trigonidium loretoense Schltr. andT. peruvianum Schltr. are lectotypified.  相似文献   

17.
The Drosophila Pax6 homolog twin of eyeless (toy) is so far the first zygotically expressed gene involved in eye morphogenesis in Drosophila. The study of its expression during embryogenesis is therefore informative of the initial events of eye development in Drosophila. We have analyzed how the initial expression domain of toy at cellular blastoderm is regulated. We show that the three maternal patterning systems active in the cephalic region (the anterior, terminal and dorsal-ventral systems) cooperate with zygotically activated gap genes to shape the initial expression domain of toy. Whereas Bicoid, Dorsal and Torso signaling synergistically act as activators, Hunchback, Knirps and Decapentaplegic act as repressors.  相似文献   

18.
A molecular phylogeny of Hebeloma species from Europe   总被引:2,自引:1,他引:1  
In order to widen the scope of existing phylogenies of the ectomycorrhizal agaric genus Hebeloma a total of 53 new rDNA ITS sequences from that genus was generated, augmented by sequences retrieved from GenBank, and analysed using Bayesian, strict consensus and neighbour joining methods. The lignicolous Hebelomina neerlandica, Gymnopilus penetrans, and two species of Galerina served as outgroup taxa. Anamika indica, as well as representatives of the genera Hymenogaster and Naucoria, were included to test the monophyly of Hebeloma, which is confirmed by the results. Hebeloma, Naucoria, Hymenogaster and Anamika indica cluster in a strongly supported monophyletic hebelomatoid clade. All trees largely reflect the current infrageneric classification within Hebeloma, and divide the genus into mostly well-supported monophyletic groups surrounding H. crustuliniforme, H. velutipes, H. sacchariolens, H. sinapizans, and H. radicosum, with H. sarcophyllum being shown at an independent position; however this is not well supported. The section Indusiata divides with strong support into three groups, the position of the pleurocystidiate Hebeloma cistophilum suggests the possible existence of a third subsection within sect. Indusiata. Subsection Sacchariolentia is raised to the rank of section.  相似文献   

19.
The reaction of chalcones and flavones with guanidine in ethanol results in 2-(2-aminopyrimidinyl-4)-phenols.  相似文献   

20.
Synopsis In a fourteen month study (May 1976 – June 1977) I examined the following characteristics of an intertidal bay goby (Lepidogobius lepidus) in Morro Bay, California, U.S.A.: annual and seasonal patterns of abundance, age composition and growth rates, survivorship and mortality patterns, and the reproductive cycle for female gobies. Fishes were collected with the aid of quinaldine and otoliths and ovaries removed. Age and growth rates were estimated from otolith annuli using a back calculation formula and a Brody-Bertalanffy growth curve. Mortality rates were derived using the methods of Heincke (1913), Robson & Chapman (1960), mean age, and a catch curve (Ricker 1975). A gonad index was used to describe the annual reproductive cycle. Results indicated that abundance fluctuated seasonally and that these fluctuations appeared to be caused by reproductive emigrations. Bay gobies reached an age of 7+ and a standard length of 87 mm. Growth was relatively constant (6 mm yr−1) until age 5, at which point it began to decline. The mean rates of survivorship, mortality, and instantaneous mortality were 0.75, 0.25, and 0.29 respectively. Mortality rates for individual age classes ranged from 0.13 to 0.51 and increased with age. This stock appears to reproduce mainly during the winter.  相似文献   

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