施氮对不同有机碳水平桉树林土壤微生物群落碳代谢的影响

土壤微生物群落碳代谢功能既受土壤氮素水平的影响,也与土壤有机碳水平密切相关,但二者如何共同影响土壤微生物群落碳代谢功能的研究尚不多见。以我国南方广泛种植的桉树林为对象,采用野外控制实验比较研究了4种施氮处理(对照:0kg/hm2,低氮:84.2 kg/hm2,中氮:166.8 kg/hm2,高氮:333.7 kg/hm2)对有机碳水平差异显著的两桉树林样地土壤微生物群落碳代谢功能的影响,结果表明:(1)两种有机碳水平桉树林土壤微生物群落碳代谢强度和代谢碳源丰富度显著不同,高有机碳水平桉树林土壤微生物群落碳代谢强度和代谢碳源丰富度显著高于低有机碳水平桉树林(P0.01);(2)施氮显著改变了桉树林土壤微生物群落的碳代谢强度和代谢碳源丰富度(P0.05),随着施氮水平的升高,土壤微生物群落碳代谢强度和代谢碳源丰富度均呈现先增加后降低的变化规律,但是高、低有机碳水平桉树林土壤微生物群落碳代谢强度和代谢碳源丰富度对施氮梯度的响应各不相同,高、低有机碳水平桉树林的土壤微生物群落碳代谢指标分别在中氮、低氮处理中达到最高值;(3)施氮影响土壤微生物群落代谢的碳源类型主要是碳水化合物类、氨基酸类和羧酸类,土壤微生物生物量是影响土壤微生物碳代谢强度和代谢碳源丰富度的重要因素。由此可知,施氮对土壤微生物碳代谢功能影响,也与土壤本底中有机碳水平的调节有关,所以在研究土壤微生物群落对施氮等条件的响应时,不能忽略土壤中有机碳水平。     

HCO-3对植物生长发育及代谢的促进作用

重碳酸盐(bicarbonate, HCO^-₃)是碳酸盐岩经岩溶作用风化的产物,它深刻地影响着植物的生长发育和岩溶地区的生态环境。以往研究大都关注HCO^-₃对植物生长代谢的负面影响,如抑制植物的光合作用、降低碳氮代谢关键酶活性、破坏离子平衡等,少有人关注其对植物生长代谢的积极作用。该文依据前人的研究结果,综述了HCO^-₃对植物生长代谢的促进作用。已有的研究工作显示,HCO^-₃不仅在干旱等逆境胁迫下为植物提供短期的碳源和水源,促进气孔打开,恢复光合作用,而且通过调节碳氮代谢关键酶活性促进植物的碳氮代谢,参与调控植物的碳同化和氮还原等复杂的生理过程; 此外,HCO^-₃还通过影响葡萄糖代谢歧化,改变植物糖酵解途径和磷酸戊糖途径的分配,以增强植物的抗逆能力,从而获取生存机会。HCO^-₃的这些积极作用不仅使之成为促进植物生理代谢的关键因子,而且成为连接光合作用和岩溶作用的纽带。阐明HCO^-₃对植物生长发育的积极作用,可为维护喀斯特生态系统的生物多样性和稳定性、优化喀斯特生态系统功能提供理论依据。     

好氧反硝化细菌碳氮代谢特点及途径的研究进展

好氧反硝化作用的发现打破了反硝化只能在严格厌氧条件下进行的传统认知,为生物脱氮提供了一条新的途径,已成为近些年的研究热点。碳源可为好氧反硝化过程提供能量和电子供体,其代谢难易程度直接影响着好氧反硝化细菌的脱氮效率,因此有必要明确碳源在好氧反硝化脱氮过程中的代谢机理。基于此,本文阐述了好氧反硝化细菌的种类及其对硝态氮与亚硝态氮的代谢途径;系统分析了不同好氧反硝化细菌对碳氮源代谢的差异与代谢机理;综合分析了碳代谢差异对好氧反硝化脱氮过程的影响,并对未来的研究方向进行了展望,旨在深入理解好氧反硝化细菌同时去除碳氮的机理,为提高废水生物脱氮除碳效率提供理论依据。     

木本植物对高氮沉降的生理生态响应

从4个方面综述了木本植物对氮沉降增加的生理生态响应研究进展。(1)氮沉降增加引起木本植物组织氮浓度增加,从而改变其体内的氮代谢：(2)氮沉降影响植物的光合作用速率及与光合作用相关的含氮组分,一定范围内氮沉降会增加光合速率、光合色素和Rubisco含量：(3)氮沉降增加将导致植物的呼吸作用增强：(4)氮沉降增加不利于植物的抗逆性,导致植物的抗寒力和抗病虫害的能力下降。     

温度对禁食大鲵碳氮代谢的影响

本文研究温度对禁食大鲵碳代谢和氮代谢的影响,结果表明：随着温度的升高、禁食大鲵的碳代谢和氮代谢均上升,其代谢率升高,禁食大鲵的代谢率很低,１５℃时,每日每公斤体重内的蛋白质消耗为０．７克左右,从理论上证明大鲵的耐饥能力很强,雄性大鲵比雌性大鲵的代谢率稍高。     

石斛属植物光合碳同化途径地理分异研究进展

系统总结了我国石斛属植物光合作用现状,结合石斛属植物光合作用碳同化途径研究,概括了兼性景天酸代谢植物的碳同化路径特征,分析了景天酸代谢表达程度与生态环境的关系,进而归纳出石斛属植物在光合作用碳同化途径方面存在地理分异。最后指出了石斛属植物系统发育研究领域存在的问题,提出从系统发育视角,采用分子系统学技术来研究石斛属植物光合碳同化途径地理分异的生物学机制。     

砷对烤烟碳氮代谢及其产量和品质的影响

采用盆栽试验,系统地研究了砷对烤烟全生育期的碳氮代谢及其产量和品质的影响。结果表明,砷毒害对烤烟全生育期的碳代谢有显著影响,抑制了碳的同化和转化,降低了整个生育期的叶绿素含量、光合速率,造成了全生育期可溶性糖的积累,导致了生育后期淀粉含量的降低,最终使碳积累减少。砷毒害也改变了烤烟的氮代谢,造成生育前期氮同化能力的降低,表现出硝酸还原酶(NR)活性下降、总氮和蛋白质含量低于CK。砷毒害烤烟的氮转化表现活跃,提高了其中的游离氨基酸含量和谷氨酸-丙酮酸转氨酶(GPT)活性,最终导致烤烟生育中后期总氮和蛋白质的积累,但使整个生育期的烟碱含量降低。研究还表明,砷毒害降低了烤烟的产量和经济性状,增加了叶片中砷的积累,可溶性总糖含量的提高和糖氮比的协调虽好,但烟碱含量的降低和总氮、蛋白质含量的增加,以及糖碱比和氮碱比的失调,不利于碳氮代谢有关的化学品质形成。     

固碳产油微藻的基因工程改造

藻种的选育和基因工程改造是微藻生物柴油研究的核心。为此,简要综述了微藻从光合作用到甘油三酯(TAG)合成过程中的关键基因及其代谢调控等方面的研究进展。从光合作用固碳、中心碳代谢、脂肪酸合成、TAG的组装、抑制TAG合成的竞争途径及脂类的分解途径等几个方面入手,浅析各个代谢途径中关键基因的作用及其表达调控。在此基础上,探讨微藻基因工程改造的可行性并指出微藻生物柴油在生物质能源领域中的前景及其综合利用的发展优势。     

植物光合碳和氮代谢之间的关系及其调节

概述了植物体内光合碳、氮代谢之间的相互作用及其代谢调控等方面的研究进展。     

干旱胁迫和遮光对印楝幼苗生长及碳氮代谢的影响

以0.5年生印楝半同胞家系实生苗为材料,设置4个干旱胁迫水平与3个遮光水平共12个处理盆栽试验,测定分析印楝叶片主要碳氮代谢酶活性、终产物含量及生长指标,以揭示印楝碳氮代谢对光照及水分胁迫的响应规律,为进一步研究印楝的物质转换及代谢规律充实理论基础。结果显示:(1)在干旱胁迫条件下,印楝可通过调节碳代谢酶(SS、SPS)和氮代谢酶(NR、GS、GOGAT)活性及加快可溶性糖、可溶性蛋白质和游离脯氨酸的积累以维持苗高较小的变幅。(2)在遮光条件下,轻度遮光就会导致印楝叶片主要碳氮代谢酶活性及代谢产物含量急剧下降,严重抑制幼苗生长。(3)在干旱胁迫和遮光共同存在的条件下,遮光(或干旱)在一定程度上可以减缓干旱(或遮光)对印楝初生代谢及生长带来的不利影响。研究发现,印楝幼苗具有较强的干旱适应能力,适度干旱胁迫(土壤相对含水量大于35%)可促进细胞碳氮代谢,但不利于净光和产物的积累;同时,印楝幼苗对光照需求较高,轻度遮光会使初生代谢及生长受到严重抑制;在苗木培育过程中要尽可能提供充足的水分和光照,在水分匮缺时可以通过适当遮光来缓解干旱对苗木生长带来的负面影响,而在光照不足的条件下则需要适当控制水分。     

Seasonal variations in nitrate reductase activity and internal N pools in intertidal brown algae are correlated with ambient nitrate concentrations

Nitrogen metabolism was examined in the intertidal seaweeds Fucus vesiculosus, Fucus serratus, Fucus spiralis and Laminaria digitata in a temperate Irish sea lough. Internal NO(3) (-) storage, total N content and nitrate reductase activity (NRA) were most affected by ambient NO(3) (-), with highest values in winter, when ambient NO(3) (-) was maximum, and declined with NO(3) (-) during summer. In all species, NRA was six times higher in winter than in summer, and was markedly higher in Fucus species (e.g. 256 +/- 33 nmol NO(3) (-) min(-1) g(-1) in F. vesiculosus versus 55 +/- 17 nmol NO(3) (-) min(-1) g(-1) in L. digitata). Temperature and light were less important factors for N metabolism, but influenced in situ photosynthesis and respiration rates. NO(3) (-) assimilating capacity (calculated from NRA) exceeded N demand (calculated from net photosynthesis rates and C : N ratios) by a factor of 0.7-50.0, yet seaweeds stored significant NO(3) (-) (up to 40-86 micromol g(-1)). C : N ratio also increased with height in the intertidal zone (lowest in L. digitata and highest in F. spiralis), indicating that tidal emersion also significantly constrained N metabolism. These results suggest that, in contrast to the tight relationship between N and C metabolism in many microalgae, N and C metabolism could be uncoupled in marine macroalgae, which might be an important adaptation to the intertidal environment.     

盐胁迫下外源NO对苜蓿幼苗生长及氮代谢的影响

为探寻增强苜蓿耐盐能力的调控途径,以甘农4号苜蓿品种为材料,采用NO供体硝普钠、NO清除剂c-PTIO及硝普钠类似物亚铁氰化钠处理苜蓿幼苗,研究盐胁迫下外源NO对苜蓿幼苗生长、光合特征、氮同化酶活性和氮代谢物含量的影响.结果表明: 外源NO能明显缓解盐胁迫对苜蓿幼苗生长及光合作用的抑制,单株干质量、叶绿素含量、净光合速率、蒸腾速率和可溶性蛋白含量增加;外源NO能增强硝酸还原酶、谷氨酰胺合成酶和谷氨酸合酶活性,抑制蛋白水解酶和谷氨酸脱氢酶活性, 降低叶片中游离氨基酸含量,提高硝态氮含量,加快铵的同化.NO供体SNP的类似物亚铁氰化钠对盐胁迫下苜蓿幼苗生长及氮代谢无调控作用;施用NO清除剂c-PTIO加剧了盐胁迫对苜蓿幼苗生长和氮代谢的抑制,添加外源NO能缓解c-PTIO的抑制效应.盐胁迫下,外源NO和内源NO均参与了苜蓿幼苗氮代谢的调控.     

Effects of addition of external nitric oxide on the allocation of photosynthetic electron flux in Rumex K-1 leaves under osmotic shock

Photosynthetic electron flux allocation, stomatal conductance, and the activities of key enzymes involved in photosynthesis were investigated in Rumex K-1 leaves to better understand the role of nitric oxide (NO) in photoprotection under osmotic stress caused by polyethylene glycol. Gas exchange and chlorophyll fluorescence were measured simultaneously with a portable photosynthesis system integrated with a pulse modulated fluorometer to calculate allocation of photosynthetic electron fluxes. Osmotic stress decreased stomatal conductance, photosynthetic carbon assimilation, and nitrate assimilation, increased Mehler reaction, and resulted in photoinhibition. Addition of external NO enhanced the stomatal conductance, photosynthetic rate, activities of glutamine synthetase and nitrate reductase, and reduced Mehler reaction and photoinhibition. These results demonstrated that osmotic stress reduced CO₂ assimilation, decreasing the use of excited energy via CO₂ assimilation which caused significant photoinhibition. Improving stomatal conductance by the addition of external NO enhanced the use of excited energy via CO₂ assimilation. As a result, less excited energy was allocated to Mehler reaction, which reduced production of reactive oxygen species via this pathway. We suppose that Mehler reaction is not promoted unless photosynthesis and nitrogen metabolism are prominently inhibited.     

Sodium nitroprusside affects the level of photosynthetic enzymes and glucose metabolism in Phaseolus aureus (mung bean)

Nitric oxide (NO) is an important signaling molecule in plants. The present study aims to investigate the downstream signaling pathways of NO in plants using a proteomic approach. Phaseolus aureus (mung bean) leaf was treated with sodium nitroprusside (SNP), which releases nitric oxide in the form of nitrosonium cation (NO+) upon light irradiation. Changes in protein expression profiles of the SNP treated mung bean leaf were analyzed by two-dimensional gel electrophoresis (2-DE). Comparison of 2-DE electropherograms revealed seven down-regulated and two up-regulated proteins after treatment with 0.5 mM SNP for 6 h. The identities of these proteins were analyzed by a combination of peptide mass fingerprinting and post-source decay using a matrix-assisted-laser-desorption-ionisation-time-of-flight (MALDI-TOF) mass spectrometer. Six out of these nine proteins found are involved in either photosynthesis or cellular metabolism. We have taken our investigation further by studying the effect of NO+ on glucose contents in mung bean leaves. Our results clearly demonstrated that NO+ rapidly and drastically decrease the amount of glucose in mung bean leaves. Moreover, four out of nine of these proteins are chloroplastic isoforms. These results suggested that chloroplasts might be one of the main sub-cellular targets of NO in plants.     

S-nitrosylated proteins of a medicinal CAM plant Kalanchoe pinnata- ribulose-1,5-bisphosphate carboxylase/oxygenase activity targeted for inhibition

Nitric oxide (NO) is a signaling molecule that affects a myriad of processes in plants. However, the mechanistic details are limited. NO post-translationally modifies proteins by S-nitrosylation of cysteines. The soluble S-nitrosoproteome of a medicinal, crassulacean acid metabolism (CAM) plant, Kalanchoe pinnata, was purified using the biotin switch technique. Nineteen targets were identified by MALDI-TOF mass spectrometry, including proteins associated with carbon, nitrogen and sulfur metabolism, the cytoskeleton, stress and photosynthesis. Some were similar to those previously identified in Arabidopsis thaliana, but kinesin-like protein, glycolate oxidase, putative UDP glucose 4-epimerase and putative DNA topoisomerase II had not been identified as targets previously for any organism. In vitro and in vivo nitrosylation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), one of the targets, was confirmed by immunoblotting. Rubisco plays a central role in photosynthesis, and the effect of S-nitrosylation on its enzymatic activity was determined using NaH14CO3. The NO-releasing compound S-nitrosoglutathione inhibited its activity in a dose-dependent manner suggesting Rubisco inactivation by nitrosylation for the first time.     

Nitric Oxide Modulates the Expression of Proteins and Promotes Epiphyllous Bud Differentiation in Kalanchoe pinnata

Nitric oxide (NO), a recent addition to the signaling molecules in plants, plays an important role in mediating both biotic and abiotic stress responses. The occurrence of reproductive/vegetative structures, known as epiphylly, on the surface of leaves is a stress survival mechanism exhibited by some plants, including Kalanchoe pinnata. In the present study the role of NO during epiphyllous bud differentiation was investigated. NO donors l-arginine, NaNO₂, and SNP promoted epiphyllous bud differentiation in a dose-dependent manner, whereas NO inhibitors reversed the effect, suggesting the involvement of NO in the process. Albeit numerous physiological processes are reported to be modulated by NO, but their correlation with NO-responsive genes and proteins needs to be established. To address this issue, NO-responsive proteins (NORPs) were identified using 2D-PAGE and MS analysis. Major NORPs that were identified belonged to photosynthesis, oxidative phosphorylation, signaling, and stress metabolism, aptly indicating their probable role in this stress-induced growth process. The present study clearly indicates the role of NO in this stress survival mechanism, thus strongly affirming its role in stress responses.     

活性氧在气孔运动中的作用

水分代谢是植物基础代谢的重要组成部分,气孔开关精细地调节着植物水分散失和光合作用。气孔运动受到多种因子的调控,保卫细胞内大量的第二信使分子是响应外界刺激、调节保卫细胞代谢方式、改变保卫细胞水势进而引起气孔开关的重要功能组分。细胞内的活性氧就是其中重要的成员之一。保卫细胞中的活性氧包括过氧化氢、超氧阴离子自由基和羟自由基等,这些活性氧可以通过光合作用、呼吸作用产生或通过专门的酶催化合成,在触发下游生理反应、完成信号转导后由专门的酶将其清除。在植物激素(脱落酸、水杨酸)、一氧化氮、质外体钙调素、细胞外ATP等因子调节气孔运动的过程中,活性氧都发挥了介导作用。该文对于近年来活性氧在气孔运动过程中发挥的作用方面的研究进展进行了综述。     

Isoprene and nitric oxide reduce damages in leaves exposed to oxidative stress

Isoprene and nitric oxide (NO) are two volatile molecules that are produced in leaves. Both compounds were suggested to have an important protective role against stresses. We tested, in two isoprene-emitting species, Populus nigra and Phragmites australis, whether: (1) NO emission outside leaves is measurable and is affected by oxidative stresses; and (2) isoprene and NO protect leaves against oxidative stresses, both singularly and in combination. The emission of NO was undetectable, and the compensation point was very low in control poplar leaves. Both emission and compensation point increased dramatically in stressed leaves. NO emission was inversely associated with stomatal conductance. More NO was emitted in leaves that were isoprene-inhibited, and more isoprene was emitted when NO was reduced by NO scavenger c-PTIO. Both isoprene and NO reduced oxidative damages. Isoprene-emitting leaves which were also fumigated with NO, or treated with NO donor, showed low damage to photosynthesis, a reduced accumulation of H(2)O(2) and a reduced membrane denaturation. We conclude that measurable amounts of NO are only produced and emitted by stressed leaves, that both isoprene and NO are effective antioxidant molecules and that an additional protection is achieved when both molecules are released.     

High temperature triggers the metabolism of S-nitrosothiols in sunflower mediating a process of nitrosative stress which provokes the inhibition of ferredoxin-NADP reductase by tyrosine nitration

High temperature (HT) is considered a major abiotic stress that negatively affects both vegetative and reproductive growth. Whereas the metabolism of reactive oxygen species (ROS) is well established under HT, less is known about the metabolism of reactive nitrogen species (RNS). In sunflower (Helianthus annuus L.) seedlings exposed to HT, NO content as well as S-nitrosoglutathione reductase (GSNOR) activity and expression were down-regulated with the simultaneous accumulation of total S-nitrosothiols (SNOs) including S-nitrosoglutathione (GSNO). However, the content of tyrosine nitration (NO(2) -Tyr) studied by high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) and by confocal laser scanning microscope was induced. Nitroproteome analysis under HT showed that this stress induced the protein expression of 13 tyrosine-nitrated proteins. Among the induced proteins, ferredoxin-NADP reductase (FNR) was selected to evaluate the effect of nitration on its activity after heat stress and in vitro conditions using 3-morpholinosydnonimine (SIN-1) (peroxynitrite donor) as the nitrating agent, the FNR activity being inhibited. Taken together, these results suggest that HT augments SNOs, which appear to mediate protein tyrosine nitration, inhibiting FNR, which is involved in the photosynthesis process.