Assessment of fatty acids in cardiac tissue as 9-anthryldiazomethane esters by high-performance liquid chromatography

A high-performance liquid chromatographic technique for the rapid assessment of fatty acids in cardiac tissue is described. A level of 50.4 ± 14.9 nmol fatty acids per g wet weight of rat myocardial tissue could be monitored. The content of the individual fatty acids C_14:0, C_16:0, C_16:1, C_18:0, C_18:1, C_18:2 and C_20:4 amounted to 1.9, 13.5, 0.6, 14.4, 6.1, 6.5 and 7.2 nmol/g wet weight, respectively. A comparison of this method with a well established gas chromatographic technique yielded good agreement. In contrast with time-consuming gas chromatographic techniques, there is no need to isolate (unesterified) fatty acids from the other lipid classes with column chromatography or thin-layer chromatography, because the derivatizing reagent 9-anthryldiazomethane reacts highly specifically with fatty acids.     

Metabolism of CO2 by leaves of different photosynthetic types of Neurachne species

Following a series of continuous exposures to ¹⁴CO₂ for different lengths of time, leaves from Neurachne munroi (C₄), N. minor (C₃-C₄) and N. tenuifolia (C₃| were estimated to assimilate 100%, 9% and 2–4%, respectively, of atmospheric CO₂ by the C₄ pathway. The percentage of ¹⁴C-label appearing in malate and aspartate in leaves of N. minor progressively increased with longer exposure times indicating that a significant proportion of its C₄ acids are formed as secondary products. In ¹⁴CO₂/¹²CO₂ pulse/chase experiments, the ¹⁴C-label in leaves of N. munroi was rapidly transferred from C₄ acids to sugar monophosphates plus sugar diphosphates, and finally to sucrose. In leaves of N. minor, the ¹⁴C-label was slowly metabolized from the C-4 carboxyl of malate and asparate (apparent half-time = 250 s), and the formation of C₄ acids as secondary products was again evident. ¹⁴C-label in serine/glycine accumulated to comparable magnitudes in both N. minor and in N. tenuifolia, but there was an initial lag phase in the accumulation of label in N. minor. C₄ photosynthesis is apparently of minimal importance in reducing photorespiration in N. minor, but leaf anatomical specializations and a possible compartmentation of photorespiratory metabolism may be of considerable importance.     

东北草原区C3、C4植物的生态分布及其适应盐碱环境的生理特性

用5种实验方法对东北草原区233种植物光合类型进行鉴定,并对其相对分布随纬度变化关系及其与土壤含盐量和PH值的关系进行分析.在此基础上对几种典型C₃、C₄牧草适应于盐碱环境的生理特点进行深入研究结果表明,在所鉴定的233种植物中,C₃植物有144种,隶属于28科94属,C₄植物有89种;隶属于17科55属,在高纬度地区C₃植物表现出更高的生长优势,在纬度较低和盐碱化区域,C₄植物分布具相对优势.尤其在盐碱化程度较重的地区,C₄植物成为明显的优势种,分布上的差别决定于它们对环境适应机制上的差异C₃植物对盐碱环境适应机制主要通过积累脯氨酸等有机溶质进行渗透调节,而C₄植物主要通过液泡中离子区域化积累作用进行调节,并且与C₃植物相比对盐碱环境具更强的适应能力.     

C3和C4植物光合途径的适应性变化和进化

高等植物大多为C₃植物, C₄植物和景天酸代谢(Crassulacean acid metabolism, CAM)植物是由C₃植物进化而来的。C₄途径的多源进化表明, 光合途径由C₃途径向C₄途径的转变相对简单。该文分析研究了植物光合途径的进化前景, 指出C₄植物是从C₃植物进化而来的高光效种类, 且地质时期以来降低的大气CO₂浓度和升高的大气温度以及干旱和盐渍化是C₄途径进化的外部动力。C₃植物的C₄途径的发现说明植物的光合途径并非是一成不变的, C₃和C₄植物的光合特征具有极大的可塑性, 某些环境的变化会引起植物光合途径在C₃和C₄途径之间转变。C₃植物具有的C₄途径是环境调控的产物, 是对逆境的适应性进化结果, 因而光合途径的转变也适用于干旱地区植被的适应性生存机理研究。该文还利用国外最新的C₄光合进化模型介绍了植物在进化C₄途径中所经历的7个重要时期(从分子基础到形态基础、结构基础, 再到物质代谢水平、光合酶活水平, 直到C₃和C₄途径协调运转时期, 最后达到形态与功能最优化阶段), 并结合全球气候变化的特点对国内外相关领域的研究进行了分析, 总结了植物光合途径的适应性转变和进化的研究成果, 为今后的相关工作提出建议。     

Photosynthetic traits in C3 and C4 grassland species in mesocosm and field environments

The North American tallgrass prairie is composed of a diverse mix of C₃ and C₄ plant species that are subject to multiple resource limitations. C₄ grasses dominate this ecosystem, purportedly due to greater photosynthetic capacity and resource-use efficiency associated with C₄ photosynthesis. We tested the hypothesis that intrinsic physiological differences between C₃ and C₄ species are consistent with C₄ grass dominance by comparing leaf gas exchange and chlorophyll fluorescence variables for seven C₄ and C₃ herbaceous species (legumes and non-legumes) in two different settings: experimental mesocosms and natural grassland sites. In the mesocosms, C₄ grasses had higher photosynthetic rates, water potentials and water-use efficiency than the C₃ species. These differences were absent in the field, where photosynthetic rates declined similarly among non-leguminous species. Thus, intrinsic photosynthetic advantages for C₄ species measured in resource-rich mesocosms could not explain the dominance of C₄ species in the field. Instead, C₄ dominance in this ecosystem may depend more on the ability of the grasses to grow rapidly when resources are plentiful and to tolerate multiple limitations when resources are scarce.     

Photoreactivity of buckminsterfullerene-bis(triphenylphosphite)platinum(0) induced by metal-to-ligand charge transfer excitation

The complex C₆₀Pt[P(OPh)₃]₂ displays C₆₀ ππ^* intraligand bands in the UV-Vis region and a long-wavelength absorption at λ_max = 770 nm which is assigned to a metal-to-ligand charge transfer (MLCT) transition from platinum to fullerene. The irradiation of the complex leads to the population of the reactive MLCT state and subsequently to the dissociation (C₆₀Pt[P(OPh)₃]₂ → C₆₀ + Pt[P(OPh)₃]₂) in the primary photochemical step. Product formation takes place by the interception of Pt[P(OPh)₃]₂ with suitable scavengers such as CHCl₃ or O₂.     

The Australasian grass flora in a global context

Australia's flora and fauna have long been considered unique, but whether this applies to its grasses is less known. This study characterises the Australasian grass flora biogeographically. We investigate the distribution of C₃ and C₄ grass genera across four continents and construct broad profiles of their grass flora. We use endemism to examine global patterns of specialisation, and inter-continental distributions as indicators of dispersal, using databases constructed over twenty years. We examined Australasian patterns with regard to endemicity and shared groups and categorised all of the region's genera into four age classes, from Australia's separation from Gondwana to the present. Globally, each continent presented a unique profile and C₄ grasses were more widely shared than C₃. Australasia's grasses equally comprise C₃ and C₄ genera; it shared two thirds of its C₄ types with other continents, whereas C₃ types split evenly between shared and endemic. Australasia shared relatively few genera with just one neighbour (7% C₃, 13% C₄), primarily with EurAsia. Australasian grass genera and species were either endemic or globally widespread, and 88% of C₃ and 93% of C₄ species were derived from lineages that originated elsewhere. We conclude Southeast Asia was the gateway for dispersal into Australasia, akin to rainforest taxa exchanges which increased from c12 Ma, with about 65% of Australasia's grass genera arriving in the past 3.5 Ma. The strong presence of C₄ grasses in Australasia implies they have infiltrated a wide range of ecosystems, many probably occupied by ancient taxa with which they had not co-evolved.     

Transformation of steroids by Bacillus strains isolated from the foregut of water beetles (Coleoptera:Dytiscidae): I. Metabolism of androst-4-en-3,17-dione (AD)

Two Bacillus strains were isolated from the foregut of the water beetle Agabus affinis (Payk.) and tested for their steroid transforming ability. After incubation with androst-4-en-3,17-dione (AD), 13 different transformation products were detected. AD was hydroxylated at C₆, C₇, C₁₁ and C₁₄, resulting in formation of 6β-, 7-, 11- and 14-hydroxy-AD. One strain also produced small amounts of 6β,14-dihydroxy-AD. Partly, the 6β-hydroxy group was further oxidized to the corresponding 6-oxo steroids. In addition, a specific reduction of the Δ⁴-double bond was observed, leading to the formation of 5-androstane derivatives. In minor yields the carbonyl functions at C₃ and C₁₇ were reduced leading to the formation of 3ξ-OH or 17β-OH steroids. EI mass spectra of the trimethylsilyl and O-methyloxime trimethylsilyl ether derivatives of some transformation products are presented for the first time.     

Surface lipid composition of C3 and C4 plants

The characteristic surface lipid compositions of several C₃ and C₄ plants are discussed. C₄ plants produce surface lipids (epicuticular waxes) made up of the ubiquitous classes of aliphatic compounds: free fatty acids, aldehydes, primary alcohols, alkanes and aliphatic linear esters. C₃ plants synthesize surface lipids comprising the ubiquitous classes and either of the two following groups of compound: (i) lβ-diketones, hydroxy lβ-diketones, alkan-2-ol esters; (il) ketones and secondary alcohols with the functional group in the middle of the hydrocarbon chain. These features are suggested to represent physioIogical characteristics of the plant and to be related to ecological adaptations. Wax class compositions might also be an ancillary method for defining the C₃ or C₄ mechanism of CO₂ assimilation in cases where uncertainty exists.     

外源Ca2+对PEG处理下转C4型PEPC基因水稻光合生理的调节

磷酸烯醇式丙酮酸羧化酶(PEPC)通过固定二氧化碳参与光合作用, 是关键的C₄植物光合作用酶。为了揭示高光效转C₄ PEPC基因水稻(Oryza sativa)对干旱胁迫的适应机理, 以高表达转C₄ PEPC水稻(PC)和野生型水稻Kitaake (WT)为供试材料, 在植株的4-5叶期, 使用不同浓度外源CaCl₂溶液处理, 测定在15%聚乙二醇6000 (polyethylene glycol-6000, PEG-6000)胁迫下叶片相对含水量、光合参数、内源钙总含量、叶片总蛋白激酶活性、PEPC酶活性以及相关基因表达和蛋白质含量。结果表明, 0.5 mmol∙L^-1 CaCl₂明显提高PC叶片相对含水量(P<0.05), 2 mmol∙L^-1和10 mmol∙L^-1 CaCl₂则作用不显著, 对WT则影响不显著。不同浓度钙处理对PEG处理PC的净光合速率影响不显著, 而通过维持气孔导度减少水分胁迫。内源总钙浓度的数据显示, 在PEG6000处理下, PC具有维持稳定内源Ca²⁺浓度的能力, 过高浓度(10 mmol∙L^-1 CaCl₂)钙处理反而降低了PEPC酶活性、PEPC基因表达和可溶性蛋白的含量。     

不同光合类型牧草对干旱-复水的光合生理响应及生长适应策略

基于干旱频率增加、强度增大这一全球降水变化背景, 探究干旱-复水条件下不同功能群(C₃和C₄)植物的光合生理响应及生长适应策略有助于预测降水格局变化条件下草地的植被组成和生态系统功能。该研究采用盆栽实验, 以松嫩草地生长的一年生C₃ (4种)和C₄ (3种)牧草为实验材料, 设置了对照、中度干旱和重度干旱3个水分处理水平, 在干旱末期及复水期对植物进行气体交换、生物量和比叶质量的测量。在干旱条件下, 各物种净光合速率和气孔导度均呈下降趋势, 水分利用效率呈上升趋势。干旱对不同植物光合指标的影响存在功能群差异, 随干旱程度的增加C₄植物逐渐丧失光合优势, 重度干旱对C₄植物净光合速率的影响较C₃植物更加明显。由于干旱条件下C₃植物光合固碳主要受气孔限制而C₄植物主要受代谢限制, 因此复水后C₄植物净光合速率恢复速度较C₃植物慢。干旱条件下, 各物种的生物量降低, 根冠比和比叶质量升高, 干旱对C₃植物各生长指标的影响均大于C₄植物; 复水处理后, C₃植物生物量随干旱强度增加呈下降趋势, 而C₄植物的生物量与对照相比无显著差异。     

Composition of triglycerides from aphids of six different families and from different seasonal forms of Aphis evonymi

The triglyceride compositions of extracts and cornicle secretions of specimens from a range of aphid families were examined by mass spectrometry and found to support earlier evidence that there is little correlation between taxonomic position and chemical constitution.

Parasites developing within Myzus persicae preferentially consumed the typical aphid triglycerides which contain hexanoic (C₆), sorbic (C_6:2), myristic (C₁₄), and palmitic (C₁₆) acid moieties, so that when parasitism was advanced, only triglycerides with three long-chain fatty acids per molecule remained. The adult parasites themselves contained very little triglyceride.

Triglycerides of Aphis evonymi and Aphis fabae were similar and varied in composition regularly throughout the year. In the apterous and alate (summer) viviparae, there were equal amounts of myristoyl (C₁₄) and palmitoyl (C₁₆) triglycerides, while in fundatrices and fundatrigeniae (spring forms) myristoyl was predominant. Males collected in autumn resembled the spring forms. However, oviparae and eggs of these and other species differed considerably from the other seasonal forms, in having more hexenoic (C_6:1), sorbic (C_6:2), and myristoleic (C_14:1) acid moieties.     

Ionic iridium-gold and rhodium-gold perfluorobenzenethiolato binuclear complexes: syntheses and solution behavior

By reacting [(C₅Me₅)M(SR_F)₂] (forM = Ir, Rf = C₆F₅ (1a) or C₆F₄H-p (1b); for M = Rh, Rf = C₆F₅ (2a) or C₆F₄H-p (2a)) in toluene with Na[AuCl₄], ionic binuclear compounds with the general formula [(C₅Me₅)M(μ-SR_F)₂AuCl₂]Cl for M = Ir, R = C₆F₅ (3a) or C₆F₄H-p (3a); for M = Rh, R_F = C₆F₅ (4a) or C₆F₄H-p (4b) can be obtained, together with small amounts of [(C₅Me₅)₂Rh₂(μ-SR_F)(μ-Cl)₂]Cl (R_F = C₆F₅ (5a) or C₆F₄H-p (5b)) as by-products when 2a and 2b were used.     

Effects of plant intraspecific variation on the prediction of C3/C4 vegetation ratio from carbon isotope composition of topsoil organic matter across grasslands

植物种内变异对草地表层有机质碳同位素组成预测C₃/C₄植被比的影响植物群落中C₃和C₄植物的比例和组成对诸多生态系统过程具有重要影响。解析C₃和C₄植物碳同位素的环境驱动过程与调控因子,对于从土壤碳同位素的角度来预测C₃/C₄植被比和组成具有重要意义。本研究旨在评估草原植物碳同位素特征的种内变异将如何影响C₃和C₄植物的碳同位素组成以及C₃/C₄植被比的预测。沿中国北方草原的自然干旱梯度选择26个植物群落,通过分析植物和土壤的碳同位素组成,采用混合模型来预测C₄植物对土壤有机碳的相对贡献。本研究对比分析了如下3种情境：(1)考虑C₃和C₄植物碳同位素的种内和种间效应;(2)仅考虑碳同位素的种间变异;(3)忽略碳同位素的种内和种间变异。研究结果表明,植物碳同位素组成沿中国北方草原自然干旱梯度的变化具有物种特异性。C₃和C₄植物的碳同位素组成与干旱指数之间呈显著负相关关系,但C₃植物比C₄植物对环境的干旱变化更为敏感。植物碳同位素特征的种内变异在驱动C₃植物功能群碳同位素沿干旱梯度的分布格局中发挥着重要作用。如果忽略植物碳同位素特征的种内变异将会显著高估C₄植物的相对贡献。本研究结果表明,草原植物碳同位素特征的种内变异对于准确预测C₃/C₄植被组成具有重要意义。     

Photosynthetic carbon metabolism in Panicum milioides, a C3-C4 intermediate species: Evidence for a limited C4 dicarboxylic acid pathway of photosynthesis

Panicum milioides, a naturally occurring species with C₄-like Kranz leaf anatomy, is intermediate between C₃ and C₄ plants with respect to photorespiration and the associated oxygen inhibition of photosynthesis. This paper presents direct evidence for a limited degree of C₄ photosynthesis in this C₃-C₄ intermediate species based on:

1. (a) the appearance of 24% of the total ¹⁴C fixed following 4 s photosynthesis in ¹⁴CO₂-air by excised leaves in malate and aspartate and the complete transfer of label from the C₄ acids to Calvin cycle intermediates within a 15 s chase in ¹²CO₂-air;

2. (b) pyruvate- or alanine-enhanced light-dependent CO₂ fixation and pyruvate stimulation of oxaloacetate- or 3-phosphoglycerate-dependent O₂ evolution by illuminated mesophyll protoplasts, but not bundle sheath strands; and

3. (c) NAD-malic enzyme-dependent decarboxylation of C₄ acids at the C-4 carboxyl position, C₄ acid-dependent O₂ evolution, and ¹⁴CO₂ donation from [4-¹⁴C]C₄ acids to Calvin cycle intermediates during photosynthesis by bundle sheath strands, but not mesophyll protoplasts.

However, P. milioides differs from C₄ plants in that the activity of the C₄ cycle enzymes is only 15 to 30% of a C₄ Panicum species and the Calvin cycle and phosphoenolpyruvate carboxylase are present in both cell types. From these and related studies (Rathnam, C.K.M. and Chollet, R. (1979) Arch. Biochem. Biophys. 193, 346–354; (1978) Biochem. Biophys. Res. Commun. 85, 801–808) we conclude that reduced photorespiration in P. milioides is due to a limited degree of NAD-malic enzyme-type C₄ photosynthesis permitting an increase in pCO₂ at the site of bundle sheath, but not mesophyll, ribulosebisphosphate carboxylase-oxygenase.     

C60-fullerenides of ytterbium and lutetium

Cp^#₂Yb (Cp^#=C₅H₄(CH₂)₂NMe₂) has been obtained by reaction of YbI₂(THF)₂ with 2 equiv. of C₅H₄(CH₂CH₂NMe₂)K in THF. The X-ray structure analysis shows a bent structure with intramolecular coordination of both nitrogen atoms to ytterbium. The reaction of C₆₀-fullerene with Cp^#₂Yb leads to the formation of the fullerenide derivative [Cp^#₂Yb]₂C₆₀, which shows an ESR signal in the solid state and in THF solution at room temperature (solid: ΔH = 50 G, G = 1.9992; solution: ΔH = 10 G, G = 2.0001) and a magnetic moment of 3.6 BM. The lutetium fullerenides CpLu(C₆₀)(DME) (3) and Cp^*Lu(C₆₀)(DME)(C₆H₅CH₃) (4), (Cp = η⁵−C₅H₅, Cp^* = η⁵−C₅Me₅), were obtained by reaction of C₆₀ with CpLu(C₁₀H₈) (DME) and Cp^*Lu(C₁₀H₈) (DME) in toluene. Both complexes are paramagnetic (μ_eff = 1.4 and 0.9 BM) and exhibit temperature-dependent ESR signals (293 K: g = 1.992 and 2.0002 respectively).     

The synthesis and structures of tantalum complexes that contain a triamido or a diamidoamine ligand

Addition of (Me₃SiNHCH₂CH₂)₂NH (H₃[N₃(TMS)]) or (Me₃SiNH-o-C₆H₄)₂NH (H₃[ArN₃(TMS)]) to a solution of TaMe₅ yields [N₃(TMS)]TaMe₂ or [ArN₃(TMS)]TaMe₂, respectively. An X-ray study of [ArN₃(TMS)]TaMe₂ showed it to have an approximate trigonal bipyramidal structure in which the two methyl groups are in equatorial positions and the triamido ligand is approximately planar. Addition of (C₆F₅NHCH₂CH₂)₂NH (H₃[N₃(C₆F₅)]) to TaMe₅ yields first [(C₆F₅NCH₂CH₂)₂NH]TaMe₃, which then decomposes to [(C₆F₅NCH₂CH₂)₂N]TaMe₂. An X-ray study of [(C₆F₅NCH₂CH₂)₂N]TaMe₂ shows it to be approximately a trigonal bipyramid, but the C₆F₅ rings are oriented so that they lie approximately in the TaN₃ plane and two ortho fluorines interact weakly with the metal. Trimethylaluminum attacks the central nitrogen atom in [N₃(TMS)]TaMe₂ to give [(Me₃SiNCH₂CH₂)₂NAlMe₃]TaMe₂, an X-ray study of which shows it to be a trigonal bipyramidal species similar to the first two structures, except that the C-Ta-C bond angle is approximately 30° smaller (106.6(12)°). Addition of B(C₆F₅)₃ to [(C₆F₅NCH₂CH₂)₂NH]TaMe₃ yields {[(C₆F₅NCH₂CH₂)₂NH]TaMe₂}⁺ {B(C₆F₅)₃Me}⁻, the structure of which most closely resembles that of [(Me₃SiNCH₂CH₂)₂NAlMe₃]TaMe₂ in that the C-Ta-C angle is 102.0(6)°. The C₆F₅ rings in {[(C₆F₅NCH₂CH₂)₂NH]TaMe₂}⁺ are turned roughly perpendicular to the TaN₃ plane, i.e. ortho fluorines do not interact with the metal in this molecule.     

Spectroscopic and electrical properties of the [W(C3Se5)3] anion complex (C3Se5 = 1,3-diselenole-2-selone-4,5-diselenolate) and the oxidized species

[NBuⁿ₄]₂[W(C₃Se₅)₃] (C₃Se₅²⁻ = 1,3-diselenole-2-selone-4,5- diselenolate(2−)) was prepared by the reaction of Na₂[C₃Se₅] with WCl₆ in ethanol, followed by addition of [NBuⁿ₄]Br. The cyclic voltammogram in dichloromethane exhibits two oxidation peaks at −0.04 and +0.03 V (versus SCE). The complex reacted with [Fe(C₅Me₅)₂][BF₄], iodine or [TTF]₃[BF₄]₂ (TTF^·+ = the tetrathiafulvalenium radical cation) in acetonitrile to afford the oxidized complexes [Fe(C₅Me₅)₂]_0.5[W(C₃Se₅)₃], [NBuⁿ₄]_0.1[W(C₃Se₅)₃] and [TTF]_0.5[W(C₃Se₅)₃], respectively. Current-controlled electrochemical oxidation of the complex in acetonitrile gave [NBuⁿ₄]_0.6[W(C₃Se₅)₃]. The oxidized complexes exhibit electrical conductivities of 4.7×10 ⁻⁵−1.5×10⁻³ S cm⁻¹ at room temperature measured for compacted pellets. Electronic absorption, IR and ESR spectra of these complexes are discussed.     

Changes in soil microbial biomass and community structure with addition of contrasting types of plant litter in a semiarid grassland ecosystem

Aims Elevated atmospheric CO₂ has the potential to enhance the net primary productivity of terrestrial ecosystems. However, the role of soil microorganisms on soil C cycling following this increased available C remains ambiguous. This study was conducted to determine how quality and quantity of plant litter inputs would affect soil microorganisms and consequently C turnover.Methods Soil microbial biomass and community structure, bacterial community-level physiological profile, and CO₂ emission caused by different substrate C decomposition were investigated using techniques of biological measurements, chemical and stable C isotope analysis, and BIOLOG-ECO microplates in a semiarid grassland ecosystem of northern China in 2006 and 2007 by mixing three contrasting types of plant materials, C₃ shoot litter (SC 3), C₃ root litter (RC 3), and C₄ shoot litter (SC 4), into the 10- to 20-cm soil layer at rates equivalent to 0 (C 0), 60 (C 60), 120 (C 120) and 240 g C m ?2 (C 240).Important findings Litter addition significantly enriched soil microbial biomass C and N and resulted in changes in microbial structure. Principal component analysis of microbial structure clearly differentiated among zero addition, C₃ -plant-derived litter, and C₄ -plant-derived litter and among shoot- and root-derived litter of C₃ plants; soil microorganisms mainly utilized carbohydrates without litter addition, carboxylic acids with C₃ -plant-derived litter addition and amino acids with C₄ -plant-derived litter addition. We also detected stimulated decomposition of older substrate with C₄ -plant-derived litter inputs. Our results show that both quality and quantity of belowground litter are involved in affecting soil microbial community structure in semiarid grassland ecosystem.     

Summer monsoon intensity controls C4/C3 plant abundance during the last 35 ka in the Chinese Loess Plateau: Carbon isotope evidence from bulk organic matter and individual leaf waxes

The natural abundance of C₃ and C₄ plants is affected by multiple environmental factors including temperature, moisture balance and atmospheric pCO₂. The relative importance of these factors is a subject of considerable debate, and may vary in different natural ecosystems. Previous studies generally focus on single loess sequences in the Chinese Loess Plateau, and conflicting conclusions on C₄/C₃ have been reached when studying carbon isotope ratios in carbonate and organic matter. In this paper we report a comprehensive carbon isotopic characterization of total organic carbon (TOC) and individual higher plant leaf waxes from five loess sequences spanning the last 35 ka from the Chinese Loess Plateau (CLP). The five coring sites encompass large gradients of annual mean temperature (9.2–13.9 °C) and precipitation (402–673 mm), allowing us to assess the controlling mechanisms on C₄/C₃ plant ratios. Glacial–interglacial sequences provide carbon isotope data for comparison with other climatic and environmental proxies such as lithology and magnetic susceptibility. Our results demonstrate that increased C₄/C₃ ratios are positively correlated with higher temperature and increased summer rainfall which characterize stronger summer monsoon in all five sites. We conclude C₄ abundance increases from the last glacial to the Holocene in response to greater monsoon activity and that the C₄ expression is suppressed in the cold and drier intervals.