Relationship Between Gene Differential Expression of Leaves in Full Opening Flower Stages of Hybrids & Their Parents and Heterosis in Pest-resistant Cotton

cDNAs of leaves of 24 pest-resistant cotton (authorization) crosses and their parents in full opening flower stages were amplified and different bands were displayed by DDRT-PCR, with 45 primer combinations. The mean percentage of bands duplicated was 70.1%, which implied that there was a high proportion of pseudopositive fragments in the amplified cDNA. These pseudopositive bands can be reduced using duplicate PCR. Correlation analysis between differential gene expression and hybrid performance and heterosis showed that M4 (bands detected in one parent and F₁) was positively correlated with all yield traits, and significantly correlated with boll number; M2 (bands observed in one parent but not in F₁ and another parent) was negatively correlated with heterosis of boll number; and M3 (bands observed only in F₁) was positively correlated with heterosis of lint yield. These results showed that genes that had dominant and specific expression in top leaves of full opening flower stages were beneficial to yield formation and heterosis occurrence.     

Comparison of foliar water use efficiency among 17 provenances of Larix gmelinii in the Mao’ershan area

 研究环境变化下的树木水分利用效率对探讨森林生态系统碳水耦联关系及其对气候变化的响应和适应对策具有重要意义。落叶松(Larix gmelinii)为我国北方森林的建群种之一。将水热条件不同的17个种源落叶松种植在帽儿山森林生态系统研究站的同质园内30年后, 测定其针叶水分利用效率(WUE)及其相关因子。结果表明: WUE、净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)、比叶面积(SLA)和叶片氮含量(N_L)均存在显著的种源差异(p < 0.05)。WUE和G_s呈显著指数相关关系, 当G_s < 0.2 时WUE随G_s的增大而明显增大, 而当G_s > 0.2时WUE趋于稳定。WUE和SLA及N_L分别呈线性负相关和正相关关系, 且随种源原地的干燥度指数(AI)的增大其相关性明显增强。WUE和种源原地年平均气温、平均年降水量及AI分别呈线性负相关、负相关和正相关关系, 并且相关系数依次增大; T_r则仅和种源原地年平均气温呈线性正相关关系, 而P_n和种源原地AI呈线性正相关关系。不同种源落叶松由于对种源原地环境条件的适应而存在针叶结构和生理特征的显著差异, 并因此引起针叶水分利用效率的差异。     

Boar sperm plasma membrane protein profile: Correlation with the zona-free hamster ova bioassay

This study was designed to compare differences among porcine sperm plasma membrane proteins with the ability of spermatozoa to interact with zona-free hamster ova. Sperm plasma membrane vesicles were recovered from 24 ejaculates from 10 fertile boars, and from cauda epididymal spermatozoa from 3 fertile and 1 very subfertile boar. Solubilized sperm plasma membrane proteins were run on 1D SDS-PAGE gels, transferred to western blots, stained, and analyzed for quantity of protein per band by scanning laser densitometry. Variation in the quantities of individual sperm plasma membrane proteins in the 20 identified bands were statistically compared with the ability of spermatozoa from the same ejaculate to penetrate zona-free hamster ova. The percentages of plasma membrane protein present in 3 bands (90, 84 and 60 kD) were positively correlated with the ability of spermatozoa from the same ejaculate to fuse with zona-free hamster ova (P = 0.002, 0.01, 0.04; R = 0.53, 0.40, 0.38, respectively). The quantities of protein in 2 other bands (69 and 35 kD) were significantly but negatively correlated with the results of the zona-free hamster ova bioassay (P = 0.02, 0.01; R = -0.42, -0.37, respectively). The sperm plasma membrane profiles were quantitatively similar between the ejaculated samples and the fertile epididymal samples. Six epididymal sperm plasma membrane proteins were present in statistically different quantities in the subfertile boar sample and the 3 fertile controls. The 90 kD band positively correlated with the hamster ova bioassay in the ejaculated samples was not detected in the subfertile epididymal sperm plasma membrane sample. These results suggest that protein(s) in one or more of the 3 positively correlated ejaculated sperm plasma membrane protein bands may be involved in sperm-oocyte interaction.     

基于遥感数据的植被碳水利用效率时空变化和归因分析

植被碳水利用效率是表征生态系统碳水循环的重要指标。采用MODIS数据,利用Google Earth Engine平台计算植被碳利用效率(Carbon Use Efficiency, CUE)与水利用效率(Water Use Efficiency, WUE)。采用趋势分析、变异系数、R/S分析及偏相关分析等方法,对2000—2020年黄河流域植被CUE与WUE的时空动态进行分析,并探究水热条件对碳水利用效率的影响。结果表明：(1)2000—2020年黄河流域植被碳水利用效率年均值分别为0.61和0.68 gC m^-2 mm^-1;研究时限内,植被CUE呈波动下降趋势,而WUE呈波动上升趋势。(2)空间上,植被CUE呈西高东低分布,WUE相反。不同土地覆被类型的CUE表现为草地>农田>灌丛>森林;WUE表现为：农田>森林>草地>灌丛。(3)总体上,黄河流域植被CUE与温度呈负相关,与降水呈正相关;黄河流域北部植被WUE与温度和降水均呈正相关关系,黄河流域西南部植被WUE与降水负相关;(4)不同土地利用类型中,草地...     

Variation among and within clones in formation of roots and shoots during micropropagation of Campanula isophylla

It is known that treatments enhancing shoot formation often suppress root formation and vice versa. It would be of interest to know if such negative correlations between formation of roots and shoots were also present among genetically different plants, given the same treatment, to ensure that selection for superior shoot formation would not lead to inadvertent decreases in the capacity for root formation. Height and dry weight of micropropagated shoot clusters and the numbers of shoots and roots were measured in 95 seedling clones. Within clones, shoot size was negatively correlated with number of shoots and positively correlated with number of roots. Among clones, however, the number of shoots was not correlated with the size of shoots, but positively correlated with the number of roots. While it is difficult to devise treatments that simultaneously optimize the initiation of roots and shoots, it is thus possible to select for fast-growing clones without compromising root formation.Abbreviations CM clonal means - DCM deviation from clonal means     

Relationship between rumen methanogens and methane production in dairy cows fed diets supplemented with a feed enzyme additive

Aims: To investigate the relationship between ruminal methanogen community and host enteric methane (CH₄) production in lactating dairy cows fed diets supplemented with an exogenous fibrolytic enzyme additive. Methods and Results: Ecology of ruminal methanogens from dairy cows fed with or without exogenous fibrolytic enzymes was examined using PCR–denaturing gradient gel electrophoresis (PCR–DGGE) analyses and quantitative real‐time PCR (qRT‐PCR). The density of methanogens was not affected by the enzyme additive or sampling times, and no relationship was observed between the total methanogen population and CH₄ yield (as g per head per day or g kg^?1 DMI). The PCR–DGGE profiles consisted of 26 distinctive bands, with two bands similar to Methanogenic archaeon CH1270 negatively correlated, and one band similar to Methanobrevibacter gottschalkii strain HO positively correlated, with CH₄ yield. Three bands similar to Methanogenic archaeon CH1270 or Methanobrevibacter smithii ATCC 35061 appeared after enzyme was added. Conclusions: Supplementing a dairy cow diet with an exogenous fibrolytic enzyme additive increased CH₄ yield and altered the composition of the rumen methanogen community, but not the overall density of methanogens. Significance and Impact of the Study: This is the first study to identify the correlation between methanogen ecology and host CH₄ yield from lactating dairy cows.     

Relationships of differential gene expression in leaves with heterosis and heterozygosity in a rice diallel cross

Using differential display analysis, we assessed the patterns of differential gene expression in hybrids relative to their parents in a diallel cross involving 8 elite rice lines. The analysis revealed several patterns of differential expression including: (1) bands present in one parent and F₁ but absent in the other parent, (2) bands observed in both parents but not in the F₁, (3) bands occurring in only one parent but not in the F₁ or the other parent, and, (4) bands detected only in the F₁ but in neither of the parents. Relationships between differential gene expression and heterosis and marker heterozygosity were evaluated using data for RFLPs, SSRs and a number of agronomic characters. The analysis showed that there was very little correlation between patterns of differential expression and the F₁ means for all six agronomic traits. Differentially expressed fragments that occurred only in one parent but not in the other parent or in F₁ in each of the respective crosses were positively correlated with heterosis and heterozygosity. And conversely, fragments that were detected in F₁s but in neither of the respective parents were negatively correlated with heterosis and heterozygosity. The remaining patterns of differential expression were not correlated with heterosis or heterozygosity. The relationships between the patterns of differential expression and heterosis observed in this study were not consistent with expectations based on dominance or overdominance hypotheses.     

盛花期抗虫杂交棉及其亲本叶片基因表达差异与杂种优势

采用DDRT-PCR技术,以棉花盛花期项尖叶片cDNA为材料,对上海生物工程公司合成的专用于基因差异显示分析的3个锚定引物和全套26个随机引物进行筛选,最后选择了15个扩增差异带丰富的随机引物。采用3个锚定引物和这15个随机引物组成的45对引物组合对24个抗虫棉杂交组合及其10亲本盛花期叶片cDNA进行扩增和差显,2次扩增重复率达70．1％,表明在扩增过程中存在较高的假阳性,通过重复PCR扩增,统计稳定扩增的条带,可减少假阳性干扰。根据基因表达方式,将其划分5种模式：MI为双亲表达沉默,双亲出现条带而杂种没有条带;M2为单亲表达沉默,带仅出现在亲本之一,包括仅母本有带而父本和杂种无带和仅父本有带而母本和杂种无带2种表达方式：M3为杂种特异表达,带仅出现在杂种,双亲无带;M4为单亲表达一致,带在双亲之一和杂种中出现,而在另一亲本中不出现,包括母本、杂种中有带而父本无带和父本、杂种中有带而母本无带2种方式;M5为基因表达一致,带在双亲和杂种中均出现。差显表达模式比例与产量性状和杂种优势分析表明：M4与所有产量性状均呈正相关,并且与单位面积铃数相关达显著水平,其他各种模式与杂种产量性状表型值均未达到显著水平;M2与单位面积铃数杂种优势呈显著负相关,M3与皮棉产量杂种优势呈显著正相关。上述结果表明,盛花期叶片中的基因显性表达和杂种特异表达有利于产量形成和杂种优势发挥。     

Dynamic G- and R-banding of human chromosomes for electron microscopy

Synchronized human lymphocytes were exposed to 5-bromo-2-deoxyuridine (BrdUrd) for incorporation in either G-or R-bands. The substituted bands were revealed by monoclonal anti-BrdUrd antibodies disclosed with either gold-labeled antibodies or with the protein A-gold complex. Sharp G-or R-banding, specific for electron microscopy (EM), was obtained. These banding patterns, referred to as GB-AAu (G-bands by BrdUrd using Antibodies and gold [Au]) and RB-AAu (R-bands by BrdUrd using Antibodies and gold [Au]), resemble dynamic band patterns (GBG and RBG) much more than they do morphologic band patterns (GTG and RHG). The G- and R- band patterns allow accurate chromosome identification and karyotyping. An actual karyotype of human GB-AAu-banded chromosomes at the 750 band level, photographed in the EM, is presented. The method produces excellent band separation and band contrast. Variations in band staining intensities were noted and correlated with BrdUrd enrichment. The C-band regions were positively stained after GB-AAu banding while they were negatively stained after RB-AAu banding. Telomeres appeared heterogeneous after GB-AAu banding suggesting that part of the telomeric bands might be late replicating.     

Usefulness of thermoluminescence in herbicide research

Many herbicides of different chemical structure inhibit photosynthetic electron flow by interrupting the photosyn‐thetic electron flow by interrupting the photosynthetic electron transport chain between the primary acceptor (Q_A) and the secondary acceptor (Q_B) of photosystem 2 (PS2). Thermoluminescence (TL) originates from PS2, and the bands of the glow curve can be related to the charge recombination between positively charged donors and negatively charged acceptors. The glow curve of TL is strongly influenced by addition of PS2 herbicides. The herbicide treatment shifts the peak position and activation energy of the TL band related to Q_A, suggesting that herbicide binding affects the midpoint redox potential not only of Q _B but also that of Q_A. On the basis of the band shift the herbicides of various chemical structures can be classified into different “thermodynamical” groups which relfect the differences in the binding properties of these herbicides. As a new approach TL seems to be a useful technique in studying the mechanism and site of action of herbicides that inhibit electron transport of PS2.     

Genotypic and within canopy variation in leaf carbon isotope discrimination and its relation to short-term leaf gas exchange characteristics in cassava grown under rain-fed conditions in the tropics

In a field rain-fed trial with 15 cassava cultivars, leaf gas exchanges and carbon isotope discrimination (Δ) of the same leaves were determined to evaluate genotypic and within-canopy variations in these parameters. From 3 to 7 months after planting leaf gas exchange was measured on attached leaves from upper, middle, and lower canopy layers. All gas exchange parameters varied significantly among cultivars as well as canopy layers. Net photosynthetic rate (P _N) decreased from top canopy to bottom indicating both shade and leaf age effects. The same trend, but in reverse, was found with respect to Δ, with the highest values in low canopy level and the lowest in upper canopy. There were very significant correlations, with moderate and low values, among almost all these parameters, with P _N negatively associated with intercellular CO₂ concentration (C _i), ratio of C _i to ambient CO₂ concentration C _i/C _a, and Δ. Across all measured leaves, Δ correlated negatively with leaf water use efficiency (WUE = photosynthesis/stomatal conductance, g _s) and with g _s, but positively with C _i and C _i/C _a. The later parameters negatively correlated with leaf WUE. Across cultivars, both P _N and correlated positively with storage root yield. These results are in agreement with trends predicted by the carbon isotope discrimination model.     

Correlations among leaf CO2-exchange rates,areas and enzyme activities among soybean cultivars

Soybean (Glycine max (L.) Merr.) genotypes varying in area per nodal unit (usually a trifoliolate) and maturity class were grown in plots at the University of Illinois experimental farm. Leaf CO₂-exchange rates per unit area (CER) were measured under sunlight on intact plants. In addition to previously reported correlations with specific leaf weight and chlorophyll, CER was positively correlated with ribulose bisphosphate carboxylase (RuBPcase) activity, specific activity, and soluble protein, and was negatively correlated with area per leaf unit. The CER: chlorophyll correlation was destroyed by high CER values in 2 chlorophyll-deficient lines. CER values for 27 of the 35 lines tested fell within the range of those for isolines of cultivar Clark varying in leaf characteristics. The CER values were highest for fully expanded leaves during rapid pod fill. These results suggested that photoperiod (maturity) genes and genes for leaf area growth interact with genes controlling photosynthetic CO₂-exchange to produce the major differences in CER values among soybean genotypes.     

Density‐dependence in common tree species in a tropical dry forest in Mudumalai,southern India

Abstract. Density‐dependence in tree population dynamics has seldom been examined in dry tropical forests. Using long‐term data from a large permanent plot, this study examined 16 common species in a dry tropical forest in southern India for density‐dependence. Employing quadrat‐based analyses, correlations of mortality, recruitment and population change with tree densities were examined. Mortality in 1–10 cm diameter trees was largely negatively correlated with conspecific density, whereas mortality in > 10 cm diameter trees was positively correlated. Mortality was, however, largely unaffected by the basal area and abundance of heterospecific trees. Recruitment was poor in most species, but in Lagerstroemia microcarpa (Lythraceae), Tectona grandis (Verbenaceae) and Cassia fistula (Fabaceae), species that recruited well, strong negative correlations of recruitment with conspecific basal area and abundance were found. In a few other species that could be tested, recruitment was again negatively correlated with conspecific density. In Lagerstroemia, recruitment was positively correlated with the basal area and abundance of heterospecific trees, but these correlations were non‐significant in other species. Similarly, although the rates of population change were negatively correlated with conspecific density they were positive when dry‐season ground fires occurred in the plot. Thus, the observed positive density‐dependence in large‐tree mortality and the negative density‐dependence in recruitment in many species were such that could potentially regulate tree populations. However, repeated fires influenced density‐dependence in the rates of population change in a way that could promote a few common species in the tree community.     

The role of the cerebellum in modulating voluntary limb movement commands

We recorded the activity of cerebellar Purkinje cells (PCs), primary motor cortical (M1) neurons, and limb EMG signals while monkeys executed a sequential reaching and button pressing task. PC simple spike discharge generally correlated well with the activity of one or more forelimb muscles. Surprisingly, given the inhibitory projection of PCs, only about one quarter of the correlations were negative. The largest group of neurons burst during movement and were positively correlated with EMG signals, while another significant group burst and were negatively correlated. Among the PCs that paused during movement most were negatively correlated with EMG. The strength of these various correlations was somewhat weaker, on average, than equivalent correlations between M1 neurons and EMG signals. On the other hand, there were no significant differences in the timing of the onset of movement related discharge among these groups of PCs, or between the PCs and M1 neurons. PC discharge was modulated largely in phase, or directly out of phase, with muscle activity. The nearly synchronous activation of PCs and muscles yielded positive correlations, despite the fact that the synaptic effect of the PC discharge is inhibitory. The apparent function of this inhibition is to restrain activity in the limb premotor network, shaping it into a spatiotemporal pattern that is appropriate for controlling the many muscles that participate in this task. The observed timing suggests that the cerebellar cortex learns to modulate PC discharge predictively. Through the cerebellar nucleus, this PC signal is combined with an underlying cerebral cortical signal. In this manner the cerebellum refines the descending command as compared with the relatively crude version generated when the cerebellum is damaged.     

三江源地区高寒草甸土壤氨氧化细菌多样性研究

目的：利用16SrDNA-PCR—DGGE方法首次对青藏高原核心区三江源自然保护区的高寒草甸样地的土壤氨氧化细菌进行了多样性研究。方法：从土壤中抽提微生物总DNA,运用巢式PCR扩增氨氧化细菌16SrRNA基因的V3可变区,结合DGGE（denaturing gradient gel electrophoresis）技术分析样品氨氧化细菌群落组成,并利用相关性分析探讨了群落结构多样性与环境因子的联系。结果：4个样地（玉树S1;囊谦S2;治多S3和S4）共检测到14个多态性条带,多样性指数为1．69～2．00。相关性分析显示多样性指数与海拔、C／N呈负相关,与NO3-呈显著正相关。结论：海拔、C／N及NO3-可能是影响土壤氨氧化细菌多样性的重要因子。     

Genetic correlations between vegetative growth traits and productivity at different within-season intervals for strawberries (Fragaria X ananassa)

Summary Genetic and environmental relationships between vegetative growth and production traits at different intervals within a single season were investigated using unselected strawberry genotypes from 20 biparental crosses and their parents. Vegetative growth and productivity patterns differed between test locations and larger yields were detected where fall growth was greatest. Positive genetic correlations were detected between fall growth increments and mid-season production traits, but fall growth was uncorrelated or negatively correlated with late-season production. Conversely, growth during the production season was genetically uncorrelated or negatively correlated to early production traits, but was positively correlated to mid and late-season production. Together, these results suggest that the growth pattern required for early vs sustained production may represent conflicting breeding objectives. Also, although vegetative and reproductive functions compete for assimilates in strawberry, sustained productivity appears dependent on adequate vegetative growth throughout the spring and early summer. Significant correlations were detected between fall plant growth and early yield, but these were attributed to environmental rather than genetic sources. Genetic correlations between spring growth and early production traits were significantly negative and large, suggesting that vegetative during this interval may indicate limited fall inflorescence development.     

Frequency-Dependent Modulation of Regional Synchrony in the Human Brain by Eyes Open and Eyes Closed Resting-States

The eyes-open (EO) and eyes-closed (EC) states have differential effects on BOLD-fMRI signal dynamics, affecting both the BOLD oscillation frequency of a single voxel and the regional homogeneity (ReHo) of several neighboring voxels. To explore how the two resting-states modulate the local synchrony through different frequency bands, we decomposed the time series of each voxel into several components that fell into distinct frequency bands. The ReHo in each of the bands was calculated and compared between the EO and EC conditions. The cross-voxel correlations between the mean frequency and the overall ReHo of each voxel’s original BOLD series in different brain areas were also calculated and compared between the two states. Compared with the EC state, ReHo decreased with EO in a wide frequency band of 0.01–0.25 Hz in the bilateral thalamus, sensorimotor network, and superior temporal gyrus, while ReHo increased significantly in the band of 0–0.01 Hz in the primary visual cortex, and in a higher frequency band of 0.02–0.1 Hz in the higher order visual areas. The cross-voxel correlations between the frequency and overall ReHo were negative in all the brain areas but varied from region to region. These correlations were stronger with EO in the visual network and the default mode network. Our results suggested that different frequency bands of ReHo showed different sensitivity to the modulation of EO-EC states. The better spatial consistency between the frequency and overall ReHo maps indicated that the brain might adopt a stricter frequency-dependent configuration with EO than with EC.     

Selective and independent associations of phospholipid transfer protein and hepatic lipase with the LDL subfraction distribution

Phospholipid transfer protein (PLTP), hepatic lipase (HL), and lipoprotein lipase (LPL) have all been reported to be intricately involved in HDL metabolism but the effect of PLTP on the apolipoprotein B-containing lipoproteins relative to that of HL and LPL has not been established. Due to our previous observation of a positive correlation of PLTP activity with plasma apoB and LDL cholesterol, the relationship of PLTP with the LDL subfractions was investigated and compared with that of HL and LPL. Plasma lipoproteins from 50 premenopausal women were fractionated by density gradient ultracentrifugation. Correlations were calculated between the cholesterol concentration of each fraction and plasma PLTP, HL, and LPL activity. Plasma PLTP activity was highly, positively, and selectively correlated with the cholesterol concentration of the buoyant LDL/dense IDL fractions, yet demonstrated a complete absence of an association with the dense LDL fractions. In contrast, HL was positively correlated with the dense LDL fractions but showed no association with buoyant LDL. LPL was also positively correlated with several buoyant LDL fractions; however, the correlations were weaker than those of PLTP. PLTP and LPL were positively correlated and HL was negatively correlated with HDL fractions. The results suggest that PLTP and HL may be important and independent determinants of the LDL subpopulation density distributions.     

Flight morphology of Neotropical butterflies: palatability and distribution of mass to the thorax and abdomen

Summary We test whether palatability of Neotropical butterflies is associated with distribution of mass to the thorax and abdomen. Thoracic mass is predominantly muscle mass, whereas abdominal mass includes organs of digestion, food storage, and reproduction. To escape from predation, butterflies palatable to the rufous-tailed jacamar (Galbula ruficauda) use fast, erratic flight, whereas unpalatable butterflies have defensive chemicals and slow, regular flight patterns. We adjusted for effects of phylogeny and report partial correlations for two levels of analysis: 1) comparisons among-lineage means, which test for correlations between traits of distantly related lineages, and 2) comparisons among deviations from lineage means (or within lineages), which test for correlations between traits of more closely related species.Among lineages for both males (n=10 lineages) and females (n=9), palatability and thoracic mass were positively correlated, whereas palatability and abdominal mass were negatively correlated. An inverse correlation between thoracic and abdominal mass is a consequence of the two segments composing 75% of the total body mass. Predation, indexed by palatability, may select for increased flight speed and thoracic mass at the expense of the abdomen, but relative flight speed and thoracic mass were not significantly correlated.Within lineages (n=45 species for each sex), thoracic mass was uncorrelated with palatability in both sexes. Relative flight speed correlated positively with thoracic mass and negatively with body mass. Palatability and abdominal mass were negatively correlated for males but not females. Hence differences between the sexes in mass distribution suggest differences in reproductive constraints and predation stress.     

Spatial patterns of photosynthetic characteristics and leaf physical traits of plants in the Loess Plateau of China

The spatial patterns of photosynthetic characteristics and leaf physical traits of 171 plants belonging to nine life-forms or functional groups (trees, shrubs, herbs, evergreen trees, deciduous trees, C₃ and C₄ herbaceous plants, leguminous and non-leguminous species) and their relationships with environmental factors in seven sites, Yangling, Yongshou, Tongchuan, Fuxian, Ansai, Mizhi and Shenmu, ranging from south to north in the Loess Plateau of China were studied. The results showed that the leaf light-saturated photosynthetic rate (P_max), photosynthetic nitrogen use efficiency (PNUE), chlorophyll content (Chl), and leaf mass per area (LMA) of all the plants in the Loess Plateau varied significantly among three life-form groups, i.e., trees, shrubs and herbs, and two groups, i.e., evergreen trees and deciduous trees, but leaf nitrogen content differed little among different life-form groups. For the 171 plants in the Loess Plateau, leaf P_max was positively correlated with PNUE. The leaf nitrogen content per unit area (N_area) was positively correlated but Chl was negatively correlated with the LMA. When controlling the LMA, the N_area was positively correlated with the Chl (partial r = 0.20, P < 0.05). With regard to relationships between photosynthetic characteristics and leaf physical traits, the P_max was positively correlated with N _area, while the PNUE was positively correlated with the Chl and negatively correlated with the N_area and LMA. For all the species in the Loess Plateau, the PNUE was negatively correlated with the latitude and annual solar radiation (ASR), but positively correlated with the mean annual rainfall (MAR) and mean annual temperature (MAT). With regard to the leaf physical traits, the leaf Chl was negatively correlated with the latitude and ASR, but positively correlated with the MAR and MAT. However, the N_area and LMA were positively correlated with the latitude and ASR, but negatively correlated with the MAR and MAT. In general, leaf N_area and LMA increased, while PNUE and Chl decreased with increases in the latitude and ASR and decreases in MAR and MAT. Electronic supplementary material The online version of this article () contains supplementary material, which is available to authorized users.