Diversity of arbuscular mycorrhizal fungi in the rhizosphere of three host plants in the farming–pastoral zone, north China

The spatial diversity and distribution of AM fungi were investigated in three plots located in farming–pastoral zone, north China. The rhizospheres of Caragana korshinskii, Artemisia sphaerocephala and Salix psammophila were sampled and thirty AM fungal species belonging to five genera were isolated. The study demonstrated that AM fungal diversity and distribution differed significantly among the three host plants and the three studied plots. Spore density of AM fungi ranged between 2 and 22 spores per g^?1 of soil and species richness between 8 and 23. Correlation coefficient analysis demonstrated that spore density was significantly and positively correlated with soil organic matter and available N (P?<?0.01). Species richness was significantly and positively correlated with soil organic matter and available P (P?<?0.01), but significantly and negatively correlated with soil pH (P?<?0.01). Finally, the Shannon–Weiner index was significantly and positively correlated with soil organic matter (P?<?0.05). In this farming–pastoral zone, Glomus reticulatum and G.melanosporum may be more adaptable to the arid conditions than other AM fungal species. This research into AM fungal diversity may lead to exploitation of AM fungi for the mitigation of soil erosion and desertification using mycorrhizal plants, such as C.korshinskii, A.sphaerocephala and S. psammophila. The results of this study support the conclusion that diversity and distribution of AM fungi might be useful to monitor desertification and soil degradation.     

Strong light inhibits germination of Artemisia sphaerocephala and A. ordosica at low temperature and its relevance to revegetation in sandy lands of Inner Mongolia, China

Artemisia sphaerocephala and A. ordosica are two dominant shrub species in Mu Us sandy land (Inner Mongolia, China) and are widely used for vegetation restoration. However, there are two different conclusions about the effect of light on their germination: light promotes germination versus light inhibits germination. The aim of this study was to evaluate these two conclusions and relate the results to instances of failure of these two species to germinate well when air-dispersed in revegetation projects. The effects of fluctuating temperature, light/dark, source (population), position on mother plant, storage condition, and storage time were tested on germination of achenes of these two species. At low temperature, final percent germination (FPG) of achenes in dark and nearly dark conditions was significantly higher than those in light. At 10:20°C, achenes of both A. sphaerocephala and A. ordosica had higher FPG in dark than in light regardless of source, position on mother plants or storage condition. At suboptimum (5:15°C) and supraoptimal (25:35°C) temperatures, germination of A. sphaerocephala and A. ordosica achenes was inhibited in both light and darkness. It was concluded that light inhibits germination of A. sphaerocephala and A. ordosica achenes at low (10:20°C) temperature but not at high (15:25°C) temperature. Since the temperature in Mu Us sandy land is around 10:20°C in early June, when air sowing is done, achenes should germinate best when they are covered by a thin layer of sand.     

4种植物水浸提液对乌丹蒿的化感作用研究

分布于科尔沁沙地西部的固沙先锋植物乌丹蒿近些年呈现出衰退趋势。本研究选取了该地区3种主要飞播植物白沙蒿、柠条、羊柴以及乌丹蒿自身进行了化感作用的研究,结果表明：3种飞播植物及乌丹蒿自身的水浸提液对乌丹蒿的生长均有不同程度的化感作用,并且不同部位（根、叶、果皮或总苞片）中存在的化感物质的作用不同。主要表现为：乌丹蒿种子的萌发率在各供体的根浸提液中均下降,除羊柴外均达到显著,白沙蒿总苞片和羊柴果皮浸提液也有着同样的结果,而乌丹蒿叶浸提液则有一定的促进作用;4种植物不同部位的水浸提液对乌丹蒿种子发芽速度及幼根的生长均有显著的抑制作用。从综合效应来看,4种植物对乌丹蒿均有抑制作用,抑制作用由强到弱的顺序为：白沙蒿>柠条>乌丹蒿>羊柴。     

沙蒿(Artemisia ordosica)水浸提液对4种伴生草本植物的化感作用

以生长在我国荒漠和半荒漠地区的特有植物沙蒿为供体植物,沙米、虫实、草木樨状黄芪、狗尾草为受体植物,研究了沙蒿根、茎、叶、种子水浸提液对受体植物种子发芽、幼苗生长以及根对NH~+_4和K~+吸收的化感效应的差异,为沙区植被恢复中伴生杂草种类的选择提供理论依据。结果表明:沙蒿水浸提液对4种受体植物种子发芽和幼苗生长均具有显著的化感效应,沙米、虫实、草木樨状黄芪表现为抑制作用,狗尾草表现为促进作用。不同部位沙蒿浸提液的化感作用不同,根浸提液对沙米、虫实、狗尾草的化感效应最强,茎浸提液对草木樨状黄芪的抑制最强。不同植物种及植物的不同发育时期对化感作用的敏感性也不同,在4种受体植物中,沙米受抑制最强,其次为虫实、草木樨状黄芪,且随浸提液浓度增加而显著增强,而狗尾草具有一定的耐受力,表现为促进作用。沙蒿浸提液对受体植物根长的影响最强,其次是种子发芽、苗高和幼苗干质量。浸提液显著降低沙米、虫实、草木樨状黄芪根对NH~+_4和K~+的吸收,增加狗尾草根对NH~+_4和K~+的吸收。研究结果表明雨水淋溶是沙蒿向环境中释放化感物质的途径之一,化感作用在增强沙蒿生存竞争力,扩大种群过程中起着不容忽视的作用,可能是沙蒿单优势种群落形成的原因之一。     

Leaf attributes and tree growth in a tropical dry forest

Questions: How are leaf attributes and relative growth rate (RGR) of the dominant tree species of tropical deciduous forest (TDF) affected by seasonal changes in soil moisture content (SMC)? What is the relationship of functional attributes with each other? Can leaf attributes singly or in combination predict the growth rate of tree species of TDF? Location: Sonebhadra district of Uttar Pradesh, India. Methods: Eight leaf attributes, specific leaf area (SLA); leaf carbon concentration (LCC); leaf nitrogen concentration (LNC); leaf phosphorus concentration (LPC); chlorophyll concentration (Chl), mass‐based stomatal conductance (Gs_mass); mass based photosynthetic rate (A_mass); intrinsic water use efficiency (WUEi); and relative growth rate (RGR), of six dominant tree species of a dry tropical forest on four sites were analysed for species, site and season effects over a 2‐year period. Step‐wise multiple regression was performed for predicting RGR from mean values of SMC and leaf attributes. Path analysis was used to determine which leaf attributes influence RGR directly and which indirectly. Results: Species differed significantly in terms of all leaf attributes and RGR. The response of species varied across sites and seasons. The attributes were positively interrelated, except for WUEi, which was negatively related to all other attributes. The positive correlation was strongest between Gs_mass and A_mass and the negative correlation was strongest between Gs_mass and WUEi. Differences in RGR due to site were not significant when soil moisture was controlled, but differences due to season remained significant. The attributes showed plasticity across moisture gradients, which differed among attributes and species. Gs_mass was the most plastic attribute. Among the six species, Terminalia tomentosa exhibited the greatest plasticity in six functional attributes. In the step‐wise multiple regression, A_mass, SLA and Chl among leaf attributes and SMC among environmental factors influenced the RGR of tree species. Path analysis indicated the importance of SLA, LNC, Chl and A_mass in determining RGR. Conclusion: A _mass, SMC, SLA and Chl in combination can be used to predict RGR but could explain only three‐quarters of the variability in RGR, indicating that other traits/factors, not studied here, are also important in modulating growth of tropical trees. RGR of tree species in the dry tropical environment is determined by soil moisture, whereas the response of mature trees of different species is modulated by alterations in key functional attributes such as SLA, LNC and Chl.     

The response of fast- and slow-growing Acacia species to elevated atmospheric CO2: an analysis of the underlying components of relative growth rate

In this study we assessed the impact of elevated CO₂ with unlimited water and complete nutrient on the growth and nitrogen economy of ten woody Acacia species that differ in relative growth rate (RGR). Specifically, we asked whether fast- and slow-growing species systematically differ in their response to elevated CO₂. Four slow-growing species from semi-arid environments (Acacia aneura, A. colei, A. coriacea and A. tetragonophylla) and six fast-growing species from mesic environments (Acacia dealbata, A. implexa, A. mearnsii, A. melanoxylon, A. irrorata and A. saligna) were grown in glasshouses with either ambient (˜350 ppm) or elevated (˜700 ppm) atmospheric CO₂. All species reached greater final plant mass with the exception of A. aneura, and RGR, averaged across all species, increased by 10% over a 12-week period when plants were exposed to elevated CO₂. The stimulation of RGR was evident throughout the 12-week growth period. Elevated CO₂ resulted in less foliage area per unit foliage dry mass, which was mainly the result of an increase in foliage thickness with a smaller contribution from greater dry matter content per unit fresh mass. The net assimilation rate (NAR, increase in plant mass per unit foliage area and time) of the plants grown at elevated CO₂ was higher in all species (on average 30% higher than plants in ambient CO₂) and was responsible for the increase in RGR. The higher NAR was associated with a substantial increase in foliar nitrogen productivity in all ten Acacia species. Plant nitrogen concentration was unaltered by growth at elevated CO₂ for the slow-growing Acacia species, but declined by 10% for faster-growing species. The rate of nitrogen uptake per unit root mass was higher in seven of the species when grown under elevated CO₂, and leaf area per unit root mass was reduced by elevated CO₂ in seven of the species. The absolute increase in RGR due to growth under elevated CO₂ was greater for fast- than for slow-growing Acacia species. Received: 21 December 1998 / Accepted: 31 May 1999     

Eight-legged swimmers: Behavioral responses to floods in two South American spiders

Arthropods inhabiting floodplains have to cope with regular cycles of wet and dry conditions. Allocosa senex and Allocosa marindia are two sympatric and synchronic sand-dwelling wolf spiders that construct burrows along South American coasts and are subject to periodic floods. Our objective was to study tolerance to immersion and describe the behavioral responses to that event in A. senex and A. marindia. We placed each spider in a terrarium with sand as substrate to allow burrow construction. Then, we gradually increased water levels and recorded the behavioral responses for 30 min. None of the individuals died during the artificial flood. More adults of A. senex performed “dives” and “floats” compared to A. marindia. Also, A. senex showed higher occurrences of “floats,” “swims,” and swam for longer than A. marindia. Finally, females of both species swam more frequently than males. Our findings indicate that both Allocosa are able to withstand floods, showing differential tactics according to the life histories of each sex and species.     

Plant species effect on the spatial patterns of soil properties in the Mu-us desert ecosystem,Inner Mongolia,China

Although Artemisia ordosica Krasch. and Sabina vulgaris Ant. are the dominant shrub species in the Mu-us desert ecosystem, they differ in their botanical traits. We investigated the spatial patterns of soil properties using geostatistical analysis to examine the effect of plant species on these spatial patterns. Comparison among three microsite types (under A. ordosica, under S. vulgaris, and the opening between vegetation) showed that A. ordosica generally had less effect than S. vulgaris on local soil properties. The long life-span, prostrate life-form, and evergreen leaf-habit of S. vulgaris may lead to a higher accumulation of organic and fine materials under S. vulgaris. The range of spatial autocorrelation found in the mass of organic matter on the soil surface was smaller than that of the coverage of S. vulgaris (11.5 m) which corresponded to the canopy patch size of this species, and was longer than the canopy patch size of A. ordosica. The ranges of total C and N, and pH (11.7–15.6 m) were similar to that of S. vulgaris. The range of available P (106.3 m) was comparable to that of the coverage of A. ordosica (86.2 m) considered to be the scale of the distribution of this species. The ranges of silt+clay and exchangeable K, Ca, and Mg (31.0–46.7 m) were not related to plant presence, and were similar to that of topography (43.1 m).     

What determines interspecific variation in relative growth rate of <Emphasis Type="Italic">Eucalyptus</Emphasis> seedlings?

The present study examines relative growth rate (RGR) and its determinants in seedlings of nine Eucalyptus species. Species were selected from mesic (1,800 mm a⁻¹ rainfall) through to semi-arid habitats (300 mm a⁻¹), and thus, notionally vary in “stress” tolerance. Seedlings were grown in a glasshouse during early summer and received between 33 mol and 41 mol PAR m⁻² day⁻¹ . The mean RGR varied among species—from a minimum of 66 mg g⁻¹ day⁻¹ in E. hypochlamydea to a maximum of 106 mg g⁻¹ day⁻¹ in E. delegatensis. RGR was positively related to rainfall at the sites of seed collection. Neither specific leaf area (SLA) nor net assimilation rate was related to rainfall or RGR. While the absence of relationships with SLA and net assimilation rate contrasts with other studies and species, we cannot rule out the effects of sample size (n=9 species) and modest ranges in SLA and RGR. The ratio of leaf mass to total mass (LMR) varied from 0.49±0.07 g g⁻¹ in E. socialis to 0.74±0.04 g g⁻¹ in E. delegatensis and was strongly positively related with rainfall (r ²=0.77). Interspecific differences in RGR were strongly related to LMR (positive relationship, r ²=0.50) and the rate of dry matter production per mol of leaf nitrogen (positive relationship, r ²=0.64). Hence, the slow RGR of low-rainfall species was functionally related to a lower growth rate per mol of leaf nitrogen than high-rainfall species. Furthermore, slow RGR of low-rainfall species was related to greater allocation to roots at the expense of leaves. Increasing allocation to roots versus leaves is likely an adaptation to soil and atmospheric water deficits, but one that comes at the expense of a slow RGR.     

Survival strategy of the endangered tree Acer catalpifolium Rehd., based on 13C fractionation

We conducted a field investigation and evaluation of ¹³C natural abundance to determine the growth habit and propagation strategy of Acer catalpifolium Rehd., a tree species native to China that is highly endangered. The results showed that A. catalpifolium is a K‐selected strategist and pioneer species. Its narrow ecological range limits its geographical distribution, and poor fecundity limits its population size. The analysis of ¹³C natural abundance showed that A. catalpifolium does not use organic matter for reproduction when its stand volume is less than 1.08 × 10⁶ cm³ or it is less than 18.6 m tall, but it does use this strategy when it has a sufficient 1.08 × 10⁶ cm³ stand volume or more or is taller than 18.6 m. If environmental conditions are not conducive (e.g., severe human disturbance, cliff edges, or fierce interspecific competition) to the continued growth of the tree, A. catalpifolium may allocate organic matter for reproduction. Human disturbance seems to promote the population expansion of A. catalpifolium. We provide our suggestions for the promotion and protection of A. catalpifolium as a species.     

Drought responses of three closely related Caragana species: implication for their vicarious distribution

Drought is a major environmental constraint affecting growth and distribution of plants in the desert region of the Inner Mongolia plateau. Caragana microphylla, C. liouana, and C. korshinskii are phylogenetically close but distribute vicariously in Mongolia plateau. To gain a better understanding of the ecological differentiation between these three species, we examined the leaf gas exchange, growth, water use efficiency, biomass accumulation and allocation by subjecting their seedlings to low and high drought treatments in a glasshouse. Increasing drought stress had a significant effect on many aspects of seedling performance in all species, but the physiology and growth varied with species in response to drought. C. korshinskii exhibited lower sensitivity of photosynthetic rate and growth, lower specific leaf area, higher biomass allocation to roots, higher levels of water use efficiency to drought compared with the other two species. Only minor interspecific differences in growth performances were observed between C. liouana and C. microphylla. These results indicated that faster seedling growth rate and more efficient water use of C. korshinskii should confer increased drought tolerance and facilitate its establishment in more severe drought regions relative to C. liouana and C. microphylla.     

Tree growth traits and social status affect the wood density of pioneer species in secondary subtropical forest

Wood density (WD) is not only an important parameter to estimate aboveground biomass but also an indicator of timber quality and plant adaptation strategies to stressful conditions (i.e., windthrow, pests, and pathogens). This study had three objectives: (1) to compare WD among seven subtropical tree species; (2) to determine how tree growth traits may influence possible differences in WD between the pioneer and shade‐tolerant species; and (3) to examine whether or not WD differs by tree social status (dominant vs. suppressed trees) within species. To do this, 70 trees were destructively harvested. From each tree, disks at different stem heights were obtained and subjected to a method of stem analysis to measure whole tree level WD. The results showed that WD differed significantly among the seven species (p < .001). Their average WD was 0.537 g/cm³, ranging from 0.409 g/cm³ for Choerospondias axillaris to 0.691 g/cm³ for Cyclobalanopsis glauca. The average WD of the four pioneer species (0.497 ± 0.13 g/cm³) was significantly lower (p < .01) than that of the three shade‐tolerant species (0.589 ± 0.12 g/cm³). The WD of the pioneers had a significant positive correlation with their stem diameter at breast height (DBH), tree height (H), and tree age, but WD had a significant negative correlation with relative growth rate (RGR). In contrast, the WD of the shade‐tolerant tree species had no significant relationships with DBH, H, tree age, or RGR. The dominant trees of the pioneer species had a higher WD than the suppressed trees, whereas the shade‐tolerant species had a lower WD for dominant trees than the suppressed trees. However, the differences in WD between dominant and suppressed trees were not significant. Taken together, the results suggest that classifying species into pioneer and shade‐tolerant groups to examine the effects of tree growth traits and social status could improve our understanding of intra‐ and interspecific variation in WD among subtropical tree species.     

Identification of species and materia medica within Angelica L. (Umbelliferae) based on phylogeny inferred from DNA barcodes

DNA barcodes have been increasingly used in authentication of medicinal plants, while their wide application in materia medica is limited in their accuracy due to incomplete sampling of species and absence of identification for materia medica. In this study, 95 leaf accessions of 23 species (including one variety) and materia medica of three Pharmacopoeia‐recorded species of Angelica in China were collected to evaluate the effectiveness of four DNA barcodes (rbcL, matK, trnH‐psbA and ITS). Our results showed that ITS provided the best discriminatory power by resolving 17 species as monophyletic lineages without shared alleles and exhibited the largest barcoding gap among the four single barcodes. The phylogenetic analysis of ITS showed that Levisticum officinale and Angelica sinensis were sister taxa, which indicates that L. officinale should be considered as a species of Angelica. The combination of ITS + rbcL + matK + trnH‐psbA performed slight better discriminatory power than ITS, recovering 23 species without shared alleles and 19 species as monophyletic clades in ML tree. Authentication of materia medica using ITS revealed that the decoction pieces of A. sinensis and A. biserrata were partially adulterated with those of L. officinale, and the temperature around 80 °C processing A. dahurica decoction pieces obviously reduced the efficiency of PCR and sequencing. The examination of two cultivated varieties of A. dahurica from different localities indicated that the four DNA barcodes are inefficient for discriminating geographical authenticity of conspecific materia medica. This study provides an empirical paradigm in identification of medicinal plants and their materia medica using DNA barcodes.     

Relative growth rate in relation to physiological and morphological traits for northern hardwood tree seedlings: species,light environment and ontogenetic considerations

The influence of ontogeny, light environment and species on relationships of relative growth rate (RGR) to physiological and morphological traits were examined for first-year northern hardwood tree seedlings. Three Betulaceae species (Betula papyrifera, Betula alleghaniensis and Ostrya virginiana) were grown in high and low light and Quercus rubra and Acer saccharum were grown only in high light. Plant traits were determined at four ages: 41, 62, 83 and 104 days after germination. In high light (610 mol m^–2 s^–1 PPFD), across species and ages, RGR was positively related to the proportion of the plant in leaves (leaf weight ratio, LWR; leaf area ratio, LAR), in situ rates of average canopy net photosynthesis (A) per unit mass (A_mass) and per unit area (A_area), and rates of leaf, stem and root respiration. In low light (127 mol m^–2 s^–1 PPFD), RGR was not correlated with A_mass and A_area whereas RGR was positively correlated with LAR, LWR, and rates of root and stem respiration. RGR was negatively correlated with leaf mass per area in both high and low light. Across light levels, relationships of CO₂ exchange and morphological characteristics with RGR were generally weaker than within light environments. Moreover, relationships were weaker for plant parameters containing a leaf area component (leaf mass per area, LAR and A_area), than those that were solely mass-based (respiration rates, LWR and A_mass). Across light environments, parameters incorporating the proportion of the plant in leaves and rates of photosynthesis explained a greater amount of variation in RGR (e.g. LWR^*A_mass, R²=0.64) than did any single parameter related to whole-plant carbon gain. RGR generally declined with age and mass, which were used as scalars of ontogeny. LWR (and LAR) also declined for seven of the eight species-light treatments and A declined in four of the five species in high light. Decreasing LWR and A with ontogeny may have been partially responsible for decreasing RGR. Declines in RGR were not due to increased respiration resulting from an increase in the proportion of solely respiring tissue (roots and stems). In general, although LWR declined with ontogeny, specific rates of leaf, stem, and root respiration also decreased. The net result was that whole-plant respiration rates per unit leaf mass decreased for all eight treatments. Identifying the major determinants of variation in growth (e.g. LWR^*A_mass) across light environments, species and ontogeny contributes to the establishment of a framework for exploring limits to productivity and the nature of ecological success as measured by growth. The generality of these relationships both across the sources of variation we explored here and across other sources of variation in RGR needs further study.     

Stemflow in two xerophytic shrubs and its significance to soil water and nutrient enrichment

Shrub canopies are expected to funnel substantial amounts of intercepted rainwater with enriched nutrients as stemflow to shrub base in the desert ecosystems characterized by limited water and nutrients. However, lacking are quantitative studies on the water and nutrient enrichment of stemflow at the shrub basal area. In this study, stemflow were quantified for two xerophytic shrubs (Caragana korshinskii and Artemisia ordosica) in a revegetated desert ecosystem of Shapotou area in northwestern China. We also measured the ion concentrations of total nitrogen (TN), total phosphors (TP), NH₄ ⁺–N, NO₃ ^?–N, Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl^?, SO₄ ^2? and the pH and electric conductivity (EC) in stemflow, throughfall and bulk precipitation. Results indicated that stemflow accounted for 8.8 and 2.8 % of the gross rainfall for C. korshinskii and A. ordosica, respectively. Individual stemflow linearly increased with increasing rainfall depth. Stemflow increased with rainfall intensity when rainfall intensity was less than 2 mm h^?1 but showed decreased tendency thereafter. An antecedent precipitation of 1.3 and 1.6 mm was necessary for stemflow initiation for C. korshinskii and A. ordosica, respectively. The mean (confidence intervals, α = 0.05) funneling ratio was 82 (17) for C. korshinskii and 26 (7) for A. ordosica. Ion concentrations in stemflow were higher than in throughfall, and the concentration of most of the ions measured were significantly higher (p < 0.05) in stemflow than in bulk precipitation, with a nutrient enrichment ratio ranged 122.8–1677.0 for C. korshinskii and 12.6–1306.0 for A. ordosica among measured ions, respectively. Overall, the larger funneling ratios and enrichment ratios for the two shrubs suggest that stemflow plays a significant positive role in soil water replenishment and nutrient enrichment at deeper soil profile of root zone in the revegetated ecosystems under arid desert conditions.     

Plant Interactions with Changes in Coverage of Biological Soil Crusts and Water Regime in Mu Us Sandland,China

Plant interactions greatly affect plant community structure. Dryland ecosystems are characterized by low amounts of unpredictable precipitation as well as by often having biological soil crusts (BSCs) on the soil surface. In dryland plant communities, plants interact mostly as they compete for water resources, and the direction and intensity of plant interaction varies as a function of the temporal fluctuation in water availability. Since BSCs influence water redistribution to some extent, a greenhouse experiment was conducted to test the hypothesis that the intensity and direction of plant interactions in a dryland plant community can be modified by BSCs. In the experiment, 14 combinations of four plant species (Artemisia ordosica, Artemisia sphaerocephala, Chloris virgata and Setaria viridis) were subjected to three levels of coverage of BSCs and three levels of water supply. The results show that: 1) BSCs affected plant interaction intensity for the four plant species: a 100% coverage of BSCs significantly reduced the intensity of competition between neighboring plants, while it was highest with a 50% coverage of BSCs in combination with the target species of A. sphaerocephala and C. virgata; 2) effects of the coverage of BSCs on plant interactions were modified by water regime when the target species were C. virgata and S. viridis; 3) plant interactions were species-specific. In conclusion, the percent coverage of BSCs affected plant interactions, and the effects were species-specific and could be modified by water regimes. Further studies should focus on effects of the coverage of BSCs on plant-soil hydrological processes.     

Variation in Polyphenolic Profiles,Antioxidant and Antimicrobial Activity of Different Achillea Species as Natural Sources of Antiglycative Compounds

A comparative study was carried out on the methanolic extracts from six Achillea species and the examined polyphenols from these plants on the formation of advanced glycation end‐products (AGE) in vitro. A. pachycephala which was richer in flavonoids (15 mg quercetin/g W) and phenolics (111.10 mg tannic acid/g DW) with substantial antioxidant activity (IC₅₀ = 365.5 μg/ml) presented strong anti‐AGE properties. Chlorogenic acid, luteolin, quercetin and caffeic acid were identified as the major polyphenols in the extracts by HPLC. In general, polyphenolic content follows the order of A. pachycephalla > A. nobilis > A. filipendulina > A. santolina > A. aucheri > A. millefolium. Most extracts exhibited marked anti‐AGE ability in the bovine serum albumin (BSA)/methylglyoxal (MG) system, though A. pachycephala showed the highest potential. The formation of AGEs was assessed by monitoring the production of fluorescent products and circular dichroism (CD) spectroscopy. Diminution in free radical production (assessed by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assays) is discussed as potential mechanism for delay or reduced AGE. The results demonstrate the antiglycative, antioxidant and antimicrobial potential of Achillea species which can be attributed to polyphenols content and the effectiveness on generation of AGEs, thus Achillea species can be considered as natural sources for slowing down glycation related diseases.     

An Analysis of the Effects of Temperature and Light Integral on the Vegetative Growth of Pansy cv. Universal Violet (Violaxwittrockiana Gams.)

Pansies (Viola xwittrockiana Gams.) cv. Universal Violet weresown on five dates between Jul. and Dec. 1992 and placed insix temperature-controlled glasshouse compartments set to providemean temperatures between 6.5 and 30 °C. Shoot dry weightand leaf number were recorded. A model was constructed, to analysethe effects of light and temperature on dry matter accumulation,which assumed that relative growth rate (RGR) declined linearlywith thermal time accumulated from sowing, reflecting ontogeneticdrift. Furthermore, it assumed that RGR was a semi-ellipsoidfunction of temperature, rising to an optimum of 25.3 °Cand declining thereafter, and a positive linear function oflight integral. When fitted to data collected in this studythe model accounted for 94% of the variance in RGR. Independentvalidation using data from four further crops grown in glasshousecompartments at four different set point temperatures showedthat the model could also be used to predict plant dry weightaccurately (r ²=0.98). The rate of mainstem leaf productionwas also linearly related to both light integral and temperature. Pansy; Viola xwittrockiana ; temperature; light integral; dry weight; relative growth rate; leaf number     

Negative effects of hydroxyl radical-generating mists (simulated dew water) on the photosynthesis and growth of Japanese apricot seedlings (Prunus mume)

The hydroxyl (OH) radical, which is generated in polluted dew water on leaf surfaces of the Japanese apricot (Prunus mume), is known to be a potent oxidant. In order to investigate the effects of the OH radical formed in polluted dew water on the photosynthesis and growth of 3-year-old seedlings of P. mume, OH radical-generating solutions simulating polluted dew water were sprayed in the early morning as a mist throughout a growing season onto the leaf surfaces of seedlings growing in experimental greenhouses. Four OH radical-generating solutions (0, 6, 18 and 54 M H₂O₂ with Fe(III) and an oxalate ion) were used in the mist treatment. Five months after the beginning of treatment, the leaves exposed to the mist containing 54 M H₂O₂ showed a significantly smaller maximum CO₂ assimilation rate (A_max) and stomatal conductance (g_s) as compared to the leaves exposed to the mist containing 0 M H₂O₂. Exposure of P. mume seedlings to the OH radical-generating mist had caused a reduction in the dry weight and relative growth rate (RGR) of the above-ground parts (stem + branch) at the end of the growing season. A significant positive correlation was shown between RGR and A_max. Thus, the effects of oxidants generated in polluted dew water on leaf surfaces can be considered to be a cause of the decrease in leaf photosynthesis and growth of P. mume.     

Plant distribution can be reflected by the different growth and morphological responses to water level and shade in two emergent macrophyte seedlings in the Sanjiang Plain

In the Sanjiang Plain (North East China), narrowleaf small reed (Deyeuxia angustifolia) usually distributes widely in typical meadow or marsh, while reed (Phragmites australis), the concomitant species, is distributed sparsely in the D. angustifolia communities or relative open sites. To date, the mechanisms responsible for their different distribution patterns are far from clear. Both water level and light are important factors determining plant distribution in wetland ecosystems and therefore, the aim of this paper was to identify the role of these two factors and their potential interaction on plant distribution in this plain. Growth responses and biomass allocation of the two macrophytes were investigated by growing them in three irradiances (300, 100, 20 μmol m⁻² s⁻¹) and two water levels (0 and 5 cm) under greenhouse conditions. Biomass accumulation, mean relative growth rate (RGR), height and mean relative elongation rate (RER) of both species significantly decreased with the reduction of light availability. Biomass accumulation, RGR, height and RER of P. australis were significantly inhibited by higher water level. However, water level had no effect on the growth of D. angustifolia. Stem mass fraction was higher at 0-cm water level in D. angustifolia, and was not affected by water level in P. australis. These data suggest that D. angustifolia has a higher adaptive ability to acclimate to flooding and shade stresses than does P. australis, which might be an important reason for their different distribution patterns.