Flavonoids of Abies amabilis needles

Seventeen flavonol glycosides were identified from needles of Abies amabilis and these were based on 6 aglycone types: syringetin, isorhamnetin, kaempferol, quercetin, laricytrin and myricetin. Glycosides were 3-O-rutinosides, 3-O-glucosides, 3-O-galactosides or 3-O-rhamnosides. Also identified as needle constituents were rhamnosylvitexin and dihydroquercetin.     

The Effect of Reduced Hydraulic Conductance on Stomatal Conductance and Xylem Cavitation

The vulnerability of xylem conduits to cavitation theoreticallydetermines the maximum flow rate of water through plants, andhence maximum transpiration (E), stomatal conductance (g_s),and leaf area (A₁. Field-grown Betula occidentalis with a favourablewater supply exhibit midday xylem pressures (     

Acclimation responses of mature Abies amabilis sun foliage to shading

This paper addresses two main questions. First, can evergreen foliage that has been structurally determined as sun foliage acclimate physiologically when it is shaded? Second, is this acclimation independent of the foliage ageing process and source-sink relations? To investigate these questions, a shading and debudding experiment was established using paired branches on opengrown Abies amabilis trees. For each tree, one branch was either shaded, debudded, or both, from before budbreak until the end of summer, while the other branch functioned as a control. Foliage samples were measured both prior to and during treatment for photosynthesis at light saturation (A _max), dark respiration, nitrogen content, chlorophyll content, chlorophyll-to-nitrogen ratio and chlorophyll a:b ratio. All age classes of foliage responded similarly during the treatment, although pre-treatment values differed between age classes. Within 1 month after the treatment began, A _max was lower in shaded foliage and remained lower throughout the treatment period. For debudded branches, A _max was lower than the controls only during active shoot elongation. At the end of the treatments in September, A _max in shade-treated sun foliage matched the rates in the true shade-formed foliage, but nitrogen remained significantly higher. By 1.5 months after treatment, chlorophyll content in shaded foliage was higher than in controls, and the chlorophyll a:b ratio was lower for the shaded foliage. On debudded branches, chlorophyll content and chlorophyll a:b ratio were similar to the values in control samples. Shading lowered the rate of nitrogen accumulation within a branch, while removing debudding decreased the amount of sequestered N that was exported from the older foliage to supply new growth. By September, chlorophyll content in shade-treated foliage was higher than that in the control sun foliage or in true shade foliage. The chlorophyll increase as a result of shading was unexpected. However, the chlorophyll-to-nitrogen ratio was identical for the shade-treated sun foliage and the true shade foliage while being significantly lower than the control sun foliage. It appears that acclimation to shading in mature foliage involves a reallocation of nitrogen within the leaf into thylakoid proteins. A redistribution of resources (nitrogen) among leaves is secondary and appears to function on a slower time scale than reallocation within the leaf. Thus, A. amabilis foliage that is structurally determined as sun foliage can acclimate to shade within a few months; this process is most likely independent of ageing and is only slightly affected by source-sink relations within a branch.     

Modification of Stomatal Conductance by Sulphur Dioxide

The mechanism of SO₂-induced changes in stomatal conductance(g) of alder was examined to determine if SO₂ affects guardcell function directly or indirectly through the SO₂-inducedchanges in photosynthesis. During experimental fumigations at SO₂ concentrations of 3–3µmol m^–3 (0.08 µl l^–1), stomatal closurepreceded declines in net photosynthetic rate (A), indicatingthat SO₂ can directly affect guard cells. From these and otherstudies it appears that the sequence of A and g responses maybe influenced by SO₂ concentration as well as by species. Fumigation with SO₂ did not cause increases in g, even whenthe intercellular substomatal CO₂ concentration (c_i) was reducedby 50 µmol mol^–1. Increases in g are not attributableto SO₂ effects on the CO₂-based stomatal control system. Key words: Air pollution, Alnus serrulata, gas exchange, stomata, sulphur dioxide     

Dynamics of ectomycorrhizae in Abies amabilis stands: The role of Cenococcum graniforme

The growth and development of the predominant mycorrhizal fungus infecting the root systems of subalpine Pacific silver fir was examined seasonally in 23 and 180 yr old stands. All data was obtained by sorting roots from intact soil cores separated into forest floor and mineral soil horizons.
The predominant mycorrhizal fungus infecting the root systems of 23 and 180 yr old Pacific silver fir was Cenococcum graniforme. C. graniforme comprised 36–97% and 40–96% of the total mycorrhizal root tips in the soil profile in the young and old stands, respectively. C. graniforme root biomass reached a maximum in autumn in the young stand, and in winter in the old. Dual mycorrhizal associations were commonly observed on the same root tip during the spring and autumn periods of root elongation in both stands. Over 80% of the C. graniforme roots were located in the forest floor and A-horizon throughout the study in both stands, Sclerotia were predominantly located in the A-horizon (38-70%) in both stands.     

Temperature-Induced Change in the Water Relations of Abies amabilis (Dougl.) Forbes

Water conductance through Abies amabilis seedlings was measured while the roots were exposed to temperatures from 15 to 0.25°C. Before conductance was measured, the seedlings were preconditioned for 3 months at either a high temperature (23°C) or a low temperature (3°C). For both groups of seedlings, conductance decreased as root temperature decreased. Conductance was lowest at 0.25°C. In addition, preconditioning at 3°C for 3 months significantly lowered conductance to water at all root temperatures. Under the same environmental conditions, seedlings preconditioned at 3°C had less than 25% of the transpirational water loss of seedlings preconditioned at high temperature. A decrease in leaf osmotic potential also resulted from low temperature preconditioning. In trees growing in the subalpine forest, which is the natural habitat of Abies amabilis, both decreased leaf conductance to water vapor and lower osmotic potentials were evident in winter. Since in winter the temperature of the soil in the subalpine zone remains less than 1°C for many months, lowered leaf conductance and decreased osmotic potentials appear to be mechanisms which aid in preventing desiccation damage.     

Components of woody-tissue respiration in young Abies amabilis (Dougl.) Forbes trees

Summary Woody-tissue respiration was measured on five different dates at three to five locations on each of 12 30-year-old Abies amabilis trees. On any given date, temperature-corrected respiration per unit surface area varied 10 to 40-fold between sampling locations. In stems, the two major components of respiration were growth respiration and sapwood maintenance respiration, which were of roughly equal importance during the growing season. There was no evidence of significant cambial maintenance respiration, suggesting that a stand with high bole surface area would not automatically have high respiration. Respiration in branches was much greater than in boles of comparable volume and growth rates, and was significantly correlated with branch height. Branch respiration may include an another significant component in addition to the two seen in bole respiration, possibly associated with carbohydrate mobilization and transport or with CO₂ efflux from the transpiration stream.     

落叶阔叶林内的光合作用和气孔传导率特征(英文)

本文根据Wang和BMdocchi(1989)最近提出的冠层辐射模型,进一步给出了一个模拟冠层光合作用速率和气孔传导率的模式.模式将冠层中每一层的叶面积分为向光叶、半影叶、和全遮荫叶三种,并分别计算其光合作用速率和气孔传导率。计算得到的光合速率廓线表明,在落叶阔叶林内,冠层下部的叶片常处于光照不足状态;半影效应使得透过林冠达于底部的辐射量增大,这对于林下植物的光合作用是有利的。 模式计算值与实测值之间的微弱差别应归因于纯辐射模型无法考虑湍流输送机制造成的CO_2传输和冠层底部耐荫性叶对于低光照的适应能力。     

Biomass and nutrient concentrations of sporocarps produced by mycorrhizal and decomposer fungi in Abies amabilis stands

Summary Sporocarps and sclerotia were collected for a one-year period in 23- and 180-year-old Abies amabilis stands in western Washington. All sporocarps were classified and chemically analyzed for N, P, K, Ca, Mg, Na and Fe. Lactarius sp. and Cortinarius sp. contributed the largest proportion of the total annual epigeous sporocarp production in both stands. Annual epigeous production was 34 kg/ha in the young stand and 27 kg/ha in the mature stand. Hypogeous sporocarp production increased from 1 kg ha^-1 yr^-1 to 380 kg ha^-1 yr^-1 with increasing stand age. High sclerotia biomass occurred in the young (2,300 kg/ha) and mature (3,000 kg/ha) stands. Peak sclerotia and epigeous sporocarp biomass in the young stand and epigeous and hypogeous sporocarp biomass in the mature stand coincided with the fall peak of mycorrhizal root biomass.In the young stand, sporocarps produced by decomposer fungi concentrated higher levels of Ca and Mn than those produced by mycorrhizal fungi. In the mature stand, sporocarps of decomposer fungi concentrated higher levels of N, P, Mn, Ca and Fe than sporocarps of mycorrhizal fungi. Epigeous and hypogeous sporocarps concentrated higher levels of N, P, and K than sclerotia or mycelium. The highest concentration of N (4.36%), P (0.76%), K (3.22%) and Na (1,678 ppm) occurred in epigeous sporocarps. Highest Mn (740 ppm) and Ca (20,600 ppm) concentrations occurred in mycelium, while highest Mg (1,929 ppm) concentrations were in hypogeous sporocarps and highest Fe (4,153 ppm) concentrations were in sclerotia.     

Oribatid mite communities in the canopy of montane Abies amabilis and Tsuga heterophylla trees on Vancouver Island, British Columbia

To study the oribatid mite community inhabiting microhabitats in the canopy of montane Abies amabilis [(Douglas ex D. Don) Lindl.] and Tsuga heterophylla [(Raf.) Sarg] tree species across five elevational sites, we collected 180 branch tips and 180 foliose/crustose lichen samples over three time periods. Thirty-three species of oribatid mites were identified from the study area. Mite species richness and abundance was significantly affected by microhabitat, and this association was independent of sampling time. At the microhabitat scale, distinct species assemblages were associated with lichen and branch tip habitats, and to a lesser degree, tree species. Conifer specificity was most apparent in the closely related species of Jugatala, where Jugatala tuberosa Ewing was only found on branch tips from A. amabilis and Jugatala sp. was primarily found on branch tips from T. heterophylla. Microhabitat specificity was most pronounced in Dendrozetes sp. where most individuals were found on branch tips and Anachiperia geminus Lindo et al. that occurred primarily on lichens. Principal components analysis of oribatid mite community composition further showed a high degree of association with microhabitat and tree species. Habitat profiles are difficult to discern for many species because tree, microhabitat, and elevation preferences confound distribution patterns. Given the significant tree-microhabitat associations in species composition in this montane canopy study, we suggest that sampling multiple microhabitats across elevations to look for patterns in community structure offers opportunities to explicitly test organizing principles in community ecology.     

Stomatal Conductance and Sulfur Uptake of Five Clones of Populus tremuloides Exposed to Sulfur Dioxide

Plants of five clones of Populus tremuloides Michx. were exposed to 0, 0.2 or 0.5 microliter per liter SO₂ for 8 hours in controlled environment chambers. In the absence of the pollutant, two pollution-resistant clones maintained consistently lower daytime diffusive conductance (LDC) than did a highly susceptible clone or two moderately resistant clones. Differences in LDC among the latter three clones were not significant. At 0.2 microliter per liter SO₂, LDC decreased in the susceptible clone after 8 hours fumigation while the LDC of the other clones was not affected. Fumigation with 0.5 microliter per liter SO₂ decreased LDC of all five clones during the fumigation. Rates of recovery following fumigation varied with the clone, but the LDC of all clones had returned to control values by the beginning of the night following fumigation. Night LDC was higher in the susceptible clone than in the other clones. Fumigation for 16 hours (14 hours day + 2 hours night) with 0.4 microliter per liter SO₂ decreased night LDC by half. Sulfur uptake studies generally confirmed the results of the conductance measurements. The results show that stomatal conductance is important in determining relative susceptibility of the clones to pollution stress.     

Responses of Soybean Leaf Angle, Photosynthesis and Stomatal Conductance to Leaf and Soil Water Potential

The hypothesis that soil water potential (_s) is better correlatedto heliotropic leaf orientation, photosaturated photosyntheticCO₂ assimilation and stomatal conductance during periods oflimited water availability than is bulk leaf water potential(₁) was examined in greenhouse-grown soybean (Glycine max) plants,submitted to a progressive drought. Paired plants were exposedto either 1000 or 100 µmol m^–2 s^–1 photonflux densities (PFD) for 45–60 mins. The higher irradianceinduced short-term decreases in ₁, due to increased transpiration,while _l in the plant exposed to low PFD did not decrease. Thesechanges in ₁ occurred independently of changes in soil waterstatus. Concurrent to the light treatments, a single attachedleaf from each of the two plants was isolated from the restof the plant by shading, and the pulvinus of its terminal leafletwas exposed to a perpendicular PFD of 500 µmol m–²S^–1. Leaf movement of this leaflet was recorded in responseto this light, until a stable leaflet angle was achieved. Valuesof _s and _l (before and after light treatment), and photosaturatedrates of photosynthesis and stomatal conductance, were thenmeasured on these leaves. Leaflet angle and gas exchange werebetter correlated with _s (r² = 0.50, 0.50 and 0.57 for angle,photosynthesis and conductance, respectively) than with _l especiallywhen _l was the result of short-term, high-light induced changesin leaf water status (r² = 0.36, 0.32 and 0.49, for the sameparameters). Leaflet angle was also correlated with stomatalconductance (r² = 0.61) and photosynthetic rate (r² = 0.60),suggesting a close association between leaf orientation, leafmetabolism and soil water availability. Glycine max (L.) Merr. cv. Essex, soybean, heliotropism, water potential, photosynthesis, stomatal conductance, solar tracking     

Hydraulic Conductance and Stomatal Sensitivity to Changes of Leaf Water Status in Six Deciduous Tree Species

The relationship between shoot hydraulic conductance (L) and stomatal sensitivity to changes in leaf water status was studied in the saplings of six deciduous tree species. L increased significantly in sequence: Acer platanoides < Tilia Cordata < Padus avium = Quercus robur < Salix caprea = Populus tremula. L was higher in the trees grown in soil with a higher nitrogen content and lower in the trees grown under mild water stress or kept in darkness for several days. L was higher in July than in September in all the species. L correlated positively with maximum photosynthesis, stomatal conductance and stomatal sensitivity to an increase in leaf water potential, but negatively with stomatal sensitivity to a decrease in leaf water potential. The correlations between L and any other parameter were approximated by three different curves: data for water-stressed plants fit to the first, data for plants kept in darkness fit to the second and all the other data fit to the third curve. The reasons of the differences of shoot hydraulic conductance in the different experimental sets and the mechanisms which may cause the correlation between L and the other characteristics are discussed.     

科尔沁沙地黄柳气孔导度和水分状况随季节和地形的变化特征①

黄柳叶片气孔导度在上午８时后即呈下降趋势,下表皮气孔导度大于上表皮。干旱季节上下表皮气孔日间开启程度不同,下表皮气孔受环境因子的影响较大;湿润季节则相同。不同季节气孔导度值不同,下表皮气孔对季节变化反应灵敏。不同季节黄柳体内水分状况参数值不同,在５、６月份抗旱性最强;沙丘不同部位各参数值亦不相同,在沙丘中部和丘脚抗旱性最强,而在丘顶水分状况最好。湿润的７月黄柳一日内各时刻的膨压值均大于０,说明经期     

Detecting the Differences in Responses of Stomatal Conductance to Moisture Stresses between Deciduous Shrubs and Artemisia Subshrubs

Shrubs and subshrubs can tolerate wider ranges of moisture stresses in both soil and air than other plant life forms, and thus represent greater nonlinearity and uncertainty in ecosystem physiology. The objectives of this paper are to model shrub/subshrub stomatal conductance by synthesizing the field leaf gas exchanges data of 24 species in China, in order to detect the differences between deciduous shrubs and Artemisia subshrubs in their responses of stomatal conductance to changes in the moisture stresses. We revised a model of stomatal conductance by incorporating the tradeoff between xylem hydraulic efficiency and cavitation loss risk. We then fit the model at the three hierarchical levels: global (pooling all data as a single group), three functional groups (deciduous non-legume shrubs, deciduous legume shrubs, and subshrubs in Artemisia genus), and individual observations (species × sites). Bayesian inference with Markov Chain Monte Carlo method was applied to obtain the model parameters at the three levels. We found that the model at the level of functional groups is a significant improvement over that at the global level, indicating the significant differences in the stomatal behavior among the three functional groups. The differences in tolerance and sensitivities to changes in moisture stresses are the most evident between the shrubs and the subshrubs: The two shrub groups can tolerate much higher soil water stress than the subshrubs. The analysis at the observation level is also a significant improvement over that at the functional group level, indicating great variations within each group. Our analysis offered a clue for the equivocal issue of shrub encroachment into grasslands: While the invasion by the shrubs may be irreversible, the dominance of subshrubs, due to their lower resistance and tolerance to moisture stresses, may be put down by appropriate grassland management.     

Enhanced Photosynthesis and Stomatal Conductance of Pima Cotton (Gossypium barbadense L.) Bred for Increased Yield

Yield of Pima cotton (Gossypium barbadense L.) has tripled over the last 40 years with the development of new cultivars. Six genetic lines representing successive stages in the breeding process (one primitive noncultivated accession, four cultivars with release dates from 1949 to 1983, and one unreleased breeding line) were grown in a greenhouse, and their gas exchange properties were compared. Among the cultivated types, genetic advances were closely associated with increasing single-leaf photosynthetic rate (A) and stomatal conductance (g_s), especially in the morning. The A and g_s of the primitive line approached those of the cultivated types early in the morning, but were much lower for the rest of the day. In both morning and afternoon, A was correlated with g_s across genotypes but was not correlated with leaf thickness, concentrations of chlorophyll or starch, or intercellular CO₂ concentration (c_i). In the oldest cultivar, the relationship of A to c_i did not change between morning and afternoon. In the two most recent lines, the slopes of the A:c_i curves at limiting c_i exceeded that of the oldest cultivar by 25 to 50% in the morning, but the differences were much smaller in the afternoon. The maximum A of the newer lines at high c_i exceeded that of the oldest cultivar only in the morning. Breeding for increasing yield has enhanced the photosynthetic capacity and stomatal conductance of Pima cotton and altered the diurnal regulation of photosynthesis.     

适应不同光环境小蜡叶片气孔导度、气孔开度和气孔密度的时空变化

对生长在强光环境和弱光环境小蜡叶片的气孔参数测定发现 :气孔导度和气孔开度在 4个取样部位存在异质性分布。气孔导度和气孔开度经回归分析呈线性、指数或多项式分布。统计分析表明 :强光下的叶片气孔导度和气孔开度的相关性明显高于弱光环境叶片的数值。无论强光环境还是弱光环境下的叶片 ,在取样部位编号为1和 3,其气孔导度和气孔开度均存在显著的线性关系。弱光环境下叶片的气孔密度要远低于强光环境下的叶片。强光环境下叶片对变化环境的敏感性要大于弱光环境下的叶片 ,这可能与强光环境叶片具有较高的气孔密度有关。     

Effect of the Mesophyll on Stomatal Opening in Commelina communis

The effect of a number of factors on the opening of stomatain the intact leaf and in the isolated leaf epidermis of Commelinacommunishas been investigated. Stomata in the intact leaf opened widein the light and closed rapidly on transfer to the dark. Theywere also sensitive to CO₂. In contrast, stomata in isolatedepidermis floated on an incubation solution containing 100 molm^–3KCl responded neither to light nor CO₂. They opened as widelyas those in the intact leaf when treated with fusicoccin. Stomata in isolated epidermis opened almost as wide as thosein the intact leaf when they were incubated with isolatedmesophyllcells in the light. The solution in which the mesophyll cellswere incubated was separated by centrifugation. Themedium fromcells previously incubated in the light caused the stomata inisolated epidermis to open but that from cells kept inthe darkhad no effect. A similar effect was observed when isolated chloroplastswere incubated with the isolated epidermis.However, the supernatantfrom the chloroplast suspension had no significant effect onstomatal opening. These results indicate that the mesophyll plays an importantrole in stomatal opening in the light. The mesophyll appearstoproduce in the light, but not in the dark, a soluble compoundwhich moves to the guard cells to bring about stomatal opening.Theexperiments with isolated chloroplasts suggest that this substanceis a product of photosynthesis. Key words: Commelina communis, stomata, light, mesophyll