18年生杉木不同部位和叶龄针叶光响应研究

在最适温度(30±1℃)、适宜湿度(70%±5％)和正常大气CO2浓度（350±10×10-6V/V）向下,采用活体测定方法,测定了18年生杉木不同部位和叶龄针叶对光照的稳态和动态响应。结果表明,不同部位和叶龄针叶净光合速率（Pn）的光响应特征有明显差异,从上部到下部、从当年生到1年生至2年生,针叶Pn、饱和光强（PSLI）和光补偿点（LCP）降低,表观量子效率（α）提高。经一定时间暗处理后,针叶需要一定光诱导才能获得相应光强下的最大Pn。光诱导期长短与猝发性光强以及叶龄和针叶在树冠中所处的部位有关。猝发性光照越强,所需的光诱导期越长;下部针叶光诱导期短于中部针叶;而1年生针叶短于当年生针叶。不同部位针叶对稳态和动态光照的响应与针叶长期适应所处的光环境有关,而不同叶龄的差异除与生理活性有关外,也可能与所处的光环境有关。     

Variation in monoterpene composition of the shoot cortical oleoresin within and between trees of Pinus contorta

Ten young Lodgepole pine trees were studied for variation in monoterpene composition of the shoot cortical oleoresin due to position within the crown. There was no significant difference between whorls, but small differences occurred between the lateral and terminal shoots of branches. The nature of the differences varied between trees; 3-carene showed the most consistent positional difference.     

纵坑切梢小蠹蛀梢期空间分布

在昆明地区,纵坑切梢小蠹（Ｔｏｍｉｃｕｓ　ｐｉｎｉｐｅｒｄａ）成虫蛀梢多集中在蛀干木附近。种群密度以蛀干木为中心向周围是指数递减,散布半径约３０ｍ。在蛀虹梢过程中,该种群逐渐向新区扩张。在树冠内,纵坑切梢小蠹主要分布在４—１０轮枝上。第７轮技虫口百分率最高。６—７轮枝受害率最大。树冠上层受害较其下属于重。从树冠水平层次考察,树冠外层虫量相对集中,约为树冠中、内层虫量之和。树冠内层虫量最少。纵坑切梢小蠹在树冠内的种群分布系由梢径、种群密度、蛀梢行为、降落方式、光照等因素综合影响的结果。     

Bud and crown architecture of white spruce and black spruce

Needle primordia in buds and branch lengths were assessed in the crown of a plantation-grown white spruce tree. There was a gradation in needle primordia in buds in branches within the crown. The largest number of primordia was in the terminal bud of the leading main stem shoot, with the number in first-order whorl lateral shoot terminal buds decreasing from whorl 1 to whorl 4, below which buds contained a similar small number of primordia (about one-third as many as in the terminal shoot). Previous year's shoot elongation followed a similar pattern (i.e., elongation of whorl branches was greater closer to the top of the tree and elongation in the fourth through ninth whorls was about one-third that of the main stem leader). Higher order branches within whorls had within-branch gradation in shoot elongation and number of needle primordia, with older branches having as few as 16–30 primordia in buds and 3–4 cm elongation for high-order branches on older main stem whorls. There were strong correlations between the number of primordia in branch terminal buds and branch length/diameter and bud length/diameter/volume. In both black spruce and white spruce, there were strong correlations of number of needle primordia in main stem leader terminal buds with number of needle primordia in terminal buds of first and second whorl leaders.     

纵坑切梢小蠹蛀梢期空间分布

在昆明地区,纵坑切梢小蠹(Tomicus piniperda)成虫蛀梢多集中在蛀干木附近。 种群密度以蛀干木为中心向周围呈指数递减,散布半径约30m。在蛀梢过程中,该种群逐渐向新区扩张。在树冠内,纵坑切梢小蠹主要分布在4-10轮枝上。第7轮枝虫口百分率最高。6-7轮枝受害率最大。 树冠上层受害较其下层严重。从树冠水平层次考察,树冠外层虫量相对集中,约为树冠中、内层虫量之和。 树冠内层虫量最少。纵坑切梢小蠹在树冠内的种群分布系由梢径、种群密度、蛀梢行为、降落方式、光照等因素综合影响的结果。     

Effect of soil temperature on stem sap flow,shoot gas exchange and water potential of Picea engelmannii (Parry) during snowmelt

Summary The effect of cold soils on stem sap flow, shoot gas exchange and water potential of Picea engelmannii (Parry) was investigated during the snowmelt period in the Medicine Bow Mountains, Wyoming, USA. Shoot net photosynthetic rates were higher in young trees (1.5–1.8 m in height) growing in cold soils (<3.5° C) associated with snowpack, than trees in warm soils until about 1500 h. Higher shoot photosynthetic rates of trees in cold soils continued after snow was removed and could not be completely explained by higher visible irradiance over highly reflective snow. Following soil warming higher photosynthetic rates were evident in these trees for five days. High nutrient availability associated with snowmelt may improve shoot nutrient status leading to higher gas-exchange rates during snowmelt. Shoot conductance to water vapor was higher in trees in cold soil until midday, when declining shoot conductance led to lower intercellular CO₂ concentrations. Midday through afternoon shoot water potentials of trees in cold soils were similar or higher than those of trees in warm soils and the lower afternoon shoot conductances in cold soils were not the result of lower bulk shoot water potentials. Decline in net photosynthesis of trees in cold soils at 1500 h paralleled increases in intercellular CO₂ concentrations, implying a nonstomatal limitation of photosynthesis. This scenario occurred consistently in mid-afternoon following higher morning and midday photosynthesis in cold soils, suggesting a carbohydrate feedback inhibition of photosynthesis. Diurnal patterns in stem sap flow of all trees (cold and warm soils) reflected patterns of shoot conductance, although changes in stem sap flow lagged 1–3 h behind shoot conductance apparently due to stem water storage. Total daily stem sap flow was similar in trees in cold and warm soils, although diel patterns differed. The morning surge and night-time drop in sap flow commenced 1–2 h earlier in trees in cold soils. Overnight stem sap flow was lower in trees in cold soils, possibly due to higher resistance to root water uptake in cold soils, which may explain lower predawn shoot water potentials. However, midday shoot water potentials of trees in cold soils equalled or exceeded those of trees in warm soils. Higher resistance to root water uptake in P. engelmannii in cold soils was apparently overshadowed by transpirational forces and significant shoot water deficits did not develop.     

Bottlenecks to water transport in Quercus robur L.: the abscission zone and its physiological consequences

Cladoptosis, the abscission of twigs, is the main mechanism of changes in crown structure in senescing pedunculate oak (Quercus robur L.). We tested the hypotheses that abscission zones in nodes of old pedunculate oak trees reduce leaf-specific hydraulic conductance of shoots and thereby limit the stomatal conductance and assimilation.Hydraulic conductance and leaf-specific hydraulic conductance, measured with a high pressure flowmeter in 0.5–1.5 m long shoots, were significantly lower in shoots of low vigour compared to vigorous growing shoots in a 165-years-old stand in the southeast of Germany. Two types of bottlenecks to water transport could be identified in shoots of old oak trees, namely nodes and abscission zones. In young twigs, vessel diameter and vessel density in nodes with abscission zones were significantly reduced compared with internodes. In nodes without abscission zones, vessel density was significantly reduced. The reduction of hydraulic conductance was especially severe in the smallest and youngest shoots with diameters less than 2 mm. Internodes of 1–5 mm sapwood diameter had an average hydraulic conductance of 7.13×10⁻⁶±0.2×10⁻⁶ kg s⁻¹ m⁻¹ MPa⁻¹, compared to 4.54×10⁻⁶±0.3×10⁻⁶ kg s⁻¹ m⁻¹ MPa⁻¹ in those with nodes.Maximum stomatal conductance and maximum net assimilation rate increased significantly with hydraulic conductance and leaf-specific hydraulic conductance. Maximum rate of net photosynthesis A_max of the most vigorous shoots (VC0) (7.34±0.55 μmol m⁻² s⁻¹) was significantly higher (P<0.001) than in shoots of other vigour classes (5.97±0.28 μmol m⁻² s⁻¹). Our data support the hypothesis that the changes in shoot and consequently crown architecture that are observed in ageing and declining trees can limit photosynthesis by reducing shoot hydraulic conductance. Abscission zones increase the hydraulic disadvantage of less vigorous compared to vigorously growing twigs. Cladoptosis might serve as a mechanism of selection between twigs of different efficiency.     

Clouds homogenize shoot temperatures,transpiration, and photosynthesis within crowns of <Emphasis Type="Italic">Abies fraseri</Emphasis> (Pursh.) Poiret

Multiple studies have examined the effects of clouds on shoot and canopy-level microclimate and physiological processes; none have yet done so on the scale of individual plant crowns. We compared incident photosynthetically active radiation (PAR), leaf temperatures, chlorophyll fluorescence, and photosynthetic gas exchange of shoots in three different spatial locations of Abies fraseri crowns on sunny (clear to partly cloudy) versus overcast days. The field site was a Fraser fir farm (1038 m elevation) in the Appalachian mountains, USA. Ten saplings of the same age class were marked and revisited for all measurements. Sunny conditions corresponded with 5–10× greater sunlight incidence on south-facing outer shoots compared to south-facing inner and north-facing outer shoots, which were shaded and received only indirect (diffuse) sunlight. Differences in spatial distribution of irradiance were mirrored in differences in shoot temperatures, photosynthesis, and transpiration, which were all greater in south-facing outer shoots compared to more shaded crown locations. In contrast, overcast conditions corresponded with more homogeneous sunlight distribution between north and south-facing outer shoots, and similar shoot temperatures, chlorophyll fluorescence (ΦPSII), photosynthesis, and transpiration; these effects were observed in south-facing inner shoots as well, but to a lesser extent. There was no significant difference in conductance between different crown locations on sunny or overcast days, indicating spatial differences in transpiration under sunny conditions were likely driven by leaf temperature differences. We conclude that clouds can affect spatial distribution of sunlight and associated physiological parameters not only within forest communities, but within individual crowns as well.     

PATTERNS IN LEAF MORPHOLOGY AND PHOTOSYNTHESIS IN SHOOTS OF SASSAFRAS ALBIDUM (LAURACEAE)

Trees of Sassafras albidum (Nuttall) Nees. display leaves that fall into discrete categories of form. Unlobed leaves, with undissected margins, predominate at proximal and distal nodes of shoots, while lobed leaves are most common at intermediate nodes. In this study we investigated the hypothesis that shoots of sassafras respond to environmental changes over the growing season by generating predictable nodal patterns for leaf morphology and physiology. We recorded leaf shape category and measured leaf surface area, node number, chlorophyll content, nitrogen content, and photosynthesis in four trees. Over 1,000 measurements of photosynthesis were made in situ, using the LI-Cor LI 6200 portable photosynthesis system. The two trees growing under heavy shade had few lobed leaves (2.0% and 18.8%) and often had negative carbon balance, with positive net photosynthesis occurring during sun flecks. The two trees growing in more open conditions had many more lobed leaves (56.3% and 61.0%) and higher, less variable net photosynthetic rates. As indicated by chlorophyll and nitrogen contents, the highest leaf photosynthetic rates occurred at intermediate nodes (nodes six to nine), and this was shifted distally along the shoot during the growing season. Leaves at intermediate nodes also had the largest surface areas and the greatest frequency of lobing. In comparative experiments with models, lobing was shown to enhance free-convectional heat loss relative to unlobed leaves of the same surface area. Due to their large surface area, these leaves also have the highest rates of whole leaf photosynthesis. Under conditions of equivalent photosynthetically active radiation, lobed leaves had higher rates of net photosynthesis than did unlobed leaves. We conclude that shoots of sassafras produce groups of leaves with predictably different morphological and physiological specializations.     

Effect of Fruiting on Leaf Gas Exchange in Olive (Olea Europaea L.)

The effect on traits of photosynthesis and water relations of assimilate demand was studied in olive tree that has strong alternate bearing. The diurnal and seasonal leaf gas exchanges, area dry mass, and saccharide and chlorophyll (Chl) contents were measured by comparing shoots with fruit of "on-trees" (heavy fruit load) with shoots without fruit on both "on-trees" and "off-trees" (light fruit load). In spite of large seasonal and diurnal differences, leaf net photosynthetic rate (P _N), stomatal conductance (g _s), sub-stomatal CO₂ concentration (C ₁), transpiration rate (E), and respiration rate (R _D) were not significantly influenced by fruit load or by the presence or absence of fruit on the shoot. An only exception was at the beginning of July when the one-year-old leaves on shoots with fruit had slightly higher P _N and E than leaves on shoots without fruit. Water content, Chl and saccharide contents, and area dry mass of the leaf were not substantially influenced by the presence/absence of fruit on the shoot or fruit load. Hence the sink demand, associated with fruit growth, did not improve leaf photosynthetic efficiency in olive. This revised version was published online in August 2006 with corrections to the Cover Date.     

Environmental and stomatal control of transpiration, canopy conductance and decoupling coefficient in young lemon trees under shading net

Sap flow, as a measure of transpiration, was monitored in 2-year-old lemon trees growing in pots. Eight trees were used in the experiment, four of which were placed under a rectangular shading net, while the other four were maintained in the open air. Daily averages of canopy conductance and photosynthesis were not affected by shading; however, the daily transpiration was reduced in shaded plants, which displayed an increase in water use efficiency compared with exposed trees. The decoupling coefficient was higher in the shaded trees, indicating that the transpiration of lemon trees was efficiently controlled by stomata in exposed plants, while the transpiration rate was mainly influenced by radiation in the plants growing under the net. This influence was more pronounced in the afternoon, when the whole tree transpiration was largely dominated by equilibrium transpiration in the plants under netting, and the relationship between transpiration and radiation showed a steeper slope in shaded trees. The reduction in transpiration and the maintenance of photosynthesis in shaded plants with respect to exposed trees indicated that screen structures in semi-arid and arid environments could be considered as an intermediate solution for reducing plant water stress and increasing water use efficiency.     

Hydrostatic constraints on morphological exploitation of light in tall Sequoia sempervirens trees

We studied changes in morphological and physiological characteristics of leaves and shoots along a height gradient in Sequoia sempervirens, the tallest tree species on Earth, to investigate whether morphological and physiological acclimation to the vertical light gradient was constrained by hydrostatic limitation in the upper crown. Bulk leaf water potential (Psi) decreased linearly and light availability increased exponentially with increasing height in the crown. During the wet season, Psi was lower in the outer than inner crown. C isotope composition of leaves (delta(13)C) increased with increasing height indicating greater photosynthetic water use efficiency in the upper crown. Leaf and shoot morphology changed continuously with height. In contrast, their relationships with light availability were discontinuous: morphological characteristics did not correspond to increasing light availability above 55-85 m. Mass-based chlorophyll concentration (chl) decreased with increasing height and increasing light availability. In contrast, area-based chl remained constant or increased with increasing height. Mass-based maximum rate of net photosynthesis (P (max)) decreased with increasing height, whereas area-based P (max) reached maximum at 78.4 m and decreased with increasing height thereafter. Mass-based P (max) increased with increasing shoot mass per area (SMA), whereas area-based P (max) was not correlated with SMA in the upper crown. Our results suggest that hydrostatic limitation of morphological development constrains exploitation of light in the upper crown and contributes to reduced photosynthetic rates and, ultimately, reduced height growth at the tops of tall S. sempervirens trees.     

Enhancement of photosynthesis in post-disturbance resprouts of two co-occurring Mediterranean <Emphasis Type="Italic">Erica</Emphasis> species

The higher growth rates of resprouting shoots compared with those of mature plants in resprouter woody species are supported by higher rates of photosynthesis and transpiration. In this contribution we hypothesize that species with higher resprouting vigour will show a larger enhancement of photosynthesis in resprouting shoots. We test this hypothesis by comparing gas exchange and leaf parameters between resprouting and mature plants in Erica scoparia and E. australis. These two Erica species co-occur in Mediterranean heathlands of the Strait of Gibraltar. Erica scoparia has a higher rate of post-disturbance starch recovery than E. australis, which makes it more resistant to recurrent disturbance. We tested the hypothesis that enhancement of photosynthesis and water use characteristics of resprouting shoots compared with mature plants should be more pronounced in E. scoparia. In both species, resprouts had higher efficiency in the use of light and higher maximum net photosynthesis than mature shoots. However, contrary to expectations, differences in the photosynthetic performance between resprouts and mature plant shoots were larger in E. australis. Higher root to shoot ratios in resprouting E. australis plants, determined by their slower above-ground recovery, together with stronger demand from carbon sinks might explain this result.     

Annual and spatial variation in shoot demography associated with masting in Betula grossa: comparison between mature trees and saplings

Backgrounds and Aims

Shoot demography affects the growth of the tree crown and the number of leaves on a tree. Masting may cause inter-annual and spatial variation in shoot demography of mature trees, which may in turn affect the resource budget of the tree. The aim of this study was to evaluate the effect of masting on the temporal and spatial variations in shoot demography of mature Betula grossa.

Methods

The shoot demography was analysed in the upper and lower parts of the tree crown in mature trees and saplings over 7 years. Mature trees and saplings were compared to differentiate the effect of masting from the effect of exogenous environment on shoot demography. The fate of different shoot types (reproductive, vegetative, short, long), shoot length and leaf area were investigated by monitoring and by retrospective survey using morphological markers on branches. The effects of year and branch position on demographic parameters were evaluated.

Key Results

Shoot increase rate, production of long shoots, bud mortality, length of long shoots and leaf area of a branch fluctuated periodically from year to year in mature trees over 7 years, in which two masting events occurred. Branches within a crown showed synchronized annual variation, and the extent of fluctuation was larger in the upper branches than the lower branches. Vegetative shoots varied in their bud differentiation each year and contributed to the dynamic shoot demography as much as did reproductive shoots, suggesting physiological integration in shoot demography through hormonal regulation and resource allocation.

Conclusions

Masting caused periodic annual variation in shoot demography of the mature trees and the effect was spatially variable within a tree crown. Since masting is a common phenomenon among tree species, annual variation in shoot demography and leaf area should be incorporated into resource allocation models of mature masting trees.     

Quantitative genetics of stamen number in the selfing Scleranthus annuus (Caryophyllaceae)

Heritability of stamen fertility—different scores were given to sterile stamens developed to different degrees as well as to fertile stamens with one or two pollen sacs—was studied in Scleranthus annuus (Caryophyllaceae), a selling annual that shows extensive phenotypic variation in stamen fertility. Variation within and among 172 maternal families, derived from plants representing 20 natural populations from southern Sweden, was used to estimate heritabilities of stamen fertility for stamens/staminoids at each of the ten stamen positions in the flower. The hierarchical design of the study allowed partitioning of variation at four levels of organization using nested analysis of variance. Heritabilities ranged from 0.631 to 0.714 for stamen positions in the outer whorl of stamens and from 0.235 to 0.555 for positions in the inner whorl. When stamen fertility was pooled across all stamen positions of a flower, the heritability was 0.807. The nested ANOVA indicated that stamen positions in the outer whorl have comparatively higher proportions of among-family and among-population variation than those in the inner whorl. Furthermore, highly significant genetic correlations exist among stamen positions within the inner whorl and among positions within the outer whorl, but not so between positions from each of the two whorls.     

Dynamics of Photosynthesis in Pine Stands

The CO₂ exchange of pine (Pinus sylvestris L.) shoots was continuously monitored over several years. The spatial and temporal variability of gas exchange was thoroughly investigated for three forest types. The net uptake of CO₂ by current-season shoots in a bilberry pine stand equaled 5.4 g CO₂ per g dry wt for the growing season. The net CO₂ assimilation by one-year-old shoots over a growing season constituted 9.9 and 2.4 g CO₂/(g dry wt year) in the upper and lower crown parts, respectively. The nighttime respiration of the current-season shoots released 0.7 g CO₂/(g dry wt year), and the respiration of one-year-old shoots in the upper and lower parts of the canopy released 0.45 and 0.36 g CO₂/(g dry wt year), respectively. Recalculation of three-year data per entire crown yielded an annual average carbon assimilation of 1.54 g C/(g dry wt year). Water relations markedly affected CO₂ fixation. Nevertheless, the daily average values of photosynthesis in the summer were similar for pine stands with bilberry, heather, and dwarf shrub–polytric as understory dominants. It is shown that the realization of changes in photosynthetic function is related in time to growth processes.     

Role of water relations and photosynthesis in the release of buds from apical dominance and the early reinvigoration of decapitated poplars

A decrease in xylem pressure potential starting 1 h after decapitation of young hybrid poplars ( Populus deltoides Bartr. × Populus nigra L. cv. DN22) reduced stomatal conductance and transpiration rates for the first 3 days after decapitation. This early moisture stress was alleviated 4 to 5 days after decapitation, resulting in substantial increases in stomatal aperture, transpiration and net photosynthetic rates which continued for the remainder of the one week measurement period. The results suggest the following sequence of events in the decapitated plant: After a brief moisture stress, decapitation increases moisture availability by increasing the root/shoot ratio and by reducing shoot competition for moisture. Improvement in hydration releases buds from apical dominance and increases stomatal conductance and rates of net photosynthesis. This, in turn, leads to the acceleration of growth observed when plants are reinvigorated by decapitation.     

HETEROGENEITY IN POLLEN ALLELE FREQUENCIES AMONG CONES,WHORLS, AND TREES OF TABLE MOUNTAIN PINE (PINUS PUNGENS)

Pinus pungens Lambert (Table Mountain pine) is characterized by serotinous cones that are borne several (two to five) per whorl. Sporophytic and gametophytic tissues from whorls collected in different canopy zones of eight trees were electrophoresed and surveyed for six allozyme loci. Pollen allele frequencies received by individual trees, whorls on trees, and cones in whorls were estimated and used to estimate outcrossing rates and the distribution of genetic diversity within and among each level. Significant differences in pollen allele frequencies were detected at all levels, indicating that the genetic composition of the pollen pool available to different female strobili is heterogeneous. The fine-scale genetic structure in the seed pool is a record of past reproductive events and is the precursor to genetic structure in the next generation.     

黄土高原森林草原区6种植物光合特性研究

 对黄土高原森林草原区6种不同植物的生理生态学特性进行了一个生长季的野外观测。测定了2002年生长季早、中、晚期植物叶片的光合、蒸腾速率及相应的微气象因子和土壤水分的含量。在此基础上,采用机理性生理生态学模型对黄土高原森林草原区6种植物净光合速率和气孔导度与环境因子的关系进行了分析,净光合速率模型和气孔导度模型分别能够解释57%～79% 和40%～59% 生长季中净光合速率和气孔导度的日变化。在此基础上根据拟合得到的参数计算了典型7月份天气的净光合速率的日变化。模拟的结果表明：沙棘(Hippophae rhamnoides L. subsp. sinensis Rousi)的生物化学光合能力最强,茵陈蒿（Artemisia capillaris）的光呼吸速率最低,这两种植物的净光合速率高于其它植物种。刺槐（Robinia pseudoacacia）、铁杆蒿 (Artemisia gmelinii)、茵陈蒿和沙棘在午后出现的净光合速率下降主要是由气孔导度减小引起的,而苹果 (Malus pumila) 和柠条 (Caragana korshinskii)午后净光合速率的降低与叶肉细胞酶的活性降低有关。这些结论为未来的实验室测定提供了野外观测佐证。     

Within-plant distribution of a galling adelgid (Homoptera: Adelgidae): the consequences of conflicting survivorship, growth, and reproduction

Abstract. 1. Adelges cooleyi (Gil.) was rarely found in the top-most whorl of shoots in its host plant Engelmann spruce.
2. The survivorship of the few Adelges fundatrices which did colonize the top whorl was at or near zero for the 3 years in which survivorship was assessed, while survivorship in the bottom whorls was at least 60%.
3. In contrast, when an Adelges fundatrix did survive in the top whorl, her growth and reproductive output, and the growth of her progeny, the gallicolae, were at least double that of bottom whorl fundatrices.
4. The distribution of fundatrices within spruce trees was strongly correlated ( R ²=0.934) with fundatrix fitness (=survivorship × fecundity × growth).
5. We hypothesize that the vigorous growth of top whorl shoots promotes Adelges growth and fecundity, but the earlier growth of these shoots results in low temperature mortality of fundatrices.