水位与光强变化对尖叶泥炭藓孢蒴生产动态的影响

选取尖叶泥炭藓(Sphagnum capillifolium)为试验材料, 在模拟水位与光强条件下, 对人工构建的苔藓植物群落进行室内培养, 每隔1-3天观察并记录植株高度、孢蒴变化过程及变化时间, 分析了不同水位与光强条件对孢蒴生产的植物功能属性动态的影响。水位上升促进了蒴柄伸长及植株高增长, 增加了孢蒴开裂率及遮蔽率。光强增加有助于孢蒴生长, 并提高了孢蒴开裂率。在孢蒴直径以及植株高增长性状上, 水位与光强存在交互作用。水位与光强对孢蒴增长率均没有影响。此外, 水位升高与光强增加使孢蒴成熟及蒴柄伸长时间提前, 总体上使孢子释放时间分别提前了4.0 d和4.8 d, 由此可能减小了孢子体因受夏季干旱影响而败育的风险。孢子释放后, 繁殖株高增长加速, 可为未来的再次繁殖奠定基础。     

PHENOLOGY AND REPRODUCTIVE ALLOCATION IN ANDROPOGON SCOPARIUS (GRAMINEAE) POPULATIONS IN COMMUNITIES OF DIFFERENT SUCCESSIONAL STAGES

Successional populations of Andropogon scoparius in Franklin Township, Somerset County, New Jersey, were compared as to their phenology and reproductive allocation. Field data from six populations in old-fields ranging in age from 2 to 40 years indicated significant differences in both phenology and reproductive effort (ratio of reproductive to total shoot biomass). Mean date of first anthesis was consistently later with increasing age of the old-field, and the later the first anthesis date for a population, the lower was the reproductive effort. Population data on mean maximum height and seed weight showed no relation to successional age. Greenhouse experiments on three of the populations revealed that most of the field differences were attributable to local habitat effects on phenotypic expression. The possibility of some genetic differentiation paralleling successional age was raised by the consistent (though sometimes statistically not significant) differences between the early (3-yr) and late (40-yr) successional populations in date of first anthesis and in reproductive effort under two light intensities and uniform greenhouse conditions.     

攀援植物绞股蓝幼苗对光照强度的形态和生长反应

 利用遮阳网产生光照强度梯度,以研究攀援植物绞股蓝(Gynostemma pentaphyllum)幼苗对光梯度的形态和生长反应。结果表明：1)相对生长速率、净同化速率和总生物量随光照强度减弱而降低,总叶面积、比茎长、株高、分枝角度、叶面积率和比叶面积却增加;2)株高生长与相对生长速率成负相关;3)幼苗生物量分配对光梯度的反应不敏感。这些结果意味着绞股蓝幼苗的形态和生长反应对不同光环境具有可塑性,比茎长和株高随光照减弱而增加有利于绞股蓝幼苗“寻找”到外界支持物。     

杉木种子萌发及幼苗生长对光强的响应

设置不同光强梯度(透光率分别为100%、40%、20%、10%和5%,光照强度PPFD分别为201.3、77.0、37.5、19.2、9.8 μmol·m^-2·s^-1),研究光对杉木种子萌发和幼苗早期生长的影响,分析杉木种子萌发、幼苗存活、生长、形态响应、生物量积累及其分配格局对不同光环境的响应策略.结果表明: 杉木种子的萌发率、存活率、建植率和萌发指数在不同光强梯度下均有显著差异,且40%的透光率是种子最适萌发条件,萌发率最高,而全光照下存活率和建植率最高;随光照强度的减弱,杉木幼苗茎长增大,根长、子叶长、子叶厚、真叶数呈降低趋势,而基径在各光照强度间无显著差异;总生物量、根生物量、茎生物量、叶生物量均表现为全光照下最大.随着光照强度的减弱,光合组织与非光合组织生物量比、叶生物量比呈降低趋势,茎生物量比呈增加趋势,根冠比和根生物量比无显著差异.弱光环境促进杉木种子萌发,不利于杉木幼苗存活和生长.在弱光环境下,杉木幼苗通过增大茎生物量来提高对弱光环境的耐受力.     

遮荫对峦大杉1年生苗木生长的影响及动态优化

以当年播种的峦大杉(Cunninghamia konishii)幼苗为材料,采用单因素试验设计3个遮荫处理(50%、75%、100%光照),每隔7 d监测地径、苗高等生长进程;应用Logistic方程拟合苗高、地径生长过程并分析其生长节律。结果表明,遮荫显著促进峦大杉幼苗全生长季的苗高、地径生长,以50%光照表现最好;不同生长阶段遮荫对峦大杉苗高、地径生长量的影响有所不同,进行动态优化十分必要。Logistic方程能较好地拟合峦大杉苗木生长动态。50%光照处理显著提高峦大杉苗高、地径的线性生长速率、最大线性生长速率和线性生长量,显著提前苗高线性生长终期、缩短线性生长持续时间,显著推迟地径线性生长始期。峦大杉苗期光照强度动态优化方案：在t≤133 d前阶段宜采用50%光照,在t＞133 d期间宜采用100%光照。     

Phenological responses to nitrogen and water addition are linked to plant growth patterns in a desert herbaceous community

Increases in nitrogen (N) deposition and variation in precipitation have been occurring in temperate deserts; however, little information is available regarding plant phenological responses to environmental cues and their relationships with plant growth pattern in desert ecosystems. In this study, plant phenology and growth of six annuals in response to N and water addition were monitored throughout two consecutive growing seasons in 2011 and 2012 in a temperate desert in northwestern China. The effects of N and water addition on reproductive phenology differed among plant species. N and water addition consistently advanced the flowering onset time and fruiting time of four spring ephemerals; however, their effects on two spring‐summer annuals were inconsistent, with advances being noted in one species and delays in another. N and water addition alone increased plant height, relative growth rate, leaf number, flower number, and individual biomass, while their combinative effects on plant growth and reproductive phenology were dependent on species. Multiple regression analysis showed that flowering onset time was negatively correlated with relative growth rate of two species, and negatively correlated with maximum plant height of the other four species. Our study demonstrates that phenological responses to increasing precipitation and N deposition varied in annuals with different life histories, whereby the effects of climate change on plant growth rate were related to reproductive phenology. Desert annuals that were able to accelerate growth rate under increasing soil resource availability tended to advance their flowering onset time to escape drought later in the growing season. This study promotes our understanding of the responses of temperate desert annuals to increasing precipitation and N deposition in this desert.     

Flowering phenology and reproductive success of native shrub Berberis darwinii Hook. along different light environments

Studies evaluating flowering phenology and reproductive success are necessary when we want to direct a domestication project in a species with a potential productive value. We studied flowering phenology and reproductive success of Berberis darwinii growing under different light conditions in its native distribution area in the Andean Patagonian forests of Argentina. We test the hypothesis that plants grown under conditions of high-light availability exhibit advanced phenology and higher reproductive success than those grown under conditions of lower light availability. Phenology and reproductive success were determined in three contrasting light conditions at two forest sites, which were, canopy, gap and forest edge. Plants did not bloom under the forest canopy. Flowering and fruiting period lengths were similar in both sites and light conditions of gap and forest edge during spring and summer. Although gap plants had more racemes per shoot, racemes of edge plants had more flowers, fruits and a higher proportion of flowers producing ripe fruit. We show that B. darwinii reproduction studied in the Andean Patagonian forests is conditioned by the canopy openness. Regarding reproductive success, edge plants invest less resources in flower production than gap plants to have similar fruit production.     

Toxin Production by Microcystis aeruginosa as a Function of Light in Continuous Cultures and Its Ecological Significance

The effects of light intensity and light quality on toxin production by Microcystis aeruginosa were examined in continuous cultures. Light intensity had a pronounced effect on toxicity and the toxin production rate. Toxicity and the toxin production rate increased with light intensity up to an intensity of about 40 microeinsteins m^-2 s^-1 and decreased at higher light intensities, while the ratio of toxin to protein was constant at intensities of more than 40 microeinsteins m^-2 s^-1. Light quality had only slight effects on toxicity. The results of our laboratory experiments were supported by the results of field work in which we examined toxin production at different depths in a lake. Our observations explain the mixed pattern of high and low toxicity found in a surface bloom of M. aeruginosa. Our findings also indicate that production of the peptide toxin can be uncoupled from general protein synthesis.     

杉木和木荷种子萌发及幼苗生长对光梯度的响应

光是影响种子萌发和幼苗生长的关键因素.为理解不同树种种子萌发及幼苗生长对光梯度变化的响应机制,本文研究了不同光照强度(分别为自然光强的100%、60%、40%、15%和5%)对杉木和木荷种子萌发及幼苗生长的影响,探讨了两树种种子萌发和幼苗生长对光照响应的差异性.结果表明: 光照强度对两树种的种子萌发和幼苗生长均具有显著影响. 随着光照强度的减弱, 杉木种子萌发率增大,萌发指数增大,木荷种子萌发率和萌发指数则先增大后减小,在40%光照强度下达到最大值.两树种幼苗存活率在全光照(100%光照)下均为0,在5%～60%光照处理下则随着光照强度的减弱而显著降低.两树种幼苗根长、地径和株高对光梯度变化的响应趋势一致,随着光照强度的减弱,根长显著减小,地径和株高则先增大后减小,在5%光照强度下达到最小.随着光照强度的减弱,杉木幼苗根、茎、叶及总生物量降低,木荷幼苗生物量积累在15%～60%光照强度下较高, 5%光照强度下最小,且相同光照强度下,木荷幼苗各部分生物量均大于杉木.两树种幼苗应对低光环境时,表现出较大的茎和叶的生物量分配比,而根生物量比和根冠比降低.表明杉木苗期生长不耐阴,需要相对较强的光照,而木荷苗期具有较强的耐阴性,对弱光环境的适应性更强,能够在郁闭的林冠下定植和正常生长.     

林下人参生理特性和生长与林内生态因子的关系

结合模拟试验,对林下人参的生理活动及生长过程与林内生态因子的关系进行 了观测研究．结果表明,林内光照、水分、温度等因子与林下人参生长的关系极为密切．一 般林内光照在中等条件下,即相对光照在１０～３５％左右．林分郁闭度约０．６～０．８,土壤含 水量在 ３５～４０％时人参生长最好;林下人参的物候进程及生长与温度的关系密切．林内 温度在５℃左右人参芽胞开始萌动,１５℃左右地上茎高生长进入速生期,６月上旬生长停 止．因此,人为调节各种生态因子在适宜的范围内有利于林下人参的生长．     

REPRODUCTIVE OUTPUT AND BIOMASS ALLOCATION IN SESBANIA EMERUS IN A TROPICAL SWAMP

This study examined the correlation of moisture, reproductive phenology, density of mature plants, and herbivory of apical meristems with the morphology and reproductive output of Sesbania emerus, an annual legume growing along a moisture gradient in a swamp in Guanacaste Province, Costa Rica. It also determined how biomass allocation varied and how it was related to reproductive output of plants growing along the moisture gradient within the swamp. Morphological changes included production of more stems and branches in response to herbivory, more and higher prop roots and more aerenchyma as water depth increased, and greater stem diameter in lower densities. Plant height varied greatly within a site, but not among habitats. Plants began to produce flowers and fruits later in wet sites than in dry sites. Reproductive output was generally more sensitive to environmental variables than was plant size. Fruit number and plant height were positively correlated for almost every treatment. Greater fruit and seed production were correlated with drier sites, earlier phenology, and lower density, but not with herbivory. Total biomass accumulation did not vary among moisture sites, but root production appeared to occur at the expense of reproductive output in the wetter sites. Plants in the wetter sites had both a greater percent and a greater absolute amount of biomass in roots, and a lower percent and a lower absolute amount of biomass in fruits and seeds than plants in drier sites. The root: shoot ratio was nearly five times higher in the wet than the dry site. Seed number per plant ranged from a mean of 6,800 at the wet site to a mean of 16,878 at the dry site. If this striking phenotypic variation in reproductive output and biomass accumulation has a genetic basis, the possibility of ecotypic differentiation exists in S. emerus.     

Effects of enhanced UV-B radiation on fitness of an alpine species Cerastium glomeratum Thuill

Aims Information about how species respond to extreme environments, such as high UV-B radiation, is very useful in estimating natural ecosystem structure and functions in alpine areas. Our aim is to examine the effect of enhanced UV-B radiation on the fitness of an alpine meadow annual species on Qinghai-Tibet Plateau.Methods Plants of Cerastium glomeratum Thuill. were exposed to ambient (control) or ambient plus supplemental UV-B radiation (enhanced), simulating a 9% ozone depletion over Gannan, China (102°53′E, 34°55′N, 2900 m in altitude), up to leaf senescence and fruit maturation. Plant height, flower phenology, biomass allocation and reproductive parameters of the species were measured.Important findings Plant height in C. glomeratum was reduced by enhanced UV-B radiation at early growth stages and compensated with ongoing development. Fruit biomass, aboveground biomass, total biomass and reproductive effort (fruit dry mass/aboveground biomass) were not affected by enhanced UV-B radiation, but a significant increase in root/shoot ratio was found. Enhanced UV-B radiation delayed onset of flowering by 1 day and shortened duration of flowering by 5 days in C. glomeratum. But because of the long period of flowering time (83–88 days), this did not make any significant effect on flower number, seed number, pollination success (number of seeds per fruit) or reproductive success (fruit to flower ratio) in C. glomeratum. Enhanced UV-B radiation had no effect on seed germination and seed mass either. And the high production and low germination rate of the seed might be the strategy of C. glomeratum to survive the extreme environments on alpine meadow. All these results showed that C. glomeratum was tolerant to enhanced UV-B radiation.     

Quantitative Determinations of the Effect of Excision on Transpiration

The temporary transpiration increase which normally occurs when a shoot or a part of a shoot is cut off in the air was studied qnantitatively in young wheat plants by the aid of the corona-hygrometer. The temporary transpiration increase can be characterized by the maximum increase in transpiration rate after the cutting, or by the total time of the temporary transpiration increase, or by the quantity of water given off by the shoot due to the temporary transpiration increase. The influences of the water vapour pressure, the speed of the air stream, and the light intensity on the temporary transpiration increase were determined. It is important to pay attention to the climate in the chamber where the shoot transpires. The maximum temporary transpiration increase was reduced more or less lineary with increasing water vaponr pressure of the air surrounding the shoot and increased with increasing speed of the air stream through the transpiration chamber. The reduction of the maximum temporary transpiration increase at higher light intensities was mainly due to the higher water vapour pressure in the chamber. The total time of the temporary transpiration increase was very little influenced by the water vapour pressure but was reduced more or less lineary with the logarithm of increasing light intensity. When the shoot was cut off in the water, there was normally no temporary transpiration increase. Only at low light intensities there could occur temporary transpiration increases similar to those found when the shoot was cut off in the air. Some hypotheses which could explain the temporary transpiration increase are discussed. The results in this investigation seem to favour the hypothesis that the temporary transpiration increase is due to a sudden reduced water transport up into the leaf, which can bring about a passive opening of the stomata.     

Production and rain use efficiency in short-grass steppe: grazing history,defoliation and water resource

Abstract. Grassland in the semiarid shortgrass steppe, subjected to 50 years of heavy, light, and no grazing intensity, was clipped to simulate the natural pattern and intensities of defoliation by cattle or not clipped. A level of water resource treatment was superimposed upon the grazing and clipping treatments. Half of the plots were supplemented with additional water to simulate a wet year and half were not supplemented in a year of average precipitation. All three treatments interactively determined above-ground production. Water treatment had the largest overall effect on above-ground production. Current-year defoliation had no direct significant effect on production, but mediated differences between both longterm grazing and watering treatments. Long-term ungrazed compared to grazed grassland was capable of responding to high amounts of precipitation, but was also most affected by low amounts of precipitation and, therefore, displayed greater variability in above-ground production and rain use efficiency. Only in the year of average precipitation, defoliation increased rain use efficiency in long-term lightly, but not heavily, grazed treatment. This suggests a water conservation mechanism of defoliation that is reduced with heavy grazing.     

Brushing effects on the growth and mechanical properties of Corispermum mongolicum vary with water regime

High water availability and mechanical stress can induce opposite responses in plants. In arid areas of Northern China the occurrence of high wind and high water availability tend to be negatively correlated. Since turgor pressure is a determinant of the mechanical stability of annuals, it is hypothesised that the effects of mechanical perturbation (MP) on annuals may depend on soil water availability. To test this proposal, we conducted an experiment in which a pioneering annual Corispermum mongolicum was subjected to two levels of MP and water supply, and then determined its growth and mechanical traits. Brushing had no effect on plant height and total biomass, but stimulated leaf and branch production. Water supply affected plant height, basal diameter, total biomass and stem rigidity, but not leaf and branch number, root/shoot ratio or flexibility. With high water availability, brushing stimulated the production of stiffer stems (thicker and with a higher Young's modulus) and more roots relative to shoot mass, but with low water availability MP induced the opposite response. This shows that both the degree and direction of plant responses to MP depend on the presence of other factors. We discuss how the interactive effects of MP and water availability on growth and mechanical properties may help C. mongolicum to establish in windy and arid environments.     

Changing water use and adaptive strategies along rainfall gradients in Mediterranean lupins

• There is growing interest in harnessing the genetic and adaptive diversity of crop wild relatives to improve drought resilience of elite cultivars. Rainfall gradients exert strong selection pressure on both natural and agricultural ecosystems. Understanding plant responses to these facilitates crop improvement.
• Wild and domesticated narrow‐leafed lupin (NLL) collected along Mediterranean terminal drought stress gradients was evaluated under contrasting reproductive phase water supply in controlled field, glasshouse and cabinet studies. Plant phenology, growth and productivity, water use and stress responses were measured over time.
• There is an integrated suite of adaptive changes along rainfall gradients in NLL. Low rainfall ecotypes flower earlier, accumulate lower seed numbers, biomass and leaf area, and have larger root:shoot ratios than high rainfall ecotypes. Water‐use is lower and stress onset slower in low compared to high rainfall ecotypes. Water‐use rates and ecotypic differences in stress response (Ψleaf decline, leaf loss) are lower in NLL than yellow lupin (YL). To mitigate the effects of profligate water use, high rainfall YL ecotypes maintain higher leaf water content over declining leaf water potential than low rainfall ecotypes. There is no evidence for such specific adaptation in NLL.
• The data suggests that appropriate phenology is the key adaptive trait to rainfall gradients in NLL because of the flow‐on effects on biomass production, fitness, transpiration and stress onset, and the lack of physiological adaptations as in YL. Accordingly, it is essential to match phenology with target environment in order to minimize risk and maximize yield potential.

     

光强对烟草幼苗形态和生理指标的影响

通过白纱布遮荫模拟不同光生境条件(透光率分别为100%、68.2%、35.4%和16.7%),研究了光强因子对烟草幼苗形态和生理指标的影响.结果表明:随相对光强的减弱,幼苗高度增加,茎粗、干鲜比、叶片厚度和单位叶面积质量均呈降低趋势,幼苗干物质积累减少,但其对叶数的影响不大.弱光条件下,叶片自由水、叶绿素、总氮和蛋白质含量增加,束缚水含量降低,叶绿素a/b值减小,转化酶活性降低;烟草幼苗根系相对不发达,根冠比和根生物量减小,根系活力降低.表明弱光条件不利于培育烟草壮苗,生产中应尽可能改善苗床的光照条件.     

Response of Sphagnum fuscum to water levels and CO2 concentration

Abstract

Sphagnum fuscum samples collected from an ombrotrophic bog were grown in a greenhouse at six water levels (0, 5, 10, 15, 25 and 30 cm) below the capitulum level and in four concentrations of CO₂ (350, 700, 1000 and 2000 ppm). The cores of S. fuscum were treated for 87 days and length increment was measured by the plastic strip method and by innate time markers. Water content of the shoot, dry mass of the capitulum, dry mass per unit length of stem and production of dry mass were measured at the end of the experiment.

The water content, capitulum dry mass, dry mass per unit length of stem, length increment and dry mass production differed markedly for S. fuscum grown in different water levels. With lower water levels, the water content of the shoot decreased and the dry mass of both the capitulum and unit length of stem increased. The total length increment was highest when the water level was at or near the capitulum level (0–10 cm). No clear trend in dry mass production on an areal basis could be found due to uncoupled responses in length increment and stem dry mass at the experimental water levels.

Neither capitulum dry mass nor dry mass per unit length of stem showed distinct trends in S. fuscum grown at different ambient CO₂ concentrations. Some increase in length increment and in dry mass production was detected at CO₂ concentrations above 350 ppm, but this effect appeared only at high water levels. It is suggested that the low response in length increment and production to CO₂ concentration resulted in part from insufficient moisture for photosynthesis at the lower water levels. Also, the possibility of increased nonstructural production is discussed.     

不同光照梯度的遮荫处理对绒毛番龙眼幼苗生长的影响

在不同光照梯度,即100%自然全光照(natural sunlight,NS)、37.3%NS、15.5%NS、4.2%NS、1.6%NS和0.6%NS的人工遮荫条件下,研究了西双版纳季节雨林冠层树种绒毛番龙眼(Pometia tomentosa)幼苗的早期生长和定居后的生长特点。结果表明,光照是影响幼苗生长的重要环境因子。生长早期的幼苗基径和复叶数随遮荫程度的增加而降低;主根长、根冠比、总干重和单株叶面积均以37.3%NS处理最大;比叶面积随遮荫程度的增加而增大,而相对生长率则降低;幼苗株高在0.6%NS下增长最快,表明种子中贮藏的营养物质对幼苗的早期生长可能具有重要作用。37.3%NS处理对定居后绒毛番龙眼幼苗的生长最有利,幼苗的株高、基径、复叶数、叶轴长、复叶最多小叶数、单株叶面积、相对生长率和净同化率均在37.3%NS处理下获得最大增长;幼苗总干重随光照强度的减弱而降低;比叶面积在15.5%NS处理时最大。幼苗比叶面积和根冠比在生长过程中的波动可能是光照和土壤水分共同作用的结果。     

A comparison of phenotypic plasticity in the native dandelion Taraxacum ceratophorum and its invasive congener T. officinale

We compared plastic responses to variation in the light environment for sympatric populations of native and exotic dandelion species, Taraxacum ceratophorum and Taraxacum officinale. Plasticity in leaf size, inflorescence height, reproductive phenology and dispersal-related traits were measured under experimentally altered light quality (red : far-red light ratio, R : FR) and light intensity (photosynthetically active radiation, PAR). To test whether differences in means and reaction norms of dispersal-related traits between species affected colonization potential, we created seed-dispersal models based on seed-fall rate and release height. Differences in plasticity between species were not systematic, but varied in direction and magnitude among traits. Taraxacum officinale produced larger leaves that exhibited greater plasticity in size under variable light intensity than T. ceratophorum. Plasticity in scape length at flowering occurred in relation to R : FR ratio in both species, but tended to be greater in T. ceratophorum. Seed-bearing scapes of T. officinale were taller and more canalized in height across light regimes than scapes of T. ceratophorum. Seeds of T. officinale were smaller than seeds of T. ceratophorum. Models predict greater dispersal in T. officinale within open and vegetated habitats. In contrast to the idea that plasticity promotes invasiveness, results suggest that the lack of plasticity in dispersal-related traits enhances the colonization potential of T. officinale.