光和基质对菹草石芽萌发、幼苗生长及叶片光合效率的影响

通过室内模拟试验,研究了基质和光照对菹草石芽萌发、幼苗生长以及不同光照对菹草生长后期叶片光合效率的影响.结果表明,在光照和缺乏基质的条件下,菹草石芽的萌发率和出苗率提高.基质的存在促进了根的生长,而光对根的生长并未起到促进作用.在无光条件下, 菹草幼苗节间长度明显大于有光处理.在暗处理中, 菹草叶片的质膜透性显著增加.在有光照条件下,有无基质对菹草幼苗叶片叶绿素a(Chla)、叶绿素b(Chlb)以及Chla/Chlb比值的影响为Chla、Chlb的含量增高,Chla/Chlb比值在3.5上下波动;Chla/Chlb最大值和最小值在有基质时分别为4.4和2.8,无基质时为4.2和2.7.但对幼苗处理40 d时,暗处理的叶片质膜透性与有光有基质、有光无基质之间差异极显著(P＜0.01).不同光照处理(自然光、50%自然光、20%自然光和10%自然光)的光合特性差异比较结果表明,在菹草生长后期,在自然光下菹草叶片的F_v/F_m和F_v/F_o的比值与其它3个遮光处理相比存在显著差异(P＜0.05),而在3个遮光处理之间差异不显著.进一步比较F_v/F_m、F_v/F_o、ETR、qP、qN和ΦPSⅡ等荧光参数值的结果显示,在生长的后期,一定程度的弱光会起到促进菹草的光合效率、延缓菹草衰老的作用.     

Effects of changes in leaf height and shoot density on the abundance of two fishes,Rudarius ercodes andAcentrogobius pflaumii, in azostera bed

The effects of changes in the structural complexity of a seagrass habitat on the densities of filefish (Rudarius ercodes) and streaked gobies (Acentrogobius pflaumii), were investigated by conducting a 9 month field experiment in aZostera marina bed at Moroiso Bay, Aburatsubo, central Japan. The experimental design included a control and 7 treatments where leaf height or shoot densities were reduced. During the period of high density of filefish, the species was more abundant in quadrats with longer leaves and denser shoots, but this tendency was not observed during the period of low density. Filefish did not frequent the quadrat cleared of seagrass or the area of sandy substratum surrounding the experimental seagrass bed at any time. The abundance of streaked gobies did not differ significantly among 8 experimental quadrats, although the species seldom appeared over the surrounding sandy substratum. The results suggested that filefish, unlike gobies, were attracted to factors associated with theZostera leaves, such as epiphytic prey and/or the complex living space.     

Responses of photosynthesis,leaf conductance and growth to different salinities in three coastal dune plants

The effects of soil-water salinity on growth and photosynthesis of three coastal dune plants were examined by salt-treatment in order to clarify the causal relationship between salinity and plant distribution in a dune habitat. Plants were cultivated hydroponically at three salinity levels: 0, 10 and 100 mM NaCl. With the 100 mM salt treatment,Calystegia soldanella (C₃ species) had the highest relative growth rate (RGR) (0.085 g g⁻¹ d⁻¹), followed byCarex kobomugi (C₃) (0.066), andIschaemum anthephoroides (C₄) (0.060). This order coincides with the distribution pattern of the three species on coastal dunes;Calystegia soldanella is generally distributed in more seaward areas whereasI. anthephoroides occurs further inland. The order of RGR was determined exclusively by leaf area ratio (LAR) among the three species. Due to its C₄ pathway,I. anthephoroides had higher net photosynthetic rate (Pn) and net assimilation rate (NAR) than the two C₃ plants at all NaCl concentrations, despite its low RGR. This apparent discrepancy is explainable by differences of LAR among the three species; LAR ofI. anthephoroides was lowest, and about half that ofCalystegia soldanella. These results suggest that LAR is one of the main determinants of salt tolerance based on RGR, whereas Pn or NAR may not be significant. This article is dedicated to Professor Hideo Iwaki, University of Tsukuba, in appreciation of the sincere encouragement he has given to the authors.     

Effects of changes in seagrass shoot density and leaf height on the abundance of juveniles of Acentrogobius pflaumii in a Zostera marina bed

The effects of changes in the structural complexity of a seagrass (Zostera marina) habitat on the density of juveniles of the streaked goby, Acentrogobius pflaumii, were investigated by field experimentation at Moroiso Bay, Miura Peninsula, Japan. The experimental design, which included seven treatments plus a control, included reduction of seagrass shoot densities and leaf heights as well as complete removal of seagrass. Throughout the study period, juvenile densities remained similar among the experimental quadrats, including the completely cleared quadrat. On the other hand, juveniles did not appear over the bare sandy substratum surrounding the experimental seagrass bed. Within the bed, prey densities were high, being similar among the experimental quadrats, whereas prey were relatively scarce over the surrounding bare substratum. This result suggested that streaked goby juveniles were not attracted to the structure of the Zostera bed per se and that their distribution patterns may be determined by other factors, such as prey availability. Received: September 25, 2000 / Revised: November 22, 2000 / Accepted: January 16, 2001     

Disentangling the link between leaf photosynthesis and turgor in fruit growth

Despite the importance of understanding plant growth, the mechanisms underlying how plant and fruit growth declines during drought remain poorly understood. Specifically, it remains unresolved whether carbon or water factors are responsible for limiting growth as drought progresses. We examine questions regarding the relative importance of water and carbon to fruit growth depending on the water deficit level and the fruit growth stage by measuring fruit diameter, leaf photosynthesis, and a proxy of cell turgor in olive (Olea europaea). Flow cytometry was also applied to determine the fruit cell division stage. We found that photosynthesis and turgor were related to fruit growth; specifically, the relative importance of photosynthesis was higher during periods of more intense cell division, while turgor had higher relative importance in periods where cell division comes close to ceasing and fruit growth is dependent mainly on cell expansion. This pattern was found regardless of the water deficit level, although turgor and growth ceased at more similar values of leaf water potential than photosynthesis. Cell division occurred even when fruit growth seemed to stop under water deficit conditions, which likely helped fruits to grow disproportionately when trees were hydrated again, compensating for periods with low turgor. As a result, the final fruit size was not severely penalized. We conclude that carbon and water processes are able to explain fruit growth, with importance placed on the combination of cell division and expansion. However, the major limitation to growth is turgor, which adds evidence to the sink limitation hypothesis.     

Effect of Pb pollution on the growth,biomass allocation and photosynthesis of Phragmites australis in flood and drought environment

Aims Reed (Phragmites australis) is a typical perennial rhizomatic plant with extensive tolerance to environmental stress. In order to better understand the adaptation and tolerance of reeds subjected to heavy metal pollution in different levels of water, we conducted a study on the effects of Pb pollution on growth, biomass and photosynthesis of reeds in flood and drought environment. This research would provide theoretical basis for application of reeds in wetland restoration and remediation.     

淹水和干旱生境下铅对芦苇生长、生物量分配和光合作用的影响

芦苇(Phragmites australis)作为典型的根茎型多年生湿地植物, 具有广泛的环境耐受性。该研究采用盆栽实验, 采取裂区实验设计, 水分处理为主区, 包括淹水和干旱两个水平, 铅(Pb)为副区, 包括0、500、1500、3β000、4β500 mg·kg^-1 5个水平, 共10个处理, 每个处理12个重复, 研究淹水和干旱条件下Pb污染对芦苇生长、生物量分配及光合作用的影响, 以期明确不同生境下芦苇适应或忍耐重金属污染而采取的策略, 为芦苇应用于湿地恢复和污染修复提供理论依据。结果表明, 在淹水处理中, Pb显著抑制地下芽形成和根茎生长, 但对子株数没有影响; 与母株相比子株具有高的日生长速率、光合速率和生物量(母株的3-7倍)。在干旱环境中, Pb显著抑制根、地下芽和根茎生长, 母株和子株生物量积累及光合作用, 且这些指标均小于淹水处理的。无论在淹水还是干旱环境中, 芦苇体内绝大部分Pb积累在根中, 根茎和子株中Pb含量较少, 被转运至母株中的Pb大约是子株的3倍。淹水条件下子株体内Pb含量小于干旱处理的。结果表明, 干旱和Pb的协同作用显著抑制芦苇生长、生物量积累和光合作用, 可能导致子株生产力和种群密度减小甚至种群衰退。但淹水芦苇能够采取相应的Pb分配策略减缓Pb污染对芦苇生长、生理和繁殖的负面影响, 有利于芦苇种群的繁衍和稳定。     

Effect of zooplankton availability on the rates of photosynthesis, and tissue and skeletal growth in the scleractinian coral Stylophora pistillata

This work investigated the effect of light and feeding on tissue composition as well as on rates of photosynthesis and calcification in the zooxanthellae (zoox) scleractinian coral, Stylophora pistillata. Microcolonies were maintained at three different light levels (80, 200, 300 μmol m⁻² s⁻¹) and subjected to two feeding regimes (starved and fed) over 9 weeks. Corals were fed both natural plankton and Artemia salina nauplii four times a weeks and samplings were made after 2, 5, and 9 weeks. Results confirmed that feeding enhances coral growth rate and increases both the dark and light calcification rates. These rates were 50-75% higher in fed corals (FC; 60±20 and 200±40 nmol Ca²⁺ cm⁻² h⁻¹ for dark and light calcification, respectively) compared to control corals (CC; 30±9 and 124±23 nmol Ca²⁺ cm⁻² h⁻¹). The dark calcification rates, however, were four times lower than the rates of light calcification (independent of trophic status). After 5 weeks, chlorophyll a (chl-a) concentrations were four to seven times higher in fed corals (7-21 μg cm⁻²) than in control corals (2-5 μg cm⁻²). The amount of protein was also significantly higher in fed corals (2.11-2.50 mg cm⁻²) than in control corals (1.08-1.52 mg cm⁻²). Rates of photosynthesis in fed corals were 2-10 times higher (1.24±0.75 μmol O₂ h⁻¹ cm⁻²) than those measured in control corals (0.20±0.08 μmol O₂ h⁻¹ cm⁻²).     

三江平原北部生态系统服务价值的时空演变

以三江平原北部地区2市5县为研究区,采用生态系统服务价值评估方法对1954—2009年间三江平原北部地区生态系统服务价值进行估算,以期全面分析土地生态系统服务价值随时空变化的特点。结果表明:(1)1954—2009年间三江平原北部地区的不同土地利用类型面积变化显著,农田变化速度最快,其次为湿地,人口数量的增加及保证粮食增产是土地利用变化的主要驱动力。(2)1954—2009年三江平原北部地区生态系统服务价值总量逐渐减少,共减少779.51亿元。长期的土地垦殖是三江平原北部地区生态系统服务价值减少的主要驱动因素。(3)就各土地利用类型生态系统服务价值而言,55年间除农田生态系统和水域生态系统生态服务价值是增加外,其余各生态系统服务价值均在减少。湿地生态系统服务价值减少值最大,其次为林地生态系统服务价值。各项生态系统服务功能除与农田相关的食物生产在增加,其余也均呈减少趋势。(4)不同地区单位面积生态系统服务价值损失量也不相同,湿地、林地面积比重下降幅度大、且农田面积比重上升幅度大的区域,其单位面积生态系统服务价值损失量也较大。     

放牧格局和生境资源对矮嵩草（Kobresia humilis）分株生物量分配和补偿性生长的影响

为研究密集型克隆植物对放牧扰动和生境资源变化的生物量分配和补偿生长响应特性,验证克隆植物的觅食模型和3个有关植物个体补偿反应的假说(①放牧优化假说,grazing optimization hypothesis,GOH;②反应连续谱假说,continuum of responses hypothesis,CRH;③增长率模型,growth rate model,GRM),在具有不同放牧利用格局和土壤养分水平的高寒矮嵩草草甸(Ⅰ.畜圈草地:重度放牧、资源丰富;Ⅱ.牧道草地:中度放牧、资源贫乏;Ⅲ.封育草地:不放牧、资源贫乏)中通过设置扣笼/无扣笼样方对其建群种矮嵩草(Kobresia humilis)进行了研究.结果表明不论当年解除家畜放牧与否,春季采摘率越高(畜圈草地),分株生物量向生长的投入越少,向贮藏器官的投入越多.繁殖分配在中度采摘下最高(牧道草地),扣笼内外分株各部分的生物量分配无差异.矮嵩草分株在中度采摘×资源贫乏条件下产生了超补偿响应,在重度采摘×资源丰富条件下为等量补偿,重度采摘导致分株密度显著减少.生物量分配格局与觅食模型的预测不符.补偿生长响应特性证实了GOH和GRM的预测,但与CRH的预测不符.这说明在研究地区放牧扰动格局对克隆植物矮嵩草分株的生物量分配和补偿生长具有重要影响,适度放牧利用更利于引起超补偿,而重度利用可能会对该种群的长期保持产生不利影响.     

Effect of jasmonic acid on the stomatal and nonstomatal limitation of leaf photosynthesis in barley leaves

The effect of long-term (7 days) and shortterm (up to 2 h) treatment of barley plants with jasmonic acid (JA) on the components contributing to stomatal and nonstomatal limitation of photosynthesis was studied. Net CO₂ assimilation rate (A) responses to intercellular CO₂ concentration (C _i ), i.e., A/C _i curves, were used to assess the photosynthetic ability. Long-term treatment of barley plants with JA led to a noticeable decrease in both the initial slope of the A/C _i curves and the maximum A at saturating C _i . The proportion of stomatal and nonstomatal factors in limitation of photosynthesis depended on the applied JA concentration. Short-term treatment with JA affected neither the stomatal conductivity for CO₂ nor the rate of photosynthetic CO₂ assimilation. We suggest that JA may affect photosynthesis indirectly, either as a stress-modulating substance, or through the alterations in gene expression.     

Specific leaf area relates to the differences in leaf construction cost,photosynthesis, nitrogen allocation,and use efficiencies between invasive and noninvasive alien congeners

Comparisons between invasive and native species may not characterize the traits of invasive species, as native species might be invasive elsewhere if they were introduced. In this study, invasive Oxalis corymbosa and Peperomia pellucida were compared with their respective noninvasive alien congeners. We hypothesized that the invasive species have higher specific leaf (SLA) than their respective noninvasive alien congeners, and analyzed the physiological and ecological consequences of the higher SLA. Higher SLA was indeed the most important trait for the two invaders, which was associated with their lower leaf construction cost, higher nitrogen (N) allocation to photosynthesis and photosynthetic N use efficiency (PNUE). The higher N allocation to photosynthesis of the invaders in turn increased their PNUE, N content in photosynthesis, biochemical capacity for photosynthesis, and therefore light-saturated photosynthetic rate. The above resource capture-, use- and growth-related traits may facilitate the two invaders' invasion, while further comparative studies on a wider range of invasive and noninvasive congeners are needed to understand the generality of this pattern and to fully assess the competitive advantages afforded by these traits.     

The influence of salinity on growth,biomass production and photosynthesis of Eucalyptus camaldulensis Dehnh. and Dalbergia sissoo Roxb. seedlings

The influence of NaCl salinity on growth, dry-matter production and leaf photosynthesis of seedlings of Eucalyptus camaldulensis Dehnh. and Dalbergia sissoo Roxb. was studied by imposing 4 levels (40, 80, 120 and 160 mM) of NaCl in pot culture. Salinity up to 160 mM did not affect plant survival, but did affect plant growth and dry-matter production depending upon the species and salt concentration. NaCl reduced leaf number and dry-weight of all the plant components, but increased stem dry-weight, especially in E. camaldulensis. Salinization also stimulated total dry-matter production at all the salinity levels in E. camaldulensis but only at 40 mM in D. sissoo. The two species varied in protein and chlorophyll concentration and in leaf photosynthetic rate. Protein and chlorophyll concentration of the plants fell at all the levels of NaCl, except at 40 mM, where stimulation in the photosynthetic carbon assimilation of the plants occurred. However, no distinct relationship between leaf photosynthetic rate and dry-matter production was found. The study indicated that low salt concentrations generally stimulated growth, biomass production and rate of photosynthesis in both the species, and E. camaldulensis appeared more NaCl salt-tolerant than D. sissoo.     

Soybean leaf photosynthesis in relation to maturity classification and stage of growth

Leaf photosynthetic rates were measured on field-grown soybeans during the 1980 season. Comparisons were made between different cultivars and isolines representative of maturity groups I–IV. Mature, fully expanded leaves at different nodes on the plant were measured in high light to determine which had the highest potential photosynthetic rates at any one time. Successive leaves during the growing season had maximum rates which increased from about 22 mol CO₂ m^-2 s^-1 on 25 June to a peak of 30–44 mol CO₂ m^-2 s^-1 in early August.The persistency and eventual decline in the maximum rate was associated with the maturity group and related dates of flowering, pod fill and onset of senescence. Early maturing cultivars (groups I and II) had higher peak rates (38–44 mol CO₂ m^-2 s^-1) than later maturing cultivars (30–35 mol CO₂ m^-2 s^-1, groups III and IV). However, the photosynthetic rates of early maturing cultivars declined rapidly after attaining their peak, whereas the leaves of later maturing cultivars maintained their photosynthetic activity for much longer.     

Temporal separation of nitrogen fixation and photosynthesis in the filamentous,non-heterocystous cyanobacterium Oscillatoria sp.

When growing in laternating light-dark cycles, nitrogenase activity (acetylene reduction) in the filamentous, non-heterocystous cyanobacterium Oscillatoria sp. strain 23 (Oldenburg) is predominantly present during the dark period. Dark respiration followed the same pattern as nitrogenase. Maximum activities of nitrogenase and respiration appeared at the same time and were 3.6 mol C₂H₄ and 1.4 mg O₂ mg Chl a ^-1·h^-1, respectively. Cultures, adapted to light-dark cycles, but transferred to continuous light, retained their reciprocal rhythm of oxygenic photosynthesis and nitrogen fixation. Moreover, even in the light, oxygen uptake was observed at the same rate as in the dark. Oxygen uptake and nitrogenase activity coincided. However, nitrogenase activity in the light was 6 times as high (22 mol C₂H₄ mg Chl a ^-1·h^-1) as compared to the dark activity. Although some overlap was observed in which both oxygen evolution and nitrogenase activity occurred simultaneously, it was concluded that in Oscillatoria nitrogen fixation and photosynthesis are separated temporary. If present, light covered the energy demand of nitrogenase and respiration very probably fulfilled a protective function.     

Boron deficiency decreases growth and photosynthesis, and increases starch and hexoses in leaves of citrus seedlings

Seedlings of sweet orange (Citrus sinensis) were fertilized for 14 weeks with boron (B)-free or B-sufficient (2.5 or 10muM H(3)BO(3)) nutrient solution every other day. Boron deficiency resulted in an overall inhibition of plant growth, with a reduction in root, stem and leaf dry weight (DW). Boron-starved leaves showed decreased CO(2) assimilation and stomatal conductance, but increased intercellular CO(2) concentrations. Activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), NADP-glyceraldehyde-3-phosphate dehydrogenase (NADP-GAPDH) and stromal fructose-1,6-bisphosphatase (FBPase) were lower in B-deficient leaves than in controls. Contents of glucose, fructose and starch were increased in B-deficient leaves while sucrose was decreased. Boron-deficient leaves displayed higher or similar superoxide dismutase (SOD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR) and glutathione reductase (GR) activities, while dehydroascorbate reductase (DHAR) and catalase (CAT) activities were lower. Expressed on a leaf area or protein basis, B-deficient leaves showed a higher ascorbate (AsA) concentration, but a similar AsA concentration on a DW basis. For reduced glutathione (GSH), we found a similar GSH concentration on a leaf area or protein basis and an even lower content on a DW basis. Superoxide anion (O(2)(-)) generation, malondialdehyde (MDA) concentration and electrolyte leakage were higher in B-deficient than in control leaves. In conclusion, CO(2) assimilation may be feedback-regulated by the excessive accumulation of starch and hexoses in B-deficient leaves via direct interference with chloroplast function and/or indirect repression of photosynthetic enzymes. Although B-deficient leaves remain high in activity of antioxidant enzymes, their antioxidant system as a whole does not provide sufficient protection from oxidative damage.     

Seasonal changes in temperature and nutrient control of photosynthesis, respiration and growth of natural phytoplankton communities

1. To investigate the influence of elevated temperatures and nutrients on photosynthesis, respiration and growth of natural phytoplankton assemblages, water was collected from a eutrophic lake in spring, summer, autumn, winter and the following spring and exposed to ambient temperature and ambient +2, +4 and +6 °C for 2 weeks with and without addition of extra inorganic nutrients. 2. Rates of photosynthesis, respiration and growth generally increased with temperature, but this effect was strongly enhanced by high nutrient availability, and therefore was most evident for nutrient amended cultures in seasons of low ambient nutrient availability. 3. Temperature stimulation of growth and metabolism was higher at low than high ambient temperature showing that long‐term temperature acclimation of the phytoplankton community before the experiments was of great importance for the measured rates. 4. Although we found distinct responses to relatively small temperature increases, the interaction between nutrient availability, time of the year and, thus, ambient temperature was responsible for most of the observed variability in phytoplankton growth, photosynthesis and respiration. 5. Although an increase in global temperature will influence production and degradation of organic material in lakes, the documented importance of ambient temperatures and nutrient conditions suggests that effects will be most pronounced during winter and early spring, while the remaining part of the growth season will be practically unaffected by increasing temperatures.     

Interactive effects of light,leaf temperature,CO2 and O2 on photosynthesis in soybean

A biochemical model of C ₃photosynthesis has been developed by G.D. Farquhar et al. (1980, Planta 149, 78–90) based on Michaelis-Menten kinetics of ribulose-1,5-bisphosphate (RuBP) carboxylase-oxygenase, with a potential RuBP limitation imposed via the Calvin cycle and rates of electron transport. The model presented here is slightly modified so that parameters may be estimated from whole-leaf gas-exchange measurements. Carbon-dioxide response curves of net photosynthesis obtained using soybean plants (Glycine max (L.) Merr.) at four partial pressures of oxygen and five leaf temperatures are presented, and a method for estimating the kinetic parameters of RuBP carboxylase-oxygenase, as manifested in vivo, is discussed. The kinetic parameters so obtained compare well with kinetic parameters obtained in vitro, and the model fits to the measured data give r ²values ranging from 0.87 to 0.98. In addition, equations developed by J.D. Tenhunen et al. (1976, Oecologia 26, 89–100, 101–109) to describe the light and temperature responses of measured CO₂-saturated photosynthetic rates are applied to data collected on soybean. Combining these equations with those describing the kinetics of RuBP carboxylase-oxygenase allows one to model successfully the interactive effects of incident irradiance, leaf temperature, CO₂ and O₂ on whole-leaf photosynthesis. This analytical model may become a useful tool for plant ecologists interested in comparing photosynthetic responses of different C₃ plants or of a single species grown in contrasting environments.Abbreviations PCO photorespiratory carbon oxidation - PCR photosynthetic carbon reduction - PPFD photosynthetic photon-flux density - RuBP ribulose bisphosphate     

Salt-induced modulation in growth,photosynthesis and antioxidant system in two varieties of Brassica juncea

The present study was carried out to examine salt-induced modulation in growth, photosynthetic characteristics and antioxidant system in two cultivars of Brassica juncea Czern and Coss varieties (Varuna and RH-30). The surface sterilized seeds of these varieties were sown in the soil amended with different levels (2.8, 4.2 or 5.6 dsm⁻¹) of sodium chloride under a simple randomized block design. The salt treatment significantly decreased growth, net photosynthetic rate and its related attributes, chlorophyll fluorescence, SPAD value of chlorophyll, leaf carbonic anhydrase activity and leaf water potential, whereas electrolyte leakage, proline content, and activity of catalase, peroxidase and superoxide dismutase enzymes increased in both the varieties at 30 d stage of growth. The variety Varuna was found more resistant than RH-30 to the salt stress and possessed higher values for growth, photosynthetic attributes and antioxidant enzymes. Out of the graded concentrations (2.8, 4.2 or 5.6 dsm⁻¹) of sodium chloride, 2.8 sm⁻¹ was least toxic and 5.6 dsm⁻¹ was most harmful. The variation in the responses of these two varieties to salt stress is attributed to their differential photosynthetic traits, SPAD chlorophyll value and antioxidant capacity, which can be used as potential markers for screening mustard plants for salt tolerance.