Photosynthetic Light Response Curves Research Articles

Modification of a photosynthetic light-response (PLR) model for modeling the vertical gradient in the response of crown PLR curves

The photosynthetic light-response (PLR) curve is a mathematical description of a single biochemical process that has been widely applied in many ecophysiological models. For trees, the heterogeneity of PLR curves within the crown is significant but rarely modeled by mathematical techniques. This paper establishes a modified model for estimating crown PLR curves based on PLR functions by linking the parameters of the PLR functions to leaf nitrogen (N), specific leaf area (SLA), and relative depth into the crown (RDINC). The modified models were assessed by considering the goodness of fit (adjusted coefficient of determination, [Formula: see text]; root mean square error, RMSE; and Akaike information criterion, AIC) and model structure. Significant correlations were observed between the parameters of PLR functions and N, SLA, and RDINC. The optimal modified PLR model, by linking RDINC into a modified Mitscherlich function, fit well due to its simple and easily understood structure. Therefore, it is feasible to simultaneously estimate the multilayered and varied PLR curves of the tree crown.

A general non-rectangular hyperbola equation for photosynthetic light response curve of rice at various leaf ages

Photosynthetic light response (PLR) curves of leaves are usually fitted by non-rectangular hyperbola (NRH) equation, and those fitted NRH parameters may change with leaf aging. The objectives of this study were 1) to reveal the response of NRH parameters of rice leaves, light-saturated net photosynthetic rate (Pnmax), quantum yield of assimilation (φ), dark respiration rate (Rd) and convexity of the curve (k), to leaf age; and 2) to improve the performance of NRH equation in simulating the PLR curves for leaves at various ages. The PLR for rice leaves at ages of 3–53 days were measured, and the general NRH equation was developed by incorporating the relationship between NRH parameters and leaf age into the NRH equation. The results showed that the NRH parameters of Pnmax, φ and Rd increased rapidly to maximum at approximately 10 days and then declined linearly toward the age of 53 days. However, the value of k was not sensitive to leaf age. The general NRH equation can be used to simulate leaf PLR continuously along with leaf aging.

Physiological and growth strategies of two Cariniana species in response to contrasting light availability

Cariniana legalis and C. estrellensis are tropical emergent trees of the Lecythidaceae family that occur naturally in different forest ecosystems and belong to different ecological groups. With the aim of providing information to better manage these two congeneric Cariniana species in secondary forest enrichment plantations, an experiment was conducted using potted plants for comparing the physiological and growth responses of young C. legalis and C. estrellensis plants under contrasting light radiation availabilities. Considering that these two congeneric species occur naturally in different forest ecosystems and belong to different ecological groups, we tested the hypothesis that young plants of C. legalis have more plastic responses of photosynthetic light response curves, anthocyanin content, growth and biomass allocation to contrasting light environments than C. estrellensis. Plants were grown for 105 days under three light conditions (26, 10 and 1 mol photons m−2 day-1), simulating the daily total photosynthetic photon flux density (PPFD) in large and small canopy gaps and in the forest understory, respectively. The photosynthetic responses to contrasting light availabilities were very similar for both species. Higher values for anthocyanin reflectance index (ARI), leaf mass per area (LMA), and changes in biomass allocation indicate that C. legalis has a greater capacity for acclimation to contrasting light environments than did C. estrellensis. In addition, a greater number of smaller leaves in C. legalis could be an advantage in the understory of forests subjected to constant changes in canopy openness through the opening and closing of small- and medium-sized canopy gaps. From a practical point of view, seedlings of C. estrellensis should be planted in more open forests with less dynamic changes in canopy gaps, and seedlings of C. legalis should be planted in forests with more fluctuations in the opening and closing of small and large canopy gaps.

Trait acclimation of the clonal fern Selliguea griffithiana to forest epiphytic and terrestrial habitats

AbstractAlthough epiphytic habitats are more stressful and heterogeneous than terrestrial habitats, how facultative epiphytes acclimate to such contrasting environments has been poorly understood. Our study focused on the variation of functional traits between epiphytic and terrestrial individuals of Selliguea griffithiana, and provided considerable functional acclimation of this species to such contrasting environments. We sampled ramets of S. griffithiana from epiphytic and terrestrial habitats of a subtropical montane moist forest, SW China. Morphological and anatomical traits, photosynthesis, biomass and ramet density of S. griffithiana were measured and it was found that these traits differed significantly between the two habitats. Frond length, stipe length, spacer length (interramet distance), stomatal density, vein density, maximal chlorophyll fluorescence and relative chlorophyll content of fronds, and biomass per ramet were all lower in epiphytic habitat than those in terrestrial habitat, whereas frond thickness and ramet density were higher in the former. Photosynthetic light–response curves revealed a higher carbon assimilation capability of individuals in terrestrial habitat than in epiphytic habitat, whereas cumulative water loss curves showed a lower water loss rate in the latter. The findings demonstrate acclimation of S. griffithiana to both habitats, that is, epiphytic ramets can mitigate water scarcity at some cost of a reduced photosynthetic capacity, whereas terrestrial ramets can afford to improve the light capture to a higher photosynthetic capacity without any water stresses.

The effects of Solidago canadensis water extracts on maize seedling growth in association with the biomass allocation pattern.

BackgroundSolidago canadensis L. is an aggressive exotic plant species in China that has potential allelopathic effects on competing plant species. Effects of hormesis are frequently observed in studies of allelopathy; however, the mechanisms of such effects need to be elucidated. Allelopathic compounds may affect the growth of recipient plants via alteration of biomass allocation patterns or photosynthetic capacity. The aim of this study was to determine how water extracts from S. canadensis affected the shoot and root growth of recipient plants and whether the underlying mechanism was related to the biomass allocation pattern or photosynthetic gas exchange capacity.MethodsThe water extracts from S. canadensis shoots at 12 different concentrations in the range of 0–0.25 g/ml were applied thrice in 9 days to maize seedlings cultivated in silica sand. The growth (shoot height, leaf length and area and root length) and biomass accumulation and allocation (specific leaf area (SLA), leaf area ratio (LAR) and leaf mass ratio (LMR)) were compared among maize seedlings exposed to different treatment concentrations. Gas exchange (photosynthetic light response curve) was measured and compared among maize seedlings exposed to three concentrations of water extract (0, 0.0125 and 0.2 g/ml) before and after the first application, and seedling growth was measured after the third and final application.ResultsThe growth of seedlings (shoot height, leaf length and area and root length) was promoted at concentrations below 0.125 g/ml and inhibited at concentrations above this level (P < 0.05). The pattern of change in biomass accumulation and allocation was similar to that of shoot growth, but biomass accumulation and allocation was not significantly affected by the water extract treatments (P > 0.05). The water extract treatments did not significantly affect the photosynthetic capacity (P > 0.05), but the dark respiration rate was higher in the low-dose treatment than that in the high-dose treatment. Shoot height was positively correlated with the biomass allocation indicators SLA and LAR (P < 0.05) but not with LMR (P > 0.05).ConclusionsThe results suggested that the effects of the water extracts from S. canadensis were highly dependent on the concentration, with the growth of maize seedlings promoted at low concentrations of water extracts. The effects of the water extracts on the growth of maize seedlings were mainly due to the effects on the LAR, the allocation to leaf area growth, whereas the effects of the water extracts on leaf gas exchange capacity cannot explain variation of seedling growth. Thus, the stimulation of plant growth was very likely due to increased biomass allocation towards the shoot.

Effects of Straw Mulching and Tillage Measures on the Photosynthetic Characteristics of Maize Leaves

Abstract. This study investigated the response mechanisms of maize leaf photosynthetic characteristics to straw mulching and tillage measures in the black soil region of northeast China. Five treatments were established based on tillage and the average straw mulch yield from prior years (6500 kg ha-1): conventional tillage with no straw mulching (CK), conventional tillage with 1.0-fold (6500 kg ha-1) mulching (CM1), no tillage with 0.5-fold (3250 kg ha-1) mulching (NM0.5), no tillage with 1.0-fold (6500 kg ha-1) mulching (NM1), and no tillage with 1.5-fold (9750 kg ha-1) mulching (NM1.5). The net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, and light response curves of maize leaves were determined and compared between the treatments with different straw mulching amounts and farming methods and between different growth stages. The photosynthetic capacity of maize leaves was greater under NM1.5 than under the other treatments except at the V6 growth stage, and the increase in yield was the most obvious effect. The photosynthetic capacity of maize leaves can be improved by increasing the quantity of straw mulch. The photosynthesis of maize was affected by nonstomatal factors at different growth stages, and straw mulching reduced the negative effects of nonstomatal factors on the photosynthesis of maize leaves. Based on a light response model of the photosynthetic rate, the maximum net photosynthetic rate, light saturation point, and apparent quantum efficiency increased as the straw mulch quantity increased, and the magnitude of the increase was greatest between the 1.0-fold and 0.5-fold straw mulching treatments. This finding indicated that straw mulching can increase the adaptability of maize to strong light and improve the efficiency of maize under weak light; moreover, the NM1.5 treatment led to the greatest improvement in the light response characteristics of maize leaves. Keywords: Photosynthetic characteristic, Photosynthetic light response curve, Straw mulching, Tillage measure.

Еxperimental test of net photosynthetic light-response curves in estimating of photosynthetic activity by the example of ornamental plants

Еxperimental test of net photosynthetic light-response curves in estimating of photosynthetic activity by the example of ornamental plants

Modeling net CO2 assimilation (AN) within the crown of young planted Larix olgensis trees

Net CO2 assimilation (AN) is an important physiological indicator that reflects the photosynthetic capacity. The seasonal and spatial variations of AN play an important role in carbon uptake simulations, especially for trees. To gain a clearer understanding of the state of the branch carbon balance, it is necessary to more carefully evaluate the dynamic variation of AN over different gradients in the crown during the growing season. Gas exchange, leaf temperature (Tleaf), vapor pressure deficit (VPD), leaf mass per area (LMA), and relative depth into crown (RDINC) were measured throughout the growing season of planted Larix olgensis A. Henry trees. A semi-empirical model for predicting multilayered crown AN was established by incorporating Tleaf, VPD, LMA, RDINC, and their combinations into a photosynthetic light response (PLR) curve model using re-parameterization. The model was assessed based on goodness of fit (adjusted coefficient of determination ([Formula: see text]), root mean square error (RMSE), and Akaike’s information criterion (AIC)) and on the validation results (mean error (ME), mean absolute error (MAE), precision estimation (P)) and performed well. The multilayered predicted model of crown AN lays the foundation for calculating the multilayered photosynthetic production within the crown and determining the range of the functional crown for individual trees.

Leaf canopy architecture determines light interception and carbon gain in wild and domesticated Oryza species

Oryza sativa has many wild relatives that exhibit a wide range of canopy architectures. Two fast-growing ecotypes of an Australian wild rice (O. meridionalis) were compared with cultivated O. sativa to analyze the efficiency of light interception in mature vegetative canopies and how well light capture predicts biomass production. Canopies of individual plants were digitized and analyzed with YplantQMC. Plants were also grown at 700 ppm CO2 as a means of increasing the canopy density and assessing the relative impact of rising CO2 levels on photosynthesis, light interception and biomass. Simulations of light interception for these morphologically diverse canopies were combined with photosynthetic light response curves to estimate theoretical carbon gain. Both O. meridionalis genotypes had more tillers and leaves, and denser canopies, than O. sativa but one (‘Howard Springs’) intercepted more light than the other two genotypes, resulting in the highest simulated carbon gains. Photosynthesis per unit leaf area (Amax) was enhanced by 20–50% in 700 ppm CO2 in all genotypes but the proportion of total leaf area intercepting light decreased as a result of denser leaf canopies in these plants. Estimated total shoot carbon gain increased strongly at elevated CO2 despite these denser canopies and increased self-shading, reaching a peak in ‘Howard Springs’ at 700 ppm CO2. Thus, while high crown density and low leaf dispersion reduced the efficiency of light interception by the canopy, elevated CO2 still enhanced growth through consistently higher assimilation rates. Simulations showed that during the Summer Solstice, carbon gain was predicted to be greater than at the Equinox through superior light capture, particularly in ‘Howard Springs’. However, the relationship between light interception and carbon gain was broadly maintained, regardless of genotype, CO2 concentration and season.

Seasonal variation in photosynthesis performance of cassava at two different growth stages under irrigated and rain-fed conditions in a tropical savanna climate

Seasonal variations in photosynthesis of cassava cv. Rayong 9 (RY9) under irrigated and rain-fed conditions were evaluated at the age of three and six months after planting (MAP). Photosynthetic light-response (PN/I) curves revealed that cassava leaves attained the highest maximum net photosynthetic rates (PNmax) in the rainy season, followed by the hot one, while the lowest PNmax was found in the cool season. Photosynthetic potential of the 3-month-old plants was mostly higher than that of the 6-month-old plants, and the seasonal variation in photosynthetic capacity was also more apparent in the younger plants. PN/I curves were used to predict daily net photosynthetic rate (PN) for each season based on daily average solar radiation data. The predicted PN were considerably lower than the PNmax values. This indicated that solar radiation is a limiting factor for photosynthesis, particularly in the rainy season. The data provided basic information for breeding cassava genotypes with enhanced photosynthesis during the period of unfavorable environment. Furthermore, the data are potentially useful in modeling photosynthesis and crop growth as affected by environmental factors.

Simulation on photosynthetic light-responses of leaves of Quercus variabilis and Robinia pseudoacacia under different light conditions.

Photosynthesis can reflect the responses of plants to environmental changes. In this study, photosynthetic light-response curves were measured by the Li-6400XT photosynthetic system in Quercus variabilis and Robinia pseudoacacia plantations in Xiaolangdi Forest Ecosystem Research Station. Photosynthetic light-response curves were fitted by Ye model. The differences of photosynthetic parameters between inner and margin forests were examined. Stomatal conductance (gs) light-response curve were fitted using the mechanism model of gs coupled with a modified model of light-response of photosynthesis. The light-response characteristics of gs were investigated. Net photosynthetic rates (Pn) of Q. variabilis in the inner forest was higher than that in the margin. The initial light efficiency (Α) was 12.4% more in the inner forest than that in the margin in July and August when photosynthetically active radiation was less than 200 Μmol·m-2·s-1. The ability to capture and utilize weak light of Q. variabilis leaves in the inner forest was obviously higher than that in the margin. When photosynthetically active radiation was higher than 200 Μmol·m-2·s-1, Pn of Q. variabilis leaves in the margin forest was larger than that in the inner. Under weak light conditions (0-200 Μmol·m-2·s-1), Pn of R. pseudoacacia in the inner forest was higher than that in the margin. Pn of R. pseudoacacia in the inner forest was less than that in the margin when light intensity was higher than 200 Μmol·m-2·s-1. The dark respiration rate (Rd) and light compensation point (Ic) in the inner forest were 50.0% and 42.8% lower than those in the margin. The less Rd and Ic of the inner forest could reduce carbon loss and adapt to low photosynthetic rate. The stomatal conductance light-response of R. pseudoacacia in the inner forest significantly differed from that in the margin. The leaves of Q. variabilis and R. pseudoacacia had strong adaptability to the changes of light condition. The values of maximum net photosynthetic rate (Pn max) and Α of Q. variabilis leaves were mainly controlled by gs, and Rd and Ic were primarily affected by air temperature. Pn max and Α of R. pseudoacacia leaves had significant positive correlation with air temperature. The Ic and the light saturation point (Is) were remarkably correlated with leaf saturation vapor pressure deficit.

Gas exchange and photosynthetic light response curves in nematode-infected tomato plants treated with Thuya occidentalis

The use of homeopathic formulations on plants may cause changes in plant metabolism and result in disease control by inducing resistance. This work aimed to study the physiological responses of tomato plants infected with nematode (Meloidogyne incognita) and treated with highly diluted preparations of Thuya occidentalis, a homeopathic remedy. The different treatments included T. occidentalis 6CH, 24CH, and 50CH (Centesimal Hahnemanian), a water control (with nematode and without treatment), and an absolute control (no treatment and no nematode). The assay was conducted in a greenhouse using a randomized block design with four replications. Gas exchange parameters were measured at specific times before and after nematode inoculation. Photosynthetic rate, stomatal conductance, transpiration, leaf internal CO2 concentration, and leaf temperature were measured at various photosynthetic photon flux densities. No significant difference was found in the different gas exchange specific measure parameters between the treatments. Untreated infected plants showed an increase in net photosynthesis and in the carboxylation capacity, as shown by the light response curve. Treatment with T. occidentalis 24CH inhibited the increase in CO2 fixation in tomato plants inoculated with M. incognita, leading to a similar behavior as healthy plants, independently of the photon density.

Photosynthetic physio-ecological characteristics in soybean leaves at different CO2 concentrations.

The availability of CO2, a substrate for photosynthesis, affects the photosynthesis process and photosynthate production. Using the Li-6400-40B, we measured the photosynthetic electron transport rate and the photosynthetic light-response curves of soybean (Glycine max) leaves at different CO2 concentrations (300, 400, 500 and 600 μmol·mol-1). By fitting these parameters with a mechanistic model characterizing the light response of photosynthesis, we obtained aseries of photosynthetic parameters, eco-physiological parameters, as well as the physical parameters of photosynthetic pigments. The results showed that the electronic use efficiency, maximum electron transport rate, and maximum net photosynthetic rate increased with the increase of CO2 concentration. The light compensation point and dark respiration rate decreased with the increase of CO2 concentration. In addition, the light-use efficiency and intrinsic (instantaneous) water-use efficiency increased with the increase of CO2 concentration, and their values differed significantly among different CO2 concentrations. There was no significant difference on the maximum carboxylation efficiency among different CO2 concentrations. Those results suggested that CO2 concentration could affect the primary light reaction of photosynthesis in soybean leaves, and thus higher CO2 concentration could decrease the minimum average lifespan of excitons at the lowest excited state, which would enhance the velocity of light energy transport and the use efficiency of photosynthetic electron flow.

Shade tolerance: an additional factor affecting the distribution of mountain beech and silver beech in New Zealand?

Increased shade tolerance and a lower thermal optimum for photosynthesis may give silver beech a photosynthetic advantage over mountain beech in cloudy regions of New Zealand, and possibly the understory. The geographic distributions of silver beech (Lophozonia menziesii) and mountain beech (Fuscospora cliffortioides) in New Zealand roughly correspond with precipitation gradients, with F. cliffortioides dominating in sunny and dry regions, and L. menziesii either dominating or co-dominating with F. cliffortiodes in regions that are more cloudy and moist. Previous research suggests that greater drought tolerance may account for dominance of F. cliffortioides in sunny/dry regions, while greater tolerance of low soil nutrients may render a competitive advantage to L. menziesii in wetter habitats vulnerable to nutrient leaching. In this short communication, we propose and provide preliminary evidence for an additional hypothesis—that greater shade tolerance and a lower thermal optimum for photosynthesis confers a photosynthetic advantage to L. menziesii relative to F. cliffortioides under heavy cloud cover, and possibly in the forest understory. Sunlight measurements were recorded under clear sky, partly cloudy, overcast, and understory conditions at four field sites in New Zealand where the species co-occur, and integrated into previously published photosynthetic light response curves to estimate predicted carbon gain at 10, 20, and 25 °C. Photosynthetic gas exchange measurements were sampled in the field to corroborate expected results. Consistent with our hypothesis, predicted carbon gain was significantly greater in L. menziesii under cool (10–20 °C), low-light ( 20 °C. We conclude that relative tolerance of cloud and canopy shade may be an additional physiological factor, in combination with those previously described in the literature, affecting geographic and ecological distribution of mountain and silver beech in New Zealand.

尾叶桉林下5种植物的耐阴性、生物量及其个体消长

PDF HTML阅读 XML下载 导出引用 引用提醒 尾叶桉林下5种植物的耐阴性、生物量及其个体消长 DOI: 10.5846/stxb201612022484 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 广东省林业科技创新项目（2014KJCX019-03，2017KJCX021）；中国科学院科技服务网络计划（STS）项目（KFJ-SW-STS-147-3） Dynamics of shade tolerance, biomass, and individual growth of five understory plant species in Eucalyptus urophylla plantations Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了解尾叶桉林下不同植物种类的生理生态特性和生长适应性，在鹤山站尾叶桉林中选取分布较多且药用价值和经济价值较高的5种林下植物为研究对象，测定各植物的叶片特征、叶绿素含量和光合-光响应曲线，同时结合2006年和2011年尾叶桉林的样方调查数据分析了5种林下植物生物量的变化和个体数量的消长。结果表明：（1）野牡丹叶片的宽度、厚度、单片叶面积等指标最大，梅叶冬青最小，桃金娘、栀子和山苍子处于两者之间；桃金娘、野牡丹和山苍子的光合速率随光照的增强迅速增大，其光饱和点较高；梅叶冬青和栀子的光合速率也随光照的增强而增大，但其斜率比野牡丹和山苍子大，并很快就达到光饱和点。综合聚类分析植物的耐阴程度，5种植物可分为2类：第1类为耐阴性较强的梅叶冬青、栀子，第2类为耐阴性较弱的野牡丹、山苍子和桃金娘。（2）随着尾叶桉林的生长，5种林下植物的生物量都有不同程度的增加，其中增幅较大的是野牡丹和桃金娘分别增加74倍和18倍，增幅最小的是栀子仅1.3倍。野牡丹、桃金娘和山苍子这3个种生物量的增加主要是由个体高度和地径的增长引起，而栀子和梅叶冬青生物量的增加是其个体数量、株高和地径做出的贡献。（3）在尾叶桉林生长过程中，耐阴种类梅叶冬青随着个体密度、株高和地径的增长，其在林内发展成为主要优势灌木种类；栀子的密度虽然有一定的增大，但其株高和地径增加量小，生物量也小，发展为次要灌木种类。野牡丹、桃金娘和山苍子等3种的个体密度都在下降，虽然其地径、株高和生物量也有一定的增长，但其较强的阳生性不能适应林内的荫蔽环境，只适于林窗或林缘光照较强的地方生长。因此，在桉树林经营管理过程中应适当保护和种植梅叶冬青和栀子；在短轮伐期经营模式下，林窗和林缘也可适当保留野牡丹、桃金娘和山苍子。 Abstract:In order to investigate the ecophysiological characteristics and growth adaptability of different understory plants in Eucalyptus urophylla plantations, five understory species with high economic and medicinal values, including Ilex asprella, Gardenia jasminoides, Melastoma candidum, Rhodomyrtus tomentosa, and Litsea cubeba, were selected to measure leaf characteristics, chlorophyll content, and photosynthetic light response curves. In addition, the dynamics of biomass and individual number were analyzed based on field sampling survey data in 2006 and 2011. Comparative analysis and cluster analysis revealed that:(1) the leaf width, thickness and, area of M. candidum were the largest, whereas those of I. asprella were the smallest. Overall, the net photosynthetic rate of the selected understory plants increased with increasing light intensity. However, the net photosynthetic rate of I. asprella and G. jasminoides increased more rapidly than that of M. candidum and L. cubeba, and reached the light saturation point more quickly. R. tomentosa, M. candidum, and L. cubeba had higher light saturation points than that of I. asprella and G. jasminoides. The selected understory plants could be classified into two groups in terms of shade-tolerance ability, based on hierarchical cluster analysis. I. asprella and G. jasminoides were assigned to the strong shade-tolerant group, whereas M. candidum, L. cubeba, and R. tomentosa were assigned to the low shade-tolerant group. (2) Biomass of the five selected understory species increased with stand age, but the range of increment varied. The greatest increase was observed in M. candidum (74 fold), followed by R. tomentosa (18 fold), and the least was observed in L. cubeba (1.3 fold). The increase in biomass of M. candidum, R. tomentosa, and L. cubeba was mainly caused by the increase in individual height and basal diameter, whereas the increase in biomass of I. asprella and G. jasminoides was mainly attributed to the increase in individual number, height, and basal diameter. (3) I. asprella, a shade-tolerant understory species with high economic value, dominated the shrub community with increasing stand age of the Eucalyptus plantations, mainly owing to the increase in density, individual height, and basal diameter. G. jasminoides showed lower dominance over the shrub community owing to lesser increase in individual height and basal diameter than those of I. asprella. The density of L. cubeba, R. tomentosa, and M. candidum showed an overall decline with minor increase in individual height, basal diameter, and biomass. L. cubeba, R. tomentosa, and M. candidum can only survive in forest gap and edge owing to light limitation. In conclusion, we suggested that I. asprella and G. jasminoides should be protected and re-introduced during Eucalyptus plantation management for biodiversity conservation. Under the short-rotation management regime, M. candidum, L. cubeba, and R. tomentosa should be retained and re-introduced in the forest gap and edge. 参考文献 相似文献 引证文献

Characterization of a heat-tolerant Chlorella sp. GD mutant with enhanced photosynthetic CO2 fixation efficiency and its implication as lactic acid fermentation feedstock

BackgroundFermentative production of lactic acid from algae-based carbohydrates devoid of lignin has attracted great attention for its potential as a suitable alternative substrate compared to lignocellulosic biomass.ResultsA Chlorella sp. GD mutant with enhanced thermo-tolerance was obtained by mutagenesis using N-methyl-N′-nitro-N-nitrosoguanidine to overcome outdoor high-temperature inhibition and it was used as a feedstock for fermentative lactic acid production. The indoor experiments showed that biomass, reducing sugar content, photosynthetic O2 evolution rate, photosystem II activity (Fv/Fm and Fv′/Fm′), and chlorophyll content increased as temperature, light intensity, and CO2 concentration increased. The mutant showed similar DIC affinity and initial slope of photosynthetic light response curve (α) as that of the wild type but had higher dissolved inorganic carbon (DIC) utilization capacity and maximum photosynthesis rate (Pmax). Moreover, the PSII activity (Fv′/Fm′) in the mutant remained normal without acclimation process after being transferred to photobioreactor. This suggests that efficient utilization of incident high light and enhanced carbon fixation with its subsequent flux to carbohydrates accumulation in the mutant contributes to higher sugar and biomass productivity under enriched CO2 condition. The mutant was cultured outdoors in a photobioreactor with 6% CO2 aeration in hot summer season in southern Taiwan. The harvested biomass was subjected to separate hydrolysis and fermentation (SHF) for lactic acid production with carbohydrate concentration equivalent to 20 g/L glucose using the lactic acid-producing bacterium Lactobacillus plantarum 23. The conversion rate and yield of lactic acid were 80% and 0.43 g/g Chlorella biomass, respectively.ConclusionsThese results demonstrated that the thermo-tolerant Chlorella mutant with high photosynthetic efficiency and biomass productivity under hot outdoor condition is an efficient fermentative feedstock for large-scale lactic acid production.

Comparison of photosynthetic traits of codominant subalpine conifers Abies veitchii and A. mariesii in central Japan

Evergreen conifers Abies mariesii and A. veitchii codominate in the subalpine zone in central Japan. This study compared the photosynthetic light response curves and related leaf traits of 1-year-old needles between the two species to examine whether photosynthetic traits of A. veitchii are more favorable for growth in bright conditions than those of A. mariesii. Saplings of the two species were sampled at forest edge (FE) and forest understory (FU). FE saplings of the two species showed more shade-intolerant traits (i.e., lower initial slope of photosynthesis light response curve, greater light compensation point and dark respiration rate) than FU saplings. Maximum photosynthetic rate and leaf nitrogen concentration were greater in A. veitchii than A. mariesii for both FE and FU saplings. Photosynthetic nitrogen use efficiency (PNUE) was also greater in A. veitchii than A. mariesii. On the contrary, leaf mass per area was greater in A. mariesii than A. veitchii for both FE and FU saplings. Therefore, this study showed that photosynthetic traits of A. veitchii are more favorable for growth in bright conditions compared with A. mariesii, and A. mariesii has more robust needles at the expense of PNUE.

Seasonal dynamics of photosynthesis and total carbon gain in bearing and nonbearing pistachio (Pistacia vera L.) shoots

Seasonal changes in leaf gas exchange, assimilation response to light and leaf area were monitored in bearing and nonbearing pistachio shoots. Shoot bearing status did not directly affect leaf photosynthetic rate. However, photosynthetic light-response curves strongly varied during the season demonstrating the dominant effect of the tree’s seasonal phenology on assimilation. Early in the season low photosynthetic rates were associated with high rates of dark respiration indicating limited photosynthesis in the young leaves. As leaves matured, dark respiration decreased and assimilation reached maximum values. Photosynthetic efficiency was strongly reduced late in the season due to leaf age and senescence. Fruit load precipitated an early leaf senescence and drop that resulted in a 53% decrease in leaf area in bearing vs. nonbearing shoots, strongly decreasing the seasonal photosynthetic performance of bearing shoots. Bearing shoots produced a 26% lower seasonal carbon gain compared to nonbearing shoots.

Performance of Arabidopsis thaliana under different light qualities: comparison of light-emitting diodes to fluorescent lamp.

For precise phenotyping, Arabidopsis thaliana (L.) Heynh. is grown under controlled conditions with fluorescent lamps as the predominant light source. Replacement by systems based on light emitting diodes (LED) could improve energy efficiency and stability of light quality and intensity. To determine whether this affects the reproducibility of results obtained under fluorescent lamps, four Arabidopsis accessions and a phytochrome mutant were grown and phenotyped under two different LED types or under fluorescent lamps. All genotypes had significantly higher rosette weight and seed mass and developed faster under LED light than under fluorescent lamps. However, differences between genotypes were reproducible independent of the light source. Chlorophyll content, photosynthetic complex accumulation and light response curves of chlorophyll fluorescence parameters were indistinguishable under LED and fluorescent light. Principal component analysis of leaf metabolite concentrations revealed that the effect of a change from fluorescent light to LED light was small compared with the diurnal effect, which explains 74% of the variance and the age effect during vegetative growth (12%). Altogether, the replacement of fluorescent lamps by LED allowed Arabidopsis cultivation and reproduction of results obtained under fluorescent light.

Three-Year Study on Diurnal and Seasonal CO2 Sequestration of a Young Fraxinus griffithii Plantation in Southern Taiwan

This study examined monthly carbon sequestration of the Himalayan ash (Fraxinus griffithii C. B. Clarke), an important plantation species in Taiwan. From January 2010 to December 2012, data were collected from an F. griffithii plantation in southern Taiwan, which experiences a typical Southeast Asia monsoon climate. To estimate CO2 sequestration rate, we conducted diurnal measurements of photosynthetic rates and seasonal measurements of photosynthetic light response curves. We also calculated leaf area index to estimate the total leaf area of individual trees. The diurnal variation in photosynthetic rate, stomatal conductance, and transpiration exhibited seasonal and annual differences. The range of net CO2 assimilation rates was 1.34–8.68 µmol·m−2·s−1 in 2010, 1.02–6.60 µmol·m−2·s−1 in 2011, and 1.13–4.45 µmol·m−2·s−1 in 2012. A single F. griffithii tree sequestrated 12.21 kg·year−1 CO2 on average. Annual CO2 sequestration occurred primarily during the summer for all years, averaging 14.89 Mg·ha−1·year−1 for three years. Correlation analyses between various environmental variables and CO2 sequestration rates indicated that air temperature and soil water content were likely the main factors influencing carbon sequestration of F. griffithii at this study site.