CO2 Exchange Rate Research Articles

Photosynthesis continuous monitoring system for CAM plants

Diurnal CO2 exchanges in crassulacean acid metabolism (CAM) plants are significantly different from those in C3 and C4 plants. The instantaneous short-time CO2 exchange of a single leaf measured by commercial portable photosynthesis measuring systems with a small leaf chamber cannot reflect the plant photosynthetic capacity for CAM plants because of the CO2 fixation property. Therefore, a photosynthesis continuous monitoring system with two canopy cuvettes was developed for measuring diurnal net CO2 exchange rates for CAM plants. To evaluate stability and applicability of the photosynthesis continuous monitoring system, continuous measurement of net CO2 exchange rates of plants with different photosynthetic pathways were conducted. An obligate CAM plant (Kalanchoe daigremontiana), four facultative CAM plants (Dendrobium officinale, D. chrysotoxum, D. nobile, and D. primulinum), a C3 plant (Strawberry, Fragaria ananassa), and a C4 plant (Corn, Zea mays) were selected as model plants. K. daigremontiana had a significant CO2 absorption during the dark period and its net CO2 exchange rates fluctuated around 0 μmol/(m2•s) during the photoperiod in a growth chamber. Net CO2 exchange rates of F. ananassa and Z. mays in a greenhouse gradually increased after sunrise, reaching a maximum at about 12:00, and then gradually decreased to negative values during the night time. It is interesting to observe that D. officinale in the greenhouse and growth chamber absorbed CO2 during both day and night times. The photosynthetic pathways of D. chrysotoxum, D. nobile, and D. primulinum were also well distinguished by this photosynthesis continuous monitoring system. The results showed that the photosynthesis continuous monitoring system is capable for quantitative evaluation of diurnal net CO2 exchange characteristics not only in the CAM plants but also in small size C3 and C4 plants with low net photosynthetic rates for long-time and high-accuracy measurements. Keywords: diurnal net CO2 exchanges, infrared CO2 analyzer, mass airflow meter, net photosynthetic rate, photosynthetic pathway DOI: 10.25165/j.ijabe.20191203.4885 Citation: Cheng Y S, He D X. A photosynthesis continuous monitoring system for CAM plants. Int J Agric & Biol Eng, 2019; 12(3): 141–146.

Real-time CO2 uptake/emission measurements as a tool for early indication of toxicity in Lemna-tests

This paper presents an application of continuous monitoring of the emission and uptake rate of CO2 in Lemna toxicity test. On a real-time basis, the CO2 concentration data were collected by the Arduino platform-based respiratory activity measuring system (ResTox) and reported as CO2 concentration dynamic curves. The results of CO2 measurements demonstrated that tested metals (Co, Cu, Hg, and Cd), as well as herbicides (nicosulfuron, diquat, and tembotrione), stimulated the CO2 exchange rates at low doses, while at high doses CO2 exchange rates were inhibited. The addition of higher concentrations of clopyralid stimulated photosynthetic activity and caused a higher increase in respiration rates indicating its mode of action as auxin mimic herbicide. The results obtained underline the necessity of considering other biological endpoints like continuous measurements of gas exchange from the very beginning of exposure to toxicants. Simultaneous measurements of real-time CO2 concentrations, as the primary effect of toxicant mode of action, and processes that are supported by carbon flux, as the secondary effect or endpoint, are needed to relate actual and substrate-induced or inhibited respiration and photosynthesis to those processes. Therefore, continuous measurements of CO2 exchange rates can be implemented for the initial screening of potential toxicity to give valuable information that is needed for further examination of toxicity mechanisms and risk assessment.

Physiological Effects of Citrus Leafminer Phyllocnistis citrella (Lepidoptera: Gracillariidae) Larval Feeding on Photosynthetic and Gaseous Exchange Rates in Citrus.

Feeding damage by arthropods exposes plants to pathogens and interferes with plant physiological processes. Feeding by the citrus leafminer (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), larva exposes leaf cuticle to the causal pathogens of the citrus canker disease. We investigated the impact of larval feeding on photosynthetic rate (Pn), CO2 exchange rate (Ci), and H2O exchange rate (Wi) in eight citrus cultivars [Citrus mandarins (Kinnow, Seedless Kinnow, Feutrell's early), Citrus sinensis (Succari, Salustiana), Citrus tangerines (Fairchild), Citrus limon (China lemon), and Citrus paradisi Macfad (Grapefruit)] under natural conditions in comparison with control plants protected from larval feeding. The effects on gas exchange parameters were tested by allowing the single first instar larvae per leaf to feed till pupation at the rate of three leaves per plant and 10 plants per cultivar. A consistent reduction in leaf Pn, Ci, and Wi rates with larval development through 19 d was observed in all cultivars except Grapefruit in which all three parameters decreased through 13 d and then increased consistently through 19 d. Reductions in Pn, Ci, and Wi were significantly correlated. All three parameters of CLM-infested plants were reduced significantly compared to their levels in control plants except Pn in Kinnow, China lemon, and Grapefruit; Ci in Grapefruit; and Wi in Succari. Pn was reduced most in Fairchild, whereas Ci and Wi were reduced most in China lemon. The consequences of these physiological alterations in regions with high CLM populations could be even more intense and negatively impact plant health, tolerance to pests and diseases, and yield.

Acclimation of Young <i>Doritaenopsis</i> Queen Beer‘Mantefon’Plants under Increased CO<sub>2</sub> Concentration

This study was conducted to investigate the CO2 exchange rate and growth characteristics of young Doritaenopsis plants acclimated to increased CO2 concentrations. Six-week-old clones of Doritaenopsis Queen Beer ‘Mantefon’ were grown for 27 weeks in four controlled-environment growth chambers maintained at 400 ± 100, 900 ± 100, 1500 ± 100, or 2100 ± 100 μmol CO2·mol-1 during the dark period. The highest CO2 uptake of the uppermost mature leaf, which existed before treatment, was observed in the 900 μmol CO2·mol-1 treatment, followed by the 2100, 1500, and 400 μmol CO2·mol-1 treatments. However, after CO2 treatment, plants acclimated at 2100 μmol CO2·mol-1 showed the highest CO2 uptake in the first newly developed mature leaf, and the amount of CO2 absorbed increased with increasing CO2 treatments. Leaf length and width of the uppermost mature leaf and total biomass decreased in the 900, 1500, and 2100 μmol CO2·mol-1 treatments, whereas new leaf development was significantly promoted under elevated CO2 conditions. These results indicate that acclimation to increased CO2 concentrations can enhance the CO2 uptake and development of new leaves in young Doritaenopsis plants, but leaf growth and biomass accumulation might decrease at concentrations over 900 μmol CO2·mol-1. Therefore, we recommend further research to investigate the effects of acclimation to high concentrations of CO2 on Doritaenopsis plants.

CO2, CH4 and N2O flux changes in degraded grassland soil of Inner Mongolia, China

The main purpose of this study was to explore the dynamic changes of greenhouse gas (GHG) from grasslands under different degradation levels during the growing seasons of Inner Mongolia, China. Grassland degradation is associated with the dynamics of GHG fluxes, e.g., CO2, CH4 and N2O fluxes. As one of the global ecological environmental problems, grassland degradation has changed the vegetation productivity as well as the accumulation and decomposition rates of soil organic matter and thus will influence the carbon and nitrogen cycles of ecosystems, which will affect the GHG fluxes between grassland ecosystems and the atmosphere. Therefore, it is necessary to explore how the exchanges of CO2, CH4 and N2O fluxes between soil and atmosphere are influenced by the grassland degradation. We measured the fluxes of CO2, CH4 and N2O in lightly degraded, moderately degraded and severely degraded grasslands in Inner Mongolia of China during the growing seasons from July to September in 2013 and 2014. The typical semi-arid grassland of Inner Mongolia plays a role as the source of atmospheric CO2 and N2O and the sink for CH4. Compared with CO2 fluxes, N2O and CH4 fluxes were relatively low. The exchange of CO2, N2O and CH4 fluxes between the grassland soil and the atmosphere may exclusively depend on the net exchange rate of CO2 in semi-arid grasslands. The greenhouse gases showed a clear seasonal pattern, with the CO2 fluxes of –33.63 –386.36 mg/(m•h), CH4 uptake fluxes of 0.113–0.023 mg/(m•h) and N2O fluxes of –1.68 –19.90 μg/(m•h). Grassland degradation significantly influenced CH4 uptake but had no significant influence on CO2 and N2O emissions. Soil moisture and temperature were positively correlated with CO2 emissions but had no significant effect on N2O fluxes. Soil moisture may be the primary driving factor for CH4 uptake. The research results can be in help to better understand the impact of grassland degradation on the ecological environment.

Asymmetric impact of oil prices, exchange rate, and inflation on tourism demand in Pakistan: new evidence from nonlinear ARDL

ABSTRACTThis study scrutinized the asymmetric impact of oil prices, exchange rate, and inflation on tourism demand in Pakistan using [Shin, Y., Yu, B., & Greenwood-Nimmo, M. (2014) Modelling asymmetric cointegration and dynamic multipliers in a nonlinear ARDL framework. In Festschrift in honor of peter schmidt (pp. 281–314). New York, NY: Springer] nonlinear autoregressive distributed lag (NARDL) model. The NARDL bounds test examined the existence of cointegration in study variables, including CO2 emissions, institutional quality, oil prices, exchange rate, inflation, and tourism demand. The evidence proposes that disregarding the intrinsic nonlinearities may misinform inference. The estimated NARDL model affirmed long-run negative and significant effect of CO2 emissions on tourism demand, while institutional quality was positively associated with tourism demand. Furthermore, the findings of the study also suggested long-run asymmetric relationship between oil prices, exchange rate, inflation, and tourism demand.

Growth and CO2 exchange in young Phalaenopsis orchids grown under different levels of humidity during the vegetative period

Phalaenopsis plants are distributed throughout tropical regions with high humidity, which is generally necessary for their cultivation. This study was conducted to determine the effects of different relative humidity (RH) conditions on the growth and photosynthetic characteristics of young Phalaenopsis plants. Three-month-old clones of Phalaenopsis ‘Blanc Rouge’ and Doritaenopsis ‘Mantefon’ plants were grown under 30 ± 10, 50 ± 10, 70 ± 10, or 90 ± 10% RH conditions. The RH treatments were maintained for approximately 6 months in environment-controlled growth chambers. The temperature and photoperiod were maintained at 28 °C and 12/12 h, respectively. At the start of the RH treatments, the mean leaf span was 14.2 and 16.7 cm in ‘Blanc Rouge’ and ‘Mantefon’ plants, respectively. In both cultivars, plants grown under 70% RH showed the longest leaf span, which was 25.3 and 20.6 cm in ‘Blanc Rouge’ and ‘Mantefon’, respectively. High-humidity conditions (i.e. 70 and 90% RH) generally promoted the length of leaf span, but the growth rate of leaf span was slightly lower at 90% RH than at 70% RH. CO2 exchange, stomatal conductance, and transpiration rate of the uppermost mature leaf were observed in ‘Blanc Rouge’ plants grown at 30, 50, and 70% RH. The highest rate of CO2 uptake was observed in the plants grown at 70% RH, followed by 50 and 30% RH. The stomatal conductance increased and transpiration decreased with increasing RH. The maximum quantum yield of photosystem II (Fv/Fm) of plants grown under 70 and 90% RH slightly decreased after 9 weeks of treatments, but there were no differences among the treatment groups at the conclusion of the study. These results indicated that high RH (e.g. 70%) slightly increases CO2 uptake and leaf span of young Phalaenopsis plants.

Canopy Chamber Measurements of Carbon Dioxide Fluxes in Corn and Soybean Fields

Core Ideas Canopy chambers were used to measure CO2 exchange rates (CER) in corn and soybean plots. Daytime and cumulative CER fluxes were calculated from measured instantaneous CER fluxes. Chamber CER fluxes were consistent with eddy covariance flux tower CER fluxes. Crop canopy CO2 exchange rate (CER) includes crop photosynthesis and soil/plant respiration. A portable canopy chamber is effective in determining crop CER values at a relatively small spatial (m2) scale. The objectives of this study were to use a canopy chamber to measure CO2 fluxes in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Chamber measurements were performed for 18 and 15 d in 2013 and 2014, respectively. The canopy chamber measures instantaneous CER fluxes, and daily and daytime cumulative CO2 values were calculated from the instantaneous CER. The chamber CER results were compared with nearby eddy covariance (EC) flux tower measurements at a variety of time scales, i.e., instantaneous, daily, and daytime cumulative (multiple months). The daily and daytime cumulative chamber CER values were within 5% of the EC results, providing evidence for the effectiveness of the portable canopy chamber method. In conclusion, the portable canopy chamber provides reliable CO2 flux measurements despite the small size of field plots.

Phosphorus deficiency alters scaling relationships between leaf gas exchange and associated traits in a wide range of contrasting Eucalyptus species.

Phosphorus (P) limitation is known to have substantial impacts on leaf metabolism. However, uncertainty remains around whether P deficiency alters scaling functions linking leaf metabolism to associated traits. We investigated the effect of P deficiency on leaf gas exchange and related leaf traits in 17 contrasting Eucalyptus species that exhibit inherent differences in leaf traits. Saplings were grown under controlled-environment conditions in a glasshouse, where they were subjected to minus and plus P treatments for 15 weeks. P deficiency decreased P concentrations and increased leaf mass per area (LMA) of newly-developed leaves. Rates of photosynthesis (A) and respiration (R) were also reduced in P-deficient plants compared with P-fertilised plants. By contrast, P deficiency had little effect on the temperature sensitivity of R. Irrespective of P treatment, on a log-log basis A and R scaled positively with increasing leaf nitrogen concentration [N] and negatively with increasing LMA. Although P deficiency had limited impact on A-R-LMA relationships, rates of CO2 exchange per unit N were consistently lower in P-deficient plants. Our results highlight the importance of P supply for leaf carbon metabolism and show how P deficiencies (i.e. when excluding confounding genotypic and environmental effects) can have a direct effect on commonly used leaf trait scaling relationships.

Effect of a semi‐permanent road on N, P, and CO2 dynamics in a poor fen on the Western Boreal Plain, Canada

AbstractPeatlands of the Western Boreal Plains are under stress from oil and gas development and associated infrastructure such as road construction and removal. An improved understanding of nutrient cycling and atmospheric carbon dioxide (CO2) exchange interactions in peatlands can assist in recommending best management practices to industry to minimize the ecohydrological disturbance footprint of road features. Peat nutrient (nitrogen, N, and phosphorus, P) supply, net mineralization, groundwater concentrations, and peatland‐atmosphere CO2 exchange rates were quantified within a poor fen bisected by a semi‐permanent road located in the Athabasca Oil Sands region of Alberta, Canada, over one growing season. Results demonstrate that the road impeded groundwater movement across the site; however, water table and moisture differences were minimal, likely due to the unusually wet season. No clear impacts of the road on nutrient dynamics were observed, but subtle differences in productivity and respiration resulted in significantly lower net CO2 sequestration (net ecosystem exchange) on the down‐flow side of the road. Differences in vegetation composition between sides of the road were apparent and likely indicate longer‐term moisture differences at the site. Elevated rates of productivity and respiration coincided with a seasonal change in the relative supplies of N and P (increased N : P ratios), suggesting that the relative availability of N versus P may be important to CO2 fluxes in Western Boreal Plains peatlands. Collectively, these findings demonstrate the need to capture interactions between hydrology, ecology and nutrient biogeochemistry when evaluating peatland carbon cycling response to road disturbances across this region.

Effect of pyraclostrobin on disease control, leaf physiology, seed yield and quality of sunflower

A two-year (2012–2013) field experiment was carried out to investigate the fungicidal activity of pyraclostrobin and its putative physiological effects on sunflower (Helianthus annuus L.) grown under rainfed, Mediterranean conditions. Five pyraclostrobin treatments were applied [single applications at rates of 100, 150 and 200 g active ingredient (ai) ha−1 at V6 growth stage (TV6/100, TV6/150, and TV6/200, respectively) and 200 g ai ha−1 at R1 growth stage (TR1/200) and a double application at V6 and R1 at a rate of 100 g ai ha−1 (TV6-R1/100)] and accompanied by untreated (TUC) and chemical control [iprodione at a rate of 750 g ai ha−1 at V6 (TCC)]. Diseases [charcoal rot (CR) caused by Macrophomina phaseolina, Phomopsis stem canker (SC) caused by Phomopsis helianthi, black stem (BS) caused by Phoma macdonaldii, and powdery mildew (PM) caused by Golovinomyces cichoracearum] were assessed twice. Leaf physiological traits [leaf chlorophyll content (SPAD), specific leaf area (SLA), carbon isotope discrimination (Δ), nitrogen (N) concentration, 15N natural abundance (δ15N), and carbon to nitrogen ratio (C/N)] were determined at R5 stage. Growth season had a significant effect on seed oil concentration (Oil) and oil yield (OY) and was higher in 2013; this season had low CR and SC incidence but high incidence of BS and severity of PM. Split application of pyraclostrobin (TV6-R1/100) or a high rate at the beginning of the reproductive phase (TR1/200) suppressed the diseases, mainly SC and BS. The former treatment (TV6-R1/100) showed the highest yields [seed yield (SY), OY, and protein yield (PY)]. All the physiological traits but Δ were not affected by fungicide treatments. The high-yielding TV6-R1/100 treatment had the highest Δ values over the growth seasons indicating a “waste” of water in turn to sustain open stomata and thus higher CO2 exchange rates. This swap leads to lower water use efficiency in the long-term but it indicates healthier and more active functioning sunflower plants that had greater yields. Phomopsis stem canker (SC) showed to be the most detrimental disease since its incidence was negatively correlated to yields (SY, OY) over the growth seasons. On the other hand, CR seemed to affect N uptake and translocation within sunflower plants. In conclusion, the physiological response (highest Δ) recorded for split application of pyraclostrobin (at V6 and R1 stages) was indirect; lower disease incidence secured water supply to sunflower plants resulting in higher yields.

Investigating sources of measured forest-atmosphere ammonia fluxes using two-layer bi-directional modelling

Understanding and predicting the ammonia (NH3) exchange between the biosphere and the atmosphere is important due to the environmental consequences of the presence of reactive nitrogen (Nr) in the environment. The dynamics of the natural sources are, however, not well understood, especially not for forest ecosystems due to the complex nature of this soil-vegetation-atmosphere system. Furthermore, the high reactivity of NH3 makes it technically complex and expensive to measure and understand the forest-atmospheric NH3 exchange. The aim of this study is to investigate the NH3 flux partitioning between the ground layer, cuticle and stomata compartments for two temperate deciduous forest ecosystems located in Midwestern, USA (MMSF) and in Denmark (DK-Sor). This study is based on measurements and simulations of the surface energy balance, fluxes of CO2 and NH3 during two contrasted periods of the forest ecosystems, a period with full developed canopy (MMSF) and a senescent period for the DK-Sor site, with leaf fall and leaf litter build-up. Both datasets indicate emissions of NH3 from the forest to the atmosphere. The two-layer NH3 compensation point model SURFATM-NH3 was used in combination with a coupled photosynthesis-stomatal conductance model to represent seasonal variation in canopy physiological activity for simulating both net ecosystem CO2 exchange rates (R2=0.77 for MMSF and R2=0.84 for DK-Sor) and atmospheric NH3 fluxes (R2=0.43 for MMSF and R2=0.60 for DK-Sor). A scaling of the ground layer NH3 emission potential (Гg) was successfully applied using the plant area index (PAI) to represent the build-up of a litter layer in the leaf fall period. For a closed green forest canopy (MMSF), unaffected by agricultural NH3 sources, NH3 was emitted with daytime fluxes up to 50ng NH3-N m−2s−1 and nighttime fluxes up to 30ng NH3-N m−2s−1. For a senescing forest (DK-Sor), located in an agricultural region, deposition rates of 250ng NH3-N m−2s−1 were measured prior to leaf fall, and emission rates up to 670ng NH3-N m−2s−1 were measured following leaf fall. For MMSF, simulated stomatal NH3 emissions explain the daytime flux observations well, and it is hypothesized that cuticular desorption is responsible for the observed NH3 emissions at night. During leaf fall in DK-Sor, ground fluxes dominate the NH3 flux with a mean emission rate of 150ng NH3-N m−2s−1. This study shows that forests potentially comprise a natural source of NH3 to the atmosphere, and that it is crucial to take into account the bi-directional exchange processes related to both the stomatal, cuticular and ground layer pathways in order to realistically simulate forest–atmosphere fluxes of NH3.

风速变化对草原生态系统的影响研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 风速变化对草原生态系统的影响研究进展 DOI: 10.5846/stxb201606161164 作者: 作者单位: 北京师范大学地表过程与资源生态国家重点实验室,北京师范大学地表过程与资源生态国家重点实验室,北京师范大学地表过程与资源生态国家重点实验室,北京师范大学地表过程与资源生态国家重点实验室,北京师范大学地表过程与资源生态国家重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金创新团队项目（41321001）；地表过程与资源生态国家重点实验室资助项目（2014-zy-04）；中央高校科研业务费专项资金资助（310421103） Research progress of the effects of wind speed change on grassland ecosystem Author: Affiliation: State Key laboratory of Earth Surface Progress and Resources Ecology,Beijing Normal University,State Key laboratory of Earth Surface Progress and Resources Ecology,Beijing Normal University,State Key laboratory of Earth Surface Progress and Resources Ecology,Beijing Normal University,State Key laboratory of Earth Surface Progress and Resources Ecology,Beijing Normal University,State Key laboratory of Earth Surface Progress and Resources Ecology,Beijing Normal University 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:在全球风速呈下降趋势的大背景下，研究风速变化对生态系统的影响具有重要意义，尤其是其重要组成部分——草原生态系统。近年来大量学者开始研究风速变化对草原生态系统的影响，主要集中在以下几个方面并得出相关的结论，（1）风速变化会影响植物的生长速率和叶片形态，适当的风速能够促进植物生长发育、提高植被初级生产力，而强风或持续大风不仅会对植物产生破坏作用，还会影响其生长发育；（2）风会最先带走地表细小颗粒，从而导致土壤质地变粗、水分下降、营养成分重新分配；（3）风引起地表边界层和大气边界层物质和能量的转移和交换，热量和水汽的交换导致地表微气候发生变化，如风速降低会导致地表温度升高；（4）风力作用使得土壤水分亏缺、营养成分变化，导致草原生态系统结构变化、草地覆盖度降低、物种生活型复杂化、耐旱植物增加；（5）大气稳定性、CO2交换速率和碳排放都会随着风速的增加而增加，碳吸收则相反，碳通量也因此发生变化。综上，风速降低对于草原生态系统的影响复杂且利弊相当，未来的发展趋势会更加侧重于以下几个方面的发展：研究对象的多样化、加强控制实验的定量化研究、综合多要素的相互作用机理研究、整体结构和功能性的研究。 Abstract:Under the context of wind-reducing worldwide, researching the effects of wind speed change on grassland ecosystem, which plays an important role in terrestrial ecosystem, has important significances. The experiment results over decades show that:(1) wind speed change impacts plant growth rates and leaf shapes. Appropriate wind speed can improve plant growth and enhance the primary productivity. But strong wind or continuous wind might damage plant; (2)Wind takes away soil fine particles (e.g., silt and clay) from soil surface first, which lead to soil structural change, soil moisture reduction and the redistribution of nutrients; (3)Wind induces the transfer and exchange of materials and energy between land surface and atmosphere, which can change the surface micro-climate. For example, soil surface temperature will rise due to reduced wind; (4) Wind can decrease the soil moisture and change the nutrient component, making grassland ecosystem structure varied, grassland cover decreased, plant life forms complicated and drought-tolerant plants increased; (5) Atmospheric stability, CO2 exchange rate and carbon emission increase with wind speed acceleration. Carbon absorption is the opposite. As a result, carbon flux also changes. Above all, It has its pros and cons for the effect of wind speed decrease on grassland ecosystem. In the future,the study will be more focused on the following aspects:Research object diversification; Quantitative study by strengthening the control of experiment; Comprehensive interaction mechanism of multi factor; the overall structure and functional study. 参考文献 相似文献 引证文献

Elevated CO2 improves growth, modifies anatomy, and modulates essential oil qualitative production and gene expression in Lippia alba (Verbenaceae)

Carbon dioxide (CO2) concentrations have grown in recent decades and will continue to increase during this century, affecting plant physiology and development. Aiming to evaluate the effect of CO2 elevation on growth, anatomy, essential oil qualitative production and expression of genes related to biosynthesis of these compounds, three chemotypes of Lippia alba (BGEN-01, BGEN-02 and BGEN-42) were cultivated in vitro. Firstly, we focused on the effects of gas exchange in the essential oil profile by comparing three CO2 exchange rates: 14, 21 and 25 µL L−1 s−1 CO2. Continuing, in addition to the previous 14 and 25 µL L−1 s−1 CO2 treatments, plants were placed into acrylic chambers with continuous forced air at 360 and 1000 μL L−1 of CO2; an additional control without allowing gas exchange was added inside the chambers, totaling five treatments with 6 replicates. After 45 days, essential oil profile, histochemical, stomatal density, growth evaluation analyses and transcript analysis were performed. The enrichment with CO2 enhanced plant dry and fresh weight, total chlorophylls and carotenoids in BGEN-01 and BGEN-02, and also increased stomatal density and lignin content for all chemotypes. The multivariate analysis showed that the essential oil profile varied, not only among the different chemotypes, but also within BGEN-01 and BGEN-02 treatments. The qualitative production was different in the treatments with forced air renovation and CO2 enrichment. Regarding the gene expression analyses, Farnesyl pyrophosphate synthase (LaFPPS) and Geranyl pyrophosphate synthase (LaGPPS) did not vary, except for the treatments with forced air ventilation (360 and 1000 µL L−1) in the BGEN-01, which had LaFPPS upregulated. Geraniol synthase (LaGES) was upregulated in all BGEN-02 treatments and for BGEN-01 treatments with 360 and 1000 µL L−1 CO2. Nerolidol/Linalool synthase (LaNES/LIS) was upregulated only in the BGEN-01, in the 360 and 1000 µL L−1 CO2 treatments. These findings provide a better understanding of how CO2 regulates secondary metabolites production, providing a basis to clarify the pathway regulation, further enabling the targeted production of essential oils with greater economic and industrial interest.

High Temperatures around Flowering in Maize: Effects on Photosynthesis and Grain Yield in Three Genotypes

To aid breeding for heat‐tolerant germplasm we analyzed the effects of high temperatures on the CO2 exchange rate (CER), crop growth rate (CGR), kernel number (KN), and grain yield (GY) in a 30‐d period bracketing flowering. Field experiments, including three maize (Zea mays L.) hybrids with temperate (Te), tropical (Tr) and temperate × tropical (Tx) adaptation were performed in two experiments (Exp. 1 and 2). Hybrids were subjected to high temperatures induced by shelters during a 15‐d period before (H1; preflowering) or after silking (H2; postflowering). Crop growth rate was measured during the 30‐d period bracketing silking (CGRCP), H1 (CGRPRE), and H2 (CGRPOST). Relative to nonstressed conditions, CER was reduced by 17 and 16% in H1 and H2. Moreover, CER was associated with CGRCP (r = 0.78; p ≤ 0.001), CGRPRE (r = 0.39; p ≤ 0.05), CGRPOST (r = 0.51; p ≤ 0.01), KN (Exp. 1, r = 0.53; p ≤ 0.01; Exp. 2, r = 0.49; p ≤ 0.01), and GY (Exp. 1, r = 0.59; p ≤ 0.01; Exp. 2, r = 0.46; p ≤ 0.05). As a result of heat stress, CGRCP (H1, −17%; H2, −29%), KN (H1, −7%; H2, −45%), and GY (H1, −10%; H2, −45%) were reduced relative to the control treatment. Stronger reductions for all traits in H2 relative to H1 emphasize the importance of sufficient CER during this period. The effect of high temperature on CER differed among hybrids (Tx > Te = Tr) and is promising for future germplasm screening.

Effects of sucrose, carrot juice and culture media on growth and net CO2 exchange rate in Phalaenopsis hybrid ‘Pink’

The successfulness of plant tissue culture in terms of propagation is greatly influenced by the nature of the medium used. This experiment was conducted to determine the effects of various sucrose concentrations as carbon source and carrot juice (CJ) in different culture media on growth and net CO2 exchange rate of Phalaenopsis hybrid ‘Pink’. Plantlets were cultured on two media (half-strength Murashige and Skoog [MS] and Vacin and Went [VW]) supplemented with 0, 10, 20, 30 and 40gL−1 sucrose either with 0, 10 and 20% (v/v) CJ as a natural additive. After four months of culture, plantlets were transferred to a greenhouse under natural environmental condition. The results showed that the combination of 30 and 40gL−1 sucrose with 10% (v/v) CJ supplemented with half-strength MS and VW medium, respectively, optimally enhanced root length, leaf length, plant height, leaf greenness, total chlorophyll content and CO2 uptake. The combination of 30gL−1 sucrose and 10% (v/v) CJ supplemented with half-strength MS medium resulted in the highest leaf length (5.00±0.07cm), plant height (7.20±0.20cm), SPAD leaf greenness (35.50±0.26), total chlorophyll (15.13±0.25μgmL−1) and CO2 uptake (1.11±0.15μmolm−2s−1). The combination of 40gL−1 sucrose and 10% (v/v) CJ supplemented with VW medium resulted in the highest leaf length (5.40±0.10cm), leaf width (2.60±0.10cm), plant height (6.50±0.22cm), SPAD leaf greenness (37.43±0.26), total chlorophyll (17.07±0.39μgmL−1) and CO2 uptake (1.77±0.04μmolm−2s−1).

Role of ephemeral vegetation of emerging river bottoms in modulating CO2 exchanges across a temperate large lowland river stretch

Rivers and marginal wetlands contribute significantly to the carbon (C) exchange rate per unit area compared to adjacent terrestrial ecosystems, due to high C inputs, metabolic activity and CO2 supersaturation. Within riverscapes, the contribution of emerging bottoms (i.e. parafluvial zones) and ephemeral vegetation (i.e. microphytobenthos or annual vascular plant communities) to the C metabolism is understudied. The aim of this study was to evaluate the CO2 exchange rates at the water- and emergent sand bar-atmosphere interfaces within a lowland large temperate river stretch. CO2 fluxes were measured seasonally, in summer (August 2007) and winter (March 2008) via static closed chambers, together with the primary producers’ biomass (microphytobenthos and vascular macrophytes). Our results showed that the river was a CO2 source (between 0.2 and 7.6 mmol CO2 m−2 day−1), whilst the vegetated parafluvial zones acted as a net sink, with assimilation rates peaking at 623.4 mmol CO2 m−2 day−1. Emerging bare sediments were on the contrary net emitting CO2 systems (2.7–60.1 mmol CO2 m−2 day−1). Within lotic environments, seasonally emergent vegetated sand bars may represent important C fixation hot spots, with summer primary production particularly contributing to offsetting CO2 emissions and counterbalancing the heterotrophic metabolism of the saturated zones. Based on these outcomes, we suggest that studies addressing the strictly aquatic fluvial environment, which is generally a CO2 emitter, should be linked to those from transitional areas in order to better integrate terrestrial and aquatic C budgets.

Performance of classic multiple factor analysis and model fitting in crop modeling

Multivariate statistical analysis and regression, which are typical methods for crop modeling, have direct influence on the accuracy of model, but the applications of these methods usually depend on experiences. In this research, the performances of some common methods of statistical analysis and regression model were compared and verified, in order to avoid the blindness in crop modeling. The monitoring data of growth environment and photosynthesis of tomato, pumpkin and cucumber were obtained by PTM-48A. For the object variable of CO2 exchange rate, selectivity on the main environmental factors by correlation analysis and path analysis were quantitatively compared. The performances of four kinds of multivariate binomial regression equations were compared using a comprehensive aggregative indicator, and the effectiveness of modeling was verified with the selected optimized multivariate statistical analysis and regression equation. Results showed that path analysis was more comprehensive and effective than correlation to discrimination of the variables, especially the path analysis ruled out some suspected independent variables which were not really independent, and the pure quadratic was more suitable to crop modeling because of its simple structure and high accuracy when the data set was small. The conclusion of this research has a general applicability, and offers a useful reference and guide for the other study and application of crops’ modeling. Keywords: crop model, multivariate statistical analysis, path analysis, regression, comparison DOI: 10.3965/j.ijabe.20160902.1023 Citation: Jiang Z H, Zhang J, Yang C H, Rao Y, Li S W. Performance of classic multiple factor analysis and model fitting in crop modeling. Int J Agric & Biol Eng, 2016; 9(2): 119－126.

Photosynthetic characteristics of leaves and fruits of Hickory (Carya cathayensis Sarg.) and Pecan (Carya illinoensis K.Koch) during fruit development stages

Fruit photosynthesis in both hickory and pecan significantly contribute to the carbon requirements of late growth stage (corresponding to seed development). Plant parts other than leaves can perform photosynthesis and contribute to carbon acquisition for fruit development. To determine the role of fruit photosynthesis in fruit carbon acquisition in hickory (Carya cathayensis Sarg.) and pecan (Carya illinoensis K.Koch), we studied changes in dry mass, surface area and CO2 exchange rate in these fruits during fruit development. Fruit development was divided into two phases: phase one involves the rapid increase of fruit size (from 0 to 59 days after pollination (DAP) for hickory; from 0 to 88 DAP for pecan); phase two involves seed development (from 59 to 121 DAP for hickory; from 88 to 155 DAP for pecan). The net photosynthetic rate (P n) in hickory leaves decreased by 48.5 % from 76 to 88 DAP, while the P n in pecan leaves decreased by 32.3 % from 88 to 123 DAP. The gross photosynthetic rate (P g) in hickory fruit was significantly greater than that of the leaf during the late stage (88 to 121 DAP) of fruit development. Pecan fruit had a significantly higher P g than leaves during ontogeny. The contribution of fruit photosynthesis to fruit carbon requirements increased during fruit development, which was estimated by the gross fruit photosynthesis divided by respiration and increased dry mass. The contribution of fruit photosynthesis to pecan carbon requirements was significantly greater than that of hickory. Fruit photosynthesis in both hickory and pecan significantly contribute to the carbon requirements of late growth stage.

Gas exchange and water-use efficiency of cv. Sangiovese grafted to rootstocks of varying water-deficit tolerance

Testing of new rootstocks for drought tolerance targets traditionally rain-fed districts where supplemental irrigation is more frequently needed due to the pressures of global warming. A seasonal evaluation of gas exchange and water-use efficiency (WUE) of cv. Sangiovese grafted to the new drought-tolerant genotype M4 in a dry-down trial against the commercial SO4 stock is reported. The experiment was conducted in 2014 on twelve 2-year-old, non-fruiting potted Sangiovese grapevines grafted on M4 and SO4 stocks and assigned to SO4-WW (well-watered), SO4-WS (water-stressed), M4-WW and M4-WS treatments. Progressive water deficit was imposed by reducing water supply to 70, 50 and 30 % of whole-canopy demand derived from concurrent measurements of transpiration in WW. Unlike SO4, M4 showed slower stress progression, as highlighted by pre-dawn leaf water potential, and retained higher whole-canopy net CO2 exchange rates (NCER) and transpiration rates per unit of leaf area at all replenishment levels as well as exhibiting higher canopy WUE at both 50 and 30 % WW. Although single-leaf assessment was in partial disagreement with data recorded on the whole-canopy basis, robust data were acquired to confirm that the M4 stock performs better than SO4 at any water replenishment level in terms of higher NCER/leaf area and/or canopy WUE. Findings feed expectations that grafting Sangiovese to the M4 rootstock should result in a problem-solving tool for rain-fed areas subject to temporary summer drought.