scholarly journals Citrus photosynthesis and morphology acclimate to phloem-affecting huanglongbing disease at the leaf and shoot levels

2021 ◽  
Author(s):  
Mark Keeley ◽  
Diane Rowland ◽  
Christopher Vincent
Keyword(s):  
Carbon Fixation ◽  
Feedback Inhibition ◽  
Co2 Assimilation ◽  
Total Carbon ◽  
Starch Accumulation ◽  
Duration Of Infection ◽  
Citrus Production ◽  
Leaf Level ◽  
Negative Impacts ◽  
Relationship Of

Huanglongbing (HLB) is a phloem-affecting disease of citrus that reduces growth and has impacted citrus production in most global production regions. HLB is caused by a phloem-limited bacterium (Candidatus Liberibacter asiaticus; CLas). By inhibiting phloem function, HLB stunts sink growth, including reducing production of new shoots and leaves, and induces hyperaccumulation of foliar starch. Despite evidence that HLB induces feedback inhibition of photosynthesis by reducing foliar carbohydrate export, its effects on net CO2 assimilation (Anet) have not been reported. In this work we assessed the relationship of bacterial distribution within the foliage, foliar starch accumulation, and Anet. Because HLB impacts canopy morphology, we developed a chamber to measure whole shoot Anet, and tested the effects of HLB at both leaf and shoot levels. Starch accumulation was correlated with bacterial population, and starch was negatively correlated with Anet at the leaf but not at the shoot level. Starch increased between the uninfected group and the shortest duration of infection, then decreased progressively with increasing length of infection. HLB infection reduced Anet at the leaf level, but increased it at the whole shoot level. We attribute this enhancement of whole shoot Anet to the increased contribution of stem photosynthesis due to the altered shoot morphology induced by the disease. Despite the increased photosynthetic efficiency, total carbon fixation per shoot decreased because shoot size and leaf area were reduced. Overall, our results indicate a localized relationship of CLas distribution with negative impacts on foliar carbohydrate export and photosynthesis. Additionally, starch accumulation and Anet acclimate over time at the shoot level to the localized impacts of the disease. Stems contribute important proportions of whole shoot Anet, and these contributions are likely increased by the morphological acclimation induced by HLB. This study highlights the importance of temporal and spatial scale in assessing photosynthesis.

scholarly journals Molecular mechanism underlying the effect of maleic hydrazide treatment on starch accumulation in S. polyrrhiza 7498 fronds

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Yerong Zhu ◽  
Xiaoxue Li ◽  
Xuan Gao ◽  
Jiqi Sun ◽  
Xiaoyuan Ji ◽  
...  
Keyword(s):  
Plant Growth ◽  
Carbon Fixation ◽  
Maleic Hydrazide ◽  
Starch Content ◽  
Vegetative Reproduction ◽  
Photosynthetic Pigment ◽  
Starch Accumulation ◽  
Chlorophyll Fluorescence Parameters ◽  
Significant Difference ◽  
Starch Production

Abstract Background Duckweed is considered a promising feedstock for bioethanol production due to its high biomass and starch production. The starch content can be promoted by plant growth regulators after the vegetative reproduction being inhibited. Maleic hydrazide (MH) has been reported to inhibit plant growth, meantime to increase biomass and starch content in some plants. However, the molecular explanation on the mechanism of MH action is still unclear. Results To know the effect and action mode of MH on the growth and starch accumulation in Spirodela polyrrhiza 7498, the plants were treated with different concentrations of MH. Our results showed a substantial inhibition of the growth in both fronds and roots, and increase in starch contents of plants after MH treatment. And with 75 µg/mL MH treatment and on the 8th day of the experiment, starch content was the highest, about 40 mg/g fresh weight, which is about 20-fold higher than the control. The I2-KI staining and TEM results confirmed that 75 µg/mL MH-treated fronds possessed more starch and big starch granules than that of the control. No significant difference for both in the photosynthetic pigment content and the chlorophyll fluorescence parameters of PII was found. Differentially expressed transcripts were analyzed in S. polyrrhiza 7498 after 75 µg/mL MH treatment. The results showed that the expression of some genes related to auxin response reaction was down-regulated; while, expression of some genes involved in carbon fixation, C4 pathway of photosynthesis, starch biosynthesis and ABA signal transduction pathway was up-regulated. Conclusion The results provide novel insights into the underlying mechanisms of growth inhibition and starch accumulation by MH treatment, and provide a selective way for the improvement of starch production in duckweed.

scholarly journals Growth and grain yield of eight maize hybrids is aligned with water transport, stomatal conductance, and photosynthesis in a semi-arid irrigated system

2021 ◽  
Author(s):  
Sean M Gleason ◽  
Lauren Nalezny ◽  
Cameron Hunter ◽  
Robert Bensen ◽  
Satya Chintamanani ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Grain Yield ◽  
Water Transport ◽  
Co2 Assimilation ◽  
Specific Conductance ◽  
Soil Conditions ◽  
Transport Pathway ◽  
Crop Species ◽  
Leaf Level ◽  
Improved Performance

There is increasing interest in understanding how trait networks can be manipulated to improve the performance of crop species. Working towards this goal, we have identified key traits linking the acquisition of water, the transport of water to the sites of evaporation and photosynthesis, stomatal conductance, and growth across eight maize hybrid lines grown under well-watered and water-limiting conditions in Northern Colorado. Under well-watered conditions, well-performing hybrids exhibited high leaf-specific conductance, low operating water potentials, high rates of midday stomatal conductance, high rates of net CO2 assimilation, greater leaf osmotic adjustment, and higher end-of-season growth and grain yield. This trait network was similar under water-limited conditions with the notable exception that linkages between water transport, midday stomatal conductance, and growth were even stronger than under fully-watered conditions. The results of this experiment suggest that similar trait networks might confer improved performance under contrasting climate and soil conditions, and that efforts to improve the performance of crop species could possibly benefit by considering the water transport pathway within leaves, as well as within the whole-xylem, in addition to root-level and leaf-level traits.

A simple dynamic model of photosynthesis in oak leaves: coupling leaf conductance and photosynthetic carbon fixation by a variable intracellular CO2 pool

2004 ◽  
Vol 31 (12) ◽  
pp. 1195 ◽  
Author(s):  
Steffen M. Noe ◽  
Christoph Giersch
Keyword(s):  
Carbon Fixation ◽  
Calvin Cycle ◽  
Target Function ◽  
Vapour Pressure Deficit ◽  
Co2 Assimilation ◽  
Leaf Conductance ◽  
Co2 Partial Pressure ◽  
Sink Term ◽  
Essential Components ◽  
Oak Leaves

Modelling the diurnal course of photosynthesis in oak leaves (Quercus robur L.) requires appropriate description of the dynamics of leaf photosynthesis of which diurnal variations in leaf conductance and in CO2 assimilation are essential components. We propose and analyse a simple photosynthesis model with three variables: leaf conductance (gs), the CO2 partial pressure inside the leaf (pi), and a pool of Calvin cycle intermediates (aps). The environmental factors light (I) and vapour pressure deficit (VPD) are used to formulate a target function G(I, VPD) from which the actual leaf conductance is calculated. Using this gs value and a CO2 consumption term representing CO2 fixation, a differential equation for pi is derived. Carboxylation corresponds to the sink term of the pi pool and is assumed to be feedback-inhibited by aps. This simple model is shown to produce reasonable to excellent fits to data on the diurnal time courses of photosythesis, pi and gs sampled for oak leaves.

Analysis of the Response of Hypolimnetic Phytoplankton in Continuous Culture to Increased Light or Phosphorus Using Track Autoradiography

1980 ◽  
Vol 37 (3) ◽  
pp. 434-441 ◽  
Author(s):  
R. Knoechel ◽  
F. deNoyelles Jr.
Keyword(s):  
Continuous Culture ◽  
Carbon Fixation ◽  
Common Species ◽  
Total Carbon ◽  
Experimental Lakes Area ◽  
Phosphorus Enrichment ◽  
Species Response ◽  
Ankistrodesmus Falcatus ◽  
Wide Range ◽  
Track Autoradiography

Phytoplankton from the hypolimnetic biomass peak in Lake 266SW (Experimental Lakes Area, northwestern Ontario) was subjected to conditions of increased light or phosphorus in continuous culture. Phosphorus enrichment increased total carbon fixation 16% relative to the control; however, the particulate fraction was initially depressed and the phytoplankton biomass was less than 2% greater after 10 d. The high light culture displayed 21% higher final biomass despite a 13% decline in total carbon fixation which was primarily due to reduced extracellular release. The 21 most common species demonstrated a wide range of positive and negative biomass responses to the experimental perturbations; however, the three dominant chrysophyte species all responded positively to higher light. Detection of population biomass changes provided a direct and accurate means of quantifying perturbation effects provided the species response was stable over several days. Measurement of carbon uptake rates of species through track autoradiography provided the additional sensitivity and temporal resolution needed to monitor low level or variable responses. Synedra radians exhibited a lengthy lag period before demonstrating a strong positive response to phosphorus enrichment, while Dinobryon sertularia shifted from neutral to strongly negative and then strongly positive within a 3-d period. These results illustrate the inadequacy of short-term bioassays for the prediction of long-term perturbation effects.Key words: growth rate, primary production, Ankistrodesmus falcatus, Dinobryon sertularia, Synedra radians

Protein Synthesis by Lake Plankton Measured Using in situ Carbon Dioxide and Sulfate Assimilation

1987 ◽  
Vol 44 (12) ◽  
pp. 2102-2117 ◽  
Author(s):  
Russell L. Cuhel ◽  
David R. S. Lean
Keyword(s):  
Carbon Dioxide ◽  
Protein Synthesis ◽  
Carbon Fixation ◽  
Total Carbon ◽  
Light Limitation ◽  
Sulfate Assimilation ◽  
Sulfate Uptake ◽  
Chl A ◽  
Total Sulfate

Sequential 4- to 6-h in situ measurements of carbon dioxide and sulfate uptake showed midday deepening of the depth of Pmax and photoinhibition of upper water column samples. Analysis of subcellular fractions accentuated total uptake measurements, with net protein synthesis providing a direct measure of growth. The percentage of carbon assimilated into protein was smallest at the depth of maximum photosynthesis and increased with light limitation. Summed incubations agreed well with all-day deployments for total carbon fixation and protein synthesis. Assimilation numbers were consistently low (<2.5 g C∙g Chl a−1∙h-1 with integrated (0–20 m) areal production of 616–1467 mg C∙m−2 and 7.5–32.4 mg S∙m−2 during the light day. Nonreductive sulfate assimilation (predominantly ester-SO4−) accounted for up to 40% of the total sulfate uptake when diatoms predominated. Protein synthesis measured with 35S (200–1000 mg protein∙m−2 during the light day) increased 57–89% overnight. Hourly rates were similar during light and scotophase incubations. Night metabolism substantially altered the biochemical composition (e.g. protein, lipid, and carbohydrate) of the plankton with respect to newly incorporated carbon. Combined plant-specific H14CO3− and general microbial 3SSO42− techniques suggested algal dominance in the mixed layer.

scholarly journals Simultaneous leaf-level measurement of trace gas emissions and photosynthesis with a portable photosynthesis system

2020 ◽  
Author(s):  
Mj Riches ◽  
Daniel Lee ◽  
Delphine K. Farmer
Keyword(s):  
Environmental Parameters ◽  
Co2 Assimilation ◽  
Trace Gas ◽  
Ionization Mass ◽  
Gas Emissions ◽  
Flow Rates ◽  
Trace Gas Emissions ◽  
Level Measurement ◽  
Online Measurements ◽  
Leaf Level

Abstract. Plants emit considerable quantities of volatile organic compounds (VOCs), the identity and amount of which vary with temperature, light and other environmental factors. Portable photosynthesis systems are a useful method for simultaneously quantifying in situ leaf-level emissions of VOCs and plant physiology. We present a comprehensive characterization of the LI-6800 portable photosynthesis system's ability to be coupled to trace gas detectors and measure leaf-level trace gas emissions, including limits in flow rates, environmental parameters, and VOC backgrounds. Instrument contaminants from the LI-6800 can be substantial, but are dominantly complex molecules such as siloxanes that are structurally dissimilar to biogenic VOCs and thus unlikely to interfere with most leaf-level emissions measurements. We validate the method by comparing CO2 assimilation calculated internally by the portable photosynthesis system to measurements taken with an external CO2 gas analyzer; these assimilation measurements agree within 1 %. We also demonstrate both online and offline measurements of plant trace gas exchange using the LI-6800. Offline measurements by pre-concentration on adsorbent cartridges enable detection of a broad suite of VOCs, including monoterpenes (e.g., limonene) and aldehydes (e.g., decanal). Online measurements can be more challenging if flow rates require dilution with ultra-pure zero air. We use high resolution time-of-flight chemical ionization mass spectrometry coupled to the LI-6800 to measure direct plant emission of formic acid.

scholarly journals Environmental drivers of coccolithophore abundance and calcification across Drake Passage (Southern Ocean)

2016 ◽  
Author(s):  
Anastasia Charalampopoulou ◽  
Alex J. Poulton ◽  
Dorothee C. E. Bakker ◽  
Mike I. Lucas ◽  
Mark C. Stinchcombe ◽  
...  
Keyword(s):  
Southern Ocean ◽  
North Atlantic ◽  
Carbon Fixation ◽  
Rank Correlation ◽  
Drake Passage ◽  
Total Carbon ◽  
Environmental Drivers ◽  
Multivariate Statistical ◽  
The North ◽  
Spearman’S Rank Correlation

Abstract. Although coccolithophores are not as common in the Southern Ocean as they are in sub-polar waters of the North Atlantic, a few species, such as Emiliania huxleyi, are found during the summer months. Little is actually known about the calcite production (CP) of these communities, or how their distribution and physiology relates to environmental variables in this region. In February 2009, we made observations across Drake Passage (between South America and the Antarctic Peninsula) of coccolithophore distribution, CP, primary production, chlorophyll-a and macronutrient concentrations, irradiance and carbonate chemistry. Although CP represented less than 1 % of total carbon fixation, coccolithophores were widespread across Drake Passage. The B/C morphotype of E. huxleyi was the dominant coccolithophore, with low estimates of coccolith calcite (~ 0.01 pmol C coccolith−1) from biometric measurements. Both cell-normalised calcification (0.01–0.16 pmol C cell−1 d−1) and total CP (< 20 μmol C m−3 d−1) were much lower than those observed in the sub-polar North Atlantic where E. huxleyi morphotype A is dominant. However, estimates of coccolith production rates were similar (0.1–1.2 coccoliths cell−1 h−1) to previous measurements made in the sub-polar North Atlantic. A multivariate statistical approach found that temperature and irradiance together were best able to explain the observed variation in species distribution and abundance (Spearman's rank correlation ρ = 0.4, p < 0.01). Rates of calcification per cell and coccolith production, as well as community CP and E. huxleyi abundance, were all positively correlated (p < 0.05) to the strong latitudinal gradient in temperature, irradiance and calcite saturation states across Drake Passage. Broadly, our results lend support to recent suggestions that coccolithophores, especially E. huxleyi, are advancing pole-wards. However, our in situ observations indicate that this may owe more to sea-surface warming and increasing irradiance rather than increasing CO2 concentrations.

scholarly journals Effect of Fruiting on Net CO2 Assimilation Rates of Peach and Nectarine Trees

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 779B-779
Author(s):  
Maria Derkacz ◽  
Calvin Chong ◽  
John Proctor
Keyword(s):  
Prunus Persica ◽  
Feedback Inhibition ◽  
Co2 Assimilation ◽  
Lag Phase ◽  
Maturity Stage ◽  
Phenotypic Differences ◽  
Net Co2 Assimilation ◽  
Rapid Enlargement ◽  
Parallel Data ◽  
Sigmoid Curve

Growth of peach fruits is characterized by a double-sigmoid curve; two periods of rapid enlargement (stages I and III) separated by a lag phase (stage II). Seasonal net CO2 assimilation rates (NAR) were compared in leaves from fruiting and non-fruiting (deblossomed) trees of `Harrow Diamond' (early), and `Vivid' (mid-summer) peach (Prunus persica L. Batsch.) and `Fantasia' (late) nectarine (P. persica) to determine 1) the influence of fruits on photosynthesis and 2) the relationship between NAR and fruit growth. Seasonal trends in NAR tended to be qualitatively similar among the three cultivars, despite genotypic and phenotypic differences. There was a distinct increase in NAR at the time of horticultural fruit maturity (stage III) of each cultivar. Shortly after harvest, NAR rates declined. The average seasonal NAR of fruiting `Harrow Diamond', `Vivid', and `Fantasia' trees was 9%, 11%, and 10% higher, respectively, than that of corresponding non-fruiting trees. Parallel data for total chlorophyll was 28%, 20%, and 19% higher, and specific leaf weight (SLW) was 3%, 5%, and 6% lower, respectively. A negative correlation between NAR and SLW may indicate a feedback inhibition of photosynthesis.

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