scholarly journals Fossil evidence for low gas exchange capacities for Early Cretaceous angiosperm leaves

Paleobiology ◽  
2011 ◽  
Vol 37 (2) ◽  
pp. 195-213 ◽  
Author(s):  
Taylor S. Feild ◽  
Garland R. Upchurch ◽  
David S. Chatelet ◽  
Timothy J. Brodribb ◽  
Kunsiri C. Grubbs ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Early Cretaceous ◽  
Leaf Gas Exchange ◽  
Exchange Capacity ◽  
Basal Angiosperm ◽  
Photosynthetic Gas Exchange ◽  
Angiosperm Evolution ◽  
Early Angiosperm ◽  
Fossil Evidence ◽  
Functional Analyses

The photosynthetic gas exchange capacities of early angiosperms remain enigmatic. Nevertheless, many hypotheses about the causes of early angiosperm success and how angiosperms influenced Mesozoic ecosystem function hinge on understanding the maximum capacity for early angiosperm metabolism. We applied structure-functional analyses of leaf veins and stomatal pore geometry to determine the hydraulic and diffusive gas exchange capacities of Early Cretaceous fossil leaves. All of the late Aptian—early Albian angiosperms measured possessed low vein density and low maximal stomatal pore area, indicating low leaf gas exchange capacities in comparison to modern ecologically dominant angiosperms. Gas exchange capacities for Early Cretaceous angiosperms were equivalent or lower than ferns and gymnosperms. Fossil leaf taxa from Aptian to Paleocene sediments previously identified as putative stem-lineages to Austrobaileyales and Chloranthales had the same gas exchange capacities and possibly leaf water relations of their living relatives. Our results provide fossil evidence for the hypothesis that high leaf gas exchange capacity is a derived feature of later angiosperm evolution. In addition, the leaf gas exchange functions of austrobaileyoid and chloranthoid fossils support the hypothesis that comparative research on the biology of living basal angiosperm lineages reveals genuine signals of Early Cretaceous angiosperm ecophysiology.

Early cretaceous fossil evidence for angiosperm evolution

1977 ◽  
Vol 43 (1) ◽  
pp. 3-104 ◽  
Author(s):  
Leo J. Hickey ◽  
James A. Doyle
Keyword(s):  
Early Cretaceous ◽  
Angiosperm Evolution ◽  
Fossil Evidence

scholarly journals Leaf Gas Exchange and Chlorophyll a Fluorescence in Wheat Plants Supplied with Silicon and Infected with Pyricularia oryzae

2014 ◽  
Vol 104 (2) ◽  
pp. 143-149 ◽  
Author(s):  
Carlos Eduardo Aucique Perez ◽  
Fabrício Ávila Rodrigues ◽  
Wiler Ribas Moreira ◽  
Fábio Murilo DaMatta
Keyword(s):  
Gas Exchange ◽  
Chlorophyll A ◽  
Electron Transport Rate ◽  
Leaf Gas Exchange ◽  
Chlorophyll Concentration ◽  
Pyricularia Oryzae ◽  
Gas Exchange Parameters ◽  
Photosynthetic Gas Exchange ◽  
Exchange Performance ◽  
Exchange Parameters

This study investigated the effect of silicon (Si) on the photosynthetic gas exchange parameters (net CO2 assimilation rate [A], stomatal conductance to water vapor [gs], internal CO2 concentration [Ci], and transpiration rate [E]) and chlorophyll fluorescence a parameters (maximum quantum quenching [Fv/Fm and Fv′/Fm′], photochemical [qP] and nonphotochemical [NPQ] quenching coefficients, and electron transport rate [ETR]) in wheat plants grown in a nutrient solution containing 0 mM (–Si) or 2 mM (+Si) Si and noninoculated or inoculated with Pyricularia oryzae. Blast severity decreased due to higher foliar Si concentration. For the inoculated +Si plants, A, gs, and E were significantly higher in contrast to the inoculated –Si plants. For the inoculated +Si plants, significant differences of Fv/Fm between the –Si and +Si plants occurred at 48, 96, and 120 h after inoculation (hai) and at 72, 96, and 120 hai for Fv′/Fm′. The Fv/Fm and Fv′/Fm′, in addition to total chlorophyll concentration (a + b) and the chlorophyll a/b ratio, significantly decreased in the –Si plants compared with the +Si plants. Significant differences between the –Si and +Si inoculated plants occurred for qP, NPQ, and ETR. The supply of Si contributed to decrease blast severity in addition to improving gas exchange performance and causing less dysfunction at the photochemical level.

scholarly journals Leaf Gas Exchange and Chlorophyll a Fluorescence in Maize Leaves Infected with Stenocarpella macrospora

2015 ◽  
Vol 105 (1) ◽  
pp. 26-34 ◽  
Author(s):  
Maria Bianney Bermúdez-Cardona ◽  
João Américo Wordell Filho ◽  
Fabrício Ávila Rodrigues
Keyword(s):  
Gas Exchange ◽  
Chlorophyll A ◽  
Chlorophyll A Fluorescence ◽  
Leaf Gas Exchange ◽  
Photochemical Quenching ◽  
Efficiency Coefficient ◽  
Gas Exchange Parameters ◽  
Photosynthetic Gas Exchange ◽  
Chl A ◽  
Fluorescence Maximum

This study investigated the effect of macrospora leaf spot (MLS), caused by Stenocarpella macrospora, on photosynthetic gas exchange parameters and chlorophyll a fluorescence parameters determined in leaves of plants from two maize cultivars (‘ECVSCS155’ and ‘HIB 32R48H’) susceptible and highly susceptible, respectively, to S. macrospora. MLS severity was significantly lower in the leaves of plants from ECVSCS155 relative to the leaves of plants from HIB 32R48H. In both cultivars, net CO2 assimilation rate, stomatal conductance, and transpiration rate significantly decreased, while the internal to ambient CO2 concentration ratio increased in inoculated plants relative to noninoculated plants. The initial fluorescence and nonphotochemical quenching significantly increased in inoculated plants of ECVSCS155 and HIB 32R48H, respectively, relative to noninoculated plants. The maximum fluorescence, maximum PSII quantum efficiency, coefficient for photochemical quenching, and electron transport rate significantly decreased in inoculated plants relative to noninoculated plants. For both cultivars, concentrations of total chlorophyll (Chl) (a + b) and carotenoids and the Chl a/b ratio significantly decreased in inoculated plants relative to noninoculated plants. In conclusion, the results from the present study demonstrate, for the first time, that photosynthesis in the leaves of maize plants is dramatically affected during the infection process of S. macrospora, and impacts are primarily associated with limitations of a diffusive and biochemical nature.

scholarly journals Machine learning enabled phenotyping for GWAS and TWAS of WUE traits in 869 field-grown sorghum accessions

2020 ◽  
Author(s):  
John N. Ferguson ◽  
Samuel B. Fernandes ◽  
Brandon Monier ◽  
Nathan D. Miller ◽  
Dylan Allan ◽  
...  
Keyword(s):  
Machine Learning ◽  
Gas Exchange ◽  
Association Study ◽  
Biomass Production ◽  
Genome Wide Association Study ◽  
Leaf Gas Exchange ◽  
Optical Tomography ◽  
Photosynthetic Gas Exchange ◽  
Biomass Sorghum ◽  
Intrinsic Water Use Efficiency

ABSTRACTSorghum is a model C4 crop made experimentally tractable by extensive genomic and genetic resources. Biomass sorghum is also studied as a feedstock for biofuel and forage. Mechanistic modelling suggests that reducing stomatal conductance (gs) could improve sorghum intrinsic water use efficiency (iWUE) and biomass production. Phenotyping for discovery of genotype to phenotype associations remain bottlenecks in efforts to understand the mechanistic basis for natural variation in gs and iWUE. This study addressed multiple methodological limitations. Optical tomography and a novel machine learning tool were combined to measure stomatal density (SD). This was combined with rapid measurements of leaf photosynthetic gas exchange and specific leaf area (SLA). These traits were then the subject of genome-wide association study (GWAS) and transcriptome-wide association study (TWAS) across 869 field-grown biomass sorghum accessions. SD was correlated with plant height and biomass production. Plasticity in SD and SLA were interrelated with each other, and productivity, across wet versus dry growing seasons. Moderate-to-high heritability of traits studied across the large mapping population supported identification of associations between DNA sequence variation, or RNA transcript abundance, and trait variation. 394 unique genes underpinning variation in WUE-related traits are described with higher confidence because they were identified in multiple independent tests. This list was enriched in genes whose orthologs in Arabidopsis have functions related to stomatal or leaf development and leaf gas exchange. These advances in methodology and knowledge will aid efforts to improve the WUE of C4 crops.

scholarly journals A stomatal model of anatomical tradeoffs between gas exchange and pathogen colonization

2019 ◽  
Author(s):  
Christopher D. Muir
Keyword(s):  
Gas Exchange ◽  
Leaf Surface ◽  
Stomatal Density ◽  
Leaf Gas Exchange ◽  
Stomatal Closure ◽  
Exchange Capacity ◽  
Pathogen Defense ◽  
Stomatal Size ◽  
Scaling Relationships ◽  
Pathogen Colonization

ABSTRACTStomatal pores control both leaf gas exchange and are one route for infection of internal plant tissues by many foliar pathogens, setting up the potential for tradeoffs between photosynthesis and defense. Anatomical shifts to lower stomatal density and/or size may also limit pathogen colonization, but such developmental changes could permanently reduce the gas exchange capacity for the life of the leaf. I developed and analyzed a spatially explicit model of pathogen colonization on the leaf as a function of stomatal size and density, anatomical traits which partially determine maximum rates of gas exchange. The model predicts greater stomatal size or density increases the probability of colonization, but the effect is most pronounced when the fraction of leaf surface covered by stomata is low. I also derived scaling relationships between stomatal size and density that preserves a given probability of colonization. These scaling relationships set up a potential anatomical conflict between limiting pathogen colonization and minimizing the fraction of leaf surface covered by stomata. Although a connection between gas exchange and pathogen defense has been suggested empirically, this is the first mathematical model connecting gas exchange and pathogen defense via stomatal anatomy. A limitation of the model is that it does not include variation in innate immunity and stomatal closure in response to pathogens. Nevertheless, the model makes predictions that can be tested with experiments and may explain variation in stomatal anatomy among plants. The model is generalizable to many types of pathogens, but lacks significant biological realism that may be needed for precise predictions.

scholarly journals Retracing the contours of the early angiosperm environmental niche

2019 ◽  
Vol 125 (1) ◽  
pp. 49-57
Author(s):  
Robin Pouteau ◽  
Santiago Trueba ◽  
Sandrine Isnard
Keyword(s):  
Null Model ◽  
Geometric Constraints ◽  
Basal Angiosperm ◽  
Support Vector ◽  
Random Pattern ◽  
Environmental Niche ◽  
Basal Angiosperms ◽  
Diversity Pattern ◽  
Angiosperm Evolution ◽  
Early Angiosperm

Abstract Background and Aims Our aim was to understand the environmental conditions of the emergence and radiation of early angiosperms. Such a question has long remained controversial because various approaches applied in the past have drawn conflicting images of early angiosperm ecology. Methods We provided a new perspective on the question by using support vector machines to model the environmental niche of 51 species belonging to ten genera of extant lineages that diverged early during angiosperm evolution (basal angiosperms). Then, we analysed the resulting pattern of niche overlap and determined whether this pattern deviates from what would be expected on the basis of a null model or whether it might mirror a legacy of a common primitive niche based on a phylogenetic reconstruction. Key Results The niche of three-quarters of the species and all genera converged towards tropical montane cloud forests (TMCFs). The latitudinal pattern of basal angiosperm richness indeed culminated in the tropics, and the elevational pattern revealed a humpback curve peaking between 2000 m and 3500 m when accounting for the effect of area. At first glance, this diversity pattern does not significantly differ from null predictions. However, we revealed a tendency for the basal-most taxa to occur in TMCFs so that phylogenetic reconstructions indicated that the niche of the common ancestor of the sampled basal angiosperms had a probability of 0.85–0.93 to overlap with TMCFs. Conclusions Our new approach indicates that the environmental convergence of extant basal angiosperms towards TMCFs would reflect a legacy of an ancestral niche from which the least basal taxa would have diverged following a random pattern under geometric constraints.

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