scholarly journals Pore constrictions in intervessel pit membranes reduce the risk of embolism spreading in angiosperm xylem

2020 ◽  
Author(s):  
Lucian Kaack ◽  
Matthias Weber ◽  
Emilie Isasa ◽  
Zohreh Karimi ◽  
Shan Li ◽  
...  
Keyword(s):  
Strong Relationship ◽  
Mechanistic Explanation ◽  
Membrane Thickness ◽  
List Type ◽  
Hydraulic Efficiency ◽  
Pit Membrane ◽  
Hydraulic Safety ◽  
Embolism Resistance

SummaryEmbolism spreading in angiosperm xylem occurs via mesoporous pit membranes between vessels. Here, we investigate how the size of pore constrictions in pit membranes is related to pit membrane thickness and embolism resistance.In three models, pit membranes are modelled as multiple layers to investigate how pit membrane thickness and the number of intervessel pits per vessel determine pore constriction sizes, the probability of encountering large pores, and air-seeding. These estimations were complemented by measurements of pit membrane thickness, embolism resistance, and number of intervessel pits per vessel (n = 31, 31, and 20 species, respectively).Constriction sizes in pores decreased with increasing pit membrane thickness, which agreed with the measured relationship between pit membrane thickness and embolism resistance. The number of pits per vessel affected constriction size and embolism resistance much less than pit membrane thickness. A strong relationship between estimated air-seeding pressures and measured embolism resistance was observed.Pore constrictions provide a mechanistic explanation why pit membrane thickness determines embolism resistance, and suggest that hydraulic safety can be uncoupled from hydraulic efficiency. Although embolism spreading remains puzzling and encompasses more than pore constriction sizes, angiosperms are unlikely to have leaky pit membranes, which enables tensile transport of water.

scholarly journals Root xylem in three woody angiosperm species is not more vulnerable to embolism than stem xylem

2020 ◽  
Author(s):  
Min Wu ◽  
Ya Zhang ◽  
Thais Oya ◽  
Carmen Regina Marcati ◽  
Luciano Pereira ◽  
...  
Keyword(s):  
Membrane Thickness ◽  
Acer Campestre ◽  
Root Segments ◽  
Pit Membrane ◽  
Significant Difference ◽  
Xylem Tissue ◽  
Angiosperm Species ◽  
Embolism Resistance ◽  
Intact Root ◽  
Intact Roots

AbstractAimsSince plants are compartmentalised organisms, failure of their hydraulic transport system could differ between organs. We test here whether xylem tissue of stems and roots differ in their drought-induced embolism resistance, and whether intact roots are equally resistant to embolism than root segments.MethodsEmbolism resistance of stem and root xylem was measured based on the pneumatic technique for Acer campestre, A. pseudoplatanus and Corylus avellana, comparing also intact roots and root segments of C. avellana. Moreover, we compared anatomical features such as interconduit pit membrane between roots and stems.ResultsWe found a higher embolism resistance for roots than stems, although a significant difference was only found for A. pseudoplatanus. Interconduit pit membrane thickness was similar for both organs of the two Acer species, but pit membranes were thicker in roots than stems of C. avellana. Also, embolism resistance of an intact root network was similar to thick root segments for C. avellana.ConclusionOur observations show that root xylem is not more vulnerable to embolism than stem xylem, although more species need to be studied to test if this finding can be generalised. We also demonstrated that the pneumatic method can be applied to non-terminal plant samples.

scholarly journals Pit and tracheid anatomy explain the hydraulic safety- but not the hydraulic efficiency of 28 conifer species

2021 ◽  
Author(s):  
Yanjun Song ◽  
Lourens Poorter ◽  
Angelina Horsting ◽  
Sylvain Delzon ◽  
Frank Sterck
Keyword(s):  
Hydraulic Conductivity ◽  
Vascular System ◽  
Common Garden ◽  
Hydraulic Efficiency ◽  
Conifer Species ◽  
Hydraulic Safety ◽  
Valve Effect ◽  
Embolism Resistance ◽  
Underlying Mechanisms ◽  
And Function

Abstract Conifers face increased drought mortality risks because of drought-induced embolism in their vascular system. Variation in embolism resistance may result from species differences in pit structure and function, as pits control the air seeding between water transporting conduits. This study quantifies variation in embolism resistance and hydraulic conductivity for 28 conifer species grown in a 50-year-old common garden experiment and assesses the underlying mechanisms. Conifer species with a small pit aperture, high pit aperture resistance and large valve effect were more resistant to embolism, as they all may reduce air seeding. Surprisingly, hydraulic conductivity was only negatively correlated with tracheid cell wall thickness. Embolism resistance and its underlying pit traits related to pit size and sealing were stronger phylogenetically controlled than hydraulic conductivity and anatomical tracheid traits. Conifers differed in hydraulic safety and hydraulic efficiency, but there was no trade-off between safety and efficiency because they are driven by different xylem anatomical traits that are under different phylogenetic control.

scholarly journals Intervessel pit membrane thickness best explains variation in embolism resistance amongst stems of Arabidopsis thaliana accessions

2020 ◽  
Author(s):  
Ajaree Thonglim ◽  
Sylvain Delzon ◽  
Maximilian Larter ◽  
Omid Karami ◽  
Arezoo Rahimi ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Growth Form ◽  
Water Shortage ◽  
Membrane Thickness ◽  
Vessel Wall Thickness ◽  
Transmission Electron ◽  
Functional Aspects ◽  
Pit Membrane ◽  
Inflorescence Stems ◽  
Embolism Resistance

Abstract Background and Aims The ability to avoid drought-induced embolisms in the xylem is one of the essential traits for plants to survive periods of water shortage. Over the past three decades, hydraulic studies have been focusing on trees, which limits our ability to understand how herbs tolerate drought. Here we investigate the embolism resistance in inflorescence stems of four Arabidopsis thaliana accessions that differ in growth form and drought response. We assess functional traits underlying the variation in embolism resistance amongst the accessions studied using detailed anatomical observations. Methods Vulnerability to xylem embolism was evaluated via vulnerability curves using the centrifuge technique and linked with detailed anatomical observations in stems using light microscopy and transmission electron microscopy. Key Results The data show significant differences in stem P50, varying 2-fold from −1.58 MPa in the Cape Verde Island accession to −3.07 MPa in the woody soc1 ful double mutant. Out of all the anatomical traits measured, intervessel pit membrane thickness (TPM) best explains the differences in P50, as well as P12 and P88. The association between embolism resistance and TPM can be functionally explained by the air-seeding hypothesis. There is no evidence that the correlation between increased woodiness and increased embolism resistance is directly related to functional aspects. However, we found that increased woodiness is strongly linked to other lignification characters, explaining why mechanical stem reinforcement is indirectly related to increased embolism resistance. Conclusions The woodier or more lignified accessions are more resistant to embolism than the herbaceous accessions, confirming the link between increased stem lignification and increased embolism resistance, as also observed in other lineages. Intervessel pit membrane thickness and, to a lesser extent, theoretical vessel implosion resistance and vessel wall thickness are the missing functional links between stem lignification and embolism resistance.

scholarly journals Similar hydraulic efficiency and safety across vesselless angiosperms and vessel-bearing species with scalariform perforation plates

2019 ◽  
Vol 70 (12) ◽  
pp. 3227-3240 ◽  
Author(s):  
Santiago Trueba ◽  
Sylvain Delzon ◽  
Sandrine Isnard ◽  
Frederic Lens
Keyword(s):  
Hydraulic Conductivity ◽  
Rain Forest ◽  
New Caledonia ◽  
Membrane Thickness ◽  
Hydraulic Efficiency ◽  
Key Innovation ◽  
Pit Membrane ◽  
Conduit Diameter ◽  
Perforation Plates

AbstractThe evolution of xylem vessels from tracheids is put forward as a key innovation that boosted hydraulic conductivity and photosynthetic capacities in angiosperms. Yet, the role of xylem anatomy and interconduit pits in hydraulic performance across vesselless and vessel-bearing angiosperms is incompletely known, and there is a lack of functional comparisons of ultrastructural pits between species with different conduit types. We assessed xylem hydraulic conductivity and vulnerability to drought-induced embolism in 12 rain forest species from New Caledonia, including five vesselless species, and seven vessel-bearing species with scalariform perforation plates. We measured xylem conduit traits, along with ultrastructural features of the interconduit pits, to assess the relationships between conduit traits and hydraulic efficiency and safety. In spite of major differences in conduit diameter, conduit density, and the presence/absence of perforation plates, the species studied showed similar hydraulic conductivity and vulnerability to drought-induced embolism, indicating functional similarity between both types of conduits. Interconduit pit membrane thickness (Tm) was the only measured anatomical feature that showed a relationship to significant vulnerability to embolism. Our results suggest that the incidence of drought in rain forest ecosystems can have similar effects on species bearing water-conducting cells with different morphologies.

INTERVESSEL PIT MEMBRANE THICKNESS AS A KEY DETERMINANT OF EMBOLISM RESISTANCE IN ANGIOSPERM XYLEM

IAWA Journal ◽  
2016 ◽  
Vol 37 (2) ◽  
pp. 152-171 ◽  
Author(s):  
Shan Li ◽  
Frederic Lens ◽  
Susana Espino ◽  
Zohreh Karimi ◽  
Matthias Klepsch ◽  
...  
Keyword(s):  
Cellulose Microfibrils ◽  
Spatial Density ◽  
Functional Explanation ◽  
Membrane Thickness ◽  
Membrane Pores ◽  
Transmission Electron ◽  
Pit Membrane ◽  
Bordered Pits ◽  
Angiosperm Species ◽  
Embolism Resistance

Pit membranes in bordered pits between neighbouring vessels play a major role in the entry of air-water menisci from an embolised vessel into a water-filled vessel (i.e., air-seeding). Here, we investigate intervessel pit membrane thickness (TPM) and embolism resistance (P50, i.e., the water potential corresponding to 50% loss of hydraulic conductivity) across a broad range of woody angiosperm species. Data on TPM and double intervessel wall thickness (TVW) were compiled based on electron and light microscopy. Fresh material that was directly fixated for transmission electron microscopy (TEM) was investigated for 71 species, while non-fresh samples were frozen, stored in alcohol, or air dried prior to TEM preparation for an additional 60 species. TPM and P50 were based on novel observations and literature. A strong correlation between TPM and P50 was found for measurements based on freshly fixated material (r = 0.78, P >0.01, n = 37), and between TPM and TVW (r = 0.79, P >0.01, n = 59), while a slightly weaker relationship occurred between TVW and P50 (r = 0.40, P >0.01, n = 34). However, non-fresh samples showed no correlation between TPM and P50, and between TPM and TVW. Intervessel pit membranes in non-fresh samples were c.28% thinner and more electron dense than fresh samples. Our findings demonstrate that TPM measured on freshly fixated material provides one of the strongest wood anatomical correlates of droughtinduced embolism resistance in angiosperms. Assuming that cellulose microfibrils show an equal spatial density, TPM is suggested to affect the length and the shape of intervessel pit membrane pores, but not the actual pore size. Moreover, the shrinking effect observed for TPM after dehydration and frost is associated with an increase in microfibril density and porosity, which may provide a functional explanation for embolism fatigue.

scholarly journals Pore constrictions in intervessel pit membranes provide a mechanistic explanation for xylem embolism resistance in angiosperms

2021 ◽  
Vol 230 (5) ◽  
pp. 1829-1843 ◽  
Author(s):  
Lucian Kaack ◽  
Matthias Weber ◽  
Emilie Isasa ◽  
Zohreh Karimi ◽  
Shan Li ◽  
...  
Keyword(s):  
Mechanistic Explanation ◽  
Xylem Embolism ◽  
Embolism Resistance

Characterization and comparison of the wood anatomical traits of plantation grown Quercus acutissima and Quercus variabilis

IAWA Journal ◽  
2021 ◽  
pp. 1-14
Author(s):  
Jie Wang ◽  
Shan Li ◽  
Juan Guo ◽  
Haiqing Ren ◽  
Yurong Wang ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Ring Width ◽  
Value Added ◽  
Lumen Diameter ◽  
Membrane Thickness ◽  
Quercus Acutissima ◽  
Fibre Wall ◽  
Growth Ring Width ◽  
Cambial Age ◽  
Pit Membrane

Abstract Oaks are important tree species, providing essential biomaterial for the wood industry. We characterize and compare wood anatomical traits of plantation grown Quercus acutissima Carruth. and Q. variabilis Blume to provide more detailed information to understand xylem radial growth, structure, and function, as well as differences between sapwood and heartwood, to provide data relevant for tree breeding and value-added wood utilization of oak plantations in China. In this study, radial strips were collected at breast height from the main trunk of the two species. Latewood percentage and growth ring width were investigated by X-ray densitometry and a Tree Ring Analysis System, respectively. Vessel and fibre lumen diameter, vessel and fibre wall thickness, vessel density, fibre wall thickness/diameter ratio, tissue proportions, and pit membrane thickness in between vasicentric tracheids were observed with light microscopy and electron microscopy and quantified. There were significant differences in a few wood anatomical traits between the two species: vessel wall thickness and vessel lumen diameter were higher in Q. acutissima than in Q. variabilis, while higher axial parenchyma proportion in sapwood was found in Q. variabilis than in Q. acutissima. More abundant tyloses were found in heartwood than in sapwood of both species. Our work showed the intraspecific and interspecific variation of the two species. Most differences between sapwood and heartwood must be attributed to differences in cambial age during their formation.

scholarly journals A Unit Pipe Pneumatic model to simulate gas kinetics during measurements of embolism in excised angiosperm xylem

2021 ◽  
Author(s):  
Dongmei Yang ◽  
Luciano Pereira ◽  
Guoquan Peng ◽  
Rafael V. Ribeiro ◽  
Lucian Kaack ◽  
...  
Keyword(s):  
Gas Diffusion ◽  
Ideal Gas ◽  
Striking Similarity ◽  
Measuring Error ◽  
List Type ◽  
Gas Phases ◽  
Ideal Gas Law ◽  
Embolism Resistance ◽  
Physical Laws ◽  
Pneumatic Method

AbstractThe Pneumatic method has been introduced to quantify embolism resistance in plant xylem of various organs. Despite striking similarity in vulnerability curves between the Pneumatic and hydraulic methods, a modeling approach is highly needed to demonstrate that xylem embolism resistance can be accurately quantified based on gas diffusion kinetics.A Unit Pipe Pneumatic (UPPn) model was developed to estimate gas diffusion from intact conduits, which were axially interconnected by interconduit pit membranes. The physical laws used included Fick’s law for diffusion, Henry’s law for gas concentration partitioning between liquid and gas phases at equilibrium, and the ideal gas law.The UPPn model showed that 91% of the extracted gas came from the first two series of embolized, intact conduits, and only 9% from the aqueous phase after 15 s of simulation. Embolism resistance measured with a Pneumatic apparatus was systematically overestimated by 2 to 17%, corresponding to a typical measuring error of 0.11 MPa for P50 (the water potential equivalent to 50% of the maximum amount of gas extracted).Because results from the UPPn model are supported by experimental evidence, there is a good theoretical and experimental basis for applying the pneumatic method to research on embolism resistance of angiosperms.

scholarly journals A simplified model for the analysis of COVID-19 evolution during the lockdown period in Italy

2020 ◽  
Author(s):  
Roberto Simeone
Keyword(s):  
Growth Rate ◽  
Early Stage ◽  
Additional Term ◽  
Strong Relationship ◽  
Compartment Model ◽  
Logistic Function ◽  
Simplified Model ◽  
Tuning Parameter ◽  
List Type ◽  
Protection Measures

AbstractA simplified model applied to COVID-19 cases detected and officially published by the italian government [1], seems to fit quite well the time evolution of the disease in Italy during the period feb-24th - may-19th 2020.The hypothesis behind the model is based on the fact that in the lockdown period the infection cannot be transmitted due to social isolation and, more generally, due to the strong protection measures in place during the observation period. In this case a compartment model is used and the interactions between the different compartments are simplified. The sample of cases detected is intended as a set of individuals susceptible to infection which, after being exposed and undergoing the infection, were isolated (‘treated’) in such a way they can no longer spread the infection.The values obtained are to be considered indicative.The same model has been applied both to the data relating to Italy and to some regions of Italy (Lombardia, Piemonte, Lazio, Campania, Calabria, Sicilia, Sardegna), generally finding a good response and indicatively interesting values (see chap. 5).The only tuning parameter is the ‘incubation period’ τ that, together with the calculated growth rate κ of the exponential curve used to approximate the early stage data, in this modelization, are in strong relationship with the compartments’ transfer rates.In particular ℛ0 and the numerical value of κ (dimensionless) in this model are linked by the relation: ℛ0 = 1/κ2Revision HistoryRevision # 1Errata corrige in section 1 (Introduction): the equations that summarize the relationship between the parameters were wrong. This revised version contains the correct equations at page 2.The synchronization criteria is updated. No need to use a threshold different to the one used to determine the growth coefficient. The results are now updated with the synchronization point near to the 20% of the maximum value of the cases detected per day: Modifications in section 4 (Model results for Italy). It is appropriate to use an exponential function instead of a logistic function to find the growth rate in the initial phase. Section 4 and the results are now updated.Some non-substantial corrections in the descriptive part.Revision # 2Errata corrige in the system differential equation 6: in the the derivative of S were reported a wrong additional term N. Now the equation 6 is correct.

Sign in / Sign up

Export Citation Format

Share Document