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 ◽  
...  

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.

IAWA Journal ◽  
2016 ◽  
Vol 37 (2) ◽  
pp. 152-171 ◽  
Author(s):  
Shan Li ◽  
Frederic Lens ◽  
Susana Espino ◽  
Zohreh Karimi ◽  
Matthias Klepsch ◽  
...  

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.


2020 ◽  
Author(s):  
Lucian Kaack ◽  
Matthias Weber ◽  
Emilie Isasa ◽  
Zohreh Karimi ◽  
Shan Li ◽  
...  

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.


IAWA Journal ◽  
2021 ◽  
pp. 1-19
Author(s):  
Shohei Yamagishi ◽  
Kengo Shigetomi ◽  
Syunya Fujiyasu ◽  
Dan Aoki ◽  
Tetsuro Uno ◽  
...  

Abstract Intervessel pit membranes are recognized as key structures for influencing water flow/embolism resistance. The mechanisms remain largely unclear owing to difficulties in examining them intact in nature. This study investigates ethanol-extractable pit membrane incrustations (PMIs), which were previously reported in certain angiosperms and may affect their water conduction. The presence of PMIs was determined for 40 angiosperms by field-emission scanning electron microscopy (FE-SEM). Candidate components of PMIs were determined by chemical analyses of wood extracts, and their distributions in the xylem were examined by time-of-flight secondary ion mass spectrometry (TOF-SIMS). Cryo-TOF-SIMS and cryo-FE-SEM were also performed to clarify the native distribution of PMIs. PMIs were observed in 11 species. Some of them were categorized as fat trees, which are known to store abundant lipids. Tilia japonica sapwood displaying PMIs contained large amounts of lipids, which were distributed in the dried xylem tissue, consistent with the distribution of the PMIs. In the frozen samples of T. japonica, however, the distributions were restricted to the parenchyma. In conclusion, PMIs consist of an artifactual coating of lipids originated from the parenchyma in dried samples at room temperature. Researchers performing surface analyses of plant cell walls should take strong precautions against such self-coating by these intrinsic chemicals.


2020 ◽  
Author(s):  
Ajaree Thonglim ◽  
Sylvain Delzon ◽  
Maximilian Larter ◽  
Omid Karami ◽  
Arezoo Rahimi ◽  
...  

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.


IAWA Journal ◽  
2021 ◽  
pp. 1-14
Author(s):  
Jie Wang ◽  
Shan Li ◽  
Juan Guo ◽  
Haiqing Ren ◽  
Yurong Wang ◽  
...  

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.


1987 ◽  
Author(s):  
I Ford ◽  
P G Newrick ◽  
R Malik ◽  
F E Preston ◽  
J D Ward ◽  
...  

We have examined coagulation parameters in 15 neuropathic (Group A) and 10 complication-free diabetic patients (Group B). Venesection and sample testing were performed under standard conditions. Group A underwent sural nerve biopsy and 14 also had measurements of endoneurial oxygen tension. Factor VIII related antigen was higher in Group A (l-617u/ml ± 0.67) compared to Group B (0.944u/ml ± 0.26); (mean ± SD; p<.0.05) perhaps suggesting endothelial cell damage, although this did not correlate with capillary basement membrane thickness or endothelial cell number nor with endoneurial oxygen levels. Platelets from Group A were more sensitive to arachidonate than those of Group B, showing aggregation thresholds in platelet rich plasma of 0.36 ± 0.17mM and 0.57 ± 0.9mM respectively compared with 0.65 ± 0.37mM in non-diabetic controls.Platelets from Group A subjects also produced more thromboxane B2 in response to arachidonate than Group B or normal controls (37.95 ± 27.5; 25.5 ± 13.0; 16.55 ± 15-5pmol/107 platelets). Blood fibrinolytic capacity measured by euglobulin clot lysis time, was diminished in NIDDs (post-occlusion ECLT 165.7 mins ± 116.0), compared to IDDs (55.5 ± 34.5) (p<0.05) due at least in part to excess of tissue plasminogen-activator inhibitor, although we found no significant difference in ECLT between Group A and Group B. Interaction between haemostatic and microvascular abnormalities in diabetes may contribute to the pathogenesis of diabetic neuropathy.


Weed Science ◽  
2013 ◽  
Vol 61 (2) ◽  
pp. 277-282 ◽  
Author(s):  
Mette Goul Thomsen ◽  
Lars-Olav Brandsæter ◽  
Haldor Fykse

In the present field study, the capability of Canada thistle to develop shoots from intact roots and root fragments at different soil depths was studied. The experiments were performed on four sites with high-density Canada thistle, with three or four replications per treatment. At each site, the soil in the plots was removed layer by layer (to 30 or 40 cm, depending on the site), within a 1 by 1-m quadrat, and spread out on a plastic sheet. All roots and other plant parts were removed, and the soil was either replaced without any root material (two sites), or the roots of the thistles were cut into 10-cm-long fragments and replaced into the source holes (two sites). The measured variables were shoot number and biomass. The number of shoots of Canada thistle decreased with increasing depth (P < 0.001) and increased with time. Additionally, the two factors interacted (P < 0.001) such that shoot development was slower from greater depths. Roots from ≤ 20 cm depth produced higher biomasses than did roots from below 20 cm depth. Replacement of root fragments did not affect the amount of biomass produced. It was concluded that the intact root system contributed considerably more to the total biomass produced by Canada thistle than did the root fragments in the upper soil layers.


1969 ◽  
Vol 47 (10) ◽  
pp. 1579-1583 ◽  
Author(s):  
R. L. Peterson

Root segments of the fern Ophioglossum petiolatum with either an intact root apex or with the apex removed were treated with distilled water (control) or a range of concentrations of kinetin or benzyladenine in aqueous solution. Buds initiated on segments treated with distilled water or low concentrations of cytokinins had an apical meristem consisting of an apical cell with derivatives and a few leaf primordia located immediately beneath an air cavity formed by the lysis of cortical cells of the parent root. There was little cortical proliferation associated with the initiation of these buds. However, application of cytokinins at relatively high concentrations induced considerable proliferation of root tissue and a concomitant organization of numerous apical meristems in this tissue. Each induced meristem was structurally similar to those initiated on control root segments or those treated with low concentrations of cytokinins with the exception that leaf primordia were not as readily visible. Groups of tracheid-like cells were present in the callus-like outgrowths and, in root segments treated with 10.0 mg/l kinetin, large starch-filled parenchyma cells were evident at the periphery of the proliferations.


2009 ◽  
Vol 23 (5) ◽  
pp. 506-511 ◽  
Author(s):  
Zi Zhang ◽  
Demin Han ◽  
Shengzhong Zhang ◽  
Yehua Han ◽  
Wei Dai ◽  
...  

Background Patients with chronic rhinosinusitis (CRS) often remain symptomatic after technically proficient functional endoscopic sinus surgery. Current hypothesis indicates biofilms may contribute to the persistence of infection. However, few studies showed biofilms in postoperative patients. This study was designed to identify bacterial biofilms on postoperative mucosa, as well as to investigate the healing of sinus mucosa after surgery. Methods After intraoperative mucosa was obtained for assessment of biofilms, 27 patients were followed up for 6 months. Postoperative medications and symptoms were recorded. As indicated by endoscopic evaluation, biopsy specimens of postoperative edema, scar, or adhesion were obtained. Samples were prepared for scanning electron microscopy (SEM) and hematoxylin and eosin (H&E) staining. Results Fifteen postoperative samples were taken from the 20 patients with intraoperative biofilms. Under SEM, postoperative biofilms were identified in 4/6 scar samples and 5/9 edema samples. There was no significant difference in biofilm presence between samples of scar and edema. Microcolonies were also identified on postoperative scar under H&E staining. The presence of intraoperative and postoperative biofilms was correlated with the severity of preoperative Lund-MacKay computed tomography score and postoperative Lund-Kennedy endoscopic score. Compared with intraoperative samples, postoperative samples from the same nine patients significantly recovered from ciliary damage, metaplasia, and basement membrane thickness. Postoperative cultures were positive in samples with and without postoperative biofilms. Conclusion Biofilms persist after treatment, and may cause the unfavorable outcomes of surgery for CRS. The mucosa with biofilms can recover after surgery. Apparent bacterial plaque can be identified by H&E staining.


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