Size effect on longitudinal MOE of microtomed wood sections and relevant theoretical explanation

It has been repeatedly observed that the mechanical properties of microtomed wood sections are significantly lower than those of samples of normal size, but few investigations have been conducted to deal with this topic, especially based on theoretical approaches. We measured the longitudinal MOE of Chinese fir on microtomed sections ranging in thickness from 70 to 200 μm and compared these with the values of samples of normal size. The results indicate that the MOE of microtomed wood sections increases with thickness from 70 to 200 μm, but is significantly less than that of normal samples. A size effect coefficient of 2.63 is inferred based on statistical data for samples of normal size and 200 μm thick microtomed sections. Finally, an explanation based on a complete shear restraint model of cell walls and a single fiber multi-ply model is proposed for the size effect on stiffness of microtomed wood sections.

Ultrasonically Assisted Cutting of Histological Sections for Reducing the Environmental and Financial Impact of Microtomy

Modern-day microtomy requires high precision equipment to thinly section biological tissues.The sectioned tissue must be of good quality not showing cutting tracks or so-called artefacts.The quality of these sections is dependent on the blade wear,which is related to the hardness of the tissue sample,cutting angle and cutting speed.A test rig has been designed and manufactured to allow these parameters to be controlled.This has allowed for the blade wear to be analysed and quantified,and this has been completed for both ultrasonically assisted and conventional cutting.The obtained results showed a 25.2%decrease in average blade roughness after 38 cuts when using the ultrasonically assisted cutting regime.The data also showed no adverse effect on the quality of the slides produced when using this cutting methodology.Finally,the cutting force measured for both cutting regimes showed that ultrasonically assisted cutting required less force compared to conventional cutting.With the reduction of surface roughness and force,it is possible to state that ultrasonically assisted cutting reduces the wear of the blade,thereby increasing the life of the blades.An increase of just 10%in blade life would yield a cost saving of approximately 25%thereby reducing the environmental and financial impact of microtomy.

Changes in Anatomical Features and Protein Pattern of Sunflower Partially Resistant and Susceptible Lines During Infection By Virulence Factors of Sclerotinia Sclerotiorum

Helianthus annuus L.as an oil seed crop is widely grown throughout the world.One of the most destructive diseases of sunflower is stem rot caused by Sclerotinia sclerotiorum.Oxalic acid is the major virulence factor of this necrotrophic pathogen.It is important to further investigate plant responses to this non-specific toxin.Therefore,in the present study,we compared the patterns of total soluble proteins and xylem morphology of partially resistant and susceptible sunflower lines after treatment with Sclerotinia culture filtrate.The basal stems of both lines were treated with 40 mM oxalic acid(pH 3.7)of fungus culture filtrate and samples were collected at 24,48 and 72 hours post treatment.In SDS-PAGE protein pattern new protein bands appeared in both lines after treatment.These observations suggest induction of stress-related proteins upon culture filtrate treatment.The identities of these new proteins need to be more clarify in future investigations.The changes in xylem morphology and degree of lignification of both lines was studied by light microscopy and microtome sectioning techniques after treatment with S.sclerotiorum culture filtrate.Anatomical investigations revealed changes in xylem diameter and xylem lignification of treated lines at various time points.More lignin deposition in xylem vessels of partially resistant line has been observed after treatment.In addition,the size of xylem vessels in partially resistant line has been sharply decreased upon pathogen filtrate treatment.The results of this study will help us gain a more complete understanding of resistance mechanisms to this cosmopolitan and devastating pathogen.