Reliable characterization of cellulose nanomaterials is critical for their utilization in various applications.

Cellulose nanofibrils (CNF) show high modulus and strength, and are already used in industrial applications. Mechanical properties of neat CNF films or CNF-polymer matrix nanocomposites, are usually much better than for polymer matrix composite films reinforced by clay, graphene, graphene oxide or carbon nanotubes. In order to obtain small CNF diameter and colloidal stability, chemical modification has so far been necessary, but this increases cost and reduces eco-friendly attributes. In this study, an unmodified holocellulose CNF (Holo-CNF) with small diameter is obtained from mildly peracetic acid (PAA) delignified wood fibers. CNF is readily defibrillated by low energy kitchen blender processing. The hemicellulose coating on individual fibrils in the wood plant cell wall is largely preserved in Holo-CNF. This “native” CNF shows well-preserved native fibril structure in terms of length (2.1µm), diameter (<5 nm), high crystallinity, high cellulose molar mass, electronegative charge, and limited mechanical processing damage. The hemicellulose coating contributes mechanical properties and high optical transmittance for CNF nanopaper, which can otherwise only be achieved with chemically modified CNF. The CNF nanopaper shows superior mechanical properties with a Young’s modulus of 21 GPa and an ultimate strength of 320 MPa. Moreover, hemicellulose imparts recyclability from dried state. Altogether, this native CNF represents a class of colloidally stable, eco-friendly, low cost CNF of small diameter for large-scale applications of nanopaper and nanomaterials.

Horticulture Research is a new Open Access, fully peer-reviewed journal which will publish the best and most interesting research focusing on all major horticultural crops from around the world.

Virus-induced gene silencing (VIGS) was used as a tool for functional analysis of cell wall-associated genes that have been suggested to be involved in leaf abscission. Tobacco rattle virus is an effective vector for VIGS in tomato (Lycopersicon esculentum). Silencing was more efficient when the plants were grown at 22 °C than when they were grown at 20 °C or 25 °C. The photobleaching phenotype resulting from silencing phytoene desaturase varied, depending on cultivar, from barely visible to photobleaching of entire leaves. To study the function of abscission-related genes, a purple transgenic tomato line constitutively expressing the maize anthocyanin regulatory gene, Leaf colour (Lc) was used. Silencing Lc expression in this line resulted in reduced anthocyanin production (reversing the colour from purple to green), thus providing a convenient silencing ‘reporter’. Silencing tomato abscission-related polygalacturonases (TAPGs), using a TAPG1 fragment, delayed abscission and increased break strength of the abscission zone in explants treated with 1 μl l⁻¹ ethylene. The abundance of TAPG1 transcripts in the green (silenced) abscission zone tissues was <1% of that in the purple (non-silenced) controls. As a highly homologous region was used for all five polygalacturonases it is assumed that the effect of delayed abscission is the result of silencing all the genes in this family. By contrast, silencing abscission-related expansins (LeEXP11 and LeEXP12) and endoglucanases (LeCEL1 and LeCEL2) had no discernible effect on break strength, even when the two endoglucanase genes were silenced concurrently. Simultaneous silencing of TAPG and LeCEL1 was no more effective than silencing TAPG alone. The data demonstrate the importance of TAPGs in the abscission of leaf petioles.