Fuyu Ito

Structures and physiological functions of silica bodies in the epidermis of rice plants

We characterized silica structures in the epidermis of rice plant leaves and investigated their physiological functions from optical and mechanical viewpoints. By treating the distribution of silica bodies as a triangular lattice in the xy plane, and performing a theoretical optical analysis on this lattice, we discovered that a reduction in the photonic density of states may inhibit leaves of rice plant from being heated markedly higher than 20 °C. Ladderlike structures in the epidermis were mechanically investigated. These structures are conjectured to inhibit flat leaves from undergoing twisting torsions, which may assist the leaf to absorb sunlight more effectively for photosynthesis.

Nanocomposite of silk fibroin nanofiber and montmorillonite: Fabrication and morphology

The purpose of our research is creating a new nanocomposite material. Generally silk fibroin (SF) is regarded as a promising base material for biomedical uses. The incorporation of montmorillonite (MMT) into SF fibers would improve physical properties of the SF fibers. We investigated a new method of combining electospun SF with MMT. Specifically, electrospun silk nanofibers were treated with methanol and dipped in a MMT suspension. We could obtain a nanosheet composite of silk nanofibers and MMT. Their ultrastructures were successfully visualized by high resolution transmission electron microscopy. This compound was comprised of individual silk nanofibers surrounded by thin layers of MMT, each with a thickness of about 1.2 nm. This structure was confirmed by elemental analysis. We also performed IR, NMR and X-ray diffraction analyses in conjunction with morphological data. Conclusively we obtained a new composite of silk nanofiber and MMT, which has never been reported. Using this unique nanocomposite biological tests of its application for a scaffold for tissue engineering are under way.

Roles of silica and lignin in horsetail (Equisetum hyemale), with special reference to mechanical properties

This research deals with detailed analyses of silica and lignin distribution in horsetail with special reference to mechanical strength. Scanning electron images of a cross-section of an internode showed silica deposited densely only around the outer epidermis. Detailed histochemical analyses of lignin showed no lignin deposition in the silica-rich outer internodes of horsetail, while a characteristic lignin deposition was noticed in the vascular bundle in inner side of internodes. To analyze the structure of horsetail from a mechanical viewpoint, we calculated the response of a model structure of horsetail to a mechanical force applied perpendicularly to the long axis by a finite element method. We found that silica distributed in the outer epidermis may play the major structural role, with lignin’s role being limited ensuring that the vascular bundle keep waterproof. These results were in contrast to more modern tall trees like gymnosperms, for which lignin provides mechanical strength. Lignin has the a...

Development of combination textile of thin and thick fiber for fog collection bioinspired by Burkheya purpurea

Fog collection is getting to be known as an important technology all over the world. Textiles and fibrous materials have been used and investigated as fog collectors. Plants and animals need to collect water from air in an arid area. We focused on Berkhera purpurea which is one of the African thistles collecting moisture or fog by hairs. This plant captures fog droplets using finer and comparatively hydrophilic hairs supported by thicker and hydorophobic hairs. Mimicking these fibers’ system of thicker fibers and thinner fibers, hydrophobic and comparatively hydrophilic, we made a thinner fiber created by electrospun cellulose acetate on a thicker fiber of Nylon mesh as a supporting material. In the experiment, fine fibers of cellulose acetate are electrospun for 1 min which gave the superior fog capturing property.

Mechanics of water collection in plants via morphology change of conical hairs

In an arid area like the Namib Desert, plants and animals obtain moisture needed for life from mist in the air. There, some plants have hairs or fibrous structures on their leaf surface that reportedly collect fresh water from the air. We examined the morphology and function of leaf hairs of plants during water collection under different circumstances. We studied the water collecting mechanics of several plants having fibrous hairs on their leaves: tomato, balsam pear, Berkheya purpurea, and Lychnis sieboldii. This plant was selected for detailed investigation as a model because this plant originated from dry grassland near Mount Aso in Kyusyu, Japan. We found a unique feature of water collection and release in this plant. The cone-shaped hairs having inner microfibers were reversibly converted to crushed plates that were twisted perpendicularly in dry conditions. Microfibers found in the hairs seem to be responsible for water storage and release. Their unique reciprocal morphological changes, cone-shaped...

Optical properties of nanoporous silica frustules of a diatom determined using a 10 µm microfiber probe

A microfiber spectroscopic method was developed to reveal the photonic crystalline characteristics of a cylindrical frustule of the diatom Melosira variance. The spectroscopy apparatus used was composed of two quartz fibers with fine ends, approximately 10 µm in diameter, set on micromanipulators to control the position of the fine ends of each fiber, which were focused at the edge of a frustule. The method had fine space resolution and sensitivity toward the propagation direction of incident light, which is suitable for analyzing photonic crystallinity. A typical absorption was observed at wavelengths of 400–500 nm, which corresponded to a quasi-stop band calculated by a finite-difference time-domain (FDTD) method for a three-dimensional (3D) slab model constructed based on an SEM image of the frustule. These results suggest that the photonic crystalline characteristics of the frustule can assist the absorption of incident light near 420 nm, which is crucial for the efficient photosynthesis of the diatom.

Roles of trichomes with silica particles on the surface of leaves in Aphananthe aspera

There exist many trichomes with silica particles on the surface of leaves in Aphananthe aspera (Muku tree). The size of the trichomes is on the order of some tens to hundreds of micrometers. Investigating the electric-field local densities of the states and distributions of electromagnetic wave propagation, we theoretically revealed that while trichomes play a role as waveguides for the far-infrared, silica particles help incident far-infrared light efficiently propagate inside the trichomes and leaves. These properties would be useful for efficiently warming plants, since absorbed far-infrared light is converted to heat.