Wood - a fascinating material

 INTRODUCTION

Wood is a wonderful material. It embodies the beauty and the odor of forests, the ecology of a natural building material and the microscopic aesthetics of a complex 3-dimensional anatomical structure.

The secondary cell wall of plants, constructed of parallel cellulose fibers embedded in an amorphous matrix is impregnated with lignin and minerals as a stabilizing factor for altitude records, e.g. the “Tall Tree”, 112 Meter height, a Sequoia tree from the California National Park. Shrubs and herbs use this principle to a lesser extent.

About tree dimensions. Look for the human. (Source)

For the increasing lack of sand and therefore of concrete as a construction material architects today tend to wood as an alternative. Asian engineers are famous for their buildings made with the help of a bamboo scaffold.

Hong Kong building with bamboo scaffold. (Source)

In Europe, architects are increasingly working with natural materials to follow the ecological demands of their customers. They reinvent proven technology with wood as a basis. From a wooden house to a wooden skyscraper: a big step.

The concept for Germany’s first high-rise building in Germany made of wood. (Source)

WOOD MICROSCOPIC VIEWS

All attributes of wood can be derived from a microscopic analysis. The odor of a Christmas tree (resin channels!), the characteristics of furniture wood, the mechanical stability of timber. A tree trunk with its 3-dimensional structure needs 3 cutting planes to be fully understood: a cross section, a tangential cut, a radial cut.

• THE CROSS SECTION

The cross section is most easy to understand: 

You need a unique sample for your teaching lesson? Have a look into your rain gutter.

It’s real life: Sometimes the good things are closer than expected. Your rain gutter not only disposes the water from your roof, but also collects detritus from its colonizers such as mosses and lichens. It’s an extreme biotope: wet and cold in winter, even freezing, dry and hot in summertime. Only few microorganisms survive this extreme change.

One of them just recently came into spotlight. In April 2019 the Israeli space probe Beresheet* crashed onto the surface of the moon; 585kg of weight caused a small caldera. Aboard there were several thousands of Tardigrada, also known like Water Bears. As they had been transported in dried condition, and apparently no water seems to be available on the moon by fog or rain, the probability of life on the moon in 2020 still is quite low.

No need to travel so far to meet this astonishing group of animals. Take a sample of detritus from your rain gutter, if dry, first let it soak in rainwater. After a few days at room temperature it is time to check the water sample. Tardigrada may be fixed on the surface of moss leaves, so it makes sense to place a moss stem on the glass slide and to strip off the leaves by using two tweezers, one fixing the stem, one stripping off the leaves against the direction of growth.

A dead Tardigrada: Sectoral structure of body clearly visible.

Honey - Try to find out its origin

Honey is one of the oldest food products. Cave paintings from the stone age give witness of how the product of wild bees has been used as the first sweetener, containing lots of positive ingredients for a general healing effect.

Nowadays honey is part of the food industry with its profit orientated mechanisms. Price is an issue, and the cold hurled product needs careful attention and efforts for maximum quality.

The origin of a product in general is essential for tracing the manufacturing steps. Latest since BIO became a quality issue in food industry, foodstuff testing laboratories are looking for hints to find out the nectar and honeydew sources which are the basis of honey. Pollen residuals within the honey give a clear indication about the region of origin. In Europe, honey from Central America is widespread, but not always clearly indicated. Eastern Europe and China are playing an important role as honey producers.

Once the pollen is detected and allocated to a defined plant species, it is easy to debunk imposters. Pollen from tropic plants found in a honey sample declared as a Central European product – a microscope will be the necessary tool to find out. Brightfield illumination is the required method, Phase contrast is not optimal as the pollen grains clearly have a significant 3D dimension, too thick for applying this contrast method. Simple POL contrast may help to find the isolated pollen grains within the honey sample.

Some examples from the Middle European flora:

Leontodon spec.

A perfect sample for understanding the fine focus procedure: Pollen grains from Cobaea scandens

Cobaea Scandens (Jacob’s ladder family) is a widespread ornamental plant for garden and balcony. Domiciled in Mexico, this climbing plant is cultivated as an annual in the temperate zones.

Beside its aesthetics with bell-shaped violet flowers, there are two more aspects worth to mention:

• This plant is pollinated by bats. 
• Tthe large (~ 160 microns Ø) pollen grains of Cobaea show a complex structure which is worth to discover.

Pollen Grains in Brighfield