S173 Plants and People - Notes from Study Period 3 - Part 1 of 2

And so, it is time for some notes on study period 3 with yet more excitingly bad drawings that will entice you to look at them the wrong way down binoculars in the attempt to make them look passable as botanical illustrations! I've had a look at the study calendar and have seen that it shows which chapters relate to which question on the end of module assignment. So while I'll not be posting anything about the EMA, I'll be quietly getting on with it in the background!

SP 3 is all about how we use wood, fibre and starch as crops. The ideal thing about these products is that because they're not fossil fuels, they are renewable as long as what is being harvested is replaced. The good thing about this is that these crops store most of their carbon while they are young, so it can lock the carbon away for a while.

Firstly we look at how plants grow and remain upright. Remaining upright is an adaptation of plants that have evolved to live out of water. Water plants don't particularly need to be strong and grow upright, as the water supports them (along with other adaptations like air bubbles). The structure of plant stem is given strength from tissue called sclereids. These have very thick cell walls that contain lignin, which provides waterproofing and strength, and have irregular shapes. The pits of peaches are an example of these tissues. This strength allows

• the transport of water upwards from the roots via xylem

and

• for the products of photosynthesis to be transported to the rest of the plant via phloem.

You may be forgiven for thinking that the first diagram is of a rainbow, but it's actually a simplified stem followed by a close up of the different layers.

Wood
Every year the water transporting tissue called xylem creates a new layer. This can be seen as a ring when looking at the cross-section of a trunk. The rings are seen best in regions that have a growing season and a dormant season (winter). The xylem dies as it matures and is impregnated with chemicals, such as lignin and suberin and over time this becomes the heartwood of the tree, providing support.

Uses of wood
Wood is often used as a building material, for example to create timber frames, flooring, roofs, sheds, benches for some, or all, of the following reasons:

• Insulating - poor conductor of heat due to small air pockets.
• Flexible - can be bent as the cells will elongate (sometimes this is helped by dipping the wood into boiling water and bending it).
• Light but strong - open structure and ligin.

To ensure availability of cheap, light building materials, engineered wood products have been created such as MDF and chipboard. They are composed of small pieces of wood that have been glued together. These sheet materials make it easy to create furniture such as shelving units, for example.

Look out for the FSC logo on wood products are this shows:

• responsible management to meet social, economic and ecological needs
• standards and trademark assurance
• accreditation to businesses and organisations that supply and manage timver in a sustainable manner.

I will write a separate post for dendrochronology and will link that and part 2 to this post when written.

ETA -
Part 2
Dendrochronology