A year in the life of a sugar factory

The leaves of plants are everywhere in Nowhere Wood, helping to keep the wood alive. Leaves are organs: collections of living tissues and cells, having adventures in time and space. This is the story of a year in the life of an oak leaf.

Leaves are factories for making sugar from sunlight, water and carbon dioxide from the air. No human factory can do this, which is why we, and all other organisms, are so dependent on plants. Leaves are the producers of food.

In is late November and the cells that will divide to make the new leaf are protected safely inside the scales of the bud. Early in March, when the days warm and get longer, stem cells within the bud start to divide many times, producing all of the cells of the new leaf. To start with, the cells are very small and all look the same.

Soon, the cells take up water and get much larger. They escape the protection of the bud and the new leaf emerges. The new cells no longer look the same: they are on different journeys of development, becoming all of the different cells and tissues that make up the leaf.

 

The leaf is a factory for making sugar. Like any factory, it has a source of energy and transport systems to get the raw materials into the factory.  It also moves the manufactured sugar out to the places in the plant where it is needed. The heart of the factory is the production line where sugar is made. These are called chloroplasts and the leaf has millions of them, all making sugar whenever the sun shines. The Spring and Summer are sugar making seasons.

Gradually, in the autumn, when the days get cooler and shorter, the sugar factories are shut down and abandoned. The chloroplasts lie in ruins as everything useful is recycled back into the branches of the tree. All that remain are the frameworks of cell walls, turning brown as they dry in the autumn air.

 

Finally, the oak tree makes a special layer of cells that separates the old leaf from the stem, and the leaf is ready to fall when the wind blows strongly. The fallen leaves are not wasted, becoming energy stores for the organisms that feed on them. Next year’s buds are forming and wait for spring and the production of new leaves.

If leaves are factories form making sugar, then trees are factories for making leaves.

Everything has its own season in Nowhere Wood.

  1. Think about how the leaf is a factory for making sugar. Where does its energy store come from? How do the raw materials get to the production line?
  2. The production of leaves is sustainable in Nowhere Wood. What do you think this sentence means?

Subterranean superheroes

Climbing the walls

A hundred years ago, Nowhere Wood was a sandstone quarry, and there is still a cliff face at the end of the wood.
How can this hart’s tongue fern grow on a vertical cliff face about two metres from the ground.

That is quite an adventure in time and space. This story explains how this fern can climb walls.


Ferns are an ancient group of plants, first appearing on Earth about 390 million years ago. That’s about 260 million years before the emergence of flowering plants.

Like fungi, another ancient group, ferns produce spores. They are the brown dots on the underside of this fern leaf. Spores are light and float in the air like particles of dust.

One spore floats up to a small crack in the rock face. Rainwater and the decaying remains of a leaf have formed a sticky, jam-like, humus inside the crack.  The spore sticks to the humus and germinates, developing into a tiny little plant, about 10 mm long.

This is a fern, but it is not the mature adult form. It has tiny roots that grow into the humus, drawing nutrients from it.
This small plant is called a gametophyte because it makes gametes for sexual reproduction. Gametes are sperm and egg cells. 


These gametes will come together to make the adult fern on the surface of the tiny gametophyte.

The gametophyte makes many small sperm that swim in the water on the surface of the plant. They swim towards eggs, which are much larger. This photograph shows a fern sperm fertilising a fern egg.

The sperm and the egg join together. A single cell is produced that will grow into the adult fern. Eventually this fern will make spores of its own.

This may sound like a long-winded and complicated adventure, but it seems to work well, because there are so many ferns in Nowhere Wood.

The fern exists in several different forms during its adventure: spores, eggs, sperm, gametophyte and adult plants. What do they have in common?

Each of these forms is made of one or many cells. Each cell contains a nucleus, and inside each nucleus is a genome. Genomes contain information. The information in the genome is the same in all of the different forms of the fern.

The genome contains the secrets of how to be a fern and how to move forward in the next step of the adventure.

  1. The fern exist in several different forms during its adventure: spores, eggs, sperm, gametophyte and adult plants. Think why is important that the genome in every form is the same? 

Life is a relay race

Moving things on

The weather is warm and wet in Nowhere Wood.

These are perfect conditions for growing the fungi that spread  everywhere throughout the soil of Nowhere Wood. Fungi are Nature’s recyclers, feeding on the fallen leaves, fruits and wood.

Fungi feed on the wood of the dead oak trees, turning it into nutrients that provide energy and chemicals needed  to grow new fungal cells.  (These cells form long threads called hyphae). Some fungi can spread out over really large areas, several kilometres wide.

At this time of the year, the fungi are busy ‘ being’.

Then one night, silently and without warning, the fungi do something else.

They produce structures that we call “mushrooms” **.

Mushrooms are  fruiting bodies. They produce thousands of tiny spores.

Spores are small and light. They are carried on air currents to new places in Nowhere Wood, where they will germinate and grow into new hyphae.

Spores have often been found in the filters of jet aircraft flying at the edge of the atmosphere, so some spores can travel right round the world. When fungi produce spores they are ‘becoming’ something new: small, light and mobile versions of themselves.

Then, almost as soon as they arrive, it is all over. The fruiting bodies die and become food for other fungi and bacteria in Nowhere Wood.

This is how it is. The precious molecules are used, recycled and become part of the growth of new organisms. Nothing is ever wasted.



 

  1. All of the atoms in the world were made when the universe began. No atoms have been made or destroyed since then. Imagine what life would be like without Nature’s recyclers.
  2. You are a collection of recycled atoms. Think about how carbon atoms enter and leave your body. [Hint, carbon atoms are found in carbohydrates and in carbon dioxide.]

You can read more about ‘being and becoming’ here.

 

**Some mushrooms are good to eat, others are really poisonous and can kill us. It is hard to tell them apart unless you are an expert, so it is sensible not to touch or eat any mushrooms you find in a wood.

Climbing the walls

Squirrel wars

One hundred and fifty years ago, the oak woods near Nowhere would have been home to red squirrels. Now they have all disappeared.

The red squirrels have been replaced by grey squirrels that were introduced into the UK from the United States in the 1870s.

Grey squirrels spread to nearly all parts of the UK, replacing the red squirrels wherever they went. Now red squirrels are only found in a few places, where they are protected.

Grey squirrels are 60% better at digesting oak acorns than red squirrels, which seem to prefer hazel nuts. Oak acorns are much more common in Nowhere Wood than hazel nuts, and this favours the grey squirrel.

The success of grey squirrels at surviving and breeding in Nowhere Wood is due to the production of acorns, which varies from year to year.

Survival is a risky journey for any squirrel: the arrival of new competitors or interruptions to the food supply can pose real challenges.

 

Their lives are  adventures.

The word ‘adventure’ has two parts:

Ad means moving towards something.

Venture means attempting something dangerous or difficult, that is risky, with no guarantee of success.

Put the two together and you get the idea that the lives of all living organisms are risky journeys into the future, with no guarantee of success or survival.

If you like, you can think of life as:

organisms having adventures in time and space

  1. Think about the squirrels and the oak trees. In what ways are their lives adventures?  [Hint: think about what the word adventure means.]

 

Being and becoming in Nowhere Wood

Being and becoming in Nowhere Wood

 

All living organisms are doing two things at the same time. They are:

Being (they are keeping themselves alive) and

Becoming (they are moving towards the next stage of their lives).

The butterfly is being and becoming at each stage of its life.

All of the animals and plants in Nowhere Wood are also “being” and “becoming”.

  1. How are the oak trees in nowhere Wood being and becoming?
  2. How are you being and becoming

 

Counting the ways to stay alive

Trampling acorns underfoot


I have never seen so many acorns in Nowhere Wood. Everywhere I step, I am treading on acorns. Acorns are the fruits of oak trees and this year it certainly has been a bumper harvest.  Biologists call this a “mast year”.

The air in Nowhere Wood in April and May was very hot and still. This allowed the oak pollen to hang in the air near the feathery stigmas of the oak flowers. Perfect conditions for pollination and making acorns.




July and August were warm and wet, ideal conditions for growing a record crop of acorns.

This is good news for the birds of the wood, like pigeons, jays and woodpeckers, which eat acorns. And for the squirrels and mice, too. Deer eat acorns, and I did once see one near the woods very early in the morning. The oak trees are producers and this is one way that they make food for the woodland herbivores.

The oak trees in the wood are perhaps seventy or eighty years old now and tower above the other trees. They are successful, but for how much longer? The oldest trees are falling down, some by lightning strikes during thunderstorms.

It is difficult for young acorns to grow into oak trees, because the floor of the wood is covered by thick ivy and brambles. There is a battle going on here for light, space and water that makes an episode of Eastenders look tame!

Some young shoots make it through to the light, but they are few and far between. The future of acorns in Nowhere Wood will depend on them.

Everything is connected together, and a change to one organism affects everything else. The squirrels and the jays will be needing the oaks to remain successful. This is the way of life in Nowhere.



 

  1. Walk round an open space or a park near where you live. How are the living organisms depending on each other to survive?



Squirrel wars