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The programme is divided into five main sections:
1. The significance of plants
2. Photosynthesis and the leaf
3. A potted history of photosynthesis
4. Making starch and cellulose from sugar
5. Designing leaves for maximum photosynthesis
Green Plants is concerned with the importance of plants as a source of useful products and the processes by which biomass is produced. The programme uses the Eden Project, which comprises the worlds largest environmentally controlled glasshouse, to illustrate the phenomenal variety of plant forms and the many uses to which species can be put.
Supermarkets are full of fresh plant produce including chives. In a vast greenhouse complex the growth of herb plants is investigated. Conditions are carefully controlled so that the most economically productive temperature, light intensity and carbon dioxide concentration are provided.
The leaf is the site of photosynthesis. A 3D graphic animation is used to explore the different structures within a leaf and to explain how they assist in the process of food production.
The chemical process of photosynthesis is summarised in a concrete way with bags of carbon dioxide and oxygen, a jug of water and a bowl of sugar. Much of the glucose made by photosynthesis is used to make cellulose or starch. An entertaining animation gives us an insight into the history of ideas about plant growth.
The programme returns to its starting point to explore the variety of leaf shapes found in the Eden Project greenhouses and to explain how these shapes are adapted to particular habitats.
Time-coded programme outline
00.0005.10 Why are plants so important?
The Eden Project in Cornwall consists of four large glasshouses where a carefully controlled environment recreates the natural habitats of thousands of plants. A tour of the rainforest biome illustrates the diversity of plant forms. We are introduced to a selection of useful plants cocoa for chocolate, pineapple, palm nuts and many others.
05.10-06.21 What would the world be like without plants?
A startling disappearing act shows the variety of everyday items that depend on plants for their production. Our hero loses his drink, his furniture, his radio and even his clothes as the items which depend on plants disappear!
06.21-07.52 How do plants make oxygen?
Without plants there would be no oxygen in the atmosphere and no animals. A demonstration clearly shows how oxygen is made by pond weed. The glowing splint test for oxygen is shown in close-up.
07.52-09.52 What do plants need to grow?
Supermarket shelves are stocked with living herb plants. We visit a commercial plant grower in Lincolnshire to find out how the ideal conditions for growth are created. A boiler and fans are used to maintain the ideal growing temperature. The boiler also produces carbon dioxide, which the plant uses as a raw material. The other important raw material is water, which is collected as rainwater. In winter it is too dark for the plants to grow quickly so special sodium lights simulate sunlight.
09.52-12.21 How does a leaf work?
The leaf is where the plant combines carbon dioxide and water. With the help of a 3D graphic, we explore the layers that make up a leaf. We follow the path taken by carbon dioxide through the stomata and into the leaf. Zooming in on the palisade layer we find cells packed with chloroplasts. The roots of a growing herb plant are revealed and time-lapse photography shows roots growing through the soil and developing root hairs. We follow the path of water into the root hairs and up the stem in xylem tubes to the leaf. The process of photosynthesis is summarised.
12.21-15.11 How did scientists find out about photosynthesis?
A cartoon animation traces the development of ideas about plant growth. We see Jan Baptista van Helmont demonstrating that a plant gains mass by absorbing material from water. Further investigation showed that plants need carbon dioxide and produce oxygen. Finally, the importance of light for oxygen production was shown. The process is summarised visually using bags of gas, a jug of water, a lamp and a bowl of sugar.
15.11-17.28 What happens to the glucose?
We see a colourful selection of fruit and vegetables. The Benedicts test for reducing sugars is demonstrated in close up. Some of the glucose made in photosynthesis is turned into starch. The chlorophyll is removed from a leaf and it is tested with iodine solution. Plant cell walls are made of cellulose. This is also made by combining glucose molecules.
17.28-End How does a plants shape help it to get enough light and water?
We return to the Eden project to examine a few of the different plant shapes in the rainforest biome. Some leaves are wide or arranged so as not to overlap each other. These plants collect most of the available light. Other plants have plenty of light but need to conserve water with smaller leaves. Animals and plants have developed complicated interrelationships. We are left to consider how such a vital resource should be protected.