Life Processes
Life processes in plants
Say what photosynthesis needs and what it gives back, read the experiment that proves each ingredient, and name the tubes that carry water up and food out.
A plant does not eat. It gets heavier year after year and nothing goes into it but water from the ground, gas from the air and light from the sky. Out of those three, in the green of its leaves, it builds sugar. This chapter is a set of experiments, each designed to remove one ingredient and see whether the plant can still make food without it.
Photosynthesis, in one line
Carbon dioxide and water, in the presence of sunlight and chlorophyll, give glucose and oxygen. The glucose is instant energy and is later stored as starch. That is why iodine turning a leaf blue-black is the standard test: it is looking for the stored form of the food the leaf has made.
Have a play
The parts of a plant, and what each one does with water and with food.
Tap any part of the picture.
Worked example
Half a leaf is sealed inside a bottle of caustic soda, which soaks up carbon dioxide; the other half stays outside in the air. The whole plant sits in sunlight for a few hours, then the leaf is tested with iodine. The outside half goes blue-black; the inside half does not. What has been shown?
List what the two halves shared. Same leaf, same plant, same sunlight, same chlorophyll, same water supply.
An experiment can prove something about one ingredient at a time, and it can do that just when the rest are held steady.
Try it together
A water plant under an inverted test tube is put in sunlight, and bubbles collect in the tube. Work out what the gas is and what it tells you.
A glowing splint is pushed into the collected gas and flares into a bright flame.
1.A flame burning more brightly points to one gas in particular. Which gas is in the tube?
Have a go
Have a go on your own. Some leaves look red or violet rather than green, because other coloured pigments in them outweigh the green one and hide it. What is that green pigment called?
Ready to practise?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.