The leaf in the image below has veins running through it. The veins carry water and nutrients from the roots into the leaf.
The veins also carry ‘sugars’ out of the leaf. These ‘sugars’ are made inside the leaf and are transported to other parts of the plant to provide energy for growing and staying healthy.
Veins give support and help the leaf keep its ‘leafy’ shape…. much like our skeleton helps us keep our ‘human’ shape.
Believe it or not every leaf has thousands of tiny mouths called ‘stomata’. The ‘stomata’ on leaves are too small to see with your own eyes. You can only see the stomata if you look at leaves under a powerful electron microscope.
This is what the ‘stomata’ of a tomato leaf looks like under an electron microscope:
Below you see what a single ‘stoma’ of a tomato leaf looks like under an electron microscope.
Carbon dioxide is an important gas that enters the ‘stomata’ in daylight. Carbon dioxide helps plants make ‘sugar’ when it is light.
At the same time as using carbon dioxide to make sugars, leaves make large quantities of oxygen. Leaves do not need all this oxygen and expel it into the atmosphere through their ‘stomata’ during daylight.
At night after the sun has set the ‘stomata’ of leaves often close up. If there is no light from the sun plants cannot make any ‘food’. If plants cannot make any food when it is dark there is no point in their ‘stomata’ being open. At night plants do not need any carbon dioxide entering their leaves.
Leaves need to soak up (absorb) light to help them make sugars. The green color of leaves really helps them ‘absorb’ large amounts of sunlight. This green color is called ‘chlorophyll’. Plants use up a lot of energy making ‘chlorophyll’.
Plants need water just like humans do. Water is sucked up into the plant from its roots. In this hollyhock water is sucked up from the roots and travels to the leaves and flowers along the stem.
This painting shows a celery plant including the roots, leaves and flowers.
It is surprising to think that potatoes are actually part of the stem of a potato plant and not part of the roots! Potatoes are underground parts of the stem which store food for the plant. This supply of food provides energy for potato plants during long cold winters.