Download Leaves adapt - Let it Grow

Workshop
Leaves adapt
1. From more to less: large or small?
2. From weak to tough.
Introduction
Leaves are the organs responsible for photosynthesis, a vital process in plants.
Through their leaves plants carry out gas exchange with the atmosphere
and capture the sunlight that provides the energy needed to perform the
photosynthesis process.
So if leaves have the same function in all plants, why aren’t all leaves the same?
They are not the same because they have adapted to the environment
so as to use resources more effectively. The amount of light received in the
middle of the desert is not the same as under the tree canopy in the forest.
So if environmental conditions are not the same, those that adapt best to
each habitat will survive.
A plant in the desert needs less surface area than a plant in the forest
to obtain the same amount of solar energy. The surface area of the leaf
varies according to the solar radiation it receives; there are two types, called
sun leaves and shade leaves, and they have different physiological and
morphological features.
1, 2 ,3, 4
Sun leaves
5, 6, 7
Shade leaves
But does it only depend on light? Then what prevents a desert plant from
having larger leaves? Because if it receives more energy, couldn’t it carry out
more photosynthesis and grow more?
There are other factors affecting how leaves grow, such as availability of
water: during gas exchange the leaves of plants lose water, so the smaller
the surface area of the leaf, the less water is lost.
Dept of Education and Activities
Parque de las Ciencias
Workshop
Leaves adapt
1. From more to less: Large or small?
Items required
• Leaves from various biomes: tropical, Mediterranean and temperate deciduous
• Pencil and paper
• Precision scale (+/– 0.1 g)
We are not going to do any complicated calculations of the surface area of leaves!
Draw outlines on paper of various selected leaves, cut them out and weigh them;
this will enable us to tell which has the largest surface area, as a value that can be
extrapolated to the irregular surface of the leaves.
Why not simply weigh the leaf itself? Because the densities of leaves vary, and the
data might not come out right. By drawing them and cutting them out you ensure
that the differences are due solely to the surface area of the leaf.
2. From weak to tough
Items required
• Leaves from various biomes: tropical, Mediterranean and temperate deciduous
• Dynamometer
• Safety pin
Place a safety pin on the end of the dynamometer. Prick the leaf with it one cm from
the end, with no main veins in the path of the safety pin.
Measure the maximum force exerted with each type of leaf until it tears.
Enter the results in a data table and draw conclusions.
Dept of Education and Activities
Parque de las Ciencias
Workshop
Leaves adapt