Any one good with the biology of leaves?????

Question

im have to answer Q's on Leaves (yep boring!) but have to do it as part of my current course. anyway they are quite easy Q's but i cant seem to find much info on the net for the specific Q's.

example:

State TWO functions of the leaf epidermis.

What would be the advantage of a leaf having no chloroplasts in the upper epidermal layer?

State TWO advantages to leaves of their thin, flattened nature and thus large surface area?

and it goes on.

could you help me with these answers or give me some advice on where to research it. thank you.

Answer 1

The epidermis (skin) of a leaf does several things. To name two, it protects against excessive water loss and regulates the exchange of gases in the leaf.

I'd say the advantage of no chloroplasts is allowing the different tissues to specialize, thus the epidermis can perform it's tasks more efficiently and act as a more robust protection against the outside. The only possible disadvantage is the loss of light through the epidermis. But most leaves have a transparent epidermis, so the loss of light energy is neglibible compared to a more robust protective coat.

More surface area means there is more light falling on the leaves per amount of tissue. Think of a sail boat. It doesn't do you much good if you roll your sail into a ball; it won't catch much wind.

A second benefit deals with efficiency. If you had thick leaves, the amount of light that would penetrate to the underside would be almost nothing. It would be a waste of resources to thicken the leaves. Using the sail boat analogy, imagine sticking two sails flat against one another. Only one of the sails is going to be catching much wind, the other is just going to sit there behind the other one taking up space.

Hope that helps.