How are leaves adapted for photosynthesis?

Question

How are leaves adapted for photosynthesis?

Answer 1

By containing chlorophyll. When light strikes this pigment, the energy is used to create glucose molecules, trapping the energy for further use.

Answer 2

There are many features of leaves that are adaptations to facilitate and optimise photosynthesis.

At the whole plant level the leaves are arranged in the canopy of the plant in such a way that they do not overlap too much and so that each leaf is in a position to absorb as much light as possible.

At the morphological level the leaves are flattened to allow for optimal absorption of light per unit volume of leaf.

At the anatomical level the cells are arranged in a particular configuration that depends on the amount of light that they are exposed to. Plants that grow under high light conditions will have more layers of cells that plants that grow under low lilght conditions. In fact leaves that grow under low light conditions are also bigger in terms of leaf area.

At the level of the photosynthetic organelles (the chloroplasts)in the cells can move within the cell to receive as much light as possible if the plant is growing under low light conditions. Under high light conditions the chloroplasts can move to shade each other so that they not exposed to too much light.

Within the chloroplasts there are pigments that are responsible for absorbing light for and there are others that are involved in protecting the photosynthetic systems when they absorb too much light.

There are even behavioural features of leaves that enable them to absorb light in optimal ways. For example some leaves can track the sun during the course of the day so that they always lie at right angles to the incident radiation. These leaves are known as heliotropic leaves. Other leaves are orientated more or less vertically. What this means is that during the morning they absorb light well but at midday when it is hot and there can be too much light for the leaves to handle, there is not much leaf area exposed directly to the sun.

There are many other features of leaves that enable them to photosynthesise optimally.

Answer 3

Leaves are adapted for efficient photosynthesis in many ways. For example:

1) Leaves are broad, so there’s a large surface area exposed to light.

2) They’re also thin, which means carbon dioxide and water vapour only have to travel a short distance to reach the photosynthesising cells where they are needed.

3) There are air spaces in the spongy mesophyll layer (the middle of the leaf). This lets gases like carbon dioxide and oxygen move easily between cells. This also means there’s a large surface area for gas exchange.

4) Leaves contain lots of chlorophyll, which is the pigment that absorbs light energy for photosynthesis. Chlorophyll is found in chloroplasts, and most of the chloroplasts are found in the upper layer (palisade layer) of the leaf where they can get the most light.

5) The upper dermis (top layer) is transparent so that light can pass through it to the palisade layer.

6) The lower surface is full of little holes called stomata. They’re there to let gases like CO2 and O2 in and out.