Photosynthesis is the metabolic pathway by which the inorganic compounds water and carbon dioxide are converted into carbohydrates using light energy absorbed by chlorophyll. Plants need to be adapted so that maximum light energy is absorbed and, therefore, maximum photosynthesis occurs. Plants have adapted in order to be able to survive in many different climates, such as high temperatures and humid conditions. Leaves play an important part in photosynthesis, as they are the first part of the plant, which is exposed to the light energy from the sun. They have a large surface area to absorb maximum light energy. The waxy cuticle and the upper epidermis are transparent so that light can pass through the leaf into the other cells, which are needed for photosynthesis.
The palisade cells in the leaf are elongated so that as much light is absorbed as possible. Palisade cells have thin cell walls so that the light has a short distance to travel before it reaches the chloroplasts. They are also tightly packed together to ensure that no light energy is lost. The palisade cells and the upper epidermis contain many chloroplasts to ensure that maximum light has been reabsorbed. These chloroplasts are mobile within the cytoplasm. This helps to ensure that maximum light is absorbed. The leaf grows at right angles to ensure the largest surface area is exposed to the sunlight.
Another adaptation of the plant known as phototropism means that the plant will grow towards the light. Leaves are broad and flat to provide a large surface area and a short path for the light to travel. It also means that there is a short diffusion path for the exchange of gases. The vascular tissues found in leaves contain the xylem vessel, which transports the water required for photosynthesis. The phloem removes the products of photosynthesis. Plants and trees arrange their leaves in a leaf mosaic to ensure that light reaches every leaf, maximizing the amount of light energy absorbed. This ultimately leads to an increase in the rate of photosynthesis.
Chloroplasts contain photosynthetic pigments such as chlorophyll “a” and “b” it also contains accessory pigments like carotene. The role of the chloroplast is to absorb light energy from the sun and convert it into chemical energy. Many different pigments are found in plants; they all absorb different wavelengths of light. This ensures that as much light energy as possible is absorbed. Chloroplasts have an envelope in their membrane, which allows carbon dioxide to diffuse into the plant and allows oxygen to diffuse out of the plant. Oxygen is a waste product of photosynthesis. Chloroplasts have a membrane system, which is made up of grana to form thylakoids. These provide a large surface area for the photosynthetic pigments. As can be seen, plants have to be well adapted to make sure that they achieve the maximum rate of photosynthesis.