Photosynthesis is the chemical change which occurs in the leaves of green plants. It is the very first step towards producing food - not just for plants but ultimately every animal on the planet. During the reaction carbon dioxide and water are converted into glucose and oxygen. The reaction requires light energy, which is absorbed by a green pigment called Chlorophyll.
Photosynthesis takes place in leaf cells. These contain chloroplasts, which are tiny organelles containing lots of chlorophyll. Most are located in the palisade mesophyll which is the top-most layer of cells therefore they are exposed to the most sunlight. Plants need to carry out photosynthesis because they manufacture their own food from sunlight, water and carbon dioxide - and these are the basis of our food web. Leaves have adapted in several ways for it to carry out the process of photosynthesis at a maximum rate. The epidermis is thin and transparent so it allows more light to reach the palisade cells which are at the top of the leaf. Leaves have a thin cuticle made of wax to protect the leaf without blocking out light. The palisade cell layer at the top of the leaf absorbs more light as the palisade cells contain many chloroplasts so they absorb all of the available light. This internal structure of the leaf is adapted to maximize the rate of photosynthesis. The more photosynthesis, the more sunlight energy can be converted into chemical energy and growth. The faster a plant can grow, the sooner it can reproduce and pass on its genes.
There are many factors that can affect the rate of photosynthesis. The most important factor that affects the rate of photosynthesis is the intensity and wave length of the light and time duration. Other factors include the surface area of the leaf; the greater the surface area, the larger the rate of photosynthesis. Another factor is the amount of water available. If the leaf is losing too much water due to drought conditions (change of temperature), the stomata closes up to converse water. This in turn prevents carbon dioxide from entering the leaf, therefore the rate of photosynthesis goes down. This is also why the 'temperature' is yet another important factor that affects the rate of photosynthesis. A low temperature limits photosynthesis since the enzymes controlling the reaction are below their optimum reactivity. If the temperature is too high it will denature the enzymes and stop the process of photosynthesis altogether. Lack of light is an important factor as the absence of light from the sun means that neither ATP or reduced NADPH will be produced so the GP cannot be converted into glucose. The concentration of carbon dioxide can also affect the rate of photosynthesis as if there is no carbon dioxide available RuBP cannot be converted into GP. therefore RuBP starts to build up and no more glucose will be produced. Other factors include the amount of chlorophyll and enzymes in a leaf. These factors, as to how extreme they are can really affect photosynthesis in a leaf and therefore could affect the rate in a plant.
