Plants come in almost countless different sizes and shapes, but they also have much in common. The processes that go on inside leaves, stems and roots are largely the same. Life processes are similar across the plant world. In fact, one of those processes - photosynthesis - is the essence of what makes a plant a plant.
The ability to carry out photosynthesis is one of the processes that characterize all plants. Using light energy, the plants convert water and carbon dioxide into food. As a byproduct, oxygen is released back into the air to fuel the animals that share the planet.
Light is absorbed by pigments in the leaves of the plants, where photosynthesis takes place. Chlorophyll absorbs red and blue light, while other colors pass through leaves without being absorbed. This includes green light, which is why chlorophyll appears green.
In the first step, a chemical reaction takes place in the leaves which turns light energy into chemical energy. Afterwards, the resulting chemical - called adenosine triphosphate, or ATP - is combined with carbon dioxide to form a glucose that is food for the plant.
The process that bookends photosynthesis is respiration. Photosynthesis creates food for the plant to use, and this food is turned into energy usable by the plant in respiration.
Like respiration that occurs in animals, carbon dioxide and water are released during the process of plant respiration. Sugars and the glucose structures that were created during photosynthesis are broken down and changed into fuel for the plant, which is then used for new growth and cellular development. Unlike photosynthesis, this process can occur when the plant is in light or in the darkness, as seen by the sprouting of bulbs in the darkness.
The germination of the seed is the beginning for many plants. The outside of the seed is called the seed coat, and it protects the delicate interior of the seed. That seed interior contains an embryo - the beginnings of leaves and roots of the plant. Also inside the seed coat are the endosperms, or food that will provide part of the fuel needed for the seed to grow and break out of the seed coat.
Depending on the plant, there could be a number of different requirements that need to be met to trigger the growth of the seed. Some seeds remain dormant until the soil around them reaches a certain temperature, some wait for there to be a certain amount of daylight. All seeds require water to start the germination process, which begins with the emergence of the root from the seed.
Plants also have a process by which they carry on a sexual reproduction. This involves the pollen being transferred from the male part of the flower to the female, which can occur within the same flower or can involve a transfer from one flower to another.
The pollen travels down a part of the plant called the style until it reaches the ovary, where it fertilizes the female cells within. From these united cells, the embryo forms and around that the seed coat.
Some plants produce both male and female flowers, while other plants - like apples and pears - require the presence of a pollinator tree. These pollinator trees are another variety of the same fruit, and allow fertilization to take place.
Fertilization results in the formation of fruits on fruit trees, as these fruits are vessels for the seeds.
Transpiration is a process that is tied closely to photosynthesis. The stomata are the structures of a plant that open to absorb carbon dioxide, a vital component of photosynthesis. As they open, they lose water that is evaporated back into the air.
This evaporation results in the plant drawing more water up from the roots, which in turn aids in the transportation of nutrients through the plant's roots, stems, and to the leaves. While at first it seems as though the loss of water is a bad thing, it helps in the plant's circulation.