Physiology (plant)

Plant physiology is a subdivision of botany, or the study of plants, that seeks to explain all aspects of plant life. It uses biology, chemistry, physics, mathematics, and more to break down how plants work and explain the functions and processes that occur in plants.

Scientists divide plant physiology into three parts: the first part concentrates on the physiology of nutrition and metabolism; the second part focuses on the physiology of growth, development, and reproduction; and the final portion deals with environmental physiology.

What Is a Plant?

A plant is a living organism that belongs to the kingdom Plantae. Flowers, grass, moss, shrubs, and trees are examples of plant species. Hundreds of thousands of different plant species exist on Earth. They come in many sizes and forms.

Plants are autotrophic, which means they can produce their own food using light, water, carbon dioxide, and other chemicals. They use a process called photosynthesis to convert light energy into chemical energy (food). Plants are made up of four main elements: carbon, hydrogen, oxygen, and nitrogen. Plants have limited mobility. They use materials from their environments to survive and grow, and they can adapt and react to these environments.

Plants are multicellular organisms composed of eukaryotic cells, or cells that have a nucleus. A nucleus is the central part of a cell that controls it and contains genetic material or sequences of deoxyribonucleic acid (DNA). Plant cells typically have regular shapes and cell membranes that surround them. A cell membrane acts like a barrier to protect the inside of a cell from the environment outside the cell. A rigid outer layer known as a cell wall surrounds the cell membrane. A plant cell also contains a thick liquid known as cytoplasm, which is made up of water and molecules such as nucleic acids, proteins, carbohydrates, and lipids. Groups of molecules sometimes form organelles. A plant cell's cytoplasm has a cavity known as a vacuole, which contains liquid to keep the cell firm, and organelles called chloroplasts that aid in photosynthesis.

Like animals, plants reproduce to create new plants. However, unlike most animals, plants reproduce through asexual and sexual reproduction. Asexual reproduction results in genetically identical offspring, while sexual reproduction results in offspring with genetic material from two plant parents.

Plants are very important to the survival of the planet. They help the environment by protecting soil from erosion and controlling water levels. Humans use plants for a variety of purposes, including for food and as medications. This is why understanding plants is so important.

History of Plant Physiology

Many researchers and scientists began to experiment with plants during the seventeenth and eighteenth centuries. They conducted experiments to determine how plants carried out their functions. These experiments helped scientists learn much about plants, including how plants used sunlight during photosynthesis, transported water, and relied on other organisms for pollination, or the transfer of pollen from one plant to another.

English researcher Stephen Hales made significant strides in botany during the eighteenth century. He founded the area of study that became known as plant physiology, publishing some of his findings about plants in Vegetable Staticks in 1727. In the publication, Hales described how the process of transpiration helped move water through plants. He discredited the original theory that water circulated through plants like blood circulated through animals' bodies. Instead, he noted that the loss of water within a plant's leaves through evaporation caused the plant to draw up more water from its roots. To prove this, Hales conducted experiments by using tree branches and measuring water levels to show the rate that water evaporated from a plant's leaves. Hale also developed a way to measure a plant's growth.

As time passed, other scientists conducted experiments in the field of plant physiology. Dutch physician and botanist Jan Ingenhousz discovered that air was vital to a plant's survival. He used an experiment by English chemist Joseph Priestley to show how a plant used light to restore some components of air when sealed in a container. Ingenhousz's findings later helped others understand the process of photosynthesis in plants.

Many scientists also focused on plant reproduction during the eighteenth century. At the time, many experts believed that similarities existed between the anatomy and physiology of both plants and animals. German botanist Rudolf Camerarius argued that plants reproduced sexually. He studied dioecious mulberry plants. Dioecious plants have two forms: one form has stamens that produce pollen and the other has a pistil that produces seeds. Camerarius discovered that the plant with a pistil would not produce seeds unless a plant with stamens was near. This led him to theorize that plants needed pollen to fertilize the seeds to reproduce. He also studied monoecious plants, which have both stamens and a pistil, to help prove his theory.

These experiments and numerous others became the basis for the area of study known as plant physiology. This early research led to many important findings, including German scientist Joseph Gottlieb Kölreuter's work in fertilization and hybrid plants, which are produced from two different species of plants. Additional studies on hybrids advanced knowledge in this subject. Today, the United States and other countries rely on many important hybrid crops, such as corn, for sustenance and other purposes.

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