Plant hormones in the context of Brassinosteroid

Plant tissue culture is a collection of techniques used to maintain or grow plant cells, tissues, or organs under sterile conditions on a nutrient culture medium of known composition. It is widely used to produce clones of a plant in a method known as micropropagation. Different techniques in plant tissue culture may offer certain advantages over traditional methods of propagation, including:

Plant tissue culture relies on the fact that many plant parts have the ability to regenerate into a whole plant (cells of those regenerative plant parts are called totipotent cells which can differentiate into various specialized cells). Single cells, plant cells without cell walls (protoplasts), pieces of leaves, stems or roots can often be used to generate a new plant on culture media given the required nutrients and plant hormones.

Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia. This process has evolved multiple times within the legumes, as well as in other species found within the Rosid clade. Legume crops include beans, peas, and soybeans.

Within legume root nodules, nitrogen gas (N₂) from the atmosphere is converted into ammonia (NH₃), which is then assimilated into amino acids (the building blocks of proteins), nucleotides (the building blocks of DNA and RNA as well as the important energy molecule ATP), and other cellular constituents such as vitamins, flavones, and hormones. Their ability to fix gaseous nitrogen makes legumes an ideal agricultural organism as their requirement for nitrogen fertilizer is reduced. Indeed, high nitrogen content blocks nodule development as there is no benefit for the plant of forming the symbiosis. The energy for splitting the nitrogen gas in the nodule comes from sugar that is translocated from the leaf (a product of photosynthesis). Malate as a breakdown product of sucrose is the direct carbon source for the bacteroid. Nitrogen fixation in the nodule is very oxygen sensitive. Legume nodules harbor an iron containing protein called leghaemoglobin, closely related to animal myoglobin, to facilitate the diffusion of oxygen gas used in respiration.

Frits Warmolt Went (May 18, 1903 – May 1, 1990) was a Dutch biologist whose 1928 experiment demonstrated the existence of auxin in plants.

Went's father was the prominent Dutch botanist Friedrich August Ferdinand Christian Went. After graduating from the University of Utrecht, The Netherlands in 1927 with a dissertation on the effects of the plant hormone auxin, Went then worked as a plant pathologist in the research labs of the Royal Botanical Garden in Buitenzorg, Dutch East Indies (now Bogor, Indonesia) from 1927 to 1933. He then took a position at the California Institute of Technology (Caltech) in Pasadena, California, first researching plant hormones. His interest gradually shifted to environmental influences on plant growth. At Caltech, he was among the first to demonstrate the importance of hormones in plant growth and development. He played an important role in the development of synthetic plant hormones, which then became the basis of much of the agricultural chemical industry.

Kenneth Vivian Thimann (August 5, 1904 – January 15, 1997) was an English-American plant physiologist and microbiologist known for his studies of plant hormones, which were widely influential in agriculture and horticulture. He isolated and determined the structure of auxin, the first known plant hormone. He spent most of his early career (1935–1965) at Harvard University, and his later career (1965–1989) at the University of California, Santa Cruz. He is credited with identifying indole-3-acetic acid as an auxin.

Thimann was born in Ashford, England. He studied chemistry and biochemistry at Imperial College, University of London (earning a B.Sc. and a Ph.D.) and also received a diploma from the University of Graz. After several years teaching at the University of London, Thimann moved to the California Institute of Technology in 1930. In 1935, he joined the Biology department of Harvard University. He authored an influential book on plant hormones, Phytohormones, in 1937 (co-authored with F. W. Went). He was elected to the American Academy of Arts and Sciences in 1938. Thimann became director of Harvard's Biological Laboratories in 1946, a position he held until 1950. He was elected to the United States National Academy of Sciences in 1948. In 1955 he wrote The Life of Bacteria, an influential book on microbiology. He was elected to the American Philosophical Society in 1959. From 1962 until leaving Harvard in 1965, Thimann was the Higgins Professor of Biology.