Plants chemical messengers

A hormone is a chemical that transfers information and instructions between cells in animals and plants. They are often described as the body s chemical messengers , but they also regulate growth and development, control the function of various tissues, support reproductive functions, and regulate metabolism (i.e. the process used to break down food to create energy). 

Throughout history, mankind has always been interested in naturally occurring compounds from prebiotic, microbial, plants and animals sources. Various extracts of flowers, plants and insects have been used for isolating compounds whose task, color and odor could be used for various purposes. Many natural products, such as plant hormones, have a regulatory role, while others function as chemical defense against pests. The role of certain compounds is to act as chemical messengers, such as sex-attractants (pheromones) in insects, terrestrial and marine animals and humans. What is the origin of natural products ... 

Receptor Agonists. By mimicking the natural chemical messenger at its receptors, psychomanipulants could cause spurious excitation or inhibition in the CNS. Two examples of receptor agonists are nicotine found in the leaves of the tobacco plant,... 

Julius Sachs studied "chemical messengers" or growth regulators in plants... 

A semiocbemical is a molecule that delivers a message between members of the same or different species of plant or animal. There are three groups of these chemical messengers allomones, kairomones, and pheromones. Each is of great ecological importance. 

Terpenoids are also used as chemical messengers. If the communication is between different parts of the same organism, the messenger is referred to as a hormone. Examples of hormones are shown in Figure 1.8. Giberellic acid is a hormone used by plants to control their rate of growth. Testosterone and oestrone are mammalian sex hormones. Testosterone is a male hormone and oestrone, a female. 

Flavonoids probably play major roles as internal physiological regulators and chemical messengers in plants. This may have been their major role in the early evolution of land plants (Stafford, 1991). 

The existence of a closed circulatory system in higher animals provides the organism with an easy and efficient route for the transport of hormones from the site of synthesis to the target tissues. In plants some hormones appear to be transported directly in the vascular tissue for example, cytokinin, GA, and ABA move from the root to the shoot in the xylem GA moves out of young leaves in the phloem and ABA is transported out of wilting leaves in the phloem (Fig. 6.1). However, auxin is not transported directly in the vascular tissue, but instead appears to be transported in cells associated with the phloem (Fig. 6.1). Ethylene poses a special problem in that it is a diffusable gas. However, its precursor, 1-aminocyclopropane-l-carboxylic acid (ACC), is transported from the root to the shoot in the xylem. Therefore, using the traditional concept of a hormone as a translocated chemical messenger, ACC may be more aptly considered to be a hormone than ethylene. 

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