May 20, 2024

Metabolic pathways in higher plants and their determination

Metabolic pathways in higher plants and their determination

Plant secondary metabolism

Secondary metabolism produces a large number of specialized compounds (estimated 200,000) that do not aid in the growth and development of plants but are required for the plant to survive in its environment.

Secondary metabolism is connected to primary metabolism by using building blocks and biosynthetic enzymes derived from primary metabolism. Primary metabolism governs all basic physiological processes that allow a plant to grow and set seeds, by translating the genetic code into proteins, carbohydrates, and amino acids.

Specialized compounds from secondary metabolism are essential for communicating with other organisms in mutualistic (e.g. attraction of beneficial organisms such as pollinators) or antagonistic interactions (e.g. deterrent against herbivores and pathogens).

In any case, a good balance between products of primary and secondary metabolism is best for a plant’s optimal growth and development as well as for its effective coping with often changing environmental conditions. Well-known specialized compounds include alkaloids, polyphenols including flavonoids, and terpenoids. Humans use quite a lot of these compounds, or the plants from which they originate, for culinary, medicinal and nutraceutical purposes.

Primary vs Secondary Plant Metabolism

Primary metabolism in a plant comprises all metabolic pathways that are essential to the plant’s survival. Primary metabolites are compounds that are directly involved in the growth and development of a plant whereas secondary metabolites are compounds produced in other metabolic pathways that, although important, are not essential to the functioning of the plant.

However, secondary plant metabolites are useful in the long term, often for defence purposes, and give plants characteristics such as colour. Secondary plant metabolites are also used in the signalling and regulation of primary metabolic pathways. Plant hormones, which are secondary metabolites, are often used to regulate the metabolic activity within cells and oversee the overall development of the plant.

Secondary plant metabolites help the plant maintain an intricate balance with the environment, often adapting to match the environmental needs. Plant metabolites that colour the plant are a good example of this, as the colouring of a plant can attract pollinators and also defend against attack by animals

Types of Secondary Metabolites in plants

There is no fixed, commonly agreed-upon system for classifying secondary metabolites. Based on their biosynthetic origins, plant secondary metabolites can be divided into three major groups:

  • Flavonoids and allied phenolic and polyphenolic compounds,
  • Terpenoids and
  • Nitrogen-containing alkaloids and sulphur-containing compounds

Primary and secondary metabolites derived from carbon metabolism in plants

Primary and secondary metabolites in plants

Suggested reading

Recommended readings: