Journal of Plant Biochemistry & Physiology
Open Access

Multifaceted Role of Carbohydrates in Plants

Sadim Khornti^{* *}Correspondence: Sadim Khornti, Department of Rural Development and Agricultural Extension, College of Agriculture, Wolaita Sodo University, Wolaita Sodo, Ethiopia, Email:

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Description

Carbohydrates are essential molecules in the multifaceted world of plant biology, serving a diverse array of roles. Primarily, they act as a primary energy source, generated through photosynthesis, where plants convert sunlight, water, and carbon dioxide into glucose. This stored energy fuels growth, reproduction, and metabolic processes. Additionally, carbohydrates function as structural components, forming the cellulose that comprises plant cell walls, providing rigidity and support. Moreover, carbohydrates participate in cell communication, as glycoproteins and glycolipids play key roles in signal transduction. Furthermore, carbohydrates serve as storage compounds, accumulating as starches in roots and seeds for later use. Their multifaceted roles underline their fundamental importance in plant life.

Role of carbohydrates

Primary energy source: Carbohydrates serve as the primary energy source for plants. Through the process of photosynthesis, plants capture sunlight and convert it into chemical energy stored in the form of carbohydrates, primarily glucose. The basic equation for photosynthesis is:

6 CO₂+12 H₂O+light energy → C₆H₁₂O₆+6 O₂

In this process, carbon dioxide and water are transformed into glucose and oxygen, with the help of chlorophyll and other pigments in plant cells.

Just as in animals, respiration is a critical biological process in plants. During respiration, carbohydrates are broken down to release energy. In this process, glucose is converted into simpler compounds, such as pyruvate, and further metabolized in the mitochondria to produce adenosine triphosphate (ATP), the universal energy currency of cells. The equation for respiration is the reverse of photosynthesis:

C₆H₁₂O₆+6 O₂ → 6 CO₂+6 H₂O+energy (ATP)

This energy is used to power various cellular activities, including growth, maintenance, and reproduction.

Structural support and rigidity

Cellulose: Carbohydrates, particularly cellulose, provide structural support and rigidity to plant cell walls. Cellulose is a complex polysaccharide composed of glucose molecules linked together in a linear fashion. It forms micro fibrils that are arranged in layers, creating a sturdy framework that gives plant cells their shape and prevents them from bursting due to the internal turgor pressure.

Hemicellulose: In addition to cellulose, hemicellulose is another carbohydrate component of plant cell walls. It is more flexible than cellulose and plays a role in binding cellulose micro fibrils together. Hemicellulose also contributes to the overall strength and resilience of plant cell walls.

Storage reservoirs

Starch: Carbohydrates in the form of starch serve as energy storage reservoirs in plants. Starch is a polysaccharide composed of glucose molecules and is stored in specialized plant structures, such as roots, tubers, and seeds. During times of plenty, when photosynthesis exceeds immediate energy needs, excess glucose is converted into starch and stored for later use.

Sucrose: In addition to starch, plants store carbohydrates in the form of sucrose, a disaccharide composed of glucose and fructose. Sucrose is commonly transported within the plant from sites of photosynthesis (e.g., leaves) to sites of storage or growth (e.g., roots, fruits, or seeds). This transport sugar serves as an energy source and carbon skeleton for various metabolic processes.

Communication and signaling

Glycoproteins: Glycoproteins are molecules that consist of proteins linked to carbohydrate chains. These complex compounds are involved in cell-cell recognition, adhesion, and signaling. In plant cell walls, glycoproteins contribute to the regulation of cell growth and response to environmental stimuli.

Hormones: Carbohydrates are integral components of some plant hormones. For example, Abscisic acid (ABA), a crucial hormone involved in responses to stress and growth regulation contains a carbohydrate moiety. These carbohydrate-based hormones help coordinate various physiological processes within plants.

Physiological processes

Carbohydrates are essential for plant growth and development. The energy derived from the breakdown of carbohydrates fuels the synthesis of new molecules, such as proteins, nucleic acids, and lipids, all of which are required for growth and reproduction. During seed germination, carbohydrates stored in seeds, primarily in the form of starch, provide the energy necessary for the embryo to grow and emerge from the seed. As the young seedling begins photosynthesis, it becomes self-sustaining and can utilize newly synthesized carbohydrates. Sugars, transported from leaves and other sources, are used to support flower development, pollination, and seed maturation. During drought stress, plants can accumulate soluble carbohydrates like sugars and sugar alcohols (e.g., sucrose and mannitol) to adjust their osmotic potential. This allows them to maintain water uptake and turgor pressure even when water availability is limited. They are also involved in the response to oxidative stress caused by environmental factors such as high light intensity or pollution. Plants produce antioxidant compounds like ascorbate (vitamin C) and glutathione, which contain carbohydrate moieties and help protect plant cells from damage.

Conclusion

Carbohydrates in plants are not merely a source of energy; they are the backbone of life in the botanical world. These versatile compounds provide the energy needed for growth and reproduction, maintain structural integrity, facilitate communication, and help plants respond to environmental challenges. Carbohydrates are essential for the development of flowers and the subsequent formation of fruits and seeds. They provide carbon skeletons for the biosynthesis of secondary metabolites, such as alkaloids, terpenoids, and phenolic compounds. These secondary metabolites have various roles in plant defense, attraction of pollinators, and adaptation to environmental stressors.