6.1 Plant Nutrition – Photosynthesis: Use and Storage of Carbohydrates
Photosynthesis is the process by which green plants convert light energy into chemical energy in the form of glucose. This glucose is then used for various life processes and stored for later use.
Use of Carbohydrates
The glucose produced during photosynthesis is the primary source of energy for the plant's metabolic activities. It is used in the following ways:
Respiration: Glucose is broken down in the mitochondria through cellular respiration to release energy for growth, repair, and other life processes. The equation for cellular respiration is:
$$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + Energy$$
Synthesis of other organic molecules: Glucose is used as a building block to synthesize other essential organic compounds, including:
Cellulose: A structural component of plant cell walls, providing support and rigidity.
Starch: A storage form of glucose.
Proteins: Glucose provides carbon skeletons for amino acid synthesis.
Lipids: Glucose is converted into lipids for membrane structure and energy storage.
Growth and Development: Energy from glucose fuels the processes of cell division, cell elongation, and differentiation, which are essential for plant growth and development.
Storage of Carbohydrates
Plants store excess glucose as starch in various parts of the plant. This stored starch can be broken down back into glucose when energy is needed.
Storage Location
Form of Starch
Function
Roots (e.g., carrots, potatoes)
Amylose and Amylopectin
Energy reserve for plant growth and survival during periods of dormancy or low light.
Stems (e.g., wheat, corn)
Amylopectin
Energy reserve for plant growth and development.
Seeds (e.g., peas, beans)
Amylopectin
Energy reserve to provide energy for germination and early seedling growth.
Fruits (e.g., apples, bananas)
Amylose and Amylopectin
Energy reserve to support fruit development and provide energy for the developing fruit.
The type of starch stored in different plant parts can vary. For example, seeds typically store mostly amylopectin, while roots and stems may store a mixture of amylose and amylopectin.
Diagram
Suggested diagram: A diagram showing glucose being converted to starch and stored in different plant parts (roots, stems, seeds, fruits). Arrows indicate the flow of glucose and the conversion to starch.