Plants engage in a form of “breathing” to sustain life, though their mechanism differs significantly from animals. This process, gas exchange, is fundamental for survival, involving continuous gas movement between the plant and atmosphere. Plants lack lungs or a circulatory system, but their internal structures are adapted for this essential biological function.
Gases Plants Exchange
Plants primarily exchange two key gases with their environment: carbon dioxide and oxygen. Carbon dioxide is absorbed from the atmosphere and serves as a primary raw material for photosynthesis, the process by which plants create their own food. Oxygen is released as a byproduct of photosynthesis, but it is also taken in by plants for respiration.
How Plants Exchange Gases
The exchange of these gases mainly occurs through specialized microscopic pores called stomata, predominantly found on the underside of leaves. Each stoma is flanked by two guard cells, which regulate its opening and closing. This regulation allows plants to control the flow of gases and water vapor, adapting to environmental conditions.
Beyond the leaves, woody stems and roots also participate in gas exchange through structures known as lenticels. Lenticels are small, raised, porous tissues providing a pathway for gases to diffuse between the plant’s internal tissues and the atmosphere. Unlike stomata, lenticels are always open, allowing continuous gas exchange, especially in older bark where stomata are absent. Gases move into and out of the plant tissues through diffusion, moving from areas of higher concentration to lower concentration.
Plant Respiration Versus Photosynthesis
Plant respiration and photosynthesis are distinct, yet interconnected, processes that involve the exchange of gases. Photosynthesis is the process by which green plants convert light energy into chemical energy, producing sugars (glucose) for food. During photosynthesis, plants absorb carbon dioxide from the air and water, releasing oxygen as a byproduct. This process primarily occurs in the chloroplasts within plant cells and requires sunlight, making it largely a daytime activity.
In contrast, plant respiration is the process where plants break down the sugars produced during photosynthesis to release energy. This process consumes oxygen and releases carbon dioxide and water as byproducts. Respiration occurs continuously, 24 hours a day, in all living plant cells, including those in leaves, stems, and roots. While photosynthesis harnesses energy, respiration releases it, making them complementary processes for a plant’s energy management.
The Purpose of Plant Respiration
The primary function of plant respiration is to generate energy in the form of adenosine triphosphate (ATP). This energy is essential for powering all cellular activities within the plant. ATP fuels processes like growth, nutrient uptake and transport, and cellular repair.
Respiration also supports metabolic functions and helps plants respond to environmental challenges. Even in the absence of light, when photosynthesis cannot occur, respiration continues to provide the necessary energy for plant survival. This energy supply ensures the plant maintains its functions, grows, and adapts to changing conditions.