Plant Metabolism: Absorption, Circulation, and Respiration

Plant Metabolism: Vital Processes

Like all living organisms, plants perform essential functions to facilitate growth, development, and reproduction.

The primary metabolic processes include:

• Absorption
• Circulation
• Respiration
• Transpiration

Absorption: Nutrient Uptake

Plants acquire nutrients not only from the soil but also from the air, primarily through their leaves, absorbing oxygen and carbon dioxide.

Water and dissolved minerals enter the roots via diffusion. Plants then convert these substances into organic molecules, such as:

• Glucose
• Fructose
• Starch
• Proteins
• Lipids (fats)

This conversion of minerals into organic compounds is unique to plants, certain bacteria, and microscopic algae. Consequently, wildlife, fungi, and protozoa rely on plants as their primary source of organic compounds.

Circulation: Transport Systems

The evolution of increasingly complex circulatory systems demonstrates the mechanisms of evolution. In single-celled organisms like amoebas and paramecia, transport occurs through protoplasmic flow.

However, in thallophytes (algae), circulatory pathways are evident. Terrestrial plants require efficient water transport systems, facilitated by specialized tissues for water and nutrient absorption and transport. Ferns, more advanced lower plants, possess fully differentiated vascular tissues.

Transpiration and Respiration

Transpiration: Water Release

Transpiration removes excess water as vapor or droplets through stomata, microscopic pores located mainly on the underside of leaves.

Stomata regulate their opening and closing based on the plant's water needs and also facilitate CO2 intake for photosynthesis.

Plant transpiration significantly contributes to the water cycle. Rainwater returns to the atmosphere through soil evaporation and plant transpiration, with the latter being three times greater.

Respiration: Energy Production

Respiration is the reverse of photosynthesis. Plants use organic substances and oxygen to produce energy, releasing CO2 and water. All plant organs respire for energy.

Roots, responsible for water and nutrient absorption, require constant oxygen for respiration to support growth. Stems respire through pores called lenticels.

Fruits often exhibit anaerobic respiration (without oxygen), releasing substances responsible for the aroma of ripe fruits.