Leaf Structure and Function

Leaf Structure and Function

• Leaves are organs, part of an organ system with stems and roots, responsible for transporting substances throughout the plant.
• Leaves are the primary site of photosynthesis, converting light energy into chemical energy (sugars) using carbon dioxide and water.
• Carbon dioxide enters through stomata, small openings on the leaf's underside.
• Thousands of stomata are scattered across the lower epidermis.
• Carbon dioxide diffuses through stomata, air spaces, and reaches the palisade mesophyll layer.
• The palisade mesophyll, rich in chloroplasts, is the primary site of photosynthesis.
• A thin, transparent upper epidermis lets sunlight reach the palisade cells below.
• Sugar produced during photosynthesis is transported throughout the plant via the phloem.

Water Regulation and Stomata

• Leaves constantly lose water through the epidermis and stomata.
• A waxy cuticle on the upper epidermis reduces water loss.
• Stomata regulate water loss and carbon dioxide intake.
• Stomata consist of two guard cells controlling the opening size.
• Turgid guard cells (full of water) open stomata, allowing carbon dioxide intake.
• Flaccid guard cells (losing water) close stomata, reducing water loss.
• Guard cells respond to light, closing at night.
• Stomata are primarily on the underside of leaves for reduced water loss due to cooler temperatures and lower evaporation.

Plant Growth and Meristem Tissue

• Meristem tissue, plant stem cells, is found at the growing tips of roots and shoots.
• Meristem cells differentiate into various specialized cell types, enabling plant growth.