Tendril – modified leaf found in many vines (peas, pumpkins) Carnivorous plants – modified leaves that trap insects Spines – protect plant

Blade – broad, flat portion; is the site of most photosynthesis Petiole – attaches most blades to stems Simple leaf – one blade Compound leaves – blade is divided into leaflets In some species, the leaflets themselves are divided

Leaves consist of three tissue systems Dermal – epidermis (single layer with waxy cuticle) with openings called stomata for gas exchange (the number varies by species) Ground – mesophyll (chloroplast-rich parenchyma cells palisade mesophyll – site of photosynthesis, located directly below epidermis spongy mesophyll – irregularly spaced cells surrounded by large air spaces

Vascular – in bundles called veins (xylem and phloem) Venation is the arrangement of veins in a leaf Monocots – parallel Dicots – netted palmate pinnate

Primary site for photosynthesis in most plants Leaves that develop in full sun are thicker, have a smaller area per leaf, and have more chloroplasts per leaf Dense coating of hairs prevent the absorption of too much sunlight

Stoma – opening in cuticle to allow gas exchange Guard cells – two kidney-shaped cells that regulate the stoma Most plants – stoma open during the day and closed at night Stomata will close if water is scarce If stomata are closed, virtually no photosynthesis takes place