Leaves Introduction to Agriculture Plant Science Unit Leaves

Leaves Introduction to Agriculture Plant Science Unit

Leaves Lateral outgrowths from a stem that constitutes a unit of the foliage of a plant and functions primarily in food manufacture by photosynthesis Provide much of the lush green scenery we see around Come in an almost endless variety of shapes and sizes

Leaves Manufacture and store food for the plant Leaves are the primary place for food storage in plants Livestock use the leaves of grass and other plants as forage

Structure of Leaves layers Cuticle are made up of several different Outermost layer Consists of a coating of waxy material Helps the leaf retain water by slowing down the rate of evaporation of the water inside the leaf Helps to prevent disease organisms from entering the plant

Structure of Leaves Epidermis Layer of cells beneath the cuticle Protects the leaf and covers the entire surface of the leaf on top and on the underside

Structure of Leaves Stoma Openings within the epidermis Allow air into the leaf and water vapor and oxygen to move out Guard cells Opening/closing of guard cells controlled by turgor High concentration of water in cells=guard cells relax and stoma opens

Structure of Leaves Low concentration of water in cells=guard cells relax and stoma closes Usually guard cells are open in the daylight and closed in darkness About 90% of the water taken in by the plant is passes out through the stoma All of the carbon dioxide used by the plant is take through the stoma Closing of the stoma prevents the loss of too much water

Structure of Leaves Mesophyll layer Layer between the epidermis layer Divided into 2 sub-layers Palisade mesophyll Consists of elongated cells that contain chloroplasts Site of photosynthesis Chloroplasts contain chlorophyll Chlorophyll captures light energy from the sun and uses it for photosynthesis

Structure of Leaves Spongy mesophyll Contains less chloroplasts than the palisade mesophyll Contains air spaces that are in contact with the atmosphere through the stoma Within the spongy mesophyll are ridge-like vascular bundles Vascular bundles are ridge-like veins that run through the leaves and contain the xylem and phloem Xylem are tubes that bring water from the roots to the leaves Phloem are tubes that carry the products of photosynthesis to the other parts of plants