Photosynthesis

Key Terms Leaves Photosynthesis Xylem Phloem Stomata Transpiration

Leaves & Photosynthesis Leaves capture the sun’s energy and carry out the food-making process of photosynthesis. A leaf’s top and bottom surface layers protect the cells inside. Between the layers of the cells are veins that contain xylem and phloem.

Xylem Xylem - the vascular tissue in plants that conducts water and dissolved nutrients upward from the root and also helps to form the woody element in the stem.

Phloem Phloem - the vascular tissue in plants that conducts sugars and other metabolic products downward from the leaves.

Stomata The surface layers of the leaf have small openings called stomata. (Stoma means mouth in Greek). The stomata open and close to control what gases enter and leave the leaf. When the stomata are open, carbon dioxide enters the leaf, and oxygen and vapor exit.

PHOTOSYNTHESIS The leaf is perfect for conducting photosynthesis. The cells that contain the most chloroplasts are located near the leaf’s upper surface, where they get the most light. The chlorophyll in the chloroplasts traps the sun’s energy.

PHOTOSYNTHESIS Carbon dioxide enters the leaf through open stomata. Water travels up the stem to the leaf through the xylem. During photosynthesis, sugar (glucose) and oxygen are produced from the carbon dioxide and water. Oxygen passes out of the leaf through the stomata. The glucose enters the phloem and travels throughout the plant giving it energy.

Transpiration There is a large area of a leaf that is exposed to the air, causing water to quickly evaporate, or to be lost, from the plant leaf into the air. This process is called transpiration. A lot of water can be lost, so a plant uses its stomata to slow down transpiration. The stomata often will close when leaves start to dry out.

Video https://www.youtube.com/watch?v=pFaBpVoQD4E