14.2 Vascular Plant Systems

1. 14.2 Vascular Plant Systems Shoot System

2. The shoot system includes stems, leaves, and flowers. • Some stems are flexible and slender. These are called herbaceous (hur BAY shuhs) stems. • Other stems, such as those of trees, are large and woody.

3. Stem Functions • Stems support the plant. • Stems hold the leaves up toward the light. • Inside a stem, water and minerals move through the xylem and sugars move through the phloem. • Stems of some plants also store water or starch. • Green stems make glucose through photosynthesis.

4. Woody Stems • A woody stem is hard, strong, and rigid. • Most plants with woody stems are dicot trees and shrubs that live for many years • Each year's growth has dark and light bands of xylem cells.

5. During wet weather, large xylem cells are produced. • In the dry summer, the xylem cells are small and close together.

6. Stem Adaptations • Plant stems have many unusual adaptations. • Cacti have green succulent stems that store water. • The stored water is used to make glucose for the plant. • Tendrils on grape plants are modified stems that help them climb.

7. Leaf Functions • Each leaf is a specialized organ with three main functions. • Leaves capture light from the sun. • Leaves make glucose through photosynthesis. • Leaves exchange gases with the environment.

8. Leaf Structure • A leaf is made of layers. • The surface layers are the waxy cuticle and the epidermis. • Inside is the moist mesophyll (MEHZ oh FIHL) layer, where photosynthesis occurs. • Gases are exchanged with the environment through stomates in the plant's surface.

9. Leaf Adaptations • The shapes and sizes of leaves vary, depending on their environment. • Plants in shady forests have large leaves to capture light. • Plants in dry environments have small, thick, wax-coated leaves to prevent drying.

10. End