StemThe two main functions of a stem are structural support and nutrient conduction. It needs to support and elevate leaves for maximal light reception. It needs to transfer water, minerals and nutrients between the roots and leaves. Stems can also function as food storage organs. |
|||
 |
 |
 |
 |
 |
|
| Tree trunks are big stems of woody plants. They need to support the trees and position the leaves as far away from the ground as possible. 80% of the trunk is made up of dead cells. The living cells are thin layers next to the growing layer of vascular cambium. |
 |
||
Phloem:(bark) |
Outer bark (dead cells) |
protection from physical damage and water loss. |
| Inner bark (living cells) |
the conductive tissue that carries photosynthesis products (mainly glucose and starch) from the leaves to other parts of the tree. | |
Vascular cambium: |
one-cell-thick growing layer; the lateral meristem that is responsible for secondary growth in gymnosperms and most dicots. It produces phloem cells outward and xylem cells inward. | |
Xylem:(wood) |
Sapwood (living cells) |
the conductive tissue that carries water and minerals from roots to leaves. Relatively thin, youngest and outermost part of xylem. |
| Heartwood (dead cells) |
the nonconducting dense core that is the main supportive structure of a tree trunk. Not all woody plants have heartwood. | |
Growth rings:Exhibit |
Trees in temperate zones grow only during part of the year, producing seasonal growth rings. Each ring represents one year's growth, so you can tell the age of a tree by counting its rings. In tropical rain forests, however, trees grow year-round so it is harder to determine their age. | |
 Different barks |
Back to Plant Lab mainpage |
Back to Conservatory |