VEGETABLE CELLS AND TISSUES

SCIENCE HOMEWORK FOR 9 A / B JULY /06/2010
LCDA. DIANA MONTERO
1.- FIND THE MAIN IDEAS
2.- FIND NEW VOCABULARY WORDS
Plant Tissue Systems Plant tissue systems include: Dermal Tissue System The dermal tissue system consists of the epidermis and the periderm. The epidermis is a single layer of closely packed cells. It both covers and protects the plant. It can be thought of as the plant's "skin." Depending on the part of the plant that it covers, the dermal tissue system can be specialized to a certain extent. For instance, the epidermis of a plant's leaves secretes a coating called the cuticle that helps the plant retain water.
Epidermis CellsImage copyright Dave Webb.
The periderm, also called bark, replaces the epidermis in plants that undergo secondary growth. The periderm consists of cork cells and protects the plant from pathogens, prevents excessive water loss and provides insulation for the plant.
Periderm formation is indicated by periclinal divisions in parenchyma cells.Image copyright Dave Webb.
Vascular Tissue System Xylem and phloem throughout the plant make up the vascular tissue system. It allows water and other nutrients to be transported throughout the plant.
Xylem and PhloemImage copyright Dave Webb.
Ground Tissue System The ground tissue system synthesizes organic compounds, supports the plant and provides storage for the plant. It is mostly made up of parenchyma cells but can also include some collenchyma and sclerenchyma cells as well. Parenchyma Cells Parenchyma cells are usually depicted as the "typical" plant cell because they are not very specialized. These cells synthesize and store organic products in the plant. Most of the plant's metabolism takes place in these cells.
Plant Parenchyma CellImage copyright Dennis Kunkel.
PLANT CELLS Collenchyma Cells Collenchyma cells have a support function in plants, particularly in young plants. These cells help to support plants while not restraining growth due to their lack of secondary walls and the absence of a hardening agent in their primary walls. Sclerenchyma Cells Sclerenchyma cells also have a support function in plants but unlike collenchyma cells, they have a hardening agent and are much more rigid. Water Conducting Cells Water conducting cells of xylem are usually of two types, tracheids and vessel elements. Both allow water to flow to different parts of a plant. Sieve Tube Members Sieve tube members of phloem conduct organic nutrients such as sugar throughout the plant.