Biology-Mr.Willets
Lab- Roots
Roots serve three basic functions in plants- 1) they anchor the plant 2) they absorb the necessary water and minerals from the soil and 3) in some cases, they store food.
The large woody parts of roots serve as anchors. The thinner root tips are more active in growth and water absorption. Today, you will examine two slides of roots. One is a longitudinal section of the root tip of an onion plant (Allium) (you may remember this slide as the one we looked at to see the phases of mitosis) The slide is marked ls and the root tip has been cut lengthwise. The other is a cross section of a root. The slide is marked cs or xs and the root has been cut through the center. Use the books in the shelf to help with your diagrams and to answer the questions.
I. Regions of the Root Tip
Observe the slide of Allium under low power and observe the following regions:
a) Root cap- this is at the very end of the root. As the root grows and pushes through the soil, these cells protect the cells behind them.
b) Meristematic region- this is the zone of cell division. New cells produced here replace damaged cells from the root cap and add cells for root growth. Meristem is the name given one type of growth tissue in plants.
c) Region of elongation- cells in this area do not divide very often but rather grow in length pushing the root into the soil.
d) Region of maturation- cells in this area become specialized. Some become vascular tissue, some become root hairs. Root hairs are very tiny extensions from the root. These are what actually absorb water and minerals from the soil.
Draw the outline of the root tip. Diagram just a few cells in each region to give the basic idea. The cells you draw should accurately represent the shape and size of the cells seen. Label each region.
II Cross Section of a Root
The main part of the root consists of several types of cells. These can be seen using a cross section of Ranunculus root. On each slide there are two sections (slices). The smaller one is usually clearer. From the outside in, the tissues are :
a) Epidermis- this is an outer layer that protects and absorbs materials from the soil. Root hairs grow from these cells
b) Cortex- these cells are very numerous. They serve mostly as storage areas.
c) Vascular cylinder- this is in the center of the root and contains cells that transport food and water (vascular tissue). Secondary roots can grow out from this area
Make a diagram of the Ranunculus root cross section. Draw in a few cells in each area to give the basic idea. Again, the size and shape of the cells you draw should be accurate. Label the three main areas.
Take a very thin slice of a carrot and examine using the stereo scopes. Compare to the Ranunculus root cross section you examined. Are the same main areas somewhat visible?
Questions-(use your own knowledge of biology, the lab instructions and the book* to answer these questions)
1) What region of the root tip did we use when we did the mitosis lab?_______________________
2) What is the purpose of the root cap?__________________________________
3) What is the function of the root hairs?_________________________________
*4) When a seed germinates, the first root to push down into the soil is called the ________________ root. If this forms the major root of the root system, it is called a _______________________
*5) Taproots can reach supplies of ______________deep in the ground. In some plants, taproots store _______________________ Give an example of this _________________________________
*6) A system of small roots spread out near the top of the soil is called _______________________
7) From what cells do the root hairs grow? _____________________________
8) What is the function of the vascular cylinder in the center of the root?______________________
__________________________________________
9) Cortex cells have mostly what function? _____________________