Lab 3: Roots

27. Name the prominent structure developing in the cross sections of the roots below:

New lateral root

28. From which CELL LAYER did this structure develop? (Do not give me the zone of development or the primary meristem.)

Pericycle

21. MATCH the terms in the wordbank to the descriptions below:

ROOT HAIRS 2. derived from the epidermis and develop from trichoblasts LATERAL ROOTS 1. derived from the pericycle and have a vascular connection with the primary root stele

7. Amyloplasts are used for storage of starch. What is their SECONDARY FUNCTION in root tips?

*Involved in the perception of gravity by the plant (gravitropism).* The stele is the cylinder of vascular tissue in the center of dicot roots. The casparian strip is a single layer of conspicuous cells that seals the cell walls of the endodermis surrounding the stele. It is covered by a waxy substance called suberin. It plays an important role in regulating the movement of water and dissolved substances into and out of the stele. It prevents water from entering the stele via the apoplast, which is the extracellular region that includes the cell wall and middle lamella. Instead, water must traverse the endodermis via the symplast, which includes the living protoplasts of cells connected by plasmodesmata. This forces materials entering the stele to pass through at least once cell membrane and therefore allows better control of what enters the plant's xylem.

22. Name the ZONES of development indicated in the root tip below.

1. Zone of division 2. Root cap

9. What is the name of the red structure between the cell walls of the endodermis in this video? a. casparian strip b. pericycle c. cuticle d. stele

A. Casparian strip

17. Use the wordbank to label the structures in the root cross section below: LATERAL ROOT ROOT CAP ROOT APICAL MERISTEM

A. Cortex B. Endodermis C. Epidermis D. Pericycle E. Root Apical Meristem F. Root cap G. Lateral root

15. Use the wordbank to label the structures in the root cross section below:

A. Phloem B. ENDODERMIS C. Cortex D. Pericycle E. Casparian Strip F. Xylem

Use the wordbank to label the structures in the cross section of the monocot root below: PITH PHLOEM

A. Pith B. Epidermis C. Endodermis D. Pericycle E. Xylem F. Cortex G. Phloem

1. Identify the roots systems below as either TAPROOT or FIBROUS.

A. Taproot B. Fibrous Roots primarily function to anchor plants in the soil and absorb water and dissolved substances into the plant. There are two basic types of root systems. Taproot systems have a primary root that grows directly downward from the stem, while lateral roots branch off to the side. Many taproots are modified as storage organs, including carrots, parsnips, radishes, and turnips. Tubers, like sweet potatoes and yams, are enlarged lateral roots modified as storage organs. Fibrous root systems have roots of about the same size that grow from the base of the stem and branch out to form a dense mass of roots.

2. The images below are all common vegetables consumed by humans. Label them as either TAPROOTS or LATERAL ROOTS.

A. Taproots B. Lateral Roots

3. Use the wordbank to label the image of the root tip below: ROOT CAP ZONE OF ELONGATION ZONE OF DIFFERENTIATION ROOT HAIR ZONE OF CELL DIVISION

A. Zone of Cell Division B. Zone of Elongation C. Root Hair D. Zone of Differentiation E. Root Cap The typical regions of a young root tip are the root cap, zone of cell division, zone of elongation, and the zone of differentiation (also referred to as the zone of maturation). The root cap is a layer of cells on the outside of the root tip that protect it as it moves through the soil. These outer cells slough off as the root moves through the soil, but they are quickly replaced. The root cap is often covered in a layer of mucus called mucigel that facilitates movement through the soil. The zone of cell division contains the small, undifferentiated meristimatic cells of the root apical meristem (RAM). So, the root is growing by the addition of cells at the root tip. The cells right above the RAM are in the zone of elongation. These cells are stretching vertically as they take in water, leading to the lengthening of the root. The zone of differentiation is where cells that were originally produced in the meristematic region become differentiated into the various cell types discussed in the Tissues lab. This is also the region where root hairs are formed from trichoblasts in the epidermis.

26. Name the FUNCTION of the structures indicated by the arrows in the images below:

Allow the plants to detect GRAVITY.

10. Pathway A in this video shows _________ movement. a. apoplastic b. symplastic c. transmembrane

Also watch this YouTube video showing the movement of water and dissolved ions into the roots' vascular tissues in the root stele (sound is required): https://bbvideo.ualr.edu/watch/TKlPpm

23. What is the function of the AIR BUBBLES seen in this root cross section?

Cavitation is the filling of a xylem vessel or tracheid with air. During transpiration, the column of water is being pulled out of the plant by evaporation at the leaf cell surface. When this 'pulling' of water out of the plant becomes greater than the ability of the water molecules to stay together, the column of water will break. Unique structural characteristics help the plant contain the air bubble so that it does not totally disrupt water movement up the plant. Plants are particularly sensitive to cavitation during the hottest part of the day when there is not enough water available from the soil to keep up with the demand for water while it is evaporating off the leaf surface. Cavitation also occurs under freezing conditions. Because the solubility of gas in ice is very low, gas comes out of solution when the xylem sap freezes. Freezing of xylem sap is a problem in the spring when the ice thaws, leaving a bubble in a xylem vessel. These bubbles can block water transport and cause water deficit in leaves.

16. Is the image below of a monocot or dicot root cross section?

Dicot

14. Is the image below of a monocot or dicot root cross section?

Dicot root The ring of cells just inside the endodermis is the pericycle. The cells of the pericycle appear very similar in form to the young primary phloem cells. In plants undergoing secondary growth, the pericycle divides to develop the vascular cambium. Dicot roots have a central vascular cylinder called the stele, with xylem forming an "X" in its center. This is surrounded by phloem cells, and finally the pericycle. The stele is completely surrounded by the endodermis. Dicot roots have the ability to produce lateral roots from the pericycle. Unlike root hairs, lateral roots maintain a vascular connection to the primary root stele. Monocot roots have a central region of ground tissue called the pith that is surrounded by a ring of vascular tissue.

25. From which TISSUE LAYER did these structures develop? (Do not give me the zone of development or the primary meristem.)

Epidermis

6. What FORCE guides plant roots to grow downwards? Hint: It is the same reason apples fall from trees.

Gravity

24. Name the external structures indicated by the arrows in the image below:

Root hairs

19. Name the water-impermeable substance found in the casparian strip.

Subernin

20. In which type of root is a pith present? a. lateral roots b. taproots c. monocot roots d. fibrous roots e. dicot roots f. all roots

c. monocot roots

8. MATCH the words in the wordbank to the descriptions below: APOPLASTIC 2. movement between the cell walls of neighboring plant cells SYMPLASTIC 3. movement between cells via plasmodesmata TRANSMEMBRANE 1. movement between cells via proteins in the cell membrane

Watch the following YouTube video showing the movement of water and dissolved ions into the roots' vascular tissues in the root stele (sound is required): https://bbvideo.ualr.edu/watch/P2kv Within a plant, the apoplast is the space outside the plasma membrane within which material can diffuse freely. It is interrupted by the Casparian strip in roots, by air spaces between plant cells and by the plant cuticle. The apoplastic and symplastic pathways. The symplast of a plant is the inner side of the plasma membrane in which water and low-molecular-weight solutes can freely diffuse. The plasmodesmata allow the direct flow of small molecules such as sugars, amino acids, and ions between cells. A transmembrane protein (TP) is a type of integral membrane protein that spans the entirety of the biological membrane to which it is permanently attached. Many transmembrane proteins function as gateways to permit the transport of specific substances across the biological membrane.

5. By the end of the video, which direction were the roots growing? a. up b. down c. left d. right

b. down

4. In which direction were the roots facing at the beginning of the video? a. up b. down c. left d. right

c. left Watch the following YouTube video showing the root growth of a seedling turned 90° to lay on its side: http://www.youtube.com/watch?v=EORgp8gxwrE&