Ch. 4 Tissues Part 2

Question 1

Complex tissues

Answer 1

o Composed ot two or more kinds of cells
o Some tissues produced by apical meristems
o Include xylem, phloem, epidermis, periderm

Question 2

Xylem

Answer 2

Chief conducting tissue for water and maternals that are absorbed by the roots

Composed of vessels, tracheids, and rays

Question 3

Vessels

Answer 3

composes xylem
Long tubes
* Thick secondary cell walls (Develop irregularly )
* Open at both walls
* Perforation plate between end walls

Question 4

Tracheids

Answer 4

composes xylem

• Tapered at the ends with pairs of pits that allow water to pass from cell to cell
• Pits: areas without secondary cell wall
• Dead at maturity (when they function)
• Thick secondary cell wall
• May have spiral thickening on cell wall

Question 5

Rays

Answer 5

composes xylem

• Function in lateral conduction and food storage
• Composed of parenchyma cells
• Produced in horizontal rays by ray initials of vascular cambium
• In woody plants, radiate out from center (like wheel spokes)

Question 6

Phloem

Answer 6

Conducts dissolved food materials produced by photosynthesis throughout plants

composed of companion cells

Question 7

Companion cells

Answer 7

composes phloem

• Narrow, tapered cells associated with sieve tubes members
  o Lack secondary cell walls
  o Lay end to end to form sieve tubes
  o Walls have sieve plates with small pores
  o Callose: forms callus plug, prevents leaking of sieve tube contents when cell injured

Question 8

Epidermis

Answer 8

 Protective layer than is one-cell layer thick
 Covers all plants organs
 Often covered with various thickness of cuticle

Question 9

Describe components of epidermis

Answer 9

one-cell thick(velamen roots can be exception), cutin, root epidermal cells produce root hairs, stomata and other modifications

Question 10

Cutin

Answer 10

fatty substance on surface of outer walls of epidermis forms cuticle
o Wax secreted on cuticle
o Cuticle and wax prevent water loss, disease, and produce bacteria resistance

Question 11

Describe importance of Root hairs

Answer 11

o Increase absorptive area of root surface
o Above ground parts of plants may have trichomes
o Outgrowths consisting of one to several cells

Question 12

Describe importance of Stomata and other modifications

Answer 12

o Leaves have stomata bordered by pairs of guard cells; Regulate gas exchange in tissues
o Glands or modified hairs; Some epidermal cells are modified as glands or modified hairs

Question 13

Periderm

Answer 13

 Replaces epidermis when cork cambium begins producing new tissues
* Consititues outer bark of woody plants
* Primarily composed of cork cells, Dead at maturity; while still alive, cytoplasm secrete suberin into walls for structures and protection

Question 14

Suberin

Answer 14

fatty substance, can make cork cells in periderm waterproof

Question 15

Lenticels

Answer 15

Loosely arranged pockets of parenchyma cells formed by cork cambium that protrude through the surface of the periderm
 Allows gas exchange
 Provides protection
 Some lenticels are obvious on tree, while others are not

Question 16

Secretory Cells and Tissues

Answer 16

Function individually or as part of secretory tissue
Examples:
 Flower nectar
 Citrus oilscork
 Glandular hair mucilage
 Latex
 Resins