Biology 1A    Oct 15, 1998
Lecture 13 - Tissues

Page Contents :

• Reading Assignment
• Overview of Lecture
• Overview of Lab
• Lecture Outline
• Vocabulary
• Study Questions

Stern: Chapter 4

Overview of Lecture:

Tissues are differentiated cell regions.
Plant tissues are produced from meristems.
There are three simple plant tissues.
Complex tissues involve more than one cell type.

Overview of Lab:

(A bullet indicates a handout.)
• Tissues.

A. Like many algae, plants are multicellular.
1. Filaments, membranes, parenchyma -- all found in plants somewhere
2. Multicellularity is achieved in plants by sharing cell walls.
3. Cell wall formation in plants
4. Plasmodesmata
B. Unlike most algae, plants have tissues.
1. Tissues are collections of specialized cells that perform a common function.
2. Most algae have no such specialization of cells, all cells are alike.
C. Ways to specialize in plants/animals:
1. protection -- skin, epidermis
2. structural -- bones, wood
3. transport -- blood vessels, xylem/phloem
4. nutrition -- digestive tissues, photosynthetic tissues
5. storage -- fat, tubers (potato)
6. secretion -- secrete defensive or waste subatances

A. Reprise: development
1. Development is the process of making a multicellular organism from a single cell.
2. Spores and zygotes are single cells, development has to happen to make GPT / SPT.
3. Development involves: division, growth, differentiation.
B. All of this development results from the activity of meristems.
1. Meristems are tissues where cells actively divide, producing new cells
a. Meristems produce tissues, and are themselves tissues.
b. Animals do not have meristems.
2. Apical meristems
a. In plants, most meristems are apical.
b. The young plant has a root apical meristem and a shoot apical meristem.
c. As the root or shoot system branches, so does the meristem.
d. Usually increase the length of a structure.
3. Primary meristems
a. Result directly from the apical meristems.
b. The three primary meristems give rise to the three primary tissue systems:
i. protoderm --> epidermis
ii. procambium --> vascular tissue
iii. ground meristem --> ground tissue
4. Secondary meristems
a. Develop in mature tissues
b. Usually increase the width of a structure.
c. Also called lateral meristems, because of location
d. The two kinds of secondary meristems:
i. vascular cambium - produces additional vascular tissue
ii. cork cambium - produces cork (bark)
C. Preview: Organs & Organ systems
1. Three plant organs - root, stem, leaf
2. Two organ systems - root system, shoot system

A. Parenchyma
1. Parenchyma is generic tissue
2. Functions of parenchyma
a. make up a great deal of tissue; filler tissue (e.g. aerenchyma)
b. capacity to replicate - important in wound healing
c. storage of photosynthates
d. metabolism, including photosynthesis (chlorenchyma)
B. Collenchyma
1. Alive at maturity
2. Usually elongated, differential thickness of cell wall in corners
3. Flexible but strong - support in movement or growing areas
C. Sclerenchyma
1. Usually dead at maturity when they start to function
2. Secondary wall laid down containing lignin.
3. Support and protection of non-growing organs
4. Elongate or spherical
a. sclereids - small spheroid sclerenchyma
b. fibers - elongate sclerenchyma

A. Vascular tissues
1. Involved in transport of materials throughout plant - distribution/circulation
2. Two types that occur together
3. Xylem
a. Dead at maturity; secondary wall thickened by lignin
b. Water transport and ions from soil
c. One or two basic types of conducting cells:
d. tracheids
e. vessel elements
4. Phloem
a. Living at maturity
b. Moves nutrients; "sap"
c. sieve cells
d. sieve tube elements & companion cells
5. Both xylem and phloem may contain other cells besides conducting cells.
B. Protective tissues
1. Epidermis
a. single layer of cells
b. boundary with environment; interface
c. functions: protection and gas exchange
d. cuticle, cutin
e. stomata for gas exchange, flanked by guard cells
f. secretory cells / glands
g. trichomes
h. root hairs
2. Periderm
a. usually many cell layers
b. replaces old epidermis as plant grows; produced by cork cambium
c. cork, suberin

• What is a tissue? How are plant tissues formed?
• Describe the structure and formation of a new cell wall in plants.
  What is the composition of the middle lamella? What is its function?
  What is the composition of the primary cell wall? of the secondary cell wall?
  What kinds of tissues have cells with secondary walls?
• In plants, which tissue protects the organism from the environment? which may be photosynthetic? which transport substances? which may function in storage? which provide structural support? which defend from predators?
• What is development? What are the three processes of development? How do meristems accomplish these tasks?
• Which mersitems produce the root and shoot? Which increase the diameter of the root and shoot?
• What are the primary meristems? Where do they come from? What does each produce?
• What are the two secondary meristems? What do they produce?
• What are the three tissue systems in plants? the three major organs? the two organ systems? [Note that organ systems are made of organs, and organs are made of tissues.]
• How is plant development different from animal development?
• How are plant tissues and organs different from animal tissues and organs?
• Consider the three simple tissues in plants:
  Which have secondary walls? Which have thickened walls? Which have thin walls?
  Which have spherical cells? Which are made of elongate cells? Which can divide?
  Which can be photosynthetic? Which are flexible? Which provide structural support?
• What is the difference between sclereids and fibers? How are the two similar?
• What is the difference between simple and complex tissues? What are some examples of each?
• What is the function of xylem? of phloem? of epidermis? of periderm?
• What is the difference between tracheids and vessel elements? Which look larger in cross section? Which have open ends? Which group of plants has vessel elements?
• Explain how sieve tubes and companion cells develop. What function does each have in phloem?
• What kinds of cells and structures could you find in plant epidermis? Which of these could be found in the shoot system? Which could be found in the root system?
• How does the epidermis regulate the flow of water into and out of the plant? How does it regulate gas flow? How are these two function at odds with one another?
• Where in a plant could you find cellulose? cutin? lignin? pectin? suberin?