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Chapter 35: Plant Structure and Growth
OBJECTIVES
After reading this chapter and attending lecture, the student should be able to:
1. List the characteristics of an angiosperm.
Characterized by flowers and fruits that function in the dispersal of seeds.
2. Explain the differences between monocots and dicots.
Monocots – a single cotyledon (seed leaf) (i.e. orchids, bamboos, and palms). Their veins are usually
parallel vascular bundles complexly arranged. They have fibrous root systems and the floral parts are
usually in multiples of three.
Dicots – have two cotyledons. (i.e. roses, sunflowers, maples). Their veins are usually net-like and their
vascular bundles are in a ring. They have taproots and their floral parts are usually in multiples of four or
five.
3. Describe the importance of root systems and shoot systems to plants and explain how they work together.
Root systems lack chloroplasts and live in the dark, therefore they would starve without sugar and other
nutrients obtained by photosynthesis. This is provided by the shoots. The shoot system depends on water
and minerals absorbed by the roots. Vascular tissues aid in transport between the two. One type is xylem
which conveys water and dissolved minerals and the other is phloem which transports food made in the
leaves and roots.
4. Describe how plant cells grow.
Developing plant cells usually have the structure of parenchyma before specializing further in structure and
function. Mature cells do not generally undergo cell division, but they retain the ability to divide and
differentiate into other types of plant cells and under special conditions.
5. Distinguish between parenchyma and collenchyma cells with regards to structure and function.
Parenchyma – relatively unspecialized with thin, flexible primary walls. These carry on most of the cell’s
metabolic functions. Most lack secondary walls. They usually have large central vacuoles and perform most
of the metabolic functions, synthesizing and storing various organic products.
Collenchyma – have unevenly thickened primary walls and provide support to parts of the plant hat are still
growing. They are grouped in strands or cylinders and provide support without restraining growth.
6. Describe the differences in structure and function of the two types of sclerenchyma cells.
Fibers – are long, slender, and tapered, usually appearing in bundles. Some are used commercially for
making things.
Sclereids – shorter than fibers and irregular in shape. They give hardness to seeds and nuts and grittiness to
some fruits.
7. Describe the functions of the dermal tissue system, vascular tissue system and ground tissue system.
Dermal tissue system – roots, extensions of this system, function in absorption of water and minerals. It
secretes a waxy coating (cuticle) that helps aerial parts of the plant retain water.
Vascular tissue system – continuous systm of xylem and phloem which functions in transport and support.
Ground tissue system – makes up the bulk of a young plant; predominantly parenchyma which functions in
photosynthesis, storage, and support.
8. Distinguish between the arrangement of vascular tissues in roots and shoots.
Roots – protoderm, the outermost primary meristem, gives rise to the epidermis (covering the root). Root
hairs increase the surface of the epidermis for water and minerals to cross it. Procambium gives rise to
central vascular cylinders (stele) where xylem and phloem develop. In most dicots, xylem cells radiate from
the center of the stele in two or more spokes with phloem in between the spokes.
Shoots – vascular tissue runs its length in several strands (vascular bundles). At the transition zone, they
converge to join the stele.
9. Using a diagram, describe the basic structure of a root, a stem, and a leaf.
Figures:
35.15, 35.16
35.18
35.19
CHAPTER 36
TRANSPORT IN PLANTS
OUTLINE
OBJECTIVES
After reading this chapter and attending lecture, the student should be able to:
1. List three levels in which transport in plants occurs and describe the role of aquaporins.
1) The uptake and release of water and solutes by individual cells.
2) Short-distance transport of substances from cell to cell at the level of tissues and organs.
3) Long-distance transport of sap within xylem and phloem at the level of the whole plant.
2. Trace the path of water and minerals from outside the root to the shoot system.
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3. Define water potential.
Water potential – the physical property predicting the direction in which water will flow, governed by solute
concentration and applied pressure.
4. Explain how solute concentration and pressure affects water potential.
Plant solute concentration and pressure make up water potential. (Potential refers to potential energy, the
capacity to perform work when water moves from higher to lower water potential). Addition of solutes
lowers water potential and increased pressure raises it.
5. Predict the direction of net water movement based upon differences in water potential between a plant cell
and a hypoosmotic environment, a hyperosmotic environment or an isosmotic environment.
6. According to the transpiration-cohesion-adhesion theory, describe how xylem sap can be pulled upward in
xylem vessels.
7. Explain why a water potential gradient is required for the passive flow of water through a plant, from soil.
8. Describe both the disadvantages and benefits of transpiration.
9. List three cues that contribute to stomatal opening at dawn.
1) Light stimulates guard cells to accumulate potassium and become turgid. It is triggered by the
illumination of a blue-light receptor in a guard cell.
2) The depletion of carbon dioxide within air spaces in the leaf. It occurs when photosynthesis begins in
the mesophyll.
3) An internal clock located in the guard cells.
10. Describe environmental stresses that can cause stomata to close during the daytime.
When the plant is suffering water deficiency, guard cells may lose turgor. Also, a hormone called abscisic
acid, produced in the mesophyll in response to water deficiency, signals guard cells to close stomata. High
temperatures also induce closing and this may combine with excessive transpiration to close stomata briefly
during midday.
CHAPTER 37
PLANT NUTRITION
OUTLINE
1. Describe the chemical composition of plants including:
a. Percent of wet weight as water
80%-85%
b. Percent of dry weight as organic substances
95%
c. Percent of dry weight as inorganic minerals
5%
2. Distinguish between macronutrient and micronutrient.
Macronutrient – element required by plants in relatively large amounts (i.e. carbon, oxygen, hydrogen,
nitrogen, sulfur, and phosphorus).
Micronutrient – element required by plants in very small amounts (i.e. iron, chlorine, copper, manganese,
zinc, and molybdenum).
3. List the nine macronutrients required by plants and describe their importance in normal plant structure
and metabolism.
Carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorous, calcium, potassium, and manganese.
4. List seven micronutrients required by plants and explain why plants need only minute quantities of these
elements.
Iron, chlorine, copper, manganese, zinc, molybdenum, boron, and nickel.
5. Explain how soil is formed.
Soil originates in weathering of solid rock. Water seeps into its cracks, freezes in winter, and breaks down
the rock. Organisms invade and speed up the decomposition. This results in topsoil which is a mix of
decomposed rock of varying texture, living organisms, and humus, a residue of partially decaying organic
material. The most fertile soils are called loams and are made of a mix of sand, silt, and clay.
6. Explain how humus contributes to the texture and composition of soil.
Prevents clay from packing together and builds a crumbly soil that retains water but is still porous enough
for roots to receive air. It also stores mineral nutrients that are gradually returned to the soil as
microorganisms decompose organic matter.
7. Explain why plants cannot extract all of the water in soil.
Sometimes water sticks so tightly to hydrophilic soil particles that plants cannot extract it.
8. List the three mineral elements that are most commonly deficient in farm soils.
1) Nitrogen
2) Phosphorous
3) Potassium
9. Describe the environmental consequence of overusing commercial fertilizers.
Elements in commercial fertilizers are available immediately, but may not be retained in the soil long
enough. These excess minerals are wasted away by rainwater or irrigation. In addition, this run-off can
enter groundwater and pollute streams and lakes.
10. Describe modifications for nutrition that have evolved among plants including parasitic plants,
carnivorous
plants, and mycorrhizae.
Parasitic Platns – (ex. Mistletoe lives in nature as a parasite on oaks and other trees. Although it is
photosynthetic, it does get xylem sap from the host plant. Some plants such as dodder receive all their
nutrition from host plants).
Carnivorous – (live in acid bogs and other habitats where soil conditions are poor; make their own
carbohydrates from photosynthesis, but obtain some minerals by killing and digesting nutrients. Insect traps
have evolved by the modification of leaves. These are usually equipped with glands that secrete digestive
juices.
Mycorrhizae – mutualistic association between roots and fungi. Secrete growth factors that stimulate roots
to grow and branch. As roots develop into mycorrhizae, fungus either sheathes the roots and extends
hyphae among the cortex cells or invades the roots themselves. Other ends of fungal mycelium provide the
root with increased surface area to get minerals and water to the plant.
CHAPTER 38
PLANT REPRODUCTION
AND DEVELOPMENT
OUTLINE
OBJECTIVES
After reading this chapter and attending lecture, the student should be able to:
1. Outline the angiosperm life cycle.
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2. List the four floral parts in their order from outside to inside of the flower.
1) Sepals
2) Petals
3) Stamens
4) Carpels
3. From a diagram of an idealized flower, correctly label the following structures and describe their function:
a. Sepals c. Stamen: filament and anther
b. Petals d. Carpel: style, ovary, ovule and stigma
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4. Explain by which generation, structure, and process spores are produced.
Spores are haploid and produced by meiosis. The come from the haploid sporophyte plants.
5. Explain by which generation, structures, and process gametes are produced.
Gametophytes are the result of the division of spores by mitosis. They are haploid.
6. Describe the formation of a pollen grain in angiosperms.
Inside the pollen sacs of an anther, diploid cells called microsporocytes form into four haploid microspores.
Each eventually divides once by mitosis and produces two cells, a generate cell and a tube cell. This twocelled structure is enclosed in a thick wall particular to plant species. Together they constitute a pollen
grain.
7. Distinguish between pollination and fertilization.
Pollination – the placement of pollen onto the stigma of a carpel by wind or animal carriers; a prerequisite
to fertilization.
Fertilization – the union of haploid gametes to produce a diploid zygote.
8. Describe how pollen can be transferred between flowers.
Some plants (i.e. grass and trees) use wind to pollinate. Others interact with animals that transfer pollen
directly between flowers. Some self-pollinate, but it’s rare.
9. From a diagram, identify the following structures of a seed and recall a function for each:
a. Seed coat d. Radicle g. Endosperm
b. Embryo e. Epicotyl h. Cotyledons
c. Hypocotyl f. Plumule i. Shoot apex
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10. Explain how a monocot and dicot seed differ.
Monocot – have one cotyledon.
Dicot – have two cotyledons.
11. Describe several functions of fruit and explain how fruits form.
Seeds develop from ovules inside the ovary which develops into a fruit that protects the seeds and aids in
their dispersal by wind or on animals. It begins to develop after hormonal changes, triggered by pollination,
cause the ovary to grow tremendously in size. The ovarian wall becomes the fruit wall. As the fruit grows,
other parts of the flower wither away.