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Bio 1620 > Exam 4 > Flashcards

Exam 4 Flashcards

Chapter 35 Plant Structure

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1
Q

Vascular plants have roots and shoots that

grow from their tips (apices).

A

Root function –
• anchors the plant
• penetrates soil to absorb water and minerals
* Roots can exert huge forces as they grow.
* Roots are adaptation to living on land.

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2
Q

Vascular plants have roots and shoots that

grow from their tips (apices).

A

Shoot function –
• stems are scaffold for positioning leaves
• leaves are main site of photosynthesis
• flowers, fruits, and seeds formed on shoot
* Repeating unit of vegetative shoot is: internode, node, leaf, and axillary bud (but NOT reproductive structures)

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3
Q

Three types of tissues composing roots and

shoots:

A

1) dermal tissue = epidermis
2) ground tissue =storage, photosynthesis, secretion, forming fibers for support and protection
3) vascular tissue = conducts fluids and dissolved substances

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4
Q

Meristems are specialized cells in the root and shoot apices and other parts of the plant

A
  • These cells act like stem cells in animals;A meristem cell divides to give rise to a differentiating daughter cell and a cell that remains as a meristem cell.
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5
Q

Apical meristems – involved with extension of roots and shoots

A
  • located at tips of roots and stems
    * new cells are added at tips
    * primary tissues = tissues derived from apical meristems
    * primary plant body = extension of root and stem
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6
Q

Apical meristems – involved with extension of roots and shoots

A
  • root cap – protects delicate cells of root apical meristem; sloughed off and replaced as root grows through soil
    * leaf primordia = shelter tender growing shoot apical meristem from desiccation
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7
Q

Apical meristem gives rise to three tissue

systems:

A

1) protoderm – forms epidermis
2) procambium – produces primary xylem (water transport) and primary phloem (nutrient transport)
3) ground meristem – differentiates into more ground tissue

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8
Q

Intercalary meristems found in horsetails and corn. They are in the internodes and add to the length of the internodes.

A

.

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9
Q

Lateral meristems – involved with increase in root and shoot diameter known assecondary growth.

A

.

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10
Q

Lateral meristems form from ground tissue that is derived from apical meristems. (Monocots are the major exception.)

A

.

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11
Q

Secondary growth can increase girth in nonwoody plants, but the effects are most striking in woody plants.

A

.

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12
Q

Woody plants have two lateral meristems:

A

1) cork cambium – contributes to outer bark of tree
2) vascular cambium – located just beneath bark; produces secondary vascular tissue

	a) secondary xylem = main component of wood
	b) secondary phloem = close to outer surface of woody stem; remove bark of tree  damage to phloem  may eventually kill tree
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13
Q

Secondary tissues = most of trunk, branches, and older roots of trees and shrubs

A

.

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14
Q

Secondary plant body = all the secondary tissues

A

.

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15
Q

Plant Tissues:

A

As previously mentioned above, there are three main categories of plant tissues. These are described as dermal, ground, and vascular tissues. Examples of each are described in more detail below.

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16
Q

1) Dermal tissue:

A

• one cell layer thick in most plants
• forms outer protective covering of plant
• cuticle composed of fatty cutin to protect young, exposed parts of plant
• desert succulents may also have several layers of wax to curb water loss and help block UV radiation
• sometimes, dermal tissue forms tree bark
• examples include . . .
a) guard cells
• paired, sausage-shaped cells that flank a stoma (opening) on the leaves, stems, and fruits of plants
• contain chloroplasts, unlike other epidermal cells
• allow passage of oxygen and carbon dioxide and diffusion of water in vapor form
• many times, stomata are more numerous on underside of leaves (minimizes water loss), but water lilies are exception

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17
Q

c) root hairs

A
  • extensions of epidermal cells, but NOT a separate cell
  • increase surface area to maximize water and mineral uptake
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18
Q

2) Ground tissue:

A

a) parenchyma
• most common type of plant cell
• function is storage of food and water, photosynthesis, and secretion
• cells may live for many years (over 100 years old in some cacti)
• most of the cells in fruits such as apples are parenchyma
• photosynthetic parenchyma is called chlorenchyma – found in leaves and outer parts of herbaceous stems

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19
Q

b) collenchyma

A
  • example is celery “strings”
    * tough, but flexible cells support plant organs allowing them to bend without breaking
    * found in stems and leaf petioles
    * have living protoplasm just likeparenchyma and can live for many years
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20
Q

c) sclerenchyma

A
  • cells have tough, thick walls
    * mature cells don’t have living protoplasm
    * cells contain lignin that makescells walls more rigid
    * two forms of sclerenchyma –
              1) fibers forming long, slender strands; linen woven from sclerenchyma fibers of flax plant
          2) sclereids vary in shape and are often branched; gritty texture of a pear is from  groups of sclereids in soft  flesh of fruit
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21
Q

3) Vascular tissue:

A

a) xylem = principal water-conducting tissue made up of vessels and tracheids

	  Water moves in an unbroken stream 		  through the xylem from roots  shoot leaves

Transpiration = diffusion of water vapor from a plant

22
Q

3) Vascular tissue:

A

b) phloem = principal food-conducting tissue in vascular plants; phloem composed of sieve cells and sieve tube members

23
Q

Roots: Anchoring and Absorption Structures

A

Roots adapted for growing underground and absorbing water and solutes.

24
Q

Roots have four regions:

A

1) root cap = protects the root and functions in perception of gravity
2) zone of cell division = contains apical meristem
3) zone of elongation = extends root through soil
4) zone of maturation = cells become differentiated

25
Q

Modified roots accomplish specialized functions.

A

1) taproots consist of single large root with smaller branching roots
2) fibrous root systems are made up of many small roots of similar size
3) adventitious roots are roots that arise from the stem or some place other than the root of the plant (See examples on p. 740 of Campbell text). Adventitious roots can function in support, stability, acquisition of oxygen, storage of water and food, or parasitism of a host plant.

26
Q

Stems: Support for Above-Ground Organs

A

Stems carry leaves and flowers and support

the plant’s weight.

27
Q

Leaves are attached to the stem at the

nodes. Leaf arrangements may be:

A

a) alternate
b) opposite
c) whorled

28
Q

Leaves are attached to the stem at the

nodes. Leaf arrangements may be:

A

but, most often the leaves are arranged
spirally around the stem 137.5° apart. This
angle relates to the golden mean, a
mathematical ratio found in nature. It is
possible that this may maximize the
exposure of leaves to the sun.

29
Q

Internal stem structure:

A

Organization of vascular bundles is a
major distinctive factor between monocots
and eudicots (also known as dicots).

30
Q

Monocots: vascular bundles are scattered
throughout the ground tissue of the
stem

A

.

31
Q

Monocots: vascular bundles are scattered
throughout the ground tissue of the
stem

A

See p. 750 for diagrams of this)

32
Q

Modified stems carry out vegetative propagation and store nutrients. Following are some examples. (See p. 741)

A

a) bulbs: swollen underground stem consisting of fleshy leaves attached to small knoblike stem with adventitious roots at base (onions,
lilies, tulips)

b)  corms:  sort of look like bulbs, but 
		when cut, there are no fleshy 					leaves.  Corms are stems with some
		brown, papery nonfunctional leaves
		on the outside and some 						adventitious roots.  (crocus, 					gladiolus)   c)  rhizomes:  horizontal stems that grow
		underground.  Adventitious roots
		grow from the lower surface. 
		(perennial grasses, ferns, bearded
		iris)

d)  runners and stolons:  horizontal stems
		with long internodes that grow just 			above the surface of the ground
		(strawberries)
33
Q

Modified stems carry out vegetative propagation and store nutrients. Following are some examples. (See p. 741)

A 
e)  tubers:  tips of rhizomes swell and 
			become tubers.  The “eye” of a
			potato is evidence of where a leaf
			formed when the tuber started to 
			grow.  The “eye” is and axillary bud
			and will grow into a new potato 
			plant.
f)  tendrils:  twining stems that aid in 
		climbing (grapes, English ivy);
		Tendrils of peas and pumpkins are
		modified leaves.
34
Q

Leaves: Photosynthetic Organs

A 
•  primary sites of photosynthesis
	•  determinate structures (i.e. they stop
		growing at maturity)
blade = main part of leaf
	petiole = stalk that attaches leaf to main
			    stem of plant
	veins = vascular bundles made of xylem
			  and phloem
		a)  monocots have parallel leaf veins
		b)  eudicots have netted or reticulate
				veins (See p. 748)
35
Q

Leaf anatomy: Most leaves have dorso-
ventral symmetry resulting in more
surface area for photosynthesis. (p. 741)
Leaves: Photosynthetic Organs

A

simple leaves = blades are not divided
compound leaves = blades divided into
leaflets

36
Q

Leaf tissues:

A

a) epidermis with guard cells
b) vascular tissue
c) mesophyll (site of photosynthesis)

37
Q

Modified leaves include:

A

a) floral leaves (bracts): surround the
true flowers (which can be quite
small) and act as showy petals
(poinsettia, dogwood)

		b)  spines:  (NOT the same as thorns
				or prickles)  Spines are modified
				leaves on cacti and some other
				plants.  They reduce water loss
				and can deter predators.
38
Q

Modified leaves include:

A

c) reproductive leaves: little plantlets
growing along margins that
when separated can grow into a
full-sized plant (Kalanchoe)

		d)  insectivorous leaves: trap insects
				to provide supplemental 
				nutrition for plant.  These plants
				often live in acid swamps that
				don’t provide all the nutrients
				the plant requires. (Venus fly 
				trap, sundews, pitcher plants)
39
Q

Chapter 37: Soil and Plant Nutrition

A

.

40
Q

Soils: The Substrates on Which Plants Depend

A

Components of topsoil:

a) mineral particles (inorganic compounds)
b) living organisms (They break down and 		             recycle organic debris.)
c) humus (partially decayed organic 	  	  	                   material)
41
Q

Going from the surface down, we would find:

A

1) leaf litter and plant life
2) topsoil
3) subsoil
4) bedrock

42
Q

Most roots are found in the topsoil. Topsoil
is characterized by the relative amounts of
sand, silt, and clay. Sand binds water and
nutrients minimally while clay binds water
and nutrients very tightly.

A

.

43
Q

Role of soil charge in transport:

A

1) Soil particles tend to have negative
charge.
2) Positive ions attracted to soil particles.
3) Negative ions stay in solution around
roots. This creates a charge gradient
that tends to “pull” positive ions out of
the root cells.
4) Active transport is required to acquire
and maintain K+ and other positive ions
in the root.

44
Q

Water and air fill pores among soil particles.

A balance of air and water in the soil is essential for root growth.

A

.

45
Q

Cultivation can result in soil loss and nutrient depletion.

A 
.  •  Up to 50 billion tons of topsoil have been 
	 lost from fields in the U.S. in a single year.
   •  Causes can be:
  	   -  erosion
	   -  poor landscaping
	   -  poor farming practices  
	   -  drought  (“Dust Bowl” in 1930s)
   •  Solutions to combat erosion:
	   -  mixing crops in a field
	   -  conservation tillage
	   -  no-till practices (not plowing under fall
		 crop detritus)
	   -  also important to minimize runoff of
		fertilizers from farms, lawns, and 
		gardens into waterways that result in 
		algal blooms
46
Q

pH and salinity affect water and mineral availablilty.

A

• Acidic soils release aluminum from rocks.
Aluminum is toxic to plants and may
combine with other nutrients making them unavailable to plants.

• Salty soils draw water out of plants causing
them to lose turgor pressure.

47
Q

Plant Nutrients

Plants require nine macronutrients and
eight micronutrients. (Table 37.1, p. 791)

A

1) Macronutrients include –
carbon, oxygen, hydrogen, nitrogen,
potassium, calcium, magnesium, phosphorus, sulfur

2) Micronutrients include –
chlorine, iron, manganese, boron, zinc,
copper, nickel, molybdenum

48
Q

Food security is related to crop productivity

and nutrient levels.

A

• Some goals of plant breeding involve
increasing nutrient levels in food crops
while they are growing in the field.

49
Q

Food security

A

1) Bacteria living in close association with
roots can provide nitrogen. Legumes
have a symbiotic relationship with
bacteria living in the nodules of their
roots.

2) Mycorrhizae aid a large portion of
terrestrial plants. More than 90% of plants have a symbiotic relationship with “fungus roots.”

3) Carnivorous plants trap and digest animals to extract additional nutrients.
These plants usually live in acidic, nitrogen-poor environments.

4) Parasitic plants exploit resources of other
plants. Some parasitic plants are photosynthetic while others are not. They
tap into a host plant to obtain nutrients,
including carbohydrates.

50
Q

Carbon-Nitrogen Balance and Global Change

Elevated CO2 levels can alter photosynthesis
and carbon levels in plants.

A

• An increase in CO2 results in an increase
in photosynthesis. This, in turn, leads to
an increase in biomass. The plant tissue
produced has a higher proportion of
carbon compared to nitrogen resulting in
a shift toward more carbohydrate and
less protein.

•  With less protein available in plants,
   herbivores must eat more plants to get
   the same amount of nutrients.  (Greater
   plant loss to herbivory.)
51
Q

Elevated temperature can affect respiration and carbon levels in plants.

A

• The higher the temperature, the greater the
rate of enzyme reactions. Plant respiration
breaks down carbohydrates and could
result in changes in plant nutrient balance.

52
Q

Phytoremediation – uses plants to remove toxic contaminants from soil or water.

A

• Poplar trees remove trichloroethylene from
soil and convert it to carbon dioxide and
chlorine compounds.

• Some plants can remove small amounts of
TNT (trinitrotoluene) in soil and degrade it.

• Heavy metals can be successfully removed
at lower costs. Contaminants accumulate in shoots of plants and then plants are removed.

Bio 1620 (4 decks)

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