Botany Test 2 Flashcards
(70 cards)
1
Q
List and Define 3 Different Arrangements of Leaves on a Node
A
Alternate- one leaf per node
Opposite- 2 leaves per node
Spiral or helical - 137 degree angle between leaves
2
Q
What is the Difference Between Simple and Compound Leaves?
A
Simple - one blade present
Compound - 2 or more leaflet blades are attached to a common axis in one plane
3
Q
The arrangement of leaves on a stem is called ___
A
phyllotaxy
4
Q
Explain vein orders in leaves
A
Commonly have 4-6 vein orders where veins get progressively smaller as they divide the leaf mesophyll into increasingly smaller groups.
The smallest veins eventually enclose 3-4 cels called areoles.
Very efficient system for transporting materials into and out of mesophyll cells
5
Q
Give 2 Functions for Vascular Bundle Sheaths
A
- enclose vascular bundles to their ends so that no part of the vascular tissue is exposed to intercellular air
- involved in loading and unloading of phloem and in distributing water and materials from xylem to the mesophyll and epidermis
6
Q
List 3 Mechanical Features of Guard Cells that are Essential for their Opening
A
- have thickened cell walls surrounding their openings
- attached to each other at their ends
- cellulose microfibrils surround each guard cell like hoops around a barrel
7
Q
Explain in detail how stomates open
A
- blue light stimulates guard cell opening
- starch in chloroplasts is broken down into malate and placed in the vacuole
- K+ enters the guard cell vacuole from subsidiary cells to balance the charge
- water follows osmotically and the stomates open
- in a closed stomate the vacuole is small
- when the stomate is open, the vacuole occupies over 90% of the cell volume
- to close the stomates, malate is transported to the chloroplast and converted to starch
- K+ leaves the guard cell and returns to subsidiary cells, water follows osmotically and the stomates close
8
Q
Explain how the design of palisade and spongy mesophyll relates to their function
A
Palisade are elongated so they capture more light, they conduct photosynthesis and are in the upper leaf
Spongy are irregularly shaped cells w/ air space and function in gas exchange
9
Q
What is the characteristic feature of C$ leaf anatomy
A
Large Bundle Sheath
10
Q
What are the differences between a leaf in the sun and one in the shade
A
Sun leaves are thicker because of more mesophyll tissue,
- darker green because of more chlorophyll
- have less surface area
11
Q
List 4 functions for water in plants
A
- cell expansion during growth
- support of plant organs through turgor pressure
- solvent for reactions and proteins
- cooling of leaves
- split to form O2 during photosynthesis
12
Q
What is the primary factor that limits plant growth on a world-wide basis
A
water
13
Q
Explain the formation of humidity shells and boundary layers around stomatal openings
A
- water molecules are very cohesive and would prefer to associate w/ other water molecules
- when water leaves the plant through stomates, it forms a humidity shell that are fairly stable b/c of cohesiveness of water
- eventually the water molecules mix sufficiently w/ air that the cohesiveness is lost and boundary layers form resulting in significant water loss
- some plants have adaptations to stabilize humidity shells and boundary layers. ex. trichomes
14
Q
Some plants have developed adaptations to help reduce transpiration. Give 4
A
- cuticle
- bulliform cells
- reduced leaf area
- leaf movement to avoid mid day sun
15
Q
What is an abscission layer?
A
- consists of a few layers of thin-walled cells at the base of a leaf
- laid down during development
- vascular system is reduced in this area, no supportive fibers are present
- function to shed leaves and their derivatives
16
Q
How does an abscission layer work?
A
- cellulases are produced that breakdown cell walls in this region
- ethylene is produced and there is an increase in respiration in the layer
- cells on the stump side of the layer enlarge to shear off the leaf
- cells on the stump become suberized to prevent water loss and pathogen invasion
17
Q
Describe how a water molecule moves from the soil solution through the plant to the atmosphere. Include the plant tissues/ organs involved.
A
- water enters through root hairs, or through cell wall space in endodermis
- at endodermis, selectivity is ensured b/c of the Casparian strip and the semipermeable membranes of the endodermal cells
- Water enters the xylem and moves through the root to the skin then out through a petiole into the leaf
- In the leaf the water is distributed through the vein orders to small groups of cells- areoles
- cell wall space in the leaf mesophyll is saturated w/ water and the air inside the leaf is at 100% relative humidity
- stomates open, water is lost to atmosphere through transpiration
18
Q
Water moves through plants based upon 3 properties. List these.
A
- adhesion of water to cell walls
- cohesiveness of water
- transpirational loss of water to environment
19
Q
When xylem is put under too much tension it can ____
A
cavitate
20
Q
Explain what root pressure is, and how it develops
A
- Pressure created when transpiration is occuring
- During the night when stomates are closed and transpiration has essentially stopped, minerals from the soil solutions accumulate in the xylem in the root
- water enters the xylem osmotically and a pressure is created
21
Q
Describe a hydathode and how its structure can result in guttation
A
Hydathode consists of a modified stomate that remains open all the time
- a vascular bundle that ends in xylem near this stomate
- loosely packed cells under the stomate
- when there is root pressure, water flows from the xylem, through the loosely packed cells, and out of the plant through permanently open stomate
- water drops leaving hydathodes is called guttation
22
Q
Explain the running of sap that occurs in some temperate plants
A
- this occurs in spring when storage starch is converted to sucrose which is put into the xylem
- sucrose is osmotically active and this results in water entering the xylem osmotically, creating pressure
- this forces the sucrose solution into the stem of the plant where it is used in respiration to provide energy for re-growth
- running of sap is easily observed in some species of maple trees, where the sap can be seen running out of cracks in the stem
23
Q
Describe the mass-flow hypothesis for phloem transport.
A
- The system is in equilibrium
- solutes added to source (sucrose loading)
- water enters source osmotically, this creates pressure
- pressure is transfered to the sink
- sink loses water to cell wall space
- get mass flow of water from source to sink until system reaches equilibrium
- In plants- sucrose loading in source and sucrose unloading in sink maintains mass flow the phloem is symplast and xylem cell wall is apoplast, water moves from source to sink and returns to source in xylem cell wall space
24
Q
When there are several sinks in a plant, how does phloem transport distribute the sucrose?
A
- Determined by strength of sink which is how much sucrose it can unload and be reused or stored
- Dependent on metabolic rate of sink and number of sucrose transporters present to unload sucrose from the phloem to surrounding cells
25
Describe how a sink can become a source and then eventually become a sink again.
It can happen in leaves or roots/ stems
- In leaves- a young leaf is not fully photosynthetic and is thus a sink
- later this leaf will become shaded by newer/younger leaves formed above it and become a sink
- when this leaf senesces, it will be mined for its resources, and thus be a source for one last time
26
During secondary growth, what happens to the pith and primary xylem?
- the pith and primary xylem become covered w/ secondary xylem and remain in their original position and form
- pith parenchyma cells remain alive for years but become non-functional
- primary xylem become filled with resins and become nonfunctional
27
What happens to primary phloem, the cortex, and epidermis during initial secondary growth?
- primary phloem is pushed outward, fragmented, and becomes nonconducting
- cortex and epidermis can persist for many years due to increase in circumference through expansion (cortex) and cell division (both)
28
What is periderm?
- replaces epidermis usually towards end of first year of growth
- is the cork cambium and its derivatives (parenchyma inside, cork outside)
- it can be a single layer or successive layers
29
The vascular cambium has 2 types of initials. List these and indicate what each produces.
- Fusiform initials (elongated)- xylem inside and phloem outside
- ray initials (isodiametric) - parenchyma cells to both inside and outside
30
What functions do vascular rays perform?
Radial movement of material in stem and storage of water, carbs, lipids, small molecules
31
In stems, the initial cork cambium forms from parenchyma cells in the outer region of the cortex. Explain how successive cork cambia form.
It is formed from either parenchyma cells from the last cork cambium or from phloem parenchyma cells
32
Bark is defined as everything outside of the what?
Vascular Cambium
33
Give 2 defining characteristics of cork cells
- dead at maturity
- suberized cell walls to prevent water loss
- usually lack visible contents
34
Stems with secondary growth have _____ to allow for air penetration into the phloem and vascular cambium regions
lenticels
35
Describe how lenticels form
- through specialized activity of cork cambium, where the cork cambium produces loosely packed parenchyma cells to the outside rather than the normal cork cells
- cork cambium in lenticels produces the usual parenchyma cells to the inside
36
Explain how heartwood becomes filled with tannins and resins
- parenchyma cells grow into the dead xylem cells through pits and form tyloses that become filled w/ tannins and resins and plug the cell, preventing bacterial or fungal invasion
- no longer functional in carrying water
37
What causes the appearance of growth rings in secondary xylem?
- early wood in spring is larger in diameter w/ thin cell walls
- late wood in summer is small in diameter with thick cell walls
- very late wood has very small thick walls, and is darker in color
- wood goes dormant in winter and restarts the next season
38
What is reaction wood and what function does it perform? How is it different between gymnosperms and angiosperms?
- when vascular cambium produces more xylem to aid in support of branches
- gymnosperms- produced on bottom of branches to support them - compression wood
- angiosperms- produced on top of branches to support them - tension wood
39
Where do latex and natural rubber come from?
Laticifers in plants such as rubber plant and milkweed
40
Describe how expression of the 3 genes, A, B, and C, result in the development of flowers
- A only - sepals
- A + B - petals
- B + C - stamens
- C alone - carpels
- A and C are mutually exclusive
- when C is expressed, the meristem gets used up (determinant)
- C results in the sexual parts of the flower
41
Give 2 primary functions of flowers?
- to achieve pollination
| - to produce seed for the next generation
42
List 4 flower parts that are non-reproductive
- peduncle
- sepals
- receptacle
- petals
43
List 2 flower parts that are reproductive
- stamens
| - anther
44
____ are normally green and leaf-like flower parts
sepals
45
____ are normally colorful flower parts
petals
46
What function do sepals perform?
Protect the immature flower from damage and water loss
47
What function do petals perform?
- attract pollinators
| - may contain volatile oils that impart the characteristic fragrance to the flowers
48
The ____ gene is responsible for the formation of bilateral flowers
cyc
49
What do archesporial cells have to do with pollen sac development?
- each pollen sac develops from a single row of archesporial cells
50
List 5 steps in anther dehiscence in the order that they occur
1. Degeneration of the tapetum and middle layer
2. formation of cell wall thickenings in the endothecial cells
3. degeneration of the septa generates a bilocular anther
4. water uptake by the endothecial cells crushes the cells of the stomium
5. water loss by the endothecial cells causes the pollen sacs to open
51
Sexual reproduction in plants can be thought of as occurring in 5 steps. List these steps in the order they occur.
1. production of gametes
2. pollination, pollen germination, and pollen tube growth
3. double fertilization
4. growth of the embryo and expansion of the endosperm
5. maturation of seed and fruit
52
Explain how a microspore mother cell develops into a pollen grain.
- each microspore mother cell undergoes meiosis to form 4 microspores
- each microspore then undergoes mitosis to form a tube cell and a generative cell
- these 2 cells then become surrounded by a common cell wall forming the pollen grain
- each pollen grain then dries down for eventual dispersal
53
Explain how the megaspore mother cell develops into the 7 celled structure ready for fertilization.
- mmc undergoes meiosis resulting in 4 megaspore cells, 3 degenerate
- remaining megaspore undergoes mitosis 3 times w/out cell divisions to result in a single cell w/ 8 nuclei
- 3 nuclei migrate to top of the cell and cell walls form around them to form 3 antipodal cells
- 3 nuclei migrate to bottom of cell and cell walls form around them to form 2 synergids and 1 egg cell
- remaining 2 nuclei are free in the large central cell and are called polar nuclei
54
What is pollination?
Transfer of pollen from an anther to a stigma
55
Describe pollen germination and subsequent development
- pollen grain on the stigma is rehydrated and a pollen tube emerges through one of the pores in the exine
- pollen tube grows through the stigma into the transmitting tract of the syle
- as pollen tube grows the tube nucleus stays close to the tip
- the generative cells then divides to form 2 sperm cells that stay close to tube nucleus
- as pollen tube grows through the style, callose plugs are laid down to keep the cytosol close to the pollen tube tip
- pollen tube grows into the ovary and up the stalk of one of the ovules
- pollen tube enters the ovule through the micropyle and enters one of the synergids where the 2 sperm are released into the embryo sac for double fertilization
- the pollen tube is attracted to the synergids by a gradient of plant hormones and proteins
56
What is double fertilization and what are its products?
- one of the defining characteristics of the flowering plants
- one sperm unites w/ the egg to form the diploid zygote, the zygote will develop into the embryo
- other sperm unites w/ the 2 polar nuclei to form a triploid nucleus, develops into the endosperm
57
Describe endosperm development following fertilization
- triploid central cell nucleus undergoes several rounds of mitosis w/out cell divisions
- you end up with central cell w/ a predictable number of free nuclei, the free nuclear state (liquid endosperm)
- in most plants, cell walls then form to cellularize the endosperm
58
In the scheme of things, the embryo and endosperm become packaged into a seed and then into a fruid. What are the seed coat and fruit derived from?
- embryo and endosperm dry
- integuments dry to form the seed coat
- the ovary wall will become the dry or fleshy fruit
59
Flowers are believed to be modified leaves. Explain how a simple pistil can be derived from a leaf. Wat does the term carpel have to do with it?
- a simple pistil is derived from one carpel, and a carpel is derived from one leaf
- the leaf is folded w/ the upper surface to the inside and the margins are sealed to form a simpil pistil
- margins are meristematic and form the placenta, the region where ovules form
60
Explain how carpels are joined in a compound pistil to result in axile and parietal placentation
Axile- if carpels are joined in a folded condition, the ovary is multiocular, and the placentae occurs in the center of the ovary where the carpellary margins meet
Parietal- if carpels are joined in an open condition, margin to margin, the ovary has one locule, and the placentae are located on the ovary wall where the capillary margins meet
61
A flower having all 4 whorls is called a ____ flower
complete
62
A flower having both sexes is called a _____ flower
perfect
63
Explain the differences between a superior and an inferior ovary
Superior- ovary is positioned above the level where the other flower parts are attached - flower is hypogynous
Inferior- ovary is positioned below the level where the other flower parts are attached - flower is epigynous
64
How is inflorescence meristem similar to the vegetative apical meristem
- it produces bracts and floral meristems at regular intervals in a phyllotaxy
- it produces nodes and internodes
65
Give 2 factors that determine initial inflorescence in architecture
- different patterns of bifurcation of the inflorescence meristem results in the different types of inflorescence observed
- equally as important is whether or not the inflorescence is determinate or indeterminate
66
Leaves associated with inflorescences are called _____
bracts
67
Define raceme
An unbranched inflorescence in which the main axis continues to grow, producing flowers w/ short pedicles laterally, such that the youngest flowers are apical, or at the center. Indeterminate
68
Give an example of modification of the basic raceme to form another type of indeterminate inflorescence. Include a diagram if useful
A spike is a type of raceme of sessile flowers
69
Define cyme
Branched inflorescence in which each flower, in turn, is formed at the tip of a growing axis and further flowers are formed on branches arising below it. Determinate
70
The composites are a large family of plants that have flowers in a heat. Describe the anatomy of these inflorescences.
- a head is an indeterminate inflorescence in which the vertical axis is flattened and the inflorescence develops on an expanded receptacle often subtended by a cluster of bracts called "involucral bracts"
- the flowers in the inflorescence develop in a spiral pattern w/ the youngest flowers towards the center of the inflorescence
- often the outer flowers develop as ray flowers w/ some petals elongated, and the inner flowers develop as disc flowers w/ reduced, symmetrical corollas
- this gives the inflorescence the appearance of being a single flower
