Plants Flashcards
(127 cards)
1
Q
What are plants?
A
Multi-celled, eukaryotic, photosynthetic autotrophs.
2
Q
What are cell walls made of?
A
Cellulose
3
Q
How is surplus carbohydrates stored?
A
It is stored as starch.
4
Q
Describe the life cycle of plants.
A
It’s an alteration of generations.
5
Q
Define alteration of generations.
A
One generation of the gametophyte generation is where all the cells of the plant are haploid. The alternate generation is the sporophyte generation where all the cells of the plant body are diploid.
6
Q
Describe the evolution of plants.
A
Plants evolved from aquatic green algae about 500 million years ago. They colonized land during the Paleozoic era. Today most species live on land and have diversified into different species.
7
Q
How do plants help the area around them?
A
Plants help stabilize the foils around them and provide a home for insects and other animals. They absorb carbon dioxide and release oxygen into the atmosphere.
8
Q
Which plants do most of the world depend on for survival?
A
Rice, beans, soy, corn and wheat.
9
Q
How are plants organized?
A
They are organized into two groups: bryophytes and tracheophytes.
10
Q
What are bryophytes?
A
The plants with no transport vessels. Their sperm must swim through water to fertilize an egg. They’re restricted to moist habitats. They grow on rocks, soil and trees. They lack liginin fortified tissue.(Ex. mosses, liverworts, hornworms)
11
Q
What are tracheophytes?
A
The plants with xylem and phloem for transport. They have lignified transport vessels. They have roots, leaves and a life cycle with a dominant sporophyte generation. They are divided into seed plants and seedless plants.
12
Q
What purpose does lignin-fortified tissue serve?
A
It supports tall plants.
13
Q
What purpose do the roots serve?
A
Roots absorbs water while also anchoring and supporting the plant.
14
Q
What are characteristics of seedless tracheophytes?
A
They are primitive and reproduce by spores which are homosporous. They are still restricted to moist habitats even though they have transport tissue because their sperm is flagellated and can swim to fertilize the egg.
15
Q
What does homosporous refer to?
A
It refers to seedless tracheophytes that produce only one type of spore which then develops into a bisexual gametophyte.
16
Q
What are characteristics of seed tracheophytes?
A
They are split into gymnosperms and angiosperms.
17
Q
What does heteroporous refer to?
A
It refers to seed tracheophytes that produce that produce megaspores and microspores. Megaspores develop into male gametophytes and microspores develop into female gametophytes. The sperm of seed plants have no flagella and do not need a a watery environment for fertilization.
18
Q
What are characteristics of gymnosperms (conifers)?
A
These were the first seed plants to appear on Earth. Their seeds are not enclosed inside a fruit; they are better adapted for dry environments. Examples are pines, firs, redwoods, junipers and sequoia.
19
Q
How are gymnosperm seeds better suited for a dry environment?
A
The seeds are on modified leaves that form cones. They include needle-shaped leaves, which have a thick, protective cuticle and a relatively small surface area. In addition, gymnosperms depend on wind for pollination.
20
Q
What are characteristics of angiosperms (flowering plants)?
A
These are seed plants whose reproductive structures are flowers and fruits. They include 90 percent of all plants. There are two groups angiosperms: monocots and dicots.
21
Q
What is the process of angiosperm seed dispersal?
A
The color and sent of a flower attracts animals that carry pollen. After pollination and fertilization the ovary becomes the fruit and the ovule becomes the seed. An animal eats and digests the fleshy (often sweet) part of the fruit while the tough seed passes through the digestive tract and is deposited with its feces in the fertilizer.
22
Q
What are the benefits of angiosperms?
A
The fruit protects dormant seeds and aids in their dispersal. Maple trees have seeds with wings that enable them to be dispersed great distances by wind. Some plants have burrs on their fruit that cling to animals’ fur.
23
Q
What are cotyledons?
A
They are seed leaves.
24
Q
What are the differences between monocots and dicots?
A
Monocots have one cotyledon, scattered vascular bundles in the stem, parallel leaf venation, floral parts usually in 3s, and fibrous roots. Dicots have two cotyledons, vascular bundles in a rind in the stem, netlike leaf venation, floral parts in 4s and 5s, and a taproot system.
25
What modifications allowed plants to move to land?
- Cell walls due to lack of water support.
- Roots and roots hairs to absorb water/nutrients from the soil.
- Stomates that are open to exchange gasses and minimize water loss.
- Cutin which helps prevent excess water loss.
- Gametangia which precent drying out.
- Sporopollenin protects spores and pollen in harsh terrestrial environments.
- A reduced gametophyte generation.
- Xylem and phloem which allows the plants to grow tall.
- Lignin embedded in xylem and in plant cells that provides support.
- Seeds and pollen with a protective coat that prevents desiccation and disperse offspring.
26
What is cutin?
It is the waxy coating on the leaves.
27
What is gametangia?
Gametes and zygotes which from a protective jacket of cells in some plants.
28
What is sporollenin?
It's a tough polymer that is resistant to almost all kind of environmental damage. It is found in the walls of spores and pollen.
29
What is the function of the meristem?
Plants contains this tissue that continually divides and generates new cells so which causes plants to grow as long as they live.
30
What is primary growth?
This is the elongation of the plant down to the soil and up into the air. The apical meristem is the source of primary growth. In herbaceous (non-woody) plants there is only primary growth.
31
What is the apical meristem?
This is located at the tips of the roots and in the buds of the shoots. It is the source of primary growth.
32
What is secondary growth?
This is an increase in girth by the lateral meristem. In woody plants secondary growth is responsible for the gradual thickening of the roots and shoots formed from primary growth.
33
What are the types of tissues in plants?
There are dermal, vascular and ground tissue.
34
What is dermal tissue and what is its purpose?
Dermal tissue covers and protects the plant. It includes epidermis and modifies cells like guard cells, root hairs and cells that produce a waxy coating.
35
What is vascular tissue and what is its purpose?
Vascular tissue consists of xylem and phloem. These transport water and nutrients around the plant.
36
What is ground tissue and what is its purpose?
This is most common tissue type which functions mainly in support, storage and photosynthesis. It consists of three cells: parenchymal, sclerenchmal, and collenchymal.
37
What is the xylem's form? Describe the tracheids and the vessel elements.
The xylem tissue consists of two elongated cells: tracheids and vessel elements. Tracheids are long, thin cells that overlap and are tapered at the ends. Water passes from one cell to another through pits. Vessel elements are wider, shorter, thinner walled and less tapered than tracheids. The vessel elements are aligned end to end and the ends are perforated to allow free flow.
38
What is the xylem's function?
It conducts water and minerals from roots to shoots. Tracheids support the plant as well. Xylem makes up wood.
39
What are pits (of the xylem's tracheids)?
They are areas with no secondary cell wall. The secondary cell walls are hardened with lignin.
40
What types of plants have tracheids?
Only seedless vascular plants and gymnosperms have tracheids. Most angiosperms have both tracheids and vessel members.
41
What is the phloem's form?
The vessels consists of chains of sieve tube members or elements whose end walls contain sieve plates. Connected to each sieve tube member is at least one companion cell that does contain a full complement of cell organelles and nurtures the sieve tube elements.
42
What is the phloem's function?
It carries sugars from the photosynthetic leaves to the rest of the plant by active transport.
43
Describe the sieve plates (of the phloem's sieve tube elements).
They facilitate the low of liquid from one cell to the next. They lack nuclei, ribosomes and vacuoles.
44
What are the characteristics of parenchymal cells?
These are classic plant cells. They have a primary cell walls that are thing and flexible and lack a secondary cell wall. They have one large vacuole and it carries out most metabolic functions.
45
What are the characteristics of collenchymal cells?
These have unevenly thickened primary cell walls but lack secondary cell walls. Mature collenchymal cells are alive and their function is to support the growing stem.
46
What are examples of parenchymal cells?
When turgid with water they give support and shape to the plant. Most parenchymal cells retain the ability to divide and differentiate into other cell types after a plant has been injured. In the mesophyll cells in the lead, these contain chloroplasts and carry out photosynthesis.
47
What are characteristics of sclerenchymal cells?
They have a very thick primary and secondary cell walls fortified with lignin. Their function is to support the plant and there are two forms: fibers and sclereids. Fibers are long, thin and fibrous like and they usually occur in bundles. Sclereids are short and irregular in shape. They make up tough seed coats and pits.
48
What is the function of the roots?
They absorb nutrients from the soil, anchor the plan and store food.
49
What is the structure of the roots?
The epidermis covers the entire surface of the root and is modified for absorption. Root hairs are located here. The cortex consists of parenchymal cells that contain many plastids for the storage of starch and other organic substances.
50
What are root hairs?
These are slender cytoplasmic projections from the epidermal cells. They extend out from the cell and increase the absorptive surface area.
51
What is the stele (of the roots)?
The vascular cylinder or stele of the root consists of vascular tissues surrounded by one or more layers of tissue called the pericycle, from which lateral roots arise.
52
What is the endoderm (of the roots)?
This is tightly packed layer of cels that surround the stele. Each endoderm cells is wrapped with a casparian strip. It's function is to select what minerals enter the vascular cylinder and the body of the plant.
53
What is the casparian strip (of the endoderm)?
It wraps each endoderm cells and is a continuous band of suberin. Suberin is a waxy material that is impervious to water and dissolved minerals.
54
Where are the three zones of cells at different states of primary growth?
These are the zone of cell division called apical meristem, the zone of elongation and the zone of differentiation.
55
What is the purpose and function of the root tip?
It is protected by a root cap which secretes a substance that helps digest the earth as the root tip grows through the soil.
56
What occurs at the zone of cell division during primary growth?
Meristem cells that are actively dividing and responsible for producing new cells that grow down into the soil.
57
What occurs at the zone of elongation during primary growth?
The cells elongate and are responsible for pushing the roots cap downward and deeper into the soil.
58
What occurs at the zone of differentiation during primary growth?
Here the cells undergo specialization into three primary meristems that give rise to these tissue systems in the plants. The protoderm becomes the epidermis and the ground meristem becomes the cortex and the procambium becomes the primary xylem and phloem.
59
What is the taproot?
It is a single, large root that gives rise to lateral branch roots. In dicots it is the primary root. Some tap water deep in the soil. Others are modified for storage of food.
60
What is a fibrous root system?
It is common in monocots (ex. grasses) and hold the plant firmly in place while decreasing soil erosion.
61
What are adventitious roots?
These are roots that arise above ground.
62
What are aerial roots?
Roots that stick up out of the water and serve to aerate the root cells. (Ex. english ivy has aerial roots that enable the ivy to cling to the sides of a building)
63
What are prop roots?
Present in tall plants that grow above ground out from the base of the stem and help support the plant.
64
What are vascular bundles?
Vascular tissue that runs the entire length of the stem in strands. Each vascular bundle contains xylem on the inside , phloem on the outside, and meristem tissue in between the two. In monocots, they're scattered through out the stem. In dicots, they're arranged in a ring around the edge of the stem.
65
Describe the ground tissue of the stem (including the pith).
It consists of the cortex and pith. Pith consists of parenchymal tissues modified for storage. The apical meristem located the tips of the shoots and roots supply cells for the plant to grow in length.
66
Describe secondary growth in stems.
It's produced by lateral meristem which replaces the epidermis with a secondary dermal tissue (ex. bark). A second lateral meristem adds layers of vascular tissue. Wood is secondary xylem that acummulated over the years.
67
What is the function of the leaf?
The leaf is organized to maximize sugar production while minimizing water loss.
68
What is the structure of the leaf?
The epidermis is covered by cutin. Guard cells are located here. The inner part of the leaf consists of palisade and spongy mesophyll cells. Vascular bundles/veins are located in the mesophyll they carry water, nutrients and sugar. Bundle sheath cells surround the veins and separate them from the rest of the mesophyll.
69
Describe the palisade and spongy mesophyll cells in the inner part of the leaves.
The cells in the palisade are packed tightly while the spongy cells are loosely packed to allow for diffusion of gases into and out of these cells.
70
Describe guard cells in the leaves.
They are modified epidermal cells that contain chloroplasts which are photosynthetic and control the opening of the stomates. Their cell walls are not uniformly thick. Cellulose microfibrils are oriented in a such a way that when the cells absorb water, they become turgid and curve like hot dogs to become open. When the lose water they become flaccid.
71
How does depletion of CO2 cause stomates to open?
Depletion of CO2 occurs when photosynthesis begins. The stomates need to be open at this time because water and more CO2 need to get in.
72
How does an increase in potassium ions in the guard cells cause stomates to open?
An increase in potassium ions lowers the water potential in guard cells and causes water to diffuse into them. As they become turgid, the guard cells swell and the stomates open.
73
How does the stimulation of the blue light receptor in a guard cell cause stomates to open?
The stimulation causes ATP-powered proton pumps in the plasma membrane of the guard cells to become activated. Ten, the guard cells promote the uptake of potassium ions and stomates open.
74
How does the active transport of protons cause the opening of stomates?
Stomates open when protons transport into the surrounding epithelial cells.
75
What factors cause stomates to close?
Lack of water, high temperatures and abscisic acid cause the stomates to close.
76
How do high temperatures cause the stomates to close?
The high temperature stimulates cellular respiration and increases CO2 concentration within air spaces of the leaf.
77
How does abscisic acid cause the stomates to close?
This acid if produced in the mesophyll cells in response to dehydration, signals guard cells to close the stomates.
78
What is the mechanism of xylem transport?
Xylem fluid rises in a plant against gravity but requires no energy. The fluids in the xylem can be pushed up by root pressure or pulled up by transpirational pull.
79
How does root pressure cause transport in the xylem?
Water flows into the stele from the soil as a result of the high mineral content in the root cells. It pushes xylem sap upward a few meters. Guttation (droplets of water on herbaceous dicots) is a result of this.
80
How does transitional pull cause transport in the xylem?
Transpiration causes negative pressure to develop in the xylem tissue from the roots to the leaves. The cohesion of water makes it possible to pull a column of water.
81
What does the transpirational pull-cohesion tension theory state?
It states that for each molecule of water that evaporates from a leaf by transpiration, another molecule of water is drawn in at the root to replace it.
82
What factors affect the rate of transpiration?
Humidity and transpiration are inversely proportional. Wind reduced humidity and therefore increases transpiration. Light intensity and the rate of transpiration are directly proportional. Closing stomates stops transpiration.
83
How do apoplasts and symplasts help in the absorption of nutrients and water?
These allow lateral movement to be accomplished. When water reaches the endodermis, it can continue to the xylem through the symplast ; but water in the apoplast must pass across the endodermis by diffusion.
84
Define lateral movement.
The movement of water and solutes across a plant.
85
What are the apoplasts?
The apoplasts are the network of cell walls and intercellular spaces within a plant body that permits short-distance extracellular movement of water within a plant.
86
What are the symplasts?
The symplast is a continuous system of cytoplasm of cells interconnected by plasmodesmata for long-distance transport.
87
How does the mycorrhizae help in absorption or nutrients and water?
If the roots lack root hairs, mycorrhizae supply that plant with water and minerals. They are the symbiotic structures consisting of the plant's roots intermingled with the hyphae (filaments) of a fungus.
88
What is rhizobium?
This is a symbiotic bacterium that lives in the nodules on roots of specific legumes and fix nitrogen gas from the air into a form of nitrogen the plant requires.
89
What is bulk flow?
This is how fluids move great distances in plants.
90
How does phloem sap travel around the plant from sugar source to sugar sink (translocation)?
Either photosynthesis or the breakdown of starch is the sugar source. Mature leaves are the primary source of sugar. The growing roots and fruit are sugar sinks. Storage organs are sinks in the growing season and become the source during the spring.
91
What is the process of asexual reproduction in plants?
Plants can clone themselves or reproduce asexually by vegetative propagation. Examples are grafting, cuttings, bulbs and runners.
92
What is vegetative propagation?
A piece of the stem, root or leaf of the plant produces and entirely new plant identical to the parent plant.
93
Sexual Reproduction: How does pollination occur?
One pollen grain containing three haploid nuclei, one tube nucleus and two sperm nuclei lans on the sticky stigma of the flower. The pollen grain absorbs moisture and sprouts, producing a pollen tube that burrows down the style into the ovary.
94
Sexual Reproduction: How does double fertilization occur?
After a pollen tube burrows down the style into the ovary, two sperm nuclei travel down the pollen tube into the ovary. Inside the ovary, the two remaining sperm nuclei enter the ovule through the micropyle. One sperm nucleus fertilizes the egg and becomes the embryo. The other sperm nucleus fertilizes the two polar bodies and triploid endosperm.
95
Sexual Reproduction: What occurs after fertilization?
The ovule becomes the seed and the ripened ovary becomes the fruit. In monocots, food reserves remain in the endosperm (in monocot coconuts it's liquid). In dicots the endosperm are transported to the cotyledons and consequently the mature dicot seeds lack an endosperm.
96
What does a plant seed consist of?
It consists of a protective seed coat, an embryo and the cotyledon or endosperm.
97
What is endosperm?
It is food for a growing embryo.
98
What does the embryo in the seed consists of?
It consists of the hypocotyl, epicotyl and radicle. The hypocotyl becomes the lower part of the stem. The epicotyl becomes the upper part of the stem. The radicle is the first organ to emerge from the germinating seed and is also known as the embryonic root.
99
What is a gametophyte and what's its role in the alternation of generations?
The gametophyte is the haploid plant and, in the process of alternation of generations, it produces gametes by mitosis.
100
What are sporophytes and what is their role in alternation of generations?
Sporophytes are diploid plants. Gametophytes produce gametes by mitosis and these gamete fuse during fertilization to yield diploid zygotes that develop into the sporophytes.
101
How do plants go from gametophyte to sporophyte during alternation of generation?
A gametophyte produces gametes by mitosis that develop into the sporophyte. The sporophyte produces haploid spores by meiosis and each haploid spore develops into a gametophyte.
102
What are some important facts to know about alteration of generations?
1. The gametophyte generation dominates.
2. Archegonia and antheridia develop on the tips of the gametophyte.
3. The sporophyte grows out of the top of the gametophyte and obtains its nutrients from the gametophyte.
4. Haploid spores are formed in mature sporangia.
103
Define antheridium.
A structure that produces sperm.
104
Define archegonium.
A structure that produces eggs.
105
Define heterosporous and homosporous.
Heterosporous means having either two kinds of spores (male and female). Homosporous means producing a single spore that grows into a bisexual gametophyte.
106
Define megaspore and microspore.
Megaspores are produced by large female cones and develop into female gametophyte. Microspores are produced by small male cones and develop into male gametophytes or pollen grains.
107
Define sori.
Raised spots located on the underside of sporophyte ferns; clusters of sporangia.
108
Describe seedless vascular plants and their patterns during alternation of generations.
The sporophyte generation is larger than and independent from the gametophyte. Flagellated sperm swim from antheridia and archegonia to form the diploid zygote. This grows into a large diploid sporophyte plant. Haploid spores emerge from sori and land on the ground to sprout the gametophyte generation.
109
Describe seed plants and their patterns during alternation of generations.
Seed plants are vascular plants that produce seeds. The two groups - flowering plants and conifers - are both heterosporous.
110
Describe angiosperms and their patterns during alternation of generations.
1. The gametophyte generation exists inside the sporophyte generation and totally depends on it.
2. Meiosis occurs in the anthers and pistils. Anthers produce microspores and pistils produce megaspores.
3. Fertilization occurs in the ovary and the zygote develop into sporophyte embryos within the ovule.
4. The ovule becomes the seed carrying the embryo and food necessary for its initial development into another sporophyte.
111
Describe gymnosperms and their patterns during alternation of generations.
1. A gymnosperm (full grown) is a sporophyte. Its sporangia are densely packed inside the cones. 2. The gametophyte generation develops from haploid spores within the sporangia.
3. Each tree has both microspores and megaspores.
112
What is the role of hormones in plants?
Plant hormones help coordinate growth, development and responses to environmental stimuli. They're produced in small quantities and are amplified by the signal transduction pathway. A plants response to a hormones depends not so much on absolute quantities but on relative amounts.
113
What are examples of auxin hormones and how do plants respond to auxin plants? How is it used?
Unequal distribution of auxin is responsible for phototropism. It enhances apical dominance. It can stimulate stem elongation and growth by softening the cell wall. Indoleacetic acid is a naturally occurring auxin. 2,4-D is human-made auxin used as a weed killer. When used as a root powder it can cause roots to develop quickly.
114
Define apical dominance.
This is the preferential growth of a plant upward (toward the sun) rather than laterally.
115
How do plants respond to the cytokinins hormone?
It stimulates cytokinesis and cell division. It delays senescence (aging) by inhibiting protein breakdown. It's produced in roots and travel upward in the plant.
116
How do plants respond to the gibberellins hormone?
It promotes stem and leaf elongation. They work with auxin to promote cell growth. About 100 different naturally occurring gibberellins hormones exist. They induce bolting or the rapid growth of a floral stalk.
117
How do plant respond to the abscisic acid (ABA) hormone?
It inhibits growth which enables plants to withstand drought. It closes stomates during times of water stress and counteracts the breaking of dormancy during a winter thaw. It promotes seed dormancy which allows seeds that have fallen on the ground to wait to sprout when environmental conditions are better.
118
How do plants respond to the ethylene hormone?
This plant hormone is a gas and promotes fruit ripening through a positive feedback mechanism (ethylene promotes ripening, in turn ethylene gas is produced). It's produced in large quantities in times of stress . It facilitates apoptosis and promote leaf abscission (when the leaf falls from the plant).
119
What is tropism? Positive tropism? Negative tropism?
Tropism is the growth of a plant toward or away from a stimulus. Positive tropism is when a plant grows toward a stimulus and negative tropism is the opposite.
120
Describe phototropism.
Auxins accumulate on the side of the plant away from the light. Auxins cause growth so the cells on the shady side will enlarge and cause the stem to bend toward the light.
121
Describe geotropism.
In this case the stimulus is gravity and tropism occurs from an interaction of auxins and specialized plastids containing dense starch grains (statoliths).
122
Describe the signal transduction pathway in plants.
There are three steps: reception, transduction and response. When a receptor is stimulates is undergoes a conformational change and activates a second messenger. The secondary messenger leads directly into a response by altering transcription factors in the nucleus of the cell and altering the expression of certain genes.
123
Describe secondary messengers in the signal transduction pathway?
They are usually cyclic nucleotides like cyclic AMP or cyclic CMP that transfer and amplify the signal from the receptor.
124
What is photoperiodism and what kind of plants arise from it?
The physiological response to the photoperiod. Long-day plants flower only when the light period is longer then a certain number of hours. Short-day plants exists and day-neutral plants flower regardless of the length of day. But plants actually respond to amount of darkness not the presence of light.
125
What is the photoperiod?
It is the environmental stimulus a plant uses to detect the time of year relative to the lengths of day and night.
126
What is the circadian rhythm?
Plants have a biological clock set to this 24-hour day.
127
What is phytochrome, what are some forms of it and how does it work?
Phytochrome is a photoreceptor responsible for keeping track of the length of day and night. Pr is a red light absorbing form of phytochrome and Pfr is an infrared absorbing form of phytochrome. Phytochrome is synthesized in Pr forms and when a plant is exposed to light Or converts to Pfr. The opposite reaction occurs in the dark. The conversion from one form to the other enables the plant to keep track of time. The plant is able to sense concentrations of the phytochromes and responds accordingly.
