Botany Flashcards
1
Q
Describe the life cycle of an angiosperm
A
- Dormant seed
- Dispersal
- Breaking dormancy
- Germination
- Growth and development
- Flowering
- Pollination
- Fertilisation and seed formation
2
Q
Angiosperm
A
Plants that produce flowers and bear seeds in their fruits. The seeds develop in the ovaries of flowers and are surrounded by a protective fruit.
3
Q
Gymnosperm
A
Plants that have seeds unprotected by an ovary or fruit eg. conifers.
4
Q
Monocotyledons (monocots)
A
Flowering plants (angiosperm).
Contains one seed leaf (cotyledon) eg corn.
5
Q
Dicotyledons (dicots).
A
Flowering plants (angiosperm).
Contains 2 seed leafs (cotyledons). eg. Broad bean.
6
Q
What is a seed?
A
It consists of an embryo plant and a food store surrounded by a protective coat.
7
Q
Name for seed coat
A
Testa or also known as a pericarp
8
Q
Endosperm
A
This is the food store inside a monocot seed
9
Q
Endosperm in a dicot
A
This is labelled as cotyledon
10
Q
Scutellum
A
This is only ever labelled in a monocot seed, and is sometimes referred to as the cotyledon
11
Q
A baby shoot in a seed
A
Plumule, sometimes labelled as epicotyl instead
12
Q
A baby root in a seed
A
Radicle
13
Q
Coleoptile
A
This is found only in monocots. It is a cap/sheath which protects the plumule, as it comes up through the soil.
14
Q
Coleorhiza
A
Only exists within monocots. It is a cap which protects the radicle as it moves through the soil - similar to coleoptile.
15
Q
Aleurone layer
A
This is the protein of the seed.
16
Q
Monocotyledon germination process
A
The scutellum absorbs digested nutrients from the endosperm (a starch store), during germination and early growth.
17
Q
Dicotyledon germination process.
A
The cotyledons form the initial food store but go on to emerge from the soil, and develop ‘seed leaves’ which look quite different from the leaves of the mature plant. They then photosynthesise, making food for the growing seedling.
18
Q
4 herbs used medicinally for their seeds
A
Avena sativa
Aesculus hippocastanum
Plantago spp.
Foeniculum vulgare.
19
Q
Why is seed dispersal important?
A
It’s vital to ensure that at least some of the offspring of a plant end up in conditions suitable for their growth.
Perennial plants - important seedlings aren’t competing with their parent for water, nutrients and light.
20
Q
Meristematic tissue
A
This is found within the radical and plumule of the dicot seed
21
Q
Hilum
A
This is where it joins to the wall of the seed, the belly button
22
Q
Micropyle
A
This is a tiny hole where the pollen shoot goes down into the seed
23
Q
Seed dispersal mechanism examples
A
Windblown fruits
Adherent fruits
Fleshy fruits
Water dispersed
Self dispersal
24
Q
Windblown fruits definition and examples
A
Dry, light, small and usually have wind-like or parachute like structures.
Eg. Acer saccharum (Sugar maple)
Asciepias syriaca (common milkweed)
25
Adherent fruits definition and examples
These have hooks or stiff hairs, to stick to the fur of animals and be taken to a different area and be rubbed off later.
Eg. Arctium spp. Geranium spp.
26
Fleshy fruits definition and examples
Juicy, fragrant, sweet or brightly coloured fruits. Attractive so that it is eaten, then softened by digestive juices and survive to be deposited with faeces rich in nitrate and phosphate.
Eg. Rubus sp.
Juniperus chinensis
27
Water dispersal definition and examples
These contain a waterproof layer of fibrous husks, and are carried via floating on water for long distances (streams etc).
Eg. Coconut
28
Self dispersal definition and examples
These are fruit walls that split open with explosive force when they are ripe. Examples include geranium spp. and urtica dioica.
29
Dormancy
Is a period which prevents the seed from germinating in unsuitable conditions and allows time for dispersal, maximising it's chance of surviving and reproducing.
During this time metabolism is minimal and hard protective outer layers protect the embryo from infection and climate extremes.
30
How is dormancy achieved?
1. Seed coat impermeability (this can be broken by a number of events, eg. fire, scarification - this happens in nature by seeds tumbling against stones, dry heat - fire, light, various chemicals)
2. Internal physiological mechanisms involving enzyme inhibition (eg by abscisic acid, temperature change such as stratification, and changes in day length).
31
Examples of breaking dormancy
1. Apium graveolens (celery) needs cool soil to germinate
2. Lactuca spp (lettuce) needs a spell of cold, called stratification
3. Many Poaceae species need a dry spell first.
4. Iris spp. have chemicals in the endosperm which must break down to allow germination to begin
5. Pinus sylvestris cones stay closed until there is a forest fire, an only then release the seeds ready for germination.
32
Germination
When the seed is in conditions suitable for growth and where necessary dormancy has been broken, water will be taken up by IMBIBITION and this will activate enzymes that break down the insoluble food store into soluble sugars which are then available to the developing embryo.
33
Imbibition
This is the uptake of water by the seed
34
Describe the germination cycle
Water is absorbed into the seed through the testa via Imbibition.
This water activates a hormone (Gibberellin),
The hormone then triggers amino acid release & enzyme synthesis from the aleurone layer.
The enzymes catalyse the hydrolysis of food stores eg. the enzyme amylase which converts starch to maltose, an the enzyme maltase converts maltose to glucose.
The glucose is then used by the embryo for respiration and the radicle grows first so that water can be taken up from the soil.
35
Meristems
This is the area of a plant which actively grows. This is where cell division by mitosis takes place. There are primary and secondary meristems.
36
Primary meristems
All plants have these just behind the apices of root and shoot. These produce an increase in height.
37
Secondary meristems
Only some plants have these. They cause an increase in girth, and are mainly found in perennial dicotyledons.
38
Mitosis
When a cell divides by mitosis it produces two cells which are identical to each other and to the parent cell. Before this can happen, all the organelles and the genetic information in the nucleus must be replicated.
39
The cell cycle
G1, S and G2 = Interphase
G1 = Cellular contents, excluding chromosomes are duplicated
S = Each of the 46 chromosomes is duplicated by the cell
G2 = The cell double checks the duplicated chromosomes for error, making any needed repairs.
Prophase
Metaphase
Anaphase
Telophase
Go = the phase when a cell leaves the cycle, either temporarily or permanently due to being damaged or it has been specialised for a [articular function
40
Where are the 3 important checkpoints during the cell cycle?
1. During the growth phase (G1)
2. At the end of the second growth phase (G2)
3. After DNA replication to check that the chromosomes have been accurately copied, and during division in metaphase to ensure accurate alignment of chromosomes.
41
Mitochondrion
The synthesis of ATP inside a plant cell
42
Envelope
Double layer - found on a chloroplast and a nucleus
43
Grana
Found within the chloroplast. They are thylakoid membranes which are very important structures. They are small, thin and can be stacked up into structures. They are connected to eachother by thin pieces of thylakoid membrane called lamellae.
Grana contain chlorophyll.
44
Rough ER
Function is protein synthesis
45
Nucleus
Contains nucelar pore, nucleolus, chromatin and nuclear envelope
46
Nuclear envelope.
Separates the contents of the nucleus from the cytoplasm and provides the structural framework of the nucleus.
46
Nucleolus
Found in the nucleus. Produces and assembles the subunits which form the ribosome
46
Nuclear pore
Found in the nucleus. Facilitates and regulates the transport of molecules across the barrier provided by the nuclear envelope
47
Chromatin
Found in the nucleus. To compress and package long DNA molecules into compact dense structures
48
Ribosomes
Performs protein synthesis from translating the information contained in mRNA molecules
49
Plasma membrane
Protects the cell from its external environment, mediates cellular transport, and transmits cellular signals
50
Smooth ER
To make cellular products like hormones or lipids
51
Vacuole
Important for the integrity of the plant and for holding water
52
Cell wall
Really strong, made of cellulose, fully permeable, allows the cell to not fill up and burst
53
Plasmodesma
A small channel between cells, for communication
54
Middle lamella
A layer that cements together the primary cell walls of two adjoining plant cells
55
Chloroplast
Produces energy through photosynthesis and oxygen release processes, which sustain plant growth and crop yield
56
Cytoplasm
Maintains the shape of the cell, provides crucial support to the internal structures and is the suspension medium for the organelles
57
Golgi apparatus
Modify, sort and package macromolecules that are synthesised by the cell. These macromolecules include proteins and lipids.
58
Auxin
A hormone which influences mitosis, it is this which brings about growth in length of shoots and roots. It is the main component of most rooting powders.
It triggers PHOTOTROPISM (a growth response to light) - When a plant is exposed to light from one side, auxin gathers in the shaded side of the shoot and causes elongation of the cells on that side, which makes it bend towards the light.
It is also involved in APICAL DOMINANCE.
59
Plant hormones
These are chemicals which allow communication between cells, and they diffuse from cell to cell.
They mainly affect aspects of growth and maturation.
The ones we need to know are:
Auxins
Gibberellins
Cytokinins
Ethene
Abscissic acid
(ALL GOOD CHILDREN EAT APPLES)
60
Apical dominance
Auxin is continually made in the shoot tip of the plant and diffuses downwards, accumulating around the nodes beside lateral buds. Its prescence here inhibits lateral shoot growth, so to get a bushy plant, the terminal region needs to be removed so to remove the area which produces auxin.
61
Gibberellin
Is produced by the embryo and plays a part in the germination of some seeds by stimulating the production of enzymes which mobilise the food reserves.
Triggers germination.
It also promotes lateral shoot growth in the absence of auxin, and in some plants like beans causes stem elongation. Drawf varieties lack the gene for making gibberellin.
They elongate the stalks of grapes so they are less compact and grapes can get bigger.
62
Phototropism
A growth response to light which is stimulated by the hormone auxin.
63
Ethene
Produced by ageing or mature tissues as a gas which diffuses through the air spaces between cells.
Promotes the ripening of fruit.
Involved in leaf drop.
64
Abscisic acid
Is produced when a plant is under stress, it stimulates the stomata to close so reduces water loss by evaporation from the leaves - it also suppresses the growth of plants by counteracting the hormones that promote their growth.
It also causes the wilting of leaves.
65
Diffusion
Substances move from a high to a lower concentration down a concentration gradient. A passive process (does not use energy).
66
Osmosis
Water moves from a high to a lower concentration across a partially permeable membrane and down a concentration gradient. Is a passive process (does not use energy)
67
Cytokinins
Are used to promote bud and shoot growth. They can also delay leaf senescence - delays the yellowing of lettuce leaves in storage.
68
What are xylem vessels?
They carry water from the root to the leaves, they consist of columns of cells which lose their end walls and become unbroken tubes.
The mature cells are dead as they lack any contents to carry out living processes.
Their walls are thickened and strengthened with a waterproof substance (lignin).
This flow of water is called TRANSPIRATION - This is strictly defined as the evaporation of water from the leaves.
69
Transpiration
Is the evaporation of water from the leaves.
As water evaporates it 'pulls' a chain of water molecules up - this is due to root pressure, cohesive forces and adhesive forces between the water molecules and sides of the xylem vessels.
Because water is continously evaporating from the upper parts, and diffusing away from the leaves, a concentration gradient is maintained, so if water is available it keeps diffusing in. This is called osmosis.
70
What are the 3 possible pathways for water to take as it moves between the root hair cells and xylem vessels?
Symplast via the cytoplasm - this is selective and able to stop toxins from getting in.
Apoplast - seeping between cell walls
Vacuolar - between vacuoles
71
What is the casparian strip?
A specialized layer of cells just outside the vascular tissue of the root. It has suberin (a waxy material) in its walls, which forces the water to take the symplast pathway and allows selective uptake of mineral ions.
72
Symptoms of magnesium defficiency in plants
Yellowing between the leaf veins, sometimes with reddish brown tints and early leaf fall.
73
Symptoms of iron defficiency in plants
Yellowing of younger leaves, stunted growth and development
74
Symptoms of nitrate defficiency
Poor growth, chlorosis especially in lower leaves
75
What are the 5 components of a cross-section of a leaf?
Waxy cuticle
Upper epidermis
Palisade mesophyll
Spongy mesophyll
Stomata
76
What is the equation for photosynthesis?
Carbon dioxide + Water = Glucose + Oxygen
77
What is photosynthesis?
The process which all living things depends.
The main photosynthetic organ is the leaf.
They have a large surface area for exposure to sunlight, but thin for gaseous exchange between leaf cells and the air.
They can orient themselves in a way to best absorb maximum light.
It is broken down into 2 stages:
1. The light dependent stage
2. The light-independant stage (calvin cycle)
Chloroplasts are the site of photosynthesis.
78
What are chloroplasts?
The site of PHS.
Small, flattened, membrane-bound organelles which contain a series of membranes called thylakoids where the light dependant reactions take place. They are surrounded by a liquid stroma which the light independant reactions happen.
They are able to move to the part of the cell where there is the most light, and are concentrated in the upper layers of the leaf which are directly exposed to the sun.
79
What is translocation?
The movement of the products of photosynthesis from the source where they are made or stored to the SINK where they are used. Eg. down the plant from the leaves to a growing bud. It is active so requires ATP.
80
Where does translocation take place?
It is in phloem tissue which is like xylem as it consists of tubes made from chains of cells, but unlike xylem it IS still living.
The end walls of the sieve tube elements do NOT break down and there are some contents in the cells. Each cell has a companion cell which carries out the metabolic processes.
The sugar travels as sucrose in most plants and is actively loaded into the sieve tube elements at the source, followed by water osmosis. This creates high hydrostatic pressure - this leads to a mass flow from source to sink cell (root).
Glucose can then be used as an energy source or coverted into other nutrients that the plant needs.
81
What are some examples of how glucose can be converted into other nutrients the plant needs?
It can be built up into polysaccharide cellulose for cell walls
It may react with nitrates to make amino acids
It can enter a pathway that produces lipids
82
Why does the plant make glucose, transport it as sucrose and store it as starch?
Glucose is the product of photosynthesis
Sucrose is soluble and less reactive than glucose
Starch is insoluble and large. which enables a large amount of carbohydrate to be stored
83
How is CO2 thats used in photosynthesis and returned to the atmosphere?
Respiration - this is carried out continously by plants, animals and microorganisms.
84
Explain the carbon cycle
It is the process where carbon moves between the atmosphere, oceans, soil and living organisms.
Carbon fixation - CO2 from the atmosphere is absorbed by plants during photosynthesis to produce organic carbon compounds.
Consumption - Animals eat plants, CO2 enters their bodies
Decomposition - Plants and animals die, they are decomposed by bacteria and fungi. Co2 is released back into the atmosphere or into the soil as organic matter.
Combustion - CO2 is released into the atmosphere when fossil fuels are burned
Ocean exchange - Ocean absorbs CO2 from atmosphere through diffusion, phytoplankton use carbon uptake through photosynthesis
Carbob sequestration - Some carbon is stored long term in soils, oceans whereas some cycle through the atmosphere relatively quickly.
85
Nitrogen gas
Is the most abundant component of the atmosphere but can only be used by living things if it is 'fixed' as nitrate. This is carried out by bacteria such as Rhizobium which live in root nodules of leguminous plants.
86
Rhizobium
Live in root nodules of leguminous plants.
They fix nitrogen into nitrate.
They have a symbiotic relationship with the plant because they gain carbohydrate from it and provide nitrate ions to it.
This means that legumes enrich the soil. eg. Trifolium.
87
Nitrates
Are used to make proteins, and excretion and death of plants animals that have eaten them releases nitrogenous compounds back into the soil. Nitrifying bacteria then oxidise them back to nitrate.
88
Where do denitrifying bacteria flourish?
In waterlogged soil. They convert nitrates to oxygen gas.
89
What is nitrification?
Nitrification is the biological process by which certain bacteria convert ammonia into nitrites and then into nitrates.
90
Where is asexual reproduction possible?
Wherever there are meristematic cells.
It will result in clones, plants which are genetically identical to each other and the parent.
91
Advantage of asexual methods of reproduction
They are FAST, especially when conditions are favourable.
Low energy cost to the plant.
92
Examples of asexual methods
Rhizomes
Tubers
Bulbs
Corms
Suckers
Stolons
93
Disadvantages of asexual reproduction
No genetic variation in the population, which means environmental changes cannot be adapted to.
If one plant is susceptible to disease, they all will be.
94
What is micropropagation or tissue culture
They are ways of producing clones from small pieces of plant material in controlled, sterile conditions.
95
What is a rhizome
Underground horizontal stem which store food and have nodes with buds, and scale or foliage leaves. Zingiber is an example.
96
What is a tuber
Swollen underground stem or root which stores food and has buds. eg. potato
97
What is a bulb
A compressed shoot with fleshy storage leaves eg allium.
98
What is a corm
A food store in a stem but do not have fleshy leaves like a bulb
99
What are suckers
Basal shoots which grow from a bud on a root.
100
What are stolons
They are runners which grow from the base of a plant eg. Fragaria spp.
101
Benefits of sexual reproduction
Genetic diversity - long term success of the plant.
Allows them to survive disease and other environmental pressures.
102
Disadvantages of sexual reproduction
Involves the production of flowers, pollen and seeds so much more expensive in energy terms.
103
What does annual mean
Where angiosperms grow from seed to flower an set their own seeds in 1 year or less,
Example - Calendula officinalis
104
What is a biennial
They take 2 years to get to the flowering stage, the first year is vegetative growth and food stores for flowering the next.
Example - Verbascum thapsus
105
What are perennials
They persist from year to year and may flower annually.
Example - Lavendula officinalis, Salvia rosmarinus
106
What is the organ of sexual reproduction?
The flower.
It has evolved a wide range of variations to carry out this role. The purpose of the flower is to make male and/or female gametes and bring about their fusion - fertillisation.
107
What does bisexual mean
That the flower has both female carpels and male stamens. Hermaphrodite also means bisexual.
108
What is pollination
It is the transfer of pollen from stamens to stigmas (ideally from different plants). This can be by an animal or by wind.
Animal pollinated flowers use colour, fragrance and nectar to attract animals such as insects, bats and birds which will inadvertently collect pollen then leave some behind at the next flower they visit.
109
Cues for beetles to animal pollinating flowers
Strong odours - fruity, spicy or foul
110
Cues for bees to animal pollinating flowers
Bright colours; yellow/blue (ultravioletic perception)
Strong fragrance
111
Cues for flies to animal pollinating flowers
Large flowers, dull or flesh-coloured
Musky to rotting odours
112
Cues for day moths and butterflies to animal pollinating flowers
Bright reds, oranges, yellows, blues
Strong fragrance
113
Cues for birds to animal pollinating flowers
Bright reds and yellows
Copious sugary nectar
A little odour
114
Cues for bats to animal pollinating flowers
Colour insignificant
Copious nectar
Fruity fermenting odours
115
Wind pollinated flowers
Inconspicous and small but produce very large quantities of very light pollen grains.
Poaceae are wind pollinated.
116
Fertilisation
When a pollen grain lands on a receptive stigma, it grows a pollen tube down through the style towards the ovary and two sperm cells are able to enter the embryo sac and effect double fertilisation.
One sperm cell fertilises the egg cell to form a diploid zygote which will develop into an embryo, the other fuses with the nuceli to form an endosperm nucleus which develops into a food store in the seed.
The redundant flower parts die away and the fruit develops from the ripe ovary.
117
What are monoecious plants
They have seperate male and female flowers on ONE plant. eg Zea mays
118
What are Dioecious plants
They have male and female flowers on different plants eg. Gingko biloba
119
What are the differences between monocots and dicots?
Monocots have 1 cotyledon, dicots have 2 cotyledons
Monocot contains the endosperm as a food store, dicot has the endosperm absorbed
Coleoptile and coleorhiza in monocot
Fibrous roots in monocot, taproot in dicot
Vascular tissue in stem is different
Monocots dont have secondary growth (this means you don’t get woody tissue plants, bamboo exception), dicots do (which give it girth and they have rings/layers)
Monocot flower parts in 3’s, dicot flowers in 4’s and 5’s
120
Whats the difference between scarification and stratification
Abrasion of the protective coat - scarification
Straftification - creating a period of cold to mimic winter
121
Whats the first role of water absorbed by a dormant seed?
It’s to trigger the hormone gibberelin which triggers the release of protein synthesis.
122
Where are meristems found? What happens there?
Primary meristems - initially cause a shoot from the root to grow, and they are found in the apices from the root and shoot. Happens via mitosis. Secondary meristems increase plant girth in perennials
Intercalary meristems are present in many monocots eg grasses. They are found at internodes where they enable the plant to grow and elongate even if the apical mersitem is frazed or cut.
123
What happens during interphase of the cell cycle?
Replication of organelles and chromosomes, growth of cell and contents.
124
What is the main role of the nucleolus?
RNA production
125
What are the differences between the roles of lignin and suberin in plants?
Lignin - strong waterproof, strengthens the xylem wall
Suberin is waterproof strip in endodermis
