Plant stuff Flashcards

Question

What are the 2 angiosperm groups?

Answer 1

Monocots (one cotyledon) |  Eudicots (two dicots)

Answer 2

Whorl 1=sepal, A genes Whorl 2=petal, A+B genes Whorl 3=stamen, B+C genes Whorl 4=carpel, C genes

Answer 3

Photoperiod - Temperature - Plant hormone signals

Answer 4

The light reactions (photo) convert solar energy to chemical energy. ○ The Calvin cycle (synthesis) uses energy from the light reactions to incorporate CO2 from the atmosphere into sugar.

Answer 5

Autotrophs sustain themselves without eating anything derived from other organisms • Autotrophs are the producers of the biosphere, producing organic molecules from CO2 and other inorganic molecules • Almost all plants are photoautotrophs, using the energy of sunlight to make organic molecules

Answer 6

6CO2 + 12H2O --> C6H12O6 + 6O2 + 6H2O

Answer 7

``` Split H2O – Release O2 – Reduce NADP+ to NADPH – Generate ATP from ADP by photophosphorylation ```

Answer 8

The Calvin cycle (in the stroma) forms sugar from CO2, using ATP and NADPH. The Calvin cycle begins with carbon fixation, incorporating CO2 into organic molecules

Answer 9

``` A photosystem consists of a reaction -center complex (a type of protein complex) surrounded by light -harvesting complexes • The light -harvesting complexes (pigment molecules bound to proteins) transfer the energy of photons to the reaction center ```

Answer 10

Photosystem II (PS II) functions first (the numbers reflect order of discovery) and is best at absorbing a wavelength of 680 nm • The reaction-center chlorophyll a of PS II is called P680 • Photosystem I (PS I) is best at absorbing a wavelength of 700 nm

Answer 11

Linear electron flow, the primary pathway, involves both photosystems and produces ATP and NADPH using light energy • This is the ‘canonical’ process of the lightdependent reactions

Answer 12

``` Cyclic electron flow uses only photosystem I and produces ATP, but not NADPH • No oxygen is released • Cyclic electron flow generates surplus ATP, satisfying the higher demand in the Calvin cycle ```

Answer 13

C4 plants minimize the cost of photorespiration by incorporating CO2 into four-carbon compounds in mesophyll cells • This step requires the enzyme PEP carboxylase • PEP carboxylase has a higher affinity for CO2 than rubisco does; it can fix CO2 even when CO2 concentrations are low; O2 does not compete. • These four-carbon compounds are exported to bundle-sheath cells, where they release CO2 that is then used in the Calvin cycle

Answer 14

Primary CO2 fixing enzyme: PEP carboxylase (phosphoenol pyruvate carboxylase) which has higher affinity for CO2 (in fact, almost no affinity for O2) • Needs bundle sheath anatomy • Advantageous in high light, high temperature, high evaporation conditions But requires high energy

Answer 15

Some plants, including succulents, use crassulacean acid metabolism (CAM) to fix carbon • CAM plants open their stomata at night, incorporating CO2 into organic acids • Stomata close during the day, and CO2 is released from organic acids and used in the Calvin cycle

Answer 16

Primary CO2 fixing enzyme: PEP carboxylase as in C4 • Separates CO2 uptake and temporary storage (during night) from final CO2 fixation (during day) • Survival mechanism in arid regions (eg deserts) • High ‘water use efficiency’ (ratio of CO2 fixed to water lost)

Answer 17

– Anchoring the plant – Absorbing minerals and water (from the soil) – Storing carbohydrates (from the leaves)

Answer 18

Most eudicots and gymnosperms have a taproot system, which consists of: – A taproot, the main vertical root – Lateral roots, or branch roots, that arise from the taproot

Answer 19

Most monocots have a fibrous root system, which consists of: – Adventitious roots that arise from stems or leaves – Lateral roots that arise from the adventitious roots

Answer 20

- Prop roots - Storage roots - Strangling/Aerial roots - Buttress roots - Pneumatophores

Answer 21

Dermal: epidermis, periderm Vascular: xylem, phloem Ground: pith and cortex

Answer 22

In nonwoody plants, the dermal tissue system consists of the epidermis • A waxy coating called the cuticle helps prevent water loss from the epidermis • Trichomes are outgrowths of the shoot epidermis and can help with insect defense

Answer 23

Tissues that are neither dermal nor vascular are the ground tissue system • Ground tissue internal to the vascular tissue is pith; ground tissue external to the vascular tissue is cortex • Ground tissue includes cells specialized for storage, photosynthesis, and support

Answer 24

The vascular tissue system carries out long-distance transport of materials between roots and shoots • The two vascular tissues are xylem and phloem • Xylem conveys water and dissolved minerals upward from roots into the shoots • Phloem transports organic nutrients from where they are made to where they are needed

Answer 25

``` – Have thin and flexible primary walls – Lack secondary walls – Large vacuole – Are the least specialized – Perform the most metabolic functions – Retain the ability to divide and differentiate – Can regenerate ```

Answer 26

Collenchyma cells are grouped in strands and help support young parts of the plant shoot • They have thicker and uneven cell walls • They lack secondary walls • These cells provide flexible support without restraining growth

Answer 27

Sclerenchyma cells are rigid because of thick secondary walls strengthened with lignin • They are dead at functional maturity • There are two types: – Sclereids are short and irregular in shape and have thick lignified secondary walls – Fibers are long and slender and arranged in threads

Answer 28

Primary for growth in height | Secondary for growth in diameter

Answer 29

Plants take up large quantities of water • > 90% of the water taken in by roots is lost from the plant as water vapour. • Very little is ‘used’ in any biochemical process • The loss of water from the plant is termed transpiration • Terrestrial plants lose water as an unavoidable consequence of having to take up CO2 • Dehydration is always a risk • But transpiration stream does distribute minerals

Answer 30

Three transport routes for water and solutes are – The apoplastic route, through cell walls and extracellular spaces – The symplastic route, through the cytosol, on the inside – The transmembrane route, across cell walls

Answer 31

Plasma membrane permeability controls short-distance movement of substances • Both active and passive transport occur in plants • In plants, membrane potential is established through pumping H by proton pumps

Answer 32

Efficient long distance transport of fluid requires bulk flow, the movement of a fluid driven by pressure • Water and solutes move together through tracheids and vessel elements

Answer 33

The two types of water-conducting cells, tracheids and vessel elements, are dead at maturity • Tracheids are found in the xylem of all vascular plants • Vessel elements are common to most angiosperms and a few gymnosperms • Vessel elements align end to end to form long micropipes called vessels

Answer 34

Xylem sap, water and dissolved minerals, is transported from roots to leaves by bulk flow • The transport of xylem sap involves transpiration, the evaporation of water from a plant’s surface • Transpired water is replaced as water travels up from the roots

Answer 35

According to the cohesion-tension hypothesis, transpiration and water cohesion pull water from shoots to roots • Xylem sap is normally under negative pressure, or tension

Answer 36

It is driven by differences in pressure potential, not solute potential – It occurs in hollow dead cells, not across the membranes of living cells – It moves the entire solution, not just water or solutes – It is much faster

Answer 37

Sieve-tube elements are alive at functional maturity, though they lack organelles • Sieve plates are the porous end walls that allow fluid to flow between cells along the sieve tube • Each sieve-tube element has a companion cell whose nucleus and ribosomes serve both cells

Answer 38

Water potential is a measurement that combines the effects of solute concentration and pressure • Water potential determines the direction of movement of water • Water flows from regions of higher water potential to regions of lower water potential

Answer 39

Rhizobacteria can play several roles – Produce hormones that stimulate plant growth – Produce antibiotics that protect roots from disease – Absorb toxic metals or make nutrients more available to roots

Answer 40

``` Ammonifying bacteria produce NH3 by breaking down nitrogen in proteins and other organic compounds in humus. Nitrogen-fixing bacteria convert N2 into NH3 In the soil, NH3 picks up another H+ to form NH4  (which plants can absorb) • Plants acquire nitrogen mainly in the form of NO3 – • Soil NO3 - formed by two step processes called nitrification. – Nitrifying bacteria oxidize NH3 to nitrite (NO2 – ) then nitrite to nitrate (NO3 – ) (2 different bacteria) • Nitrogen is lost to the atmosphere when denitrifying bacteria convert NO3 – to N2 ```

Answer 41

Mycorrhizae (fungus roots) are mutualistic associations of fungi and roots • The fungus benefits from a steady supply of sugar from the host plant • The host plant benefits because the fungus increases the surface area for water uptake and mineral absorption • Mycorrhizal fungi also secrete growth factors that stimulate root growth and branching and produce antibiotics that protect the root.

Answer 42

In ectomycorrhizae, the mycelium of the fungus forms a dense sheath over the surface of the root • These hyphae form a network in the apoplast, but do not penetrate the root cells • Ectomycorrhizae occur in about 10% of plant families including pine, spruce, oak, walnut, birch, willow, and eucalyptus

Answer 43

in arbuscular mycorrhizae, microscopic fungal hyphae extend into the root • These mycorrhizae penetrate the cell wall but not the plasma membrane to form branched arbuscules within root cells • Hyphae can form arbuscules within cells; these are important sites of nutrient transfer • Arbuscular mycorrhizae occur in about 85% of plant species, including grains and legumes

Answer 44

``` An epiphyte grows on another plant and obtains water and minerals from rain • Epiphytes do not tap into hosts for sustenance ```

Answer 45

Macronutrients – need about 1-20 g kg-1 dry weight – Nitrogen, Potassium Calcium Magnesium, Phopshorus Sulphur

Answer 46

Micronutrients – need about 100 mg g kg-1 dry weight – Chloride Iron Manganese Boron Zinc Copper Nickel Molybdenum – Often enzyme co-factors for occasional processes

Answer 47

A biome is an area of the planet that can be classified according to the plants and animals that live in it. Temperature, soil, and the amount of light and water help determine what life exists in a biome. Differs from an ecosystem; “interaction between living and non-living things in the environment” vs biome; a specific geographic area notable for the species living there. A biome can consist of a number of ecosystems.

Answer 48

major physical features climatic (temp and ppt) Vegetation (and adaptations) Microorganisms, fungi and animals adapted to that particular environment.

Answer 49

VERTICAL LAYERING (STRATIFICATION) - Determined by the shapes and sizes of vegetation within the biome. FORESTS Upper canopy > low-tree layer > shrub layer > ground layer of herbaceous plants > forest floor (litter layer) > root layer. Grasslands (similar but less pronounced) Herbaceous layer of grasses and forbs > litter layer > root layer.

Answer 50

``` ‘Live fast, die young’ ¡ Quantity ¡ Unstable environments ¡ Earlier maturity ¡ Deciduous ```

Answer 51

``` ‘grow slow, die old’ ¡ Quality ¡ Stable environments ¡ Later maturity ¡ Evergreen ```

Answer 52

``` Diffusion • gradual movement • several generations • Across suitable terrain ``` ``` Jump • long distance • Short time scale • Across unsuitable terrain ``` ``` Secular • Diffusion over evolutionary time • genetically modified species ```

Answer 53

Biotic factors that affect the distribution of organisms may include ¡ Disease + Parasitism ¡ Predation; inc herbivory ¡ Competition ¡ Mutualism

Answer 54

The chemical inhibition of one plant (or other organism) by another, due to the release into the environment of substances acting as germination or growth inhibitors. ¡ Secondary metabolites that are not required for the growth, development and reproduction of the allelopathic plant. e.g. English Laurel, garlic mustard weed, eucalyptus. Applications; ¡ Agriculture – intercropping - crop rotation - insect biocontrol

Answer 55

``` ¡ Temperature ¡ Water ¡ Oxygen ¡ Salinity ¡ Sunlight ¡ Soil Most abiotic factors vary in space and time. ```

Answer 56

Species can extend their distributions by local adaptations to limiting environmental variables. ¡ Ecotype – genetic varieties within a single species. How? All differences are phenotypic, seeds transplanted from one place to another will all perform the same as the resident individuals. 2) All differences are genotypic, if seeds are transplanted between areas the seedlings will retain physiology identical to their home site. 3) A combination of phenotypic and genotypic variation causes an intermediate results.

Answer 57

Natural populations are shaped by natural selection – Competition for survival and reproduction – Individuals with most advantageous traits are more likely to survive and reproduce ``` Allele frequencies change in population to become better adapted to the environment • Higher survival and reproduction of individuals with specific traits • Highly selective process increasing alleles associated with specific traits ```

Answer 58

``` individual plants respond to changes in the environment, by altering their physiology or morphology allowing them to survive the new environment. ```

Answer 59

Polyploid (multi-genome) plants are often bigger and so selected for propagation

Answer 60

The food we eat comes from plants already extensively modified from their original form. Even heritage varieties are extensively genetically modified.

Answer 61

Conventional breeding based on phenotypes. Cross plants, Look in subsequent generations for “best” Repeat Often only one crop per year LONG process

Answer 62

Crops were typically bred for high yield under optimal growth conditions Loss of genetic variation in other important traits Modern Agriculture involved planting large areas with a single crop (monoculture) Pros: ease of planting, harvesting, and looking after your crop Cons: May lack resilience against disease and other stresses Older and wild varieties of crop plants can be excellent resources for increasing genetic variation (i.e. stress tolerance)

Answer 63

Molecular breeding 1. Desired trait must be present in population 2. Genetic resources must be available 3. Plant should be propagated sexually

Answer 64

GM 1. Gene can come from any source 2. Genetic resources not required 3. Plant can be propagated vegetatively

Answer 65

To work directly with specific genes, scientists prepare well defined DNA segments in multiple identical copies by a process called DNA cloning Plasmids are small, circular DNA molecules that replicate separately from the bacterial chromosome Researchers can insert DNA into a plasmid to produce a recombinant DNA molecule, which contains DNA from two different sources

Answer 66

Small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently through their own origin of replication Can be manipulated to include foreign genes into bacteria and from there into plants

Answer 67

Propagate plasmid vector in E. coli Isolate plasmid vector from E. coli and introduce foreign gene Amplify by reintroducing to E. coli Isolate engineered binary vector and introduce into Agrobacterium containing modified Ti plasmid Infect plant tissues with engineered Agrobacterium

Answer 68

Four major physical components of climate are: Sunlight Temperature Precipitation Wind.

Answer 69

INCREASED CARBON GAIN FROM INCREASED RATES OF CARBOXYLATION AND DECREASED RATES OF OXYGENATION AND PHOTORESPIRATION

Answer 70

Homosporous plants produce one kind of spore, which usually produces a bisexual gametophyte • Heterosporous plants produce two types of spores, which develop into either male or female gametophytes • Ferns and other close relatives are homosporous; seed plants are heterosporous

Answer 71

Have seeds (by definition) • Reduction in gametophyte generation – microscopic • Heterospory – Single large megaspore , many small microspores • Ovules – contain, megaspore, megasporangium, and integuments • Pollen – protected male gametophytes can travel & disperse widely

Answer 72

The process by which one species splits into two or more species, is at the focal point of evolutionary theory

Answer 73

Microevolution consists of changes in allele frequency in a population over time • Macroevolution refers to broad patterns of evolutionary change above the species level – when different habitats occur at the same time with little competition, results in gradual refinement of existing structures for new functions that lead to an advantage in these different habitats

Answer 74

A flower is a specialized shoot with up to four types of modified leaves – floral organs  Sepals, which enclose the flower  Petals, which are brightly colored and attract pollinators  Stamens, which produce pollen  Carpels, which produce ovules • A stamen consists of a stalk called a filament, with a sac called an anther where the pollen is produced • A carpel consists of an ovary at the base and a style leading up to a stigma, where pollen is received

Answer 75

Pollen develops from microspores within the microsporangia, or pollen sacs, of anthers • Each microspore undergoes mitosis to produce two cells: the generative cell and the tube cell • A pollen grain consists of the two-celled male gametophyte and the spore wall • If pollination succeeds, a pollen grain produces a pollen tube that grows down into the ovary and discharges two sperm cells near the embryo sac

Answer 76

The embryo sac, or female gametophyte, develops within the ovule • Within an ovule, two integuments surround a megasporangium • One cell in the megasporangium undergoes meiosis, producing four megaspores, only one of which survives • The megaspore divides, producing a cell partitioned into a multicellular female gametophyte, the embryo sac

Answer 77

``` Plants produce new organs via meristems • Meristems are pools of stem cells that can be activated to produce specific tissue types. • The shoot apical meristem produces vegetative growth • The inflorescence and floral meristems produce the reproductive structures that will ultimately become flowers. • These transitions are promoted by genes encoding transcription factors (TFs). ```

Answer 78

``` Phytochromes are pigments that regulate many of a plant’s responses to light throughout its life • These responses include seed germination and flowering ```

Answer 79

Some processes, including flowering in many species, require a certain photoperiod • Plants that flower when a light period is shorter than a critical length are called short-day plants • Plants that flower when a light period is longer than a certain number of hours are called long-day plants • Flowering in day-neutral plants is controlled by plant maturity, not photoperiod

Answer 80

``` Flowering time is regulated by coordinated genetic changes that respond to: - Photoperiod - Temperature - Plant hormone signals ```

Answer 81

During the light reactions, there are two possible routes for electron flow: cyclic and linear • Linear electron flow, the primary pathway, involves both photosystems and produces ATP and NADPH using light energy • This is the ‘canonical’ process of the lightdependent reactions

Answer 82

Carbon enters the cycle as CO2 and leaves as a sugar named glyceraldehyde 3-phospate (G3P) • For net synthesis of 1 G3P, the cycle must take place three times, fixing 3 molecules of CO2 • The Calvin cycle has three phases – Carboxylation/ Carbon fixation (catalyzed by rubisco) – Reduction – Regeneration of the CO2 acceptor (RuBP)

Answer 83

C4 plants minimize the cost of photorespiration by incorporating CO2 into four-carbon compounds in mesophyll cells • This step requires the enzyme PEP carboxylase • PEP carboxylase has a higher affinity for CO2 than rubisco does; it can fix CO2 even when CO2 concentrations are low; O2 does not compete. • These four-carbon compounds are exported to bundle-sheath cells, where they release CO2 that is then used in the Calvin cycle

Answer 84

In nonwoody plants, the dermal tissue system consists of the epidermis • A waxy coating called the cuticle helps prevent water loss from the epidermis • Trichomes are outgrowths of the shoot epidermis and can help with insect defense

Answer 85

Tissues that are neither dermal nor vascular are the ground tissue system • Ground tissue internal to the vascular tissue is pith; ground tissue external to the vascular tissue is cortex • Ground tissue includes cells specialized for storage, photosynthesis, and support

Answer 86

Plants take up large quantities of water • > 90% of the water taken in by roots is lost from the plant as water vapour. • Very little is ‘used’ in any biochemical process • The loss of water from the plant is termed transpiration • Terrestrial plants lose water as an unavoidable consequence of having to take up CO2 • Dehydration is always a risk • But transpiration stream does distribute minerals

Answer 87

Three transport routes for water and solutes are – The apoplastic route, through cell walls and extracellular spaces – The symplastic route, through the cytosol – The transmembrane route, across cell walls

Answer 88

Plasma membrane permeability controls short-distance movement of substances • Both active and passive transport occur in plants • In plants, membrane potential is established through pumping H by proton pumps

Answer 89

• To survive, plants must balance water uptake and loss • Osmosis determines the net uptake or water loss by a cell and is affected by solute concentration and pressure • Water potential is a measurement that combines the effects of solute concentration and pressure • Water potential determines the direction of movement of water • Water flows from regions of higher water potential to regions of lower water potential

Answer 90

Water potential affects uptake and loss of water by plant cells • If a flaccid (limp) cell is placed in an environment with a higher solute concentration, the cell will lose water and undergo plasmolysis • Plasmolysis occurs when the protoplast shrinks and pulls away from the cell wall

Answer 91

It is driven by differences in pressure potential, not solute potential – It occurs in hollow dead cells, not across the membranes of living cells – It moves the entire solution, not just water or solutes – It is much faster

Answer 92

Sieve-tube elements are alive at functional maturity, though they lack organelles • Sieve plates are the porous end walls that allow fluid to flow between cells along the sieve tube • Each sieve-tube element has a companion cell whose nucleus and ribosomes serve both cells

Answer 93

A xerophyte is a species of plant that has adaptations to survive in an environment with little liquid water. Desert or an ice- or snow-covered region. Types: ¡ 1) Succulents; store water in their stems or leaves (enlargement of vacuoles) e.g. (cacti&euphorbs) ¡ 2) Non-succulent ‘drought endurers’ perrenials‘true xerophytes’. Lose 70% water. Effects growth processes such as cell elongation; usually small and weak. ¡ 3) Ephemerals ‘drought escaping’ – rain > seeds germinate > r-growth > flower and set seed before soil dries.

Answer 94

1) Incoming solar radiation. 2) The distribution of land and sea. Water heats and cools slowly due to high specific heat. Land heats and cools quickly so land controlled (continental) climates have large daily and seasonal variation

Answer 95

``` High latitudes/elevation ¡ Treeline – above which no trees can grow. 1. Lack of soil 2. Desiccation of leaves in cold weather 3. Short growing season 4. Lack of snow, exposing plants to winter drying 5. Excessive snow through the summer 6. Strong winds 7. Rapid heat loss at night 8. Excessive soil temp during the day 9. Drought ```

Answer 96

Protein kinase add phosphates to proteins in a process called phosphorylation, ¡ Protein phosphatases rapidly remove the phosphates from proteins, a process called dephosphorylation ¡ This phosphorylation and dephosphorylation system acts as a molecular switch, turning activities on and off or up or down, as required ¡ Many signaling pathways involve second messengers ¡ These are small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion (Calcium ions (Ca2+), cyclic GMP (cGMP), inositol triphosphate (IP3) and diacylglycerol (DAG))

Answer 97

Genetic variation among individuals is caused by differences in genes or other DNA segments • Phenotype is the product of inherited genotype and environmental influences • Natural selection can only act on variation with a genetic component • Artificial selection can only act on variation with a genetic component

Answer 98

Genome sequencing provides: complete gene catalogue for a species, • regulatory elements that control their function • framework for understanding genomic variation Genome sequence is a prerequisite resource for: Understand the roles of genes in plant development and adaptation • Exploit the natural genetic diversity of an organism for plant breeding (artificial selection)

Answer 99

AUTOPOLYPLOIDS: duplicate genome of same Species Autotetraploid: duplicate genome of same diploid species ALLOPOLYPLOIDS: duplicate genome of different species Allohexaploid: six complete sets of chromosomes derived from different species.

Answer 100

Seed dormancy increases the chances that germination will occur at a time and place most advantageous to the seedling • The breaking of seed dormancy often requires environmental cues, such as temperature or lighting changes • Germination depends on imbibition, the uptake of water due to low water potential of the dry seed • The radicle (embryonic root) emerges first • Next, the shoot tip breaks through the soil surface

Answer 101

``` • During transition to reproductive development, the inflorescence meristem is formed. In turn, it leads to production of floral meristems • Both will form the organs of an individual flower. • The inflorescence meristem is indeterminate, meaning that it can keep producing new tissue. • The floral meristem is determinate, meaning that it makes only one set of the specified whorls. ```

Answer 102

``` Plants produce new organs via meristems • Meristems are pools of stem cells that can be activated to produce specific tissue types. • The shoot apical meristem produces vegetative growth • The inflorescence and floral meristems produce the reproductive structures that will ultimately become flowers. • These transitions are promoted by genes encoding transcription factors (TFs). ```

Answer 103

• It’s critical that plants turn on floral development genes at the right time to initiate flower formation. • It is also critical that plants do NOT turn on those genes before the plant is ready to flower. • If a plant flowers at the wrong time, it may lack the appropriate environmental conditions for successful pollination and seed development.

Answer 104

Responses to Pfr: seed germination, inhibition of vertical growth and stimulation of branching, setting internal clocks and control of flowering. Phytochromes exist in two photo reversible states, with conversion of Pr to Pfr triggering many developmental responses • Red light triggers the conversion of Pr to Pfr • Far-red light triggers the conversion of Pfr to Pr • The conversion of Pr to Pfr is faster than the reverse process

Answer 105

``` Circadian rhythms are cycles that are about 24 hours long and are governed by an internal “clock” • These cycles can be free-running, varying from 21 to 27 hours, when organisms are kept in a constant environment • The 24-hour period arises from the transcription of “clock genes” regulated through negative-feedback loops ```

Answer 106

``` Photoperiod is detected by leaves, which cue buds to develop as flowers • The flowering signal molecule is called florigen • Florigen may be a protein governed by the FLOWERING LOCUS T (FT) gene • This is a mobile protein moving from the leaf to the meristem ```

Answer 107

CO2 enters and O2 exits the leaf through microscopic pores called stomata • The chlorophyll is in the membranes of thylakoids (connected sacs in the chloroplast); thylakoids may be stacked in columns called grana • Chloroplasts also contain stroma, a dense interior fluid

Answer 108

Carbon enters the cycle as CO2 and leaves as a sugar named glyceraldehyde 3-phospate (G3P) • For net synthesis of 1 G3P, the cycle must take place three times, fixing 3 molecules of CO2 • The Calvin cycle has three phases – Carboxylation/ Carbon fixation (catalyzed by rubisco) – Reduction – Regeneration of the CO2 acceptor (RuBP)

Answer 109

On hot, dry days, plants close stomata, which conserves H2O but also limits photosynthesis • The closing of stomata reduces access to CO2 and causes O2 to build up • These conditions favor an apparently wasteful process called photorespiration

Answer 110

In most plants (C3 plants), initial fixation of CO2, via rubisco, forms a three-carbon compound (3- phosphoglycerate) • In photorespiration, rubisco adds O2 instead of CO2 in the Calvin cycle, producing a two-carbon compound • Photorespiration consumes O2 and organic ‘fuel’ and releases CO2 without producing ATP or sugar

Answer 111

``` A stem is an organ consisting of – An alternating system of nodes, the points at which leaves are attached – Internodes, the stem segments between nodes ```

Answer 112

Bulbs: leaf bases and short stem Tubers: swollen underground stems Rhizomes: underground stems Stolons: aboveground horizontal shoots

Answer 113

Leaves: – main photosynthetic organ – Leaf blade and petiole Roots: – main organ for water and nutrient uptake – Taproots with laterals in eudicots and gymnosperms – Adventitious roots in monocots (from the stem) – Root hairs for absorption – Also anchorage ``` Stem: – Nodes and internodes – Terminal bud with apical meristem – support and transport tissues – Storage ```

Answer 114

Lateral meristems add thickness to woody plants, a process called secondary growth • There are two lateral meristems: the vascular cambium and the cork cambium • The vascular cambium adds layers of vascular tissue called secondary xylem (wood) and secondary phloem • The cork cambium replaces the epidermis with periderm, which is thicker and tougher Secondary growth is characteristic of gymnosperms and many eudicots, but not monocots

Answer 115

Plasma membrane permeability controls short-distance movement of substances • Both active and passive transport occur in plants • In plants, membrane potential is established through pumping H by proton pumps

Answer 116

Efficient long distance transport of fluid requires bulk flow, the movement of a fluid driven by pressure • Water and solutes move together through tracheids and vessel elements of xylem, and sieve-tube elements of phloem – Water primarily through Xylem – Solutes primarily through Phloem

Answer 117

The two types of water-conducting cells, tracheids and vessel elements, are dead at maturity • Tracheids are found in the xylem of all vascular plants • Vessel elements are common to most angiosperms and a few gymnosperms • Vessel elements align end to end to form long micropipes called vessels

Answer 118

Sieve-tube elements are alive at functional maturity, though they lack organelles • Sieve plates are the porous end walls that allow fluid to flow between cells along the sieve tube • Each sieve-tube element has a companion cell whose nucleus and ribosomes serve both cells Depending on the species, sugar may move by symplastic (passing through plasmodesmata)or both symplastic and apoplastic pathways • Companion cells enhance solute movement between the apoplast and symplast • In many plants, phloem loading requires active transport • Proton pumping and cotransport of sucrose and H+ enable the cells to accumulate sucrose • At the sink, sugar molecules diffuse from the phloem to sink tissues and are followed by water

Answer 119

1) major physical features 2) climatic (temp and ppt) 3) Vegetation (and adaptations) 4) Microorganisms, fungi and animals adapted to that particular environment.

Answer 120

organisms share similar characteristics as they undergo natural selection independently, but in similar environments

Answer 121

``` r- strategists ¡ ‘Live fast, die young’ ¡ Quantity ¡ Unstable environments ¡ Earlier maturity ¡ Deciduous ``` ``` K- strategists ¡ ‘grow slow, die old’ ¡ Quality ¡ Stable environments ¡ Later maturity ¡ Evergreen ```

Answer 122

* Structural components * Metabolic Components * Enzyme activators * Osmosis * Cell permeability/membrane functioning

Answer 123

Depends on soil characteristics: pH, the size and composition of soil particles • Most soil particles are negatively charged • Rainfall leaches out the –ve anions, such as NO3 -, PO4 - , SO4 2- • Cations held more strongly: K+ , Ca2+, Mg2+

Answer 124

Plants and soil microbes have a mutualistic relationship – Dead plants provide energy needed by soildwelling microorganisms – Secretions from living roots support a wide variety of microbes in the near-root environment • The layer of soil bound to the plant’s roots is the rhizosphere • The rhizosphere contains bacteria (Rhizobacteria) that act as decomposers and nitrogen-fixers

Answer 125

Free-living rhizobacteria thrive in the rhizosphere, and some can enter roots • The rhizosphere has high microbial activity because of sugars, amino acids, and organic acids secreted by roots • Rhizobacteria can play several roles – Produce hormones that stimulate plant growth – Produce antibiotics that protect roots from disease – Absorb toxic metals or make nutrients more available to roots

Answer 126

Ammonifying bacteria produce NH3 by breaking down nitrogen in proteins and other organic compounds in humus. Nitrogen-fixing bacteria convert N2 into NH3 In the soil, NH3 picks up another H+ to form NH4+ (which plants can absorb) • Plants acquire nitrogen mainly in the form of NO3 – • Soil NO3 - formed by two step processes called nitrification. – Nitrifying bacteria oxidize NH3 to nitrite (NO2 –) then nitrite to nitrate (NO3 –) (2 different bacteria) • Nitrogen is lost to the atmosphere when denitrifying bacteria convert NO3 – to N2

Answer 127

Mycorrhizae (fungus roots) are mutualistic associations of fungi and roots • The fungus benefits from a steady supply of sugar from the host plant • The host plant benefits because the fungus increases the surface area for water uptake and mineral absorption • Mycorrhizal fungi also secrete growth factors that stimulate root growth and branching and produce antibiotics that protect the root.

Answer 128

``` may include: Disease + Parasitism Predation; inc herbivory Competition Mutualism ```

Answer 129

``` Adaptation: genetic changes in the entire population fixed by natural or artificial selection over many generations. ``` ``` Acclimation: individual plants respond to changes in the environment, by altering their physiology or morphology allowing them to survive the new environment. ```

Answer 130

Protein kinase add phosphates to proteins in a process called phosphorylation, ¡ Protein phosphatases rapidly remove the phosphates from proteins, a process called dephosphorylation ¡ This phosphorylation and dephosphorylation system acts as a molecular switch, turning activities on and off or up or down, as required ¡ Many signaling pathways involve second messengers ¡ These are small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion

Answer 131

Crops were typically bred for high yield under optimal growth conditions Loss of genetic variation in other important traits Modern Agriculture involved planting large areas with a single crop (monoculture) Pros: ease of planting, harvesting, and looking after your crop Cons: May lack resilience against disease and other stresses Older and wild varieties of crop plants can be excellent resources for increasing genetic variation (i.e. stress tolerance)

Answer 132

Use restriction enzymes to cut plasmid DNA at a specific site Use restriction enzymes to cut plasmid DNA at a specific site Amplify “target” DNA sequence with PCR from other organism, cut with same RE, and ligate Use restriction enzymes to cut plasmid DNA at a specific site Amplify “target” DNA sequence with PCR from other organism, cut with same RE, and ligate Plasmid has maintained ori, will replicate in bacteria

Answer 133

First thing is the warming of the atmosphere to allow for survival of life. Solar radiation hits the earths surface, some is absorbed, some is reflected. And some is trapped in the greenhouse gases that makeup the ozone. Roughly half is absorbed by the earths surface. Ozone largely depleted by CFC’s. But huge prohibition of these in 1987 Montreal Protocol. Phase out use of CFC’s internationally. Hole over Antarctica is decreasing in size. The hole is over Antarctica because conditions must be cool enough to allow for formation of Polar Stratospheric Clouds which requires much cooler temperatures. CFC’s and halons (containing bromine) are produced mostly in the N hemisphere, and are distributed polewards via wind circulation. Formation of PSC promote production of chemically active chlorine and bromine. Leads to rapid ozone loss when sunlight returns in sept/oct. Sun strikes the earth at oblquie angles in the upper and lower regions, but at 90 degree angles at the equator. More diffuse at higher latitudes.

Answer 134

At the equator; low pressure, warm moisture rich air rises and then forms clouds as it cools, falls as rain and high storm risk. At 300 N/S; high pressure, dry cool air draws moisture from the soil.

Answer 135

Winds - atmospheric circulation. Earth’s rotation – Coriolis force. Changes in water density – temperature and salinity This can be confounded by: Topography of the ocean floor – this can modify the speed and direction of ocean currents. Two types of currents: Surface currents – 10%. At the shore these are affected by wind and tide. In the ocean wind is the major driving force. Deep ocean currents – 90%

Answer 136

Strong influence of heating and cooling of coastal regions by ocean currents. During a hot day (when the land is warmer than the water), air over the land heats up and rises, drawing cooler air from across the ocean. By contrast, land loses heat faster (such as during cool nights), this causes air above the ocean to rise (because it is now warmer), drawing cooler air from over the land across the ocean.

Answer 137

Plants in the desert can have a waxy cuticle which stops water molecules from dissipating or being absorbed into the air. Furthermore, stomata cycles are also another important feature for desert plants. This is because they can open their stomata during the night to obtain CO2 for photosynthesis and can then close their stomata during the day to reduces water loss through transpiration. A third and final strategy is that leaves are reduced to spines which reduce the surface area for transpiration. Stomata are a result of acclimation because they are temporarily closed and opened. However, a waxy cuticle and spines are a result of adaptation because they are long term/ permanent and they are a change in physical composition.

Answer 138

Long distance transport of water from the soil to the leaves happens due to root hair cells and roots absorbing the water due to water potential. Moreover, the water is absorbed via the apoplastic and the symplastic route. The water is then taken up in the xylem, where Water and solutes move together through tracheid and vessel elements of xylem. Water is brought up through the xylem because of bulk flow where there is a movement in fluid due to pressure. Some water is lost due to transpiration. Stomata can help reduce water loss by closing during certain conditions such as in arid regions of hot or cold climates where the stomata can open at night to let in CO2, but close during the day to minimize water loss.

Answer 139

During the light reactions, there is one possible route for electron flow to produce ATP and NADPH which is linear flow. In linear electron flow, the primary pathway which involves both photosystems and produces ATP and NADPH using light energy. This happens due to a primary electron acceptor in the reaction centre accepting a excited electron from chlorophyll a which takes place at both reaction centres. ATP and NADPH are produced on the side facing the stroma, where the Calvin cycle takes place. The 3 phases of the Calvin cycle are: Carbon fixation, reduction and regeneration. During carbon fixation a CO2 molecule combines with five-carbon acceptor molecules and is catalysed by rubisco. Next is reduction, where NADPH donates electrons to, or reduces, a three-carbon intermediate to make G3P. Finally is regeneration. where Some G3P molecules go to make glucose, while others must be recycled to regenerate the RuBP acceptor. Photorespiration is the process of light-dependent uptake of molecular oxygen (O2) concomitant with release of carbon dioxide (CO2) from organic compounds. The gas exchange resembles respiration and is the reverse of photosynthesis where CO2 is fixed and O2 released. Furthermore, Photorespiration generally occurs on hot, dry, sunny days causing plants to close their stomata and the oxygen (O2) concentration in the leaf to be higher than the carbon dioxide (CO2) concentration.

Answer 140

Bryophytes: are considered the simplest of the four types, because they lack a full vascular system, true roots and true leaves. These include mosses and other small plants that grow in wet areas and use spores to reproduce. Pteridophytes: Like ferns, are plants that also use spores to reproduce, however they have evolved a vascular system and so are considered to be more sophisticated than bryophytes. These were the earliest trees on earth; as soon as plants gained vascular systems they were able to grow quite tall as fern trees. They do not have a tap root but have roots that adventitiously sprout from the stem. Gymnosperms: Include plants like conifers and pines. These plants use seeds to reproduce instead of spores, which is an improvement upon the pteridophyte model because seeds are much more durable than spores. This means the genetic information is safer and more likely to be successful. The seeds of gymnosperms are not enclosed in an ovule; they require both male and female cones to reproduce. Male cones are smaller and softer than their female counterparts, and pollination occurs via insects, animals or the wind. Angiosperms are the most sophisticated plants on earth, and include all flowering plants. They can be broken down further into two groups: monocots and dicots.

Answer 141

Plants alternate between two multicellular stages, a reproductive cycle called alternation of generations • The gametophyte (“gamate-producing plant”) is haploid and produces haploid gametes by mitosis (egg and sperm) • Fusion of the gametes gives rise to the diploid sporophyte, which produces haploid spores by meiosis

Answer 142

Microspores develop into pollen grains, which contain the male gametophytes • Pollination is the transfer of pollen to the part of a seed plant containing the ovules – contrast with bryophytes and seedless v plants • Pollen eliminates the need for a film of water and can be dispersed great distances by air or animals • If a pollen grain germinates, it gives rise to a pollen tube that discharges sperm into the female gametophyte within the ovule

Answer 143

Three key features of the gymnosperm life cycle are – Dominance of the sporophyte generation • Miniaturization of their gametophytes – Production/development of seeds from fertilized ovules – The transfer of sperm to ovules by pollen The pine tree is the sporophyte that produces sporangia in male and female cones • Pollen cones are small and consist of modified leaves (microsporophylls) that bear microsporangia • Cells called microsporocytes undergo meiosis to produce haploid microspores inside the microsporangia Ovulate cones are larger and consist of both modified leaves (megasporophylls bearing megasporangia) and modified stem tissue • Within each ovule, megasporocytes undergo meiosis to produce haploid megaspores While pollen tube develops – megasporocytes undergoes meiosis – produces 4 haploid cells – one survives as a megaspore. The megaspore develops into a female gametophyte that contains two or three archegonia – each will form an egg. By the time eggs are mature, sperm cells have developed into pollen tube and fertilization occurs when sperm and egg unite.

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