Plant Biology 5

Front 1

What are four very important environmental factors that effect plant growth?

Back 1

temperature, light, water, nutrients

Front 2

What are the enzymatic effects of high, low and optimum temperatures.

Back 2

-High:enzymes and proteins denature
-optimum:biochemical reactions are best
-low:metabolism stops or ice damage may occur

Front 3

What is hardening?

Back 3

The gradual exposure of a plant to colder temperatures in order to improve its cold hardiness. (natural process)

Front 4

What is the difference between hardening and acclimation?

Back 4

Acclimation is a slow change in physiology due to constant cold conditions. Hardening is a more temporary solution to the cold, ie in winter.

Front 5

What are some mechanisms to avoid desiccation?

Back 5

-rolled leaves
-sunken stomata
-hairs
-alternative photosynthate cycles
-heliotropism
-desiccation tolerance

Front 6

What are the effects of excessive heat on plant metabolism?

Back 6

Rapid respiration leads to a shortage of oxygen leads to anearobic respiration resulting in accumulation of toxic products and plant degeneration.

Front 7

Is photoperiodism due to the length of day or night?

Back 7

night

Front 8

What do long day plants need in order to flower?

Back 8

A maximum number of hours of uninterupted darkness. If they receive too much (more then the critical photoperiod) they will not flower.

Front 9

What do short day plants need in order to flower?

Back 9

A minimum number of hours of uninterupted darkness. If they receive less then the critical photoperiod they will not flower.

Front 10

What are the two forms of phytochrome?

Back 10

-phytochrome red (inactive, neutral form) absorbs red light
-phytochrome far red (active form) absorbs far red light

Front 11

What form is phytochrome in at the end of the day and why?

Back 11

Pfr because sunlight has more red light then far red light. During the night the Pfr converts back to Pr.

Front 12

What does phytochrome far red promote in long day and short day plants.

Back 12

-Long day - promotes flowering
-Short day - inhibits flowering

Front 13

Which type of photosynthesis is most productive in full light?

Back 13

C4

Front 14

What are three things saltmarshes are subject to?

Back 14

-Erosion
-accretion
-progradation

Front 15

What are marshes called that are only occasionally submerged?

Back 15

emergent marshes - variable soil salinity

Front 16

What are marshes that are only occasionally emerged called?

Back 16

submergent marshes - constant soil salinity

Front 17

Why do many saltmarshes show a mosaic of salinities?

Back 17

-some parts are more commonly flooded then others
-rainfall decreases salinity
-dry periods increase salinity

Front 18

What are three factors in saltmarshes that are inimical to growth?

Back 18

-high salinity
-low nutrient content of soil
-anaerobic soil conditions

Front 19

What are three reasons for the adverse effects of salt?

Back 19

1. Direct toxicity
2. Interference with uptake of essential nutrient ions
3. Lowered external H2O potential

Front 20

Why is saltmarsh soil having a low h2O potential inimical to water uptake by plants?

Back 20

Because the root of a plant must have a lower H2O potential then the external environment.

Front 21

What are three ways plants can lower their H2O potential?

Back 21

1. Synthesis of organic solutes
2. Uptake of inorganic salts from external envt
3. Dehydration

Front 22

What are 6 ways plants cope with high salinity?

Back 22

1. Ion selection/exclusion
2. Growth and succulence
3. Secretion
4. Shedding of parts and ion redistribution
5. Reduced transpiration
6. Localization of ions

Front 23

3 features that optimise light

Back 23

-interception
-absorbtion
-processing

Front 24

Sun plant features

Back 24

-leaves vertical
-large cells
-chloroplasts small
-leaves small/thick
-high photosynthetic capacity

Front 25

Shade plant features

Back 25

-leaves horizontal
-small cells
-larg chloroplasts
-leaves large/thin
-low photosythetic capacity

Front 26

What are the benefits of vertical leaf orientation?

Back 26

Enhances light interception in the morning and late afternoon while minimising sun exposure in the heat of the day. ie eucalypts

Front 27

What are the benefits of horizontal leaves?

Back 27

They are able to intercept light all day long, especially at high noon.

Front 28

What is heliotropism?

Back 28

A trophic response in leaf andgle/orientation to light.

Front 29

How can light interception be regulated at tissue level?

Back 29

-isobilateral/dorsiventral leaf arrangement
-arrangement of chloroplasts

Front 30

What are the costs of higher photosyhtesis capacity in sun plants?

Back 30

-increased transpiration and respiration
-increased costs of maintaining sun leaf

Front 31

What are some mechanisms plants use to avoid excess light?

Back 31

-assimilatory photochemistry eg CO2 fixation
-non assimilatory photochemistry eg nitrate reduction
-external photoprotection eg leaf orientation
-re emission of photons as fluorescence
-

Front 32

Some features of shade tolerant species include...

Back 32

-large seeds; added nutrient for seedling
-can germinate in low light
-seedlings can persist in under story for years
-high resistance to herbivory and pathogens
-

Front 33

Some features of shade intolerant plants...

Back 33

-wide dispersal of high number of small seeds
-germination in high light only
-seed viable for years
-rapid growth to maturity
-low p/s ability to changed light conditions

Front 34

Out of UVA, UVB and UVC which is photochemically active? What is it absorbed by?

Back 34

UVB is absorbed by DNA and RNA

Front 35

Common adverse effects of UVB on UVB sensitive plants are

Back 35

decreased
-leaf size
-stem growth (stunting)
-total plant growth

Front 36

What kinds of plants are more sensitive to UVB?

Back 36

Dicots, young seedlings, mature plants in transition to reproductive phase

Front 37

What are the two classes of UVB protection mechanisms?

Back 37

1.those that repair, negate or minimize UV damage
2.those that reduce amount of UV light reaching sensitive areas. eg pigments in leaf epidermi

Front 38

What temperature range do most plants grow in?

Back 38

-5 to 45 degrees C

Front 39

What are some factors that influence plant temperatures.

Back 39

-plant form (erect, prostrate)
-leaf area
-aspect
-irradiance
-air flow

Front 40

Plant characteristics that can minimise damage in above optimal temperatures include

Back 40

-leaf orientation
-leaf angle
-leaf cooling by transpiration

Front 41

What aspects of plant form are altered by temperature?

Back 41

height, organ shape/quantity, branching patter in roots or shoots, leaf area ratio

Front 42

What are the three categories of drought stress adaptive responses?

Back 42

1. Plants that escape drought eg desert ephemerals
2. those that can tolerate drought
3. those that can dehydrate

Front 43

Drought tolerance mechanisms involve -

Back 43

-increased root depth and density
-reduced leaf canopy area and light interception

Front 44

What are the four categories of plant responses to fire (and smoke)

Back 44

1.Stimulation of seed release from woody capsules by heat eg eucalyptus
2.Stimulation of soil stored seed by fire eg acacia
3.Stimulation of bud development after fire eg eucalyptus
4.Stimulation of flowering

Front 45

What effects do season and climate have on plant responses to fire?

Back 45

If a fire occurs in a time of low rainfall germination may not occur or seedlings wont survive.
High rainfall washes seeds away.
Drought prevents seeds germinating.

Front 46

What are the three orders of the Pterophyta?

Back 46

Orphioglossales
Marattiales
Filicales (makes up 95% of all)

Front 47

Is the sporophyte or gametophyte dominant in the Pterophyta?

Back 47

Sporophyte is dominant, unlike in the Bryophytes

Front 48

What is the name of the type of structure/development of the sporangia in Ficiliales?

Back 48

Leptosporangial development

Front 49

Describe Leptosporangial development.

Back 49

A single cell on the underside of the frond divides into an inner and outer cell. The later of which gives rise to a stalked sporangium.
The inner cell undergoes meiosis to produce spores.
The capsule cell wall becomes the annulus.

Front 50

What are the four stages in spore release in Leptosporangial Pterophytes?

Back 50

1.Outer wall of annulus dries
2.faster shrinking then the inner walls
3.causes a tear in the lip cells
4. annulus straightens and flicks spores out

Front 51

What are the clusters of sporangia called in the Pteridophyta?

Back 51

Sorus (pl Sori)

Front 52

What do Pterophyte spores give rise to? And what is the next stage in the reproductive cycle?

Back 52

An individual bisexual gametophyte with antheridia and archegonia. Sperm swim to the egg in a water medium. The zygote develops directly. The sporophyte develops in the archegonia and the gametophyte dies.

Front 53

How do some ferns reproduce asexually?

Back 53

-fragmentation of the rhizome
-diploid spores produced without meiosis which gives rise to a diploid prothallus with no sex organs. This then gives rise to a sporophyte

Front 54

What are the three most important genera of water ferns in Australia? Are they hetero or homo sporus?

Back 54

Salvinia, Marsilea, Azolla.
All are heterosporus

Front 55

What are the three extant divisions of fern allies?

Back 55

Psilophyta (whisk ferns)
Lycophyta (club mosses)
Sphenophyta (horsetails)

Front 56

What kind of gametophyte do homospores give rise to?

Back 56

Bisexual