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56 Cards in this Set
- Front
- Back
What are four very important environmental factors that effect plant growth?
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temperature, light, water, nutrients
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What are the enzymatic effects of high, low and optimum temperatures.
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-High:enzymes and proteins denature
-optimum:biochemical reactions are best -low:metabolism stops or ice damage may occur |
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What is hardening?
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The gradual exposure of a plant to colder temperatures in order to improve its cold hardiness. (natural process)
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What is the difference between hardening and acclimation?
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Acclimation is a slow change in physiology due to constant cold conditions. Hardening is a more temporary solution to the cold, ie in winter.
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What are some mechanisms to avoid desiccation?
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-rolled leaves
-sunken stomata -hairs -alternative photosynthate cycles -heliotropism -desiccation tolerance |
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What are the effects of excessive heat on plant metabolism?
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Rapid respiration leads to a shortage of oxygen leads to anearobic respiration resulting in accumulation of toxic products and plant degeneration.
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Is photoperiodism due to the length of day or night?
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night
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What do long day plants need in order to flower?
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A maximum number of hours of uninterupted darkness. If they receive too much (more then the critical photoperiod) they will not flower.
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What do short day plants need in order to flower?
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A minimum number of hours of uninterupted darkness. If they receive less then the critical photoperiod they will not flower.
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What are the two forms of phytochrome?
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-phytochrome red (inactive, neutral form) absorbs red light
-phytochrome far red (active form) absorbs far red light |
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What form is phytochrome in at the end of the day and why?
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Pfr because sunlight has more red light then far red light. During the night the Pfr converts back to Pr.
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What does phytochrome far red promote in long day and short day plants.
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-Long day - promotes flowering
-Short day - inhibits flowering |
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Which type of photosynthesis is most productive in full light?
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C4
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What are three things saltmarshes are subject to?
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-Erosion
-accretion -progradation |
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What are marshes called that are only occasionally submerged?
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emergent marshes - variable soil salinity
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What are marshes that are only occasionally emerged called?
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submergent marshes - constant soil salinity
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Why do many saltmarshes show a mosaic of salinities?
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-some parts are more commonly flooded then others
-rainfall decreases salinity -dry periods increase salinity |
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What are three factors in saltmarshes that are inimical to growth?
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-high salinity
-low nutrient content of soil -anaerobic soil conditions |
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What are three reasons for the adverse effects of salt?
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1. Direct toxicity
2. Interference with uptake of essential nutrient ions 3. Lowered external H2O potential |
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Why is saltmarsh soil having a low h2O potential inimical to water uptake by plants?
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Because the root of a plant must have a lower H2O potential then the external environment.
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What are three ways plants can lower their H2O potential?
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1. Synthesis of organic solutes
2. Uptake of inorganic salts from external envt 3. Dehydration |
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What are 6 ways plants cope with high salinity?
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1. Ion selection/exclusion
2. Growth and succulence 3. Secretion 4. Shedding of parts and ion redistribution 5. Reduced transpiration 6. Localization of ions |
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3 features that optimise light
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-interception
-absorbtion -processing |
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Sun plant features
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-leaves vertical
-large cells -chloroplasts small -leaves small/thick -high photosynthetic capacity |
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Shade plant features
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-leaves horizontal
-small cells -larg chloroplasts -leaves large/thin -low photosythetic capacity |
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What are the benefits of vertical leaf orientation?
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Enhances light interception in the morning and late afternoon while minimising sun exposure in the heat of the day. ie eucalypts
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What are the benefits of horizontal leaves?
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They are able to intercept light all day long, especially at high noon.
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What is heliotropism?
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A trophic response in leaf andgle/orientation to light.
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How can light interception be regulated at tissue level?
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-isobilateral/dorsiventral leaf arrangement
-arrangement of chloroplasts |
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What are the costs of higher photosyhtesis capacity in sun plants?
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-increased transpiration and respiration
-increased costs of maintaining sun leaf |
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What are some mechanisms plants use to avoid excess light?
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-assimilatory photochemistry eg CO2 fixation
-non assimilatory photochemistry eg nitrate reduction -external photoprotection eg leaf orientation -re emission of photons as fluorescence - |
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Some features of shade tolerant species include...
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-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 - |
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Some features of shade intolerant plants...
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-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 |
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Out of UVA, UVB and UVC which is photochemically active? What is it absorbed by?
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UVB is absorbed by DNA and RNA
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Common adverse effects of UVB on UVB sensitive plants are
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decreased
-leaf size -stem growth (stunting) -total plant growth |
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What kinds of plants are more sensitive to UVB?
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Dicots, young seedlings, mature plants in transition to reproductive phase
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What are the two classes of UVB protection mechanisms?
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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 |
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What temperature range do most plants grow in?
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-5 to 45 degrees C
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What are some factors that influence plant temperatures.
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-plant form (erect, prostrate)
-leaf area -aspect -irradiance -air flow |
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Plant characteristics that can minimise damage in above optimal temperatures include
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-leaf orientation
-leaf angle -leaf cooling by transpiration |
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What aspects of plant form are altered by temperature?
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height, organ shape/quantity, branching patter in roots or shoots, leaf area ratio
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What are the three categories of drought stress adaptive responses?
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1. Plants that escape drought eg desert ephemerals
2. those that can tolerate drought 3. those that can dehydrate |
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Drought tolerance mechanisms involve -
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-increased root depth and density
-reduced leaf canopy area and light interception |
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What are the four categories of plant responses to fire (and smoke)
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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 |
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What effects do season and climate have on plant responses to fire?
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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. |
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What are the three orders of the Pterophyta?
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Orphioglossales
Marattiales Filicales (makes up 95% of all) |
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Is the sporophyte or gametophyte dominant in the Pterophyta?
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Sporophyte is dominant, unlike in the Bryophytes
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What is the name of the type of structure/development of the sporangia in Ficiliales?
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Leptosporangial development
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Describe Leptosporangial development.
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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. |
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What are the four stages in spore release in Leptosporangial Pterophytes?
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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 |
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What are the clusters of sporangia called in the Pteridophyta?
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Sorus (pl Sori)
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What do Pterophyte spores give rise to? And what is the next stage in the reproductive cycle?
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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.
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How do some ferns reproduce asexually?
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-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 |
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What are the three most important genera of water ferns in Australia? Are they hetero or homo sporus?
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Salvinia, Marsilea, Azolla.
All are heterosporus |
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What are the three extant divisions of fern allies?
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Psilophyta (whisk ferns)
Lycophyta (club mosses) Sphenophyta (horsetails) |
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What kind of gametophyte do homospores give rise to?
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Bisexual
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