Forest Bio exam 3
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- What controls the site productivity?What is the major factor influencing plant growth and distribution?
- the amount of available water;
- Which slopes get more direct solar radiation, what type of soil do they have and what type of trees grow on them usually?
- south, southwest, dryer and warmer, pines usually only grow, very little production here
- What does water have an influence on?
- cell division and stem elongation
- What is the largest component of plants, how much of it makes up growing tissue and how much of it makes up woody plants?
- water, 80-90%, 45-60%
- What does water serve as?
- a solvent which transports minerals and dissolved carbohydrates throughout the plant
- What are some of the functions of water?
- used for turgidity, dissolves a great many chemical substances, reactant in chemical reactions, serves in photosynthesis for source of electrons
- What is turgidity?
- serves for pressure in plants, necessary for cell enlargement, growth and even maintenance of form in some plants
- What is water potential?
- movement of water from cell to cell in plants, measure of free energy of water
- What is the conversion of a megapascal?
- 10 bars
- What makes up water potential?
- turgor potential and osmotic potential
- What is osmotic potential due to?
- dissolved solutes in the water,(sugar and salt), the more dissolved solutes the lower the osmotic potential
- When you see wilted leaves, whats wrong with the water potential?
- the turgor potential is at zero
- What happened to the water potential when there is dead xylem in trees?
- negative turgor pressure, "under tension"
- What are auxins?
- Produced in growing tips, signal response responsible for curvature.
- What is development?
- Differentiation of cells into the various tissues and organs.
- What is growth?
- Refers to an increase in size by cell division and enlargement.
- What is osmotic adjustment?
- An acclimation where the plant lowers its osmotic potential in response to a drought and in this way maintains turgor despite lower water potential.
- What is dessication tolerators?
- The ability of plants to still dessicate but still survive
- What is dessication postponement?
- Decrease water loss, or increase water uptake,
- What are drought tolerators?
- Have portions during their active life cycle during periods which drought can be expected.
- What are drought avoiders?
-
Plants that complete their entire life cycles before a drought occurs
Ex. Desert species - What are four mechanisms for a drought?
- Drought tolerator, avoider, dessication postponement and tolerator
- What is acclimation?
- A modification of a characteristic in response to the environment
- What is adaptation?
- Characteristics which are heritable or passed on from generation to generation.
- What are two drought mechanisms?
- Adaptation and acclimation
- What is a drought?
- A meteorological event which can be defined as a period without rainfall of sufficient duration that plant growth is impacted negatively.
- What is a tensiometer?
- Used to measure the water potential of soil
- What is the pressure chamber used for?
- To measure the water potential in the xylem of woody plants.
- Which has more water potential; pure water or a solution?
- Pure water
- In which direction does water move?
- High to low regions of water potential
- What are selectively permeable membranes?
- All the free movement of water to pass through, but not solutes to pass through the membrane of cells
- What makes it so that the turgor pressure doesn’t cause the cell’s membrane to rupture?
- Rigid cell walls
- What is the cohesion-tension theory?
- The way that water gets up to the top of trees; the act of the water being “pulled up†by the act of transpiration (evaporation).
- What are tropisms?
- Movement in plants in response to unidirectional signals
- What do auxins play a role in?
- Apical dominance-the tip inhibits the growth of lateral buds
- What does auxin do to dormant buds?
- Keeps the buds from sprouting
- What happens to stems when they are exposed to a lot of light?
- The auxin breaks down, allowing dormant buds to sproud into epicormic sprouts.
- What is phototropism? How is auxin involved?
- Bending towards the light, auxin is on the shaded side causing more curvature towards the light
- What is gravitropism?
- Movement in response to gravity
- What happens to roots when the shoot is dipped in auxin?
- They grow more quickly
- What is parthenocarpic fruit?
- Seedless fruit;growth without fertilization; b/c of auxin
- What are gibberellins?
-
Large group of chemical compounds, stem elongation
Longer days; elongation of plants (bolt)
Flower formation and fruit development - What are “anit-gibberellins used for?
- Power lines-instead of so many top clippings, and for greenhouse growth purposes
- What are cytokinins?
- produced in meristematic regions, called zeatin, cell division and cell and organ enlargement, promote lateral bud development
- What are cytokinins used for?
- on the fascicular buds of christmas trees, to promote growth
- What type of trees are cytokinins applied to?
- christmas trees, and fraser firs
- What is etylene?
- gas produced by ripening fruit, also produced in combustion reactions, causes abscission, causes fruit ripening
- What is abscission?
- shedding of a plant part, occurs in plants once auxin levels decrease later in the growing season, cells slowly break down creating a line where the shedding occurs
- What is abscisic acid?
- seed dormancy, induce a resting bud, inhibits seed germination and furthers dormancy, signal of stomata closure,
- Which growth regulator causes the witches broom?
- cytokinin
- Which growth regulator is directly related to broadleaf weed killer?
- auxin
- Which growth regulator is related to seedling vigor during storage?
- ethylene
- Which growth regulator is related to stem/internode elongation?
- gibberellin
- Which growth regulator is related to stomatal closure?
- ABA
- Which growth regulator is related to rotting fruit?
- ethylene
- Which growth regulator is related to the crazy rice disease?
- gibberellin
- Which growth regulator is related to cell division?
- cytokinin
- What is a condition in which helps temperate woody trees survive harsh winter periods?
- dormancy
- When are trees generally in cold hardy?
- when they are deep in dormancy
- What is dormancy in shoots?
- period of ceased growth and a resting bud that is enclosed in scales.
- When will true dormancy be broken?
- when adequate chilling has occured
- What is quiescence?
- a resting state in response to adverse environmental conditions
- What are the stages of dormancy and describe each?
-
pre-dormancy-reversible of favorable growing conditions take place
true dormancy- non-reversible- only if there is a period of sustained chilling will it break
post-dormancy-bud is still capable of growing but supressed by adverse environmental conditions - What is the main environmental signal that triggers the onset of dormancy?
- short Daylength, long nights short days
- What happens when daylength changes?
- growth regulators are produced, abscisic acid-builds up during fall
- When are the best environmental conditions for a plant to enter true dormancy?
- cool temperatures and short days
- How does water and nutrition effect dormancy?
- if the plant is water stressed then it will promote dormancy, if there is high nutrition it will delay dormancy
- What conditions help a plant enter post-dormancy?
- between the degrees of 2-4 degrees celcius, and with chilling
- What does chilling do to ABA?
- breaks it down
- What is a way that dormant trees survive freezing temps?
- cold hardiness
- What are frost cracks?
- when the pressure from the expanding ice exceeds the strength of the wood
- What do temperate trees do to prevent freezing in living tissues as part of the mechanisms of cold hardiness?
- deep supercooling, intracellular dehydration
- What is deep supercooling?
- maintaining water in cells in a liquid state below 0 degrees but above nucleation state
- What is intracellular dehydration?
- plants can survive at temps. below 40 degrees celsius, but the extracellular spaces are the only liquids that will freeze b/c the liquid is pulled out of the cells, just causing damage from dehydration