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what are the 2 principle types of root systems?
1) taproot root system
2) fibrous root system
how does the taproot RS differ from the fibrous RS?
-in taproot RS: the primary root is taproot, lateral roots are branching, and is in all seed plants BUT monocots
-in fibrous RS: adventitious roots (no taproot), lateral roots are fibrous, and is in monocots
what changes occur to the rootcap during elongation of the root?
-cells are replaced as root pushes through soil, new cells generated in root apical meristem, move towards RC
-newly formed cells elongate
-as cells move from RC, they differentiate
what are the functions of the rootcap?
protective parenchyma cells that control direction of movement & aid in protection
what tissues are found in a root at the end of primary growth? how are they arranged?
1) protoderm meristem in the epidermis
2) ground meristem in the ground tissue
3) procambium meristem in the vascular tissue
describe the effect of secondary growth on the primary body of the root
-increased thickness through production of secondary xylem & phloem by vascular cambium
-epidermis replaced by cork cambium
-lateral roots form
-enhanced transport & structural support
what are the principle functions of roots?
1) absorption
2) transport
3) hormone prod
4) storage
5) specialized roots
what are the principle pigments involved in photosynthesis?
1) chlorophyll a
2) chlorophyll b
3) chlorophyll c
4) carotenoids & phycobilins
why are leaves green?
chlorophyll absorbs blue-violet light, and reflects/transmits green light
what are the main products of light reactions in PS?
-oxygen
-ATP
-NADPH
what are the main products of carbon-fixation reactions in PS?
1) sucrose
2) starch
what are the main events associated with each of the 2 photosystems in light rxns?
PSI:
absorbs light energy exciting e- that are used to reduce NADP+ to NADPH
PSII:
water photolysis (split) yields oxygen & protons are released to lumen of thylakoid generating a proton gradient
what is the difference between antenna pigments & rxn center pigments?
antenna pigment molecules act as a funnel & rxn center pigments convert light to chemical energy
what are the principle differences between C3, C4, and CAM pathways for carbon fixation?
C3:
-uses rubisco
-low energy cost
-plants in cool/wet envir.
-prone to PR
C4:
-uses PEP carboxylase
-high energy cost
-plants in tropical envir.
-spatial sep avoids PR
CAM:
-temporal sep avoids PR
-stomata opens at night to reduce water loss
what are the similarities between C3, C4, and CAM pathways?
-C4 & CAM both use PEP carboxylase
-C4 & CAM both have low rates of PR
what is photophosphorylation?
process of converting light energy to chemical energy in form of ATP during PS
what is photorespiration and what are its implications?
process where the enzyme rubisco oxygenates RuBP causing the release of CO2
occurs when rubisco uses oxygen instead of CO2 as a substrate
causes E loss, reduced PS efficiency, and C loss
in what ways do C4 plants have an advantage over C3 plants?
spatial separation helps avoid photorespiration which C3 is prone to
explain temporal separation in CAM plants
at night CAM plants open their stomata for CO2 intake which is then converted to malic acid & stored in vacuoles
during day, stomata closes to minimize water loss: stored malic acid broken down to release CO2 used for the calvin cycle
why might CAM plants taste sweet during the day and sour at night?
during night, CO2 converted to organic acids
during day, acids break down to release CO2, sugars prod. during PS
what is the balanced equation for photosynthesis?
6CO2 + H2O -> C6H12O6 + 6O2
what is the overall equation for cellular respiration?
C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy (ATP)
what is the principle function of cellular respiration?
shifting stored energy to usable energy
why would plants do cellular respiration if the plant can already do photosynthesis?
during the night or when photosynthesis is not possible
what are the main events that occur during glycolysis?
glucose (6C molecule) is broken down to 2 pyruvate (3C each), 2 molecules of NAD+ reduced to 2 NADH, 2 ATP per molecule of glyceraldehyde 3-phosphate produced (4 ATP total)
what is produced in glycolysis?
1) 2 NADH
2) 2 ATP
3) 2 pyruvate
where in the cell does the citric acid cycle occur?
matrix of mitochondria
what are the products of the citric acid cycle?
1) oxaloacetate
2) 2 ATP
3) 6 NADH
4) 2 FADH2
how does the flow of electrons in the electron transport chain result in the formation of ATP?
flow of electrons through ETC generates proton gradient & this energy is used by ATP synthase to produce ATP (oxidative phosphorylation)
how/why does the net energy yielded under aerobic conditions differ from that obtained under anaerobic conditions?
more NE yielded under aerobic compared to anaerobic
aerobic: oxygen is final e- acceptor in ETC which allows efficient prod of ATP through ox. phos.
no oxygen in anaerobic, ETC cant function, cells rely on fermentation (less efficient)
what is the central role of the citric acid cycle in cell metabolism?
glucose completely oxidized to CO2 & oxaloacetate regenerated
yields NADH & FADH2 for ATP prod. in ETC
what are the 6 major groups of plant hormones?
1) auxin
2) cytokinins
3) ethylene
4) abscisic acid
5) gibberellins
6) brassinosteroids
how do auxins contribute to plant development?
-signal devel. of lateral roots at pericycle
-vasc. tissue diff
-initiate adventitious roots
how do cytokinins contribute to plant development?
promote cell division
how does abscisic acid contribute to plant development?
prevents break in dormancy
how do gibberellins contribute to plant development?
-stimulate cell division & elongation
-hastens germination
how do brassinosteroids contribute to plant development?
vascular tissue differentiation
how does ethylene contribute to plant development?
regulates fruit ripening & leaf abscission
where is auxin synthesized?
shoot, roots, young leaves, seeds
where are cytokinins synthesized?
root tips, dividing seeds, fruits, leaves
where is abscisic acid synthesized?
leaves, roots, seeds
where are gibberellins synthesized?
young shoots, seeds
where are brassinosteroids synthesized?
throughout the plant, young tissue
where is ethylene synthesized?
ripening tissue
what is a tropism?
directional growth response of a plant part in response to external stimulus
by what mechanism do plants respond to light?
phototropism: shoot, petiole growth toward light
by what mechanism do plants respond to gravity?
gravitropism:
root growth downward, shoot growth upward
by what mechanism do plants respond to a moisture gradient?
hydrotropism
explain the starch-statolith hypothesis as it applies to roots:
amyloplasts in plants perceive gravity in the starch sheath (cells surrounding the vascular tissue)
why is it important that plants be able to "tell time"?
photoperiodism allows plants to undergo seasonal & developmental changes: some plants have to reach certain level of maturity before flowering, and others respond to photoperiod when seedlings
what are some characteristics of the circadian clock in plants?
-used to coordinate daily events & allow response to changing seasons by measuring daylength
-entrainment: periodic repetition of light & dark synchronize w/ an external factor
what is the effect of daylength on flowering?
short-day plants (early spring, fall) flower during LP shorter than critical length
long-day plants (summer) flower in LP longer than critical length
day-neutral plants flower regardless of LP
what elements are essential for plant growth?
nitrogen, potassium, phosphorus
what is the function of nitrogen as an essential element?
component of amino acids, proteins, nucleotides, nucleic acids, chlorophylls
what is the function of potassium as an essential element?
involved in osmosis & ionic balance, opening/closing of stomata
what is the function of phosphorus as an essential element?
component of energy-carrying phosphate compounds (ATP, ADP), nucleic acids, and phospholipids
what are the common symptoms associated with nitrogen deficiency?
general chlorosis or some plants exhibit purple coloration due to accumulation of anthocyanins
what are the common symptoms associated with potassium deficiency?
mottled/chlorotic leaves, small spots of necrotic tissue at tips, weak/narrow stems
affects older leaves
what are the common symptoms associated with phosphorus deficiency?
dark green, accumulate anthocyanins to become red/purple, stems stunted
why are nutrient cycles so important for plants?
-ensure nutrients are continuously recycled + available to plants
-maintain soil fertility
-vital to PS, respiration, protein + DNA synthesis
-ecosystem balance: nutrients aren't depleted in one area, accumulated in another
How does the mobility of a nutrient affect the symptoms associated with its deficiency?
mobile nutrients such as N, P, and K can reallocate from older to newer tissues when there is a deficiency
immobile nutrients such as Ca, Fe, and B cannot reallocate so deficiency symptoms appear in younger leaves first
what are the main components of the nitrogen cycle?
-nitrogen fixation: N2 converted to NH3 by N-fixing bacteria
-NH3 converted to nitrites, then to nitrates by soil bacteria
-nitrates absorbed
-organic N converted back to NH3
-nitrates converted back to N gas and released to atmosphere
what are the main components of the phosphorus cycle?
-P released from rocks through weathering, enters soil
-absorbed by plants
-animals consume P through plants
-when plants/animals die, organic matter broken down & P is returned to soil
-P carried to water bodies, form sedimentary rock
in what ways have humans disrupted nutrient cycles?
-fertilizer use
-burning fossil fuels
-mining P rocks: excess P from Ag runoff causes eutrophication & water pollution
how is plant nutrition research contributing to solutions for problems associated with agriculture & horticulture?
-more efficient fertilization strategies increase crop yield
-healthier soils are more productive
-reduces nutrient runoff & leaching that cause H2O pollution
what attributes of loam soils help make them ideal agricultural soils?
-fine soil particles good for nutrient retention
-coarse particles help with drainage
how does the size of the spaces around soil particles influence the amount of water that is available to plants?
-course soil: large pores, water moves quickly through, drain rapidly
-fine soils:
small pores, water moves slowly through, retain water
-loam:
mix of large & small pores, balance of retention/drainage
what advantages do molecular techniques have over comparative morphology & anatomy in assessing phylogenetic relationships?
they are easier to quantify, have the potential to provide many more characters for phylogenetic analysis, and allow comparison of organisms that are morphologically very different
how do we classify organisms?
-cladistics: analyzes branching, produces cladogram
-molecular systematics: phylogenetic trees, DNA barcoding
what is taxonomy?
the science of naming and classifying organisms by organizing species into hierarchical groups based on shared characteristics & evolutionary relationships
