9. Plant Sciences Flashcards
Draw & Label showing distribution of tissues in stem and leaf of dicotyledous plant.
What are the differences in structure of monotyledons and dicotuyledons?
(at least 3)
- Number of cotyledon: 1 vs.2
- Leaf veins: Parallel venation vs. Reticulateral ventaion
- Roots: Fibrous adventitious vs. Tap roots w/ lateral branches
- Floral organs: x3 vs. x4/x5
- Stem vascular arrangement: Scattered vs. In a ring
- Pollen: Single furrow/pore(monosulcate) vs. 3 furrows (trisulcate)
Explain the relatioship between tissue distribution and structure in leaf.
**1. Upper epidermis **
F: Water conservation (Secrete cuticle => Waxy outer boundary)
D: Top of laeves where light I + heat highest (Transperant)
**2. Palisade Mesophyll **
F: Photosynthetic tissue; absorption of light - cell contains chloroplast
D: Upper half of leaf; light I greatest
**3. Spongy mesophyll **
F: Gas exchange
D: Loosely packed cells with spaces, lower half, near stomatal pores (where gases and water exchanged w/ atmosphere)
4. Vascular Tissue
F: Transport water(xylem) + products of photosynthesius (phloem)
D: Middle of leaf => All cells optimal access
Identify modification of roots + stems = leaves for dfferent function.
- Storage roots: Modified roots -> Store H2O/food
e. g. carrots - Stem Tubers: Horizontal underground stems that store carbohydrates
e. g. potato - Bulbs: Modified leaf bases (ex.underground vertical shoots) that contains layers called scales
e. g. onion - Tendrils: Modified leaf/stem for climbing support attachement
e. g. Vines
What are meristems?
What are the two types of meristems in dicotyledonous plants?
Meristem = Tissue(plant) w/ undofferentiated cells, found in zones where growth take place
The two types of meristems are apical and lateral.
Compare growth due to apical vs. lateral meristems in dicotyledonous plants
Similarity
- Composed of totipotent cells
- Found in dicotyledounous plant
**Differences **
- Occue @ Tip of root + shoot vs. Cambum
- Vertical growth (root/shoot) vs. Lateral (stem)
- Primary growth vs. Secondary
- Primary xylem/phloem vs. Secondary
- Produce leaves + flowers vs. Bark
Explain the role of auxin in phototroposim.
- Phototropism = growing/turning (organism) response unilateral light
- Auxin (IAA) = plant hormone produced by tup of shoot and control 1). Destory by light
- Auxin => Cell enlarge/grow
- Accumulation(IAA) -> Shaded area cause shaded side legnthen, => shoot bend towards ligth
- Auxin => cell elongation by activating proton pumps => expel H+ ions from cytoplasm -> Cell wall
- Decrease pH (Cell wall) => cellulose fibre lossen (break bonds)
- Cell wall ^flexible + capable(stretching). H2O influx promote cell turgor.
- Auzin also alter gene expression => Cell growth (upregulation of expansins)
Explain how root systems provides larger SA for mineral ion + H2O uptake.
- Function of root = Absorb H20, minerals, support
- Monotyledon: Root = fibrous, highly branched structure ^SA
- Dicotyledon: Main top root (deep penetration) soil access deep reseviour.
Lateral branches max. SA
- Root epidermis extension = root hairs
- Root hair: Carreier protein + ion pumps in plasmomembrane + mitochondria in cytoplasm => Aid active transport
- Cortex cell wall permeable <=> osmosis
- 6) absorb by capillary action
- Mineral / H2O transport other parts <=> xylem
List 3 ways which mineral ion in soil move to the root
- Diffusion: [gradient]
- Mass flow: hydrostatic pressure gradient
a) Water -> Root via osmosis => -ve hyrostatic pa. in soil
b) mineral H Bond w/ H2O & dragged to root, []ing for absorbtion - Fungal Hyphae: Mutualism - Exchange w/ sugar
Explain process of mineral ion absorption from soil into roots by active transport.
- Minerals = K+, Na+, Ca2+, NH4+, PO43-, NO3-
- Fertile soil = -ve clay particle + +ve minerals
1. Root cell proton pump H+ -> Soil
Cation: Ion exchange: Displace the mineral => Absorbtion
Anion: Symport: -ve mineral bind H+ => Reabsorb w/ proton
- 1) = Indirect active tranport: energy ( + proton pump) => electrochemical gradient by which mineral ion absorbed via diffusion
- Direct active transport: Proton pump translocate ion against [gradient]
How do terrestrial plants support themselves?
1) Thickened cellulose: Cell wall = structural support
2) Cell turgor: ^hydrostatic pa. w/in cell exert pa. -> cell wall => Cells turgid
3) Lignified xylem: Stem to Branch = extra support
Define transpiration
Transpiration is the loss of water vapour from the leaves and stems of plants
Explain how H2O is carried by transpiration stream.
- Light => Leaf => Heat
H2O(spongy mesophyll) -> Vapour
- Vapour =>(diffusion, stomata) evaporate => -ve pa. gradient in leaf
- New H2O drawn from xylem (mass flow), replaced by H2O from roots (from soil via. osmosis)
- Roots —–H2O—-(Xylem)—> Leaf = Transpiration Stream
- H2O Rise becasue of
a) Cohesion: Weakly attract ea. other via. H-Bond
b) Adhesion H2O form H-bond w/ xylem cell wall - a)+b) = sunction effect / Transpiration pull in xylem
7) Xylem specialised structure:
a) Inner lining = dead cells fused => Continuous tube
b) a) lack cell membrane, H2O enter xylem freely
c) Perforated (contain pores) outer later, allow H2O move out -> leafs
d) Outer cell wall : Annular lignin rings
=> Strengthen xylem against tension
from transpiration stream
Guard cells. Why are they?
Guard cells can regulate transpiration by opening/closing stomata:
- Transpiration pull by -ve hydrostatic pa.
by evaporation (water vapour) from leaf
- Guard cell lines stomata, regulate transpiration by control n(water vapour) exit leaf
- Stomata open => ^ r.o. transpiration
close => Decrease r.o.t.
Abscisic acid. Why are they?
- Plant wilt from H2O stress, dehydrated mesophyll cells release plant hormone abscisic acid (ABA)
- Abscisic acid trigger efflux of potassium from guard cell, decrease H2O pa. w/in cells -> Flaccid
- Stomotal pane closes
Explain how abiotic factor - light, temp, wind, humudity affect r.o.transpiration in typical terestrial plant.
**1. Light **
a) ^lux ^r.o.t.
b) Light => stimulate stomata open
(gas exchange for photosynthesis)
c) Light => Heat ^r.o.evaporation
**2. Temperature **
a) ^C ^ r.o.t.
b) ^Temp => ^ H2O vaporisation in spongy mesophyll
^ evaporation from surface of leaf
c) ^ Diffusion H2O vapour out of laef (via stomata)
^ r.o.t.
**3. Wind **
a) ^ Air flow ^ r.o.t.
b) Wind removes H2O vapour ( decrease [vapour] ) on leaf surface
^ rate of diffusion from w/in spongy mesophyll
4. Humidity
a) ^ Humidity, decrease r.o.t.
b) Humidity = H2O vapour in air
^ Humidity = ^ [H2O Vapour] in air
c) Decrease r.o.diffusion(H2O Vapour) from inside leaf smaller [gradient] => decrease net flow
Outline 4 adaptions of xerophytes that help decrease transpiration
- Xerophytes tolerate dry conditions (desert/high attitude):
1. Reduced leaves
Decrease SA, Decrease H2O loss,
Decrease Transpiration
**2. Rolled levaes **
Lower epidermis inside, decrease exposore (stomata) to air (decrease transpiration)
3. Thick waxy cutcile
Prevent H2O loss from surface of leaf
**4. Stomata in pits **
Surrounded by hairs, concentrate H2O vapour near stomata
5. Low growth
Decrease exposure to wind + shaded
**6. C4/CAM physiology **
Requires less CO2, stomata stay closed longer
Outline role of phloem in active translocation of sugars + amino acid from source to sink
- Organic molecule(sugar,amino acid) : source(photosynthetic tissue/storage organ) -> tube system = phloem
- Sugar transport as sucrose (soluble + metabolically inert) in fluid of phloem (sap)
- Actively loaded by companion cells => [High] draw H2O from xylem via osmosis
- Sap (Vol. + pa) increase => mass flow
=> drive sap along phloem
- Actively unloaded by companion cells
=> store in sink (fruit, seed, root)
- Sucrose stored as starch (insoluble), H2O in phloem released and return to xylem.
Draw and label structure of dicotyledonous animal-pollinated flower structure.
Define
- Pollination
- Fertilisation
- Seed dispersal
Pollination : Transfer (pollen grain: anther -> sigma(usually other plant) )
facilated by animal/wind/H2O movement/
Fertilisation: Fusion(male gamete nuclei(in pollen grain) w/female gamate(in ovule) to form zygote
Seed dispersal: Fertilised ovules form seded, move away from parental plant before germination. (Fruit, wind, water, animals)
Decrease competition for resources.
Draw & Label external + internal structure of named dicotyledonous seed.
Explain the conditions for germination
Germination: Process = seed emerge from period of dormancy => starts to sprout
1) O2 : Aerobic respiration (ATP to grow)
2) H2O: Metabolically active cells, stimulate release of gibberalin
3) Temp: Optimal enzyme function
4) Other speciliased conditions
- Fire, burning
- Light/darkness
- Freezing, period of cold temperature
- Prior animal digestion
- Erosion(seed coat)
- Washing/removal of inhibitors
Outline the metabolic process during strachy seed germination
- Absorption of H2O, regydrate seed, cause production of gibberellin / gibberellic acid (GA)
- GA cause amylase synthesis -> Break strach => Maltose
- Maltose transport -> amylase
a) hydrolysed to glucose (energy)
b) polymerised to cellulose (formation of cell wall) - Stored protein + lipid —hydrolysed, addition of H2O—-> enzymes, triglycerides, phospholipids
- Food stored in cotyledon used as energy source until shoot reach light + begin photosynthesis.
Explain how flowering is controlled in long day & short day plants and the role of phytochrome
- Control by phytochrome (affected by light = photoperiodicitiy)
- 2 forms(phytochrome)
a) Inactive 1. Red Pr absorb red light, covert to Pfr
b) Active 2. Far red Pfr absorb far red light => Pr - Sunlight more red light, Pfr dominant during day
- Night: Gradual reversino to Pr
- Long day plants: Active Pfr form promotor(flowering)
Flowering induced when
a) night period < critical length
b) Pfr high
- Short day plants: Active Pfr inhibitor(flowering)
Flowering induced when
a) night > critical legnth
b) Pfr low
