plant requirements / coordination

Question 1

what are requirements for autotrophs

Answer 1

• light: photosynthesis, produce sucrose / ATP, increase potential energy of e-
• water: 80% water, central vacuole = turgid pressure, medium in which minerals / sugars dissolve, blood supply of plant, transport mechanism
• carbon dioxide: carbon source that provides atoms to make up macromolecules
• oxygen: cellular respiration
• macro nutrients: large amounts (C, O, H, N, K, P, Mg, Ca, S), building tissue, photosynthesis
• micro nutrients: needed in trace amounts (Mn, Mo, Cu, Zn, Fe, Cl, B, Ni), help with turgid pressure, movement
• turgid pressure: cells coming together to form leaves, can change direction of leaves in order to gain largest amount of sunlight (petiole = flaccid, hangs low, petiole = turgid, sits high)

Question 2

how does transport of water occur in plants

Answer 2

• xylem, circulatory system of plants, water movement

- water uptake through endodermis (root system, large cortex to regulate movement), vascular stele, casparian strip

Question 3

what are the two pathways that are possible in water transport

Answer 3

• apoplastic: pink, least resistance, through cell walls and intracellular spaces, fibrous material, take in water / expand
• symplastic: blue, across plasma membrane, cell to cell connections through cytoplasm, regulation, through plasmodesmata

Question 4

what is the casparian strip

Answer 4

• suberin, waxy material, only laid down along 4 walls
• connections between cells are water proof
• regardless of pink or blue forced to cross symplastic (blue) due to cell wall being waterproof (casparian strip)

Question 5

how does water move upward in the plant

Answer 5

• water moves down water potential gradient, high water to low water
• psi (water potential symbol, devil stick)
• in relation to pure water (0), presence of solutes (-ve)
• measured in Mpa (megapascal)
• Mpa becomes more -ve as you travel further upwards, hence upward movement of water through plant, soil (-0.1), root (-0.2), xylem (-1.1), leaf (-1.5) and atmosphere (-30)

Question 6

what is the water column

Answer 6

• column of water in the xylem, h bonds (weak bond, easily formed / broken)
• cohesion: allows water molecules to come together (fluid medium)
• adhesion: water adheres to xylem wall / other polar substances
• evaporation: of water from surface of leaf cells (transpiration), allows water column to be sucked upwards
• transpirational pull: responsible for evaporation of water from the leafs surface, pulling water column up from roots to leaves

Question 7

how is prevention of too much water loss controlled

Answer 7

• leaf boundary layer: under leaf, reduce large gradient of water potential, boundary of humid air (contains water)
• hairs: trap water as it is being pulled out
• stomata: open / shut, turgid pressure, pore, guard cells, cell loses water guard cells = flaccid (pores shut), guard cells take on water they bow outwards (open pore), also controlled by K levels

Question 8

describe the transport of photosynthetic products and the reason for sucrose production

Answer 8

• circulatory system of plant, photosynthetic products down plant
• create own sugar, formation of sucrose
• easier to store, non reducing agent, transported throughout plant without impacting or reducing anything / affecting other molecules
• leaves leaf to root system, or is stored in fruit, enzymes break it down easily

Question 9

describe the steps in movement of photosynthetic products

Answer 9

1. loading of sugar: sugar into phloem cells (sieve tubes), actively accumulated (leaf = lots of chloroplasts, produce sugar)
2. uptake of water: water enters phloem from xylem by osmosis, creates hydrostatic pressure (increases pressure, forces water down plant)
3. unloading of sugar: root cells (sink), passive, phloem unload sugar / water at root, relieves pressure
4. water recycling: water reabsorbed into xylem, moves up plant via water column

Question 10

what are plant hormones and growth responses

Answer 10

• no evolution / growth without, low conc. to produce response, high conc. = herbicide (death)
• control growth, division, development, elongation, differentiation
• produced in one area and move to xylem / phloem
• bind to receptor, cause change and activation of cellular responses
• auxin, gibberellin, abscisic acid, cytokinin and ethylene

Question 11

what is auxin

Answer 11

• produced by: shoot apical meristem, root meristem, young leaves
• found in: seeds / fruit
• function: primary growth
• characteristic feature: phototropism (bend towards light) / gravitropism (against gravity), fruit development
• stem elongation: acid growth hypothesis (breaks cell wall, acidifies = elongation / growth), increase central vacuole
• lateral / adventitious root formation
• prevents lateral growth (removal = shrub / bush)
• achenes: fruit development, each cell = different time / conc., characteristic sizes

Question 12

what is gibberellin (GA)

Answer 12

• produced by: young leaves. stem / root meristem, immature seeds, developing anthers
• function: growth, elongation, germination, pollen development
• characteristic feature: mobilisation of endosperm, production of amylase (breakdown endosperm to glucose)
• rapid shoot / growth, internodes (stem in between leaves = longer, increased area for development of fruit / leaves)

Question 13

what is cytokinin

Answer 13

• produced by: actively growing tissue (roots, cell division)
• function: division / growth laterally, delay leaf senescence (anti-ageing, prevent breaking down, stay youthful)
• characteristic feature: regulates cell division (stimulates cytokinesis, start dividing)

Question 14

what is ethylene

Answer 14

• produced by: all structures
• function: similar to auxin, seed germination, stem growth / shoot elongation, root hair formation, flowering, fruit ripening
• characteristic feature: gas (all others diffuse via aqueous environment), ability to diffuse out of plant body, affect surroundings
• thigmomorphogenesis: response to mechanical disturbance, touched = stunted growth
• abscission / senescence: death, dead at functional maturity (xylem and sclerenchyma), opposite of cytokinin
• stress response: hardier in structure, slowing of stem elongation, thickening, sturdier, move around an obstacle

Question 15

what is abscisic acid (ABA)

Answer 15

• produced by: all structures
• function: promotes stomatal closure during drought stress (controls osmotic balance of guard cells, opening (turgid) / closing (flaccid) of pores)
• characteristic feature: inhibits growth, promotes seed dormancy (inhibits early germination
• rain: washes ABA away, promotes growth after
• seed remains dormant until soil conditions are favourable (water / sunlight)