Seminar 23: Plant transport

Question 1

what tissue allows the plant to grow taller?

Answer 1

VASCULAR

Question 2

xylem cells are ____

Answer 2

DEAD

Question 3

tracheids allow vascular plants to reach ___ ___

Answer 3

HIGH HEIGHTS

Question 4

structural support from tracheids are req for plants to … (2)

Answer 4

1. grow UPWARDS
2. COMPETE for SUN

Question 5

what are the func of H2O in plants? (4)

Answer 5

1. Photosynthesis to occur
2. Transport of nutrients: roots > rest of plant body
3. Cool the plant in hot temperatures (via latent heat loss as transpiration occurs)
4. acts as struc support (provides turgor pressure)

Question 6

how does a plant cool itself via latent heat loss (transpiration) (4)

Answer 6

• H2O moves from vascular tissue > nearby mesophyll cells
• Transpiration occurs when H2O moves from these cells > intercellular spaces (changes from liquid > gas when it does this)
• H2O vapour diffuses out via stomata
• Change from (l) > (g) takes a lot of energy: what cools the leaf from the surrounding air

Question 7

what are the main plant macronutrients ? (2)

Answer 7

N & P

Question 8

func of N as a macronutrient (2)

Answer 8

• protein & DNA synthesis
• plant growth
• high in demand cause plants cont grow

Question 9

lack of N = ….

Answer 9

stunt in growth

Question 10

func of P as a macronutrient (2)

Answer 10

• DNA & ATP synthesis
• phospholipid struc

Question 11

lack of P = (2)

Answer 11

• plants become dark green cause they accumulate stress pigments
• stunted in growth

Question 12

sources are … (& give e.x)

Answer 12

photosynthetic tissue, where sugars prod (shoot/leaves)

Question 13

sinks are … (& give e.x)

Answer 13

non-photosynthetic tissue, where sugars are consumed for growth (roots)

Question 14

Low turgor pressure = ____ cells, high turgor pressure = ___ cells

Answer 14

1. FLACCID
2. TURGID

Question 15

Reduction in turgor pressure results in

Answer 15

less rigid plant cells, wilting plant (plants capacity to bend increased)

Question 16

how are nutrients made available to plants?

Answer 16

CATION EXCHANGE

Question 17

desc the process of cation exchange (3)

Answer 17

1. CO2 & H+ released from roots
2. CO2 reacts w/ H2O, forms bicarbonate anion & additional H+
3. H+ bind to -vely charged soil particles: releasing +vely charged ions (e.g K+) into soil sol.

Question 18

what are the 2 journeys of H2O from roots > shoots?

Answer 18

1. Apoplast
2. Symplasy

Question 19

desc APOPLAST (speed, where it flows, regulation etc) (4)

Answer 19

• FAST LANE
• Interconnected cell wall & intercellular spaces b/w cells
• Unregulated & rapid movement
• Continuous meshwork where H2O & solutes can flow w/o having to cross a membrane

Question 20

desc SYMPLAST (speed, where it flows, regulation etc) (4)

Answer 20

• Interconnected cytoplasm via plasmodesmata (membrane lined tunnels that are across adj plant cell walls)
• Slow & regulated movement
• Enable movement of small metabolites, H2O & ions b/w adj cells
• Must cross cell membrane before entering symplast

Question 21

the casparian strip is found w/ in….

Answer 21

WALLS of the ENDODERMAL cells (cells that surround pericycle - layer around vascular bundles)

Question 22

func of the casparian strip: (2)

Answer 22

• HYDROPHOBIC : prevents H2O & ions from moving through it via the APOPLAST
• Forces solutes to enter the CYTOPLASM of the endodermis cells (SYMPLAST PATHWAY) before gaining entry into vascular tissue

Question 23

what does the casparian strip contain for struc support?

Answer 23

LIGNIN

Question 24

the caspatian strip is the plant equivalent to ___ ____

Answer 24

TIGHT JUNCTIONS

Question 25

why is the Endodermis called the "INTERNAL SKIN"?

Answer 25

allows SELECTIVE UPTAKE of solutes, protects the roots from toxic substances

Question 26

what are the 2 types of H2O conducting cells?

Answer 26

1. Tracheids 2. Vessel elements

Question 27

desc Tracheids (2)

Answer 27

- spindle shaped cells w/ cavities ("PITS") in 2ndary cell wall - cell walls stiffened w/ lignin, giving struc support

Question 28

what are the func of PITS w/in TRACHEIDS? (2)

Answer 28

- facilitate H2O & nutrient movement b/w adj cells (to be dispersed throughout the plant) - allow comm & exchange of material b/w adj cells

Question 29

desc vessel elements

Answer 29

- larger in diameter than tracheids - meet end to end, forming a continuous tube like struc - partially brokendown end walls : forms open pipeline for H2O conduction

Question 30

vessel elements & tracheids are both ___ @ maturity & have ___ secondary cell walls composed of ____

Answer 30

1. DEAD 2. THICK 3. LIGNIN

Question 31

what are the 3 features of H2O conducting elements that make them well adapted for transporting H2O?

Answer 31

1. Lignin strengthened walls : prevent them from collapsing under -ve pressure made from H2O transpiration 2. Continuous columns : allows H2O to flow uninterruptedly from roots > leaves 3. Pits (small opening in cell walls) : allows lateral movement of H2O b/w xylem vessels & tracheids & b/w xylem & other cells

Question 32

cohesion is the tendency for ___ ____ of ____ to stick together due to IM forces

Answer 32

SAME TYPE of MOLECULES

Question 33

desc the Transpiration-cohesion-tension mechanism (4)

Answer 33

1. Transpiration : H2O vapour diffuses out of stomata down conc gradient 2. H2O evaporates from surface of mesophyll cells, creating surface tension 3. Increased surface tension pulls H2O out of veins into the apoplast of mesophyll cells (because -ve pressure potential generated) 4. Tension in leaf veins pulls H2O from the stem

Question 34

why is H2O movement in 1 direction only? (3)

Answer 34

1. Because -ve pressure/tension from transpiration draws H2O UP from roots to replace the H2O lost during transpiration 2. Cohesion of H2O molecules maintains a continuous column of H2O w/in xylem, pulling it UP 3. H2O potential gradient : HIGH H2O POTENTIAL (ROOTS) > LOWER H2O POTENTIAL (LEAVES)

Question 35

bulk flow is the ....

Answer 35

movement of a solution from region of high pressure potential > lower pressure potential

Question 36

WHAT ARE THE 2 PHLOEM CELL TYPES?

Answer 36

1. Sieve tube elements 2. Companion cells

Question 37

desc sieve tube elements (4)

Answer 37

1. living cells arranged end-end to create long tubes 2. Retain end walls 3. plasmodesmata connect adj cells 4. lack: nucleus, ribosomes, golgi & cytoplasm (absent cause they flow out of cells via their large pores)

Question 38

desc companion cells (4)

Answer 38

1. surround each sieve tube element 2. Provide metabolites & proteins > sieve tube cells "life support for it" 3. Connected to each other via plasmodesmata, free diffusion b/w cells 4. Performs metabolic func for the sieve cells

Question 39

translocation is the ...

Answer 39

- process that distributes the prod of photosynthesis to other plant tissues Sugar reaches roots by: 1. Travelling via extracellular space & cell walls (apoplast) 2. Through pores that directly connect cytoplasm (symplast)

Question 40

what is phloem sap composed of? (4)

Answer 40

1. sugar 2. a.a 3. hormones 4. minerals

Question 41

phloem sap flows through ___ ____ _____

Answer 41

SIEVE TUBE ELEMENTS

Question 42

What does the mass flow hyp/model provide an explanation for?

Answer 42

how the pressure req for bulk flow is generated