Lecture 5

Question 1

Transpiration stream

Answer 1

flow of water through plant due to loss of water from leaves drawing water from soil into roots

Question 2

ratio of water loss per CO2 fixed during photosynthesis

Answer 2

700-1300 mols of H2O per mole of CO2

Question 3

what is the main driving force for transpiration stream

Answer 3

evaporative water loss from leaves; cohesion-tension

Question 4

cohesion

Answer 4

attraction between water molecules

Question 5

adhesion

Answer 5

attraction of water to xylem to form a strong column of water

Question 6

how is water lost from plant

Answer 6

majority through stomata, some lost at night through epidermal cells and cuticle

Question 7

what physiological processes require transpiration stream?

Answer 7

turgor pressure
cytoplasmic solute concentrations
transport of nutrients
transport of phytohormones
phloem loading 
evaporative cooling

Question 8

apoplastic water movement in the root

Answer 8

transpiration rate is high

Question 9

symplastic water movement in the root

Answer 9

transpiration rate is low

Question 10

casparian strip

Answer 10

controls ion movement into the xylem; located in endodermis apoplastic pathway;

Question 11

aquaporins

Answer 11

transmembrane protein water channels

Question 12

purpose of the casparian strip

Answer 12

forces water moving in root apoplast to cross the plasma membrane which filters the water allowing plant to control what enters the inner root and what accesses the xylem

Question 13

phloem

Answer 13

composed of sieve elements and companion cells; moves sugars and other molecules from source to sink

Question 14

sieve elements

Answer 14

stacked into long vessels
sieve plates between elements
nucleus and vacuole lost
few and small ribosomes, chloroplast, er, golgi

Question 15

companion cells

Answer 15

contain all sub cellular structures
provide sieve elements with physiological functions and products such as proteins
large plasmodesmata between sieve element and companion cells

Question 16

pressure flow

Answer 16

process by which sugars move into sieve elements

Question 17

source of sucrose loading from mesophyll cells into phloem

Answer 17

small veins in leaves

Question 18

apoplastic phloem loading

Answer 18

sucrose moved to CC by energy consuming sucrose transporter in plasma membrane causing high SE sugar concentration resulting in water moving into SE from near xylem down water concentration gradient creating high phloem pressure

Question 19

SWEETs

Answer 19

sugar efflux transporters transport sucrose from mesophyll to CC apoplastically

Question 20

symplastic phloem loading

Answer 20

sucrose moves through plasmodesmata from mesophyll to CC where it is converted to larger raffinose which moves into SE via larger plasmodesmata

Question 21

indicator of apoplastic phloem loading pathway:

Answer 21

invaginated plasma membrane to increase surface area form transporter proteins and lacking plasmodesmata between mesophyll and CC

Question 22

evidence of symplastic vs apoplastic loaders

Answer 22

symplastic: transport larger sugars and have lots of mesophyll-CC plasmodesmata
apoplastic: transport sucrose - invaginated cell walls/plasma membrane in CCs to facilitate active transport of sugars

Question 23

tobacco example:

Answer 23

transgenic tobacco with yeast gene encoding invertase enzyme in cell wall which breaks down sucrose.

if symplastic sucrose will be found in CC because it never enters cell wall

if apoplasitc no sucrose in CC because broken down by invertase while travelling through cell wall

Result: transgenic tobacco reduced growth therefore apoplastic loader

Question 24

macronutrients

Answer 24

nitrogen, potassium, calcium, magnesium, phosphorus, sulfur

Question 25

function of nitrogen

Answer 25

amino acid, nucleotides, other n containing compounds

Question 26

function of potassium

Answer 26

osmotic and ionic balance, activator of enzymes in respiration and photosynthesis

Question 27

function of calcium

Answer 27

intracellular signal transduction, forms a complex with pectin in cell walls

Question 28

function of magnesium

Answer 28

component of chlorophyll, activator of enzymes

Question 29

function of phosphorus

Answer 29

atp and phosphorylation reactions

Question 30

function of sulphur

Answer 30

sulphur containing compounds such as methionine

Question 31

Nitrogen assimilation

Answer 31

plants need reduced forms of N like NH3; plant uptakes nitrate which is reduced in root cells or transported to leaves to be reduced

Question 32

bacterial symbiosis of legumes

Answer 32

symbiotic relationship with bacteria to fix nitrates into NH3; plant provides protected home and food sources, bacteria provides NH3

Question 33

legumes

Answer 33

beans, chickpeas, peas, honey locust tree

Question 34

legume nodule

Answer 34

home for bacteria on roots, looks like a bump

Question 35

methods of obtaining phosphate

Answer 35

high affinity transporters in root plasma membrane

symbiotic relationship with mycorrhizal fungi

Question 36

what do fertilizers provide?

Answer 36

N, P, K,

Ca, S, Mg,

B, Cl, Mn, Fe, Zn, Cu, Mo, Se,

Question 37

p deficiency

Answer 37

stunted growth

Question 38

k deficiency

Answer 38

dead edges of leaves

Question 39

n deficiency

Answer 39

pale colour

Question 40

mg deficiency

Answer 40

necrosis between veins in leaf

Question 41

stele

Answer 41

core of root containing vascular tissue

Question 42

fast root absorption method

Answer 42

symplastic

Question 43

slow root absorption method

Answer 43

apoplastic

Question 44

What are the three basic steps of water moving through a plant from soil to atmosphere?

Answer 44

1. water uptake in roots
2. transport in the xylem
3. transport through the leaf and into the air

Question 45

p-protein

Answer 45

when plant is wounded, p-proteins are produced to block sieve plates to prevent sugar loss—similar to blood clots