Textbook

Question 1

Stele:

Answer 1

core of vascular stem and root

contains vascular tissues/bundles

Question 2

guttation:

Answer 2

secretion of xylem fluid from hydathodes of leaves (formation of dew drops)

Question 3

source organs:

Answer 3

photosynthetic parts of the plant that synthesize sucrose (eg. leaves, some stems)

Question 4

sink organs:

Answer 4

non photosynthetic parts of the plant that cannot synthesize sucrose and therefore have a demand for sucrose (eg. roots, meristems, flowers, seeds, fruits, tubers, rhizomes)

Question 5

rhizosphere:

Answer 5

zone of influence in the soil surrounding a root

Question 6

hydathodes:

Answer 6

specialized structures on the margin of leaves which are responsible for exudation of xylem fluids during periods of positive xylem pressure. (location of dew excretion)

Question 7

symplast:

Answer 7

continuous network of interconnected plant protoplasts connected by plasmodesmata. (symplastic pathway)

Question 8

sieve plates:

Answer 8

widened plasmodesmata between two sieve element cells which allow movement of solutes and proteins without resistance.

Question 9

p-proteins:

Answer 9

sieve element specific proteins thought to be important in plugging the sieve plates to prevent loss of sugars if the phloem is damaged. synthesized in companion cells and transported to sieve elements for use.

Question 10

two types of cell in the phloem:

Answer 10

sieve elements and their companion cells

Question 11

companion cells:

Answer 11

provide a route of entry of sugars into the sieve elements and provide metabolic functions for the sieve elements (which do not have many sub cellular structures)

Question 12

pressure flow:

Answer 12

process used for movement of sugars in the phloem using a pressure gradient caused by phloem loading in leaves and unloading in sink organs

Question 13

phloem loading:

Answer 13

sugars are loaded into the phloem from the leaf mesophyll cells resulting in a large difference in sucrose concentration between cytosol of the mesophyll cells and the phloem causing osmotic transfer from xylem resulting in high phloem pressure.

Question 14

apoplast:

Answer 14

region outside the plasma membrane consisting mainly of cell walls

Question 15

symplast:

Answer 15

cellular volume bounded by the plasma membrane and connected by plasmodesmata

Question 16

apoplastic phloem loading:

Answer 16

sucrose moves out of mesophyll cells into the apoplast then into companion cells or sieve elements against the concentration gradient using an active sucrose transporter protein.

Question 17

symplastic phloem loading:

Answer 17

sucrose moves via plasmodesmata from mesophyll into companion cells where it is converted to higher molecular weight sugars which cannot reverse back to mesophyll and are therefore required to continue to sieve cells.

Question 18

sucrose-proton co-transporters:

Answer 18

protein responsible for movement of sucrose from the apoplast to the phloem in apoplastic loaders which operate in conjunction with an ATP driven proton pump H+ ATPase

Question 19

transpiration stream:

Answer 19

flow of water through the plant soil>root>xylem>leaves>atmosphere
replaces water lost through stomata and is responsible for maintaining physiological processes.

Question 20

cohesion:

Answer 20

strong mutual attraction between water molecules

Question 21

adhesion:

Answer 21

attraction of water molecules to solid surfaces

Question 22

cohesion-tension theory:

Answer 22

hydraulic explanation for water movement involving water potential, adhesion, and cohesion.

Question 23

apoplastic water movement pathway:

Answer 23

water moves from soil to xylem in apoplast; resistance is present due to the Casparian strip in the endodermis walls

Question 24

Casparian strip:

Answer 24

a band of Suberin which is a hydrophobic material

Question 25

symplastic water movement pathway:

Answer 25

water moves from soil via plasmodesmata into the stele where it moves out of cells into the xylem vessels

Question 26

symplastic and aplastic water movement pathway:

Answer 26

water moves from cell to cell via aquaporins in the plasma membrane; aquaporin gene function is regulated by environmental stimuli

Question 27

root conductivity:

Answer 27

permeability of the root to water; ease with which water can flow from soil to xylem; changes with conditions by using different pathways, (high resistance apoplastic pathway is only used under high shoot demand for water)

Question 28

Nitrate (NO3-)

Answer 28

the main source of nitrogen in the soil for most plants

Question 29

nitrogen fixing bacteria:

Answer 29

form symbiotic relationships with plants like legumes

Question 30

location of nitrate assimilation:

Answer 30

herbaceous plants: primarily leaves trees and shrubs: roots location of assimilation in a single plant is often determined by nitrate availability; nitrate plentiful-leaves nitrate limited-roots

Question 31

nitrate transporters:

Answer 31

facilitate transfer of nitrate from soil to epidermal and cortical root cells

Question 32

elements required for growth (in addition to carbon, hydrogen, oxygen, nitrogen)

Answer 32

13 of them: Macronutrients: potassium, calcium, magnesium, phosphorus, sulfur Micronutrients: chlorine, iron, manganese, boron, zinc, copper, molybdenum, nickel

Question 33

Macronutrients and their functions:

Answer 33

Nitrogen: amino acid, nucleotide, N-containing compound Potassium: osmotic and ionic balance in cells; activator of enzymes in respiration and photosynthesis Calcium: intracellular signal transduction; formation with pectin in cell wall Magnesium: component of chlorophyll; activator of enzymes Phosphorus: ATP and phosphorylation reactions Sulphur: sulphur containing compounds (methionine)

Question 34

meristems:

Answer 34

responsible for development of all plant organs after germination

Question 35

plant development stimuli:

Answer 35

temperature, day length, light, gravity, availability of water and nutrients

Question 36

growth regulators or phytohormones:

Answer 36

small signalling molecules responsible for mediation of response to surroundings

Question 37

dormancy:

Answer 37

an adaptive trait that ensures germination occurs at times and in environments likely to be favourable to plant growth; selected against in crop domestication

Question 38

far-red light

Answer 38

sunlight that has passed through vegetation is rich in far-red light; an indicator of shading for plants

Question 39

germination and dormancy controls:

Answer 39

light, temperature, hydration, niche characteristics (such as heat and smoke of wildfires), host plant signals for parasites,

Question 40

photoreceptor:

Answer 40

convert physical energy of light to chemical energy; perceive light quality, quantity, duration, direction

Question 41

skotomorphogenesis:

Answer 41

developmental pathway of plants grown in the dark

Question 42

etiolation:

Answer 42

occurs when a plant is grown in the dark; embryonic stems become long and spindly, seedling is pale yellow or white due to lack of chloroplast formation, apical hook remains, cotyledons remain unexpanded, shoot apical meristem is inactive

Question 43

photomorphogenesis:

Answer 43

developmental pathway of plants grown in sunlight; short embryonic stems, no apical hook, green expanded cotyledons, leaf and internode development at shoot apical meristem

Question 44

de-etiolation:

Answer 44

process of switching from skotomorphogenesis to photomorphogenesis after emerging from soil and becoming exposed to light

Question 45

phytochrome:

Answer 45

a family of photoreceptors which respond especially to red and far-red light; a developmental switch that is controlled by sensitivities to red and far red light. red induces growth responses and far red inhibits them. ex. lettuce seed germination

Question 46

crypto chromes:

Answer 46

detect and mediate responses to light in the blue and ultraviolet regions

Question 47

phototropins:

Answer 47

responsible for blue light activated phototropism and mediate the photoreceptor of blue light in guard cells controlling the blue light induced opening of stomata

Question 48

chromophore:

Answer 48

attached to an apoprotein to make a phytochrome; captures a light signal and undergoes isomerization causing a conformational change in the protein and a different gene expression

Question 49

apoprotein:

Answer 49

the polypeptide chain attached to the chromophore to constitute a phytochrome

Question 50

PIF3

Answer 50

phytochrome that has been activated by absorption of light in the cytoplasm enters the nucleus and interacts with PIF3 to alter the regulation of gene transcription

Question 51

shade avoidance response:

Answer 51

plants ability to detect shade cast by other plants and to alter growth accordingly by investing more resources into the elongation of stems and less into the expansion of leaves

Question 52

phytochrome B

Answer 52

major phytochrome involved in mediating shade avoidance and end of day responses as inferred from lab tests

Question 53

phototropism:

Answer 53

directional growth of plants toward a light source

Question 54

PHOT1 gene:

Answer 54

encodes the blue light photoreceptor phototropin1 which contains a serine/threonine kinase domain called a LOV domain (Light, Oxygen, Voltage)

Question 55

FMN

Answer 55

flavin mononucleotide; the chromophore attached to LOV to make a phot1 protein

Question 56

chloroplast migration:

Answer 56

chloroplast migrate in response to changes in light intensity, at low light intensities chloroplast distribute to maximize exposure but at high light intensities they position to minimize exposure and thereby photodamage

Question 57

triple response:

Answer 57

response to protect delicate structures such as shoot apical meristem when forcing through soil; hypocotyls become shorter and thicker, roots become shorter and thicker, apical hook becomes exaggerated; triggered by interaction between ABA and ethylene

Question 58

ETR1:

Answer 58

ethylene receptor; etr1 mutants don't exhibit a triple response

Question 59

ethylene receptors:

Answer 59

Negatively regulate: ethylene receptors inhibit ethylene responses until ethylene binds to them at which point inhibition stops and the signalling cascade proceeds unimpeded

Question 60

ETR1

Answer 60

Ethylene triple response 1 gene

Question 61

CTR1

Answer 61

Constitutive triple response 1 gene; a kinase

Question 62

Kinase

Answer 62

enzyme that catalyzes transfer of a phosphate group from ATP to another molecule

Question 63

EIN2

Answer 63

integral membrane protein; downstream of CTR1 in the signal transduction pathway of ethylene

Question 64

EIN3

Answer 64

regulator of ethylene response; transcription factor that binds to the promoter region of ethylene-inducible genes in the presence of ethylene

Question 65

ABA

Answer 65

abscisic acid; represses germination

Question 66

embryo dormancy:

Answer 66

independent from seed dormancy, controlled by growth regulators (phytohormones) GA and ABA which act antagonistically

Question 67

GA

Answer 67

gibberellin; initiates germination

Question 68

radicle

Answer 68

embryonic root

Question 69

testa

Answer 69

seed coat

Question 70

water deficit:

Answer 70

occurs as a result of drought, salinity, freezing temperatures