Ecosystems - UV Radiation on Plants

Question 1

What forms in winter at Antarctica?

Answer 1

Polar vortex

Question 2

Polar Vortex

Answer 2

This is a high pressure system trapping within cold air, at extremely cold temperatures isolated from external warm air.

Question 3

What degrades ozone?

Answer 3

CFC’s and Halons

Question 4

Photosynthetically Active Radiation

Answer 4

This is the EM spectrum range of which light can be assimilated

Question 5

What determines the PAR?

Answer 5

The properties of the two pigments Cpa and Cpb in chloroplasts

Question 6

UV-A

Answer 6

This is 315-400nm, being lowest energy and least harmful

Question 7

UV-B

Answer 7

This is 280-315nm being most associated with skin damage like cancer and sunburn, absorbed primarily by O3.

Question 8

UV-C

Answer 8

100-280nm being the most harmfu however all absorbed in the atmosphere

Question 9

Photoabsorption

Answer 9

This is transfer of all the energy of a photon to an atom or molecule resulting in excition or ionization.

Question 10

Franck-Condon Principle

Answer 10

This explains vibronic transitions stating electronic transistions is most likely if the two vibrational wave functions overlap more significantly

Question 11

Vibronic Transistions

Answer 11

These are simultaneous changes in electronic and vibrational energy levels of a molecule due to absorption/emission of a photon at approporaite energies

Question 12

What molecules primarily facilitate photoabsorption?

Answer 12

O2 and O3 due to the FC principle.

Question 13

What does the FC principle explain?

Answer 13

The relaxation of an excited energy state to the ground state.

Question 14

What is the absorption coefficent of ozone?

Answer 14

240nm

Question 15

What is absorption coefficient determined by?

Answer 15

Geometry and electronic structure, that being V shape creating a dipole moment.

Question 16

When do electronic interactions occur?

Answer 16

When photon interacts with ozone electrons exciting to higher states, the coefficient thus depending on different in energy level.

Question 17

What does UVB interact with?

Answer 17

O2, O3 and H2O

Question 18

How does UVB interact with O3?

Answer 18

Produces O2 and O

Question 19

How does UVB affect human health?

Answer 19

Generate cyclobutane pyrimidine dimers in skin cells resulting in oxidative stress and biomolecular damage

Question 20

Photosensitiziation

Answer 20

This is the increased susceptibility of skin to damage caused by UV light

Question 21

When might photosensitization occur?

Answer 21

When chromophores in the skin absorb UVB generate excited states that react with skin O2

Question 22

What does CPD generation derive from?

Answer 22

Pyrimidine bases in DNA photochemistry, between two adjacent pyrimidine bases

Question 23

What repiar systems in plants act on CPD?

Answer 23

NER pahway and Photoreactivation pathway

Question 24

Photoreactivation Pathway

Answer 24

This is a repair pathway with enzymatic reversal of dimerizied pyrimidines in a DNA strand.

Question 25

How quick does PR pathway repair?

Answer 25

6 hours

Question 26

What is the most negative affect of UVB exposure in plants?

Answer 26

Aromatic amino acid damage like tyrosine, tryptophan and phenylalanine

Question 27

How are aromatic AA affected?

Answer 27

ROS species generation, tryptophan forming 6-formylindolo [3,2-b] carbazole regulating plant growth and development

Question 28

What is DNA repair driven by in plants?

Answer 28

UV-A wavelengths?

Question 29

How does UVA drive DNA repair?

Answer 29

Due to the requirement of photolyases

Question 30

Photolyases

Answer 30

These are enzymes repairing pyrimidine dimers by use of light energy to break covalent bonds between the damaged bases, activated at 320-380nm, effective at CPD repair.

Question 31

How do photolyases work?

Answer 31

Contains two chromophores at active site, absorbing photons when binding the pyrimidine dimer in its active site

Question 32

How does reduced growth in plants occur bt UVB?

Answer 32

ROS generation and signal pathway disruption

Question 33

How are Gibberellins affected in plants by UVB?

Answer 33

Reduced by UVB radiation

Question 34

Auxin

Answer 34

This functionally activates enzymes involved in many metabolic pathways and ion channels in mutrient/water uptake/release

Question 35

What morphological changes occur due to UVB radiation?

Answer 35

Cotyledon Expansion
Hypocotyl lenght
Leaf and rosette size
Stomatal aperture
Root/shoot branching

Question 36

Phenolic Compounds

Answer 36

These are a group of small molecules characterised by having at least one aromatic ring with one or more hydroxyl groups.

Question 37

How is stomatal cllosure stimulated by UVB?

Answer 37

ROS generation activating K ion efflux channels decreasing interior turgor causing shrinking

Question 38

How does UV relate to phenolic compounds?

Answer 38

Induce pathways involved in its synthesis like MYB12 TF activation regulate phenolic compound gene expression

Question 39

Why are phenolic compounds important?

Answer 39

Predation defence and pollinator attraction and UV protection

Question 40

What is the synthesis pathway of Phenolic Compounds?

Answer 40

Precuros is phenylalanine converted to trans-cinnamic acid by lyases, then to flavonoids, anthocyanines or lignin

Question 41

Why is phenolic ocmpound accumulation important?

Answer 41

Influences interactions with herbivores due to build up of plant defences.