herbivory and medicinal plants

Question 1

how do plants protect themselves

Answer 1

1) mechanical protection on the surface
2) reduction in digestibility
3) phytotoxins

Question 2

give an example of mechanical protection seen in plants

Answer 2

1) spines e.g. cacti or thistles
2) thorns e.g. brambles or roses
both deter large animals

Question 3

what are trichomes and what sort of animals do they deter

Answer 3

a form of mechanical protection, they are small hairs which deter smaller animals such as insects

Question 4

how does the stinging nettle (urtica dioca) mechanically protect itself

Answer 4

has sharp, stinging hairs which release substances into the skin causing irritation

Question 5

give some examples of dosage dependant (need alot to show affect) substances which reduce digestability

Answer 5

1) cellulose
2) pectin
3) ligins
4) cutins and waxes
5) tannins
6) silica

Question 6

what are phytotoxins

Answer 6

secondary metabolites which exhibit qualitative effects (only a small amount is needed)

Question 7

what is secondary metabolism

Answer 7

when compounds formed in primary metabolism such as the formation of lipids, amino acids etc from carbon/nitorgen assimilation are used to form new compounds in the plant

Question 8

what do lipids form after secondary metabolism

Answer 8

1) steroids
2) terpenoids

Question 9

what do amino acids produce after secondary metabolism

Answer 9

1) alkaloids
2) nitroaliphatics
3) cyanogenic compounds

Question 10

what are some nitogen based phytotoxins

Answer 10

1) cyanogenic glycosides
2) glucosinolates
3) alkaloids
4) proteins

Question 11

what are some non nitrogen based phytotoxins

Answer 11

1) iridoids = intermediate in the synthesis of alkaloids
2) terpenoids
3) saponins
4)isoflavonoids

Question 12

give an example of some plant toxins

Answer 12

1) nicotine - alkaloid
2) strychnine - alkaloid
3) cyanogenic glycosides

Question 13

outline the use of phytotoxins in milkweeds, omarch butterflies and bluejays to aid protetcion

Answer 13

1) milk weed produces several cardiac glycoisdes which are very toxic
2) monarch catepillars ingest the milkweed tissue therefore sequestering the toxin within their own tissue
3) this toxin survives into the adult butterfly stage
4) which when eaten by blue jays exhibits its effect so blue jays learn to avoid butterflies

Question 14

outline how ragworts and the cinnabar moth use phytotoxins to avoid ingestion or damage

Answer 14

1) ragworts contain phytotoxin pyrrolisidine alkaloids
2) cinnabar moths are resistant to this phytotoxin so ingest ragworts and sequester toxin into their own tissues for protection

Question 15

what are the different theories as to why animals eat some plants but not others

Answer 15

1) classical plant defence theory = ehrilich and raven
2) the plant apparency theory= feeny
3) resource availability theory

Question 16

outline the plant apparency (likelihood of being found by a herbivore) theory

Answer 16

long lived, late successional plants are more apparent (easy to find) so must employ more generalist stratergies so use quantitative methods such as increased lignin, cellulose, tannins
compared to short lived plants which are not as east to find, therefore use more specalist stratergies = qualitative methods

Question 17

what compound does clover or members of the pea family make

Answer 17

hydrogen cyanide

Question 18

how does clover and members of the pea family make hydrogen cyanide

Answer 18

1) within the leaves there is a secondary metabolite (cyanogenic glycoside) which contains a triple bond which is energentically expensive
2) in a seperate compartment of the leaf is the enzyme glucosidase
3) when something eats the leaf the enzyme and compound react producing an unstable product which breaks down forming a ketone and hydrogen cyanide

Question 19

what are the two genes which control if clover or members of the pea family produce hydorgen cyanide

Answer 19

1) G = synthesis of the secondary metabolite cyanogenic glucoside

2) E= synthesis of the enzyme glucosidase
only when both genes are dominant (GE) will the plant produce hydrogen cyanide

Question 20

what is meant by doctrine of signatures

Answer 20

the old philosophy that herbs which resemble various parts of the body can be used to treat ailments of that part of the body

Question 21

give some examples of plant based medicines which can be brought over the counter

Answer 21

1) rubiaceae = cough mixture
2) cassia = laxatives
3) eucalyptus = inhalers
4) papayer and salix = pain killers

Question 22

give some examples of powerful drugs extracted directly from plants

Answer 22

1) atropine = pupil dilation
2) morphine = pain killer
3) quinine= antimalarial
4) vincristine = antitumour

Question 23

outline how vincristine and vinblastine are used in medicenes

Answer 23

plants native to madagascar with powerful anti-cancer properties
1) vinblastine = used to increase survival in childhood leukaemia from 10-95%
2)vincristine used to treat hodgkins disease

Question 24

what are some stratergies for surveying plant world for mediciens

Answer 24

1) screen everything
2) systematic approach
3) ethnopharmacological approach based on ethnobotany

Question 25

what is ethnopharmacy

Answer 25

an interdisciplinary science which investigates the perception and use of pharmaceuticals within a human society

Question 26

evaluate the approach of screening everything to explore plant medicene

Answer 26

= nearly impossible
= expensive

Question 27

outline the systematic approach

Answer 27

based on phytochemistru where certain types of chemicals can only be found in certain plants