Lecture 9 Success Of Flowering Plants

Question 1

Vegetative and apomictic plant reproduction

Answer 1

Rhizomes- underground stems e.g. bamboo
Bulbs - daffodil
Plantlets - form on edge of leaf e.g. Kalanchoe
Stolons - aka runners e.g. strawberries
Apomixis - asexual production of seeds e.g. dandelions

Question 2

Wind pollination/ self pollination

Answer 2

E.g. wheat selectively bred to self pollinate before anthers emerge to avoid alternate pollination

Question 3

Interactions w/pollinators

Answer 3

Colour/scent/ food reward

Insects see in UV so some colour patterns aren’t visible to human eye
Insects consume nectar and some eat pollen - plants create excess to accommodate this

Nectar guide on foxglove - spots show bee the way, nectary behind anthers so bee collects pollen on its body while harvesting nectar

Also scent particularly to attract night pollinators may be specific e.g. corpse flower attracts flies with smell of rotting meat

Question 4

Plant/pollinator coevolution

Answer 4

Darwin’s orchid - 30cm nectary behind flower that only Darwin’s hawkmoth with extra long proboscis can reach. This specific relationship prevents irrelevant pollen from reaching stigma but makes plant/pollinator deeply interependent

Question 5

Orchids - ospyrys bee orchid

Answer 5

Stick a clump of pollen on top of visiting insects head.

Bee orchid (ospyrys) flowers mimick female bee so that males attempt to mate with them and spread pollen - previously male bees emerged before females - global warming is changing this so less bees are pollinating the flowers causing decline

Question 6

Promoting outcrossing - In Mimulus aurantiacus

Answer 6

In Mimulus aurantiacus while stigma is open anthers are blocked and unreachable to insects
Once pollinated by hummingbird the pollen on stigma causes lobe to retract creating path to anthers allowing pollen dispersal by subsequent hummingbirds

(Self pollination prevented)

Question 7

Promoting outcrossing: heterostyly

Answer 7

E.g. primula vulgaris
Pin and thrum flower forms are self-incompatible. Both have anthers and stigma. In pin the stigma is at the front and in thrum anthers are at the front. This causes cross pollination between flower types to be favoured

Question 8

Proteins outcrossing: genetic self incompatibility

Answer 8

When pollen grain lands on stigma germination or pollen tubule growth is inhibited due to allele incompatibility

Question 9

Fruit protects and aids seed dispersal

Answer 9

Ovary wall becomes fruit
Acorn is a fruit
Runner bean - fruit is bean pod and beans are the seeds
Humans selectively breed fruit to be larger

Aggregate fruit: e.g. blackberry each carpel is one ‘bobble’ of the fruit

Strawberry - not a fruit but a swollen carpal

Corn kernel has a thin fruit layer surrounding the seed w/embryo

Question 10

Physical defence

Answer 10

Magnolia grandiflora have tough tepals as they are fertilised by a heavy jawed beetle that may chew the flower

Spines protect solanum pyrocanthum

Rubber used by Hevea brasiliensis to seal injury and protect from insect damage/ infection

Amber traps insects - solidified tree sap

Question 11

Stinging nettle

Answer 11

Urtica dioica has two types of epidermal protection:

Simple non-stinging trichomes - structurally complex stinging hairs

Stinging cell loaded with irritants such as formic acid, serotonin, acetylcholine and histamine break of easily on contact

Shoots which regenerate after grazing have more stinging cells

Question 12

How insects make use of plants

Answer 12

Devonian - early forms detrivory
Carboniferous - pteridophytes - leaf piercing, eating and gall forming
Triassic - leaf mining
Present - angio/gymnosperms - pollen and nectar consumption

Question 13

Chemical defence against insects/ animals

Answer 13

Alkaloids- neonic pesticides derived from :

Tobacco: nicotine is an alkaloid that acts as neurotoxin inhibiting insect nervous system - considered an early pesticide - unsuitable as it kills bees

Herbs such as mint have volatile scents/ flavours that contain protective alkaloids

Angelica sylvestris and asafoetida contain ambelifrome that blocks cell division in insects - also present in fennel, cumin and corriander

Plants produce pyrethrins - insecticides that can be used in lice shampoo

Induced defences - jasmonate

Primula farinosa (Birdseye primrose) produces a floury substance called farina on its leaves and stems which is an irritant and reduces predation

Question 14

Induced defence: jasmonate

Answer 14

Attacks insect w/protease inhibitors

1) perception of tissue damage causes formation and release of elicitator
2) elicitator binds to receptor on phloem companion cell
3) receptor activation causes hydrolysis of membrane lipid forming jasmonate
4) jasmonate passes through plasmodesmata from companion cell to phloem sieve cells
5) jasmonate from sieve tube phloem enters mesophyll in damaged shoots
6) jasmonate binds to JAZ inhibitor releasing transcription factor
7) transcription factor enters nucleus causing expression of gene that codes protein inhibitor

Question 15

Some insects utilise plant chemical defences

Answer 15

E.g. monarch caterpillars consume toxic milkweed storing the toxins in their flesh which makes predators sick so they avoid consuming them

Question 16

Why angiosperms grow faster

Answer 16

Smaller genomes = smaller cells with more space for veins and stomata