Co-evolution: flowers & pollinators

How a bee sees a flower…insects see UV light = a bulls-eye to the nectar

Angiosperm: fruiting plants

Other fruits…

Seed & Plant embryo

• Seed offers…• protection for embryo

(new plant)• stored nutrients for

growth of new plant

seed coat

food for new plant

seed leaves

embryo(new plant)

Cotyledon (“seed” leaves) = first leaves of new plantCotyledon (“seed” leaves) = first leaves of new plant

Seed dispersal

• 4 types• Wind• Water• Animal• Explosive

Plant Hormones (how plant cells talk)• Hormone = chemical messages between cells;

regulate cellular processes• Formation of flowers, stems, leaves• Shedding of leaves• Formation/ripening of fruit• Growth – up or down• Sex of flower• Plant length of life; death

Plant hormone groups• Auxins

• Growth direction• Flower formation• Fruit set and growth• Formation of adventitious

roots (fibrous)

• Gibberellins• Stimulate cell division• Break seed dormancy; speed

germination

Plant hormone groups• Cytokins

• Aging and senescence (death)• Used to delay these processes

• Ethylene• Gaseous form only• Induces fruit ripening• Cause leaves to droop (epinasty)

and drop (abscission)• Produced in response to stress• Promotes senescence

Tropism • Directional movement responses that occur in response to a directional stimulus

• Phototropism = response to light• Thigmotropism = response to touch• Hydrotropism = response to water• Gravitropism/geotropism = response to gravity• Chemotropism = response to chemicals

• Tropisms can be positive or negative

• Positive = towards stimulus

• Negative = away from stimulus

Positive: with gravity

Negative: against gravity

Nastic Movement• Plant movement that occurs

in response to environment• Not dependent on the

direction of the stimulus

• Examples: Venus fly trap, mimosa leaf

Nastic movement VIDEO