Chapter  5  Plant  Life  Cycle:  

Flowers  

Lecture  Outline  Structure  of  a  flower  Alterna(on  of  genera(ons,  the  plant  life  cycle  •  Gametophyte  and  sporophyte  defined  Meiosis  –  cell  division  that  halves  the  #  of  chromosomes  Double  fer(liza(on  in  flowering  plants  Flowers,  fruits  and  seeds  movie  Pollina(on  -­‐  wind-­‐  and  animal-­‐pollinated  plants    

Tradescan(a  ohiensis    

The  evolu?onary  success  of  the  angiosperms  is  due  in  large  part  to  

flowers  and  fruits  

basal    angiosperms   monocots   eudicots  

Vegeta?ve  Body  

Reproduc;ve  Body  

Root  

Shoot  

Stamen Anther

Filament

Petal

Receptacle

Stigma Style

Ovary

Carpel

Sepal

Structure of an idealized flower

Monocot  Characteris;cs  

Eudicot  Characteris;cs  

Vascular  ;ssue  usually  arranged  

in  ring  

Veins  usually  parallel  

Vascular  ;ssue  scaBered  

Leaf  vena;on  

One  cotyledon  

Embryos  

Two  cotyledons  

Stems  

Veins  usually  netlike  

Roots  

Pollen  

Root  system  usually  fibrous  (no  main  root)  

Pollen  grain  with  three  openings  

Pollen  grain  with  one  opening  

Floral  organs  usually  in  

mul;ples  of  three  

Flowers  

Floral  organs  usually  in  mul;ples  of    four  or  five  

Monocot  Characteris;cs  

Eudicot  Characteris;cs  

Taproot  (main  root)  usually  present  

pollen  contains  the  sperm  (male  gamete)  

the  ovule  contains  the  egg  (female  gamete)  

A  flower  that  has  both  stamens  and  carpels  is  called  perfect.  

Painted  trillium,  Trillium  undulatum    

A  flower  that  is  lacking  either  stamens  or  carpels  is  imperfect.  

Begonia  staminate  (male)   carpellate  (female)  

Water  lily:  symmetry  is  radial    

Radial symmetry

orchid:  symmetry    is  bilateral  

Bilateral Symmetry

Key

Haploid (n)

Diploid (2n)

Gametes (eggs, sperm)

n

n

n

2n 2n Zygote

MEIOSIS FERTILIZATION

Mitosis

Diploid multicellular organism

The  life  cycle  of  an  animal  (like  humans)  

•  gametophyte  =  the  mul?cellular  haploid  form  that  produces  haploid  gametes  by  mitosis  

•  sporophyte  =  the  mul?cellular  diploid  form  that  results  from  the  union  of  gametes  and  produces  spores  by  meiosis  

Alterna(on  of  genera(ons,  the  plant  life  cycle  

Fig  5.6  

Meiosis  is  special  type  of  cell  division  that  results  halving  the  number  of  chromosomes.  

MEIOSIS FERTILIZATION

Diploid  2n  

Haploid  n  

diploid  (2n)  à  haploid  (n)    

Mitosis  occurs  in  meristems  

Meiosis  occurs  in  sexual  organs  

Pollina(on  –  the  transfer  of  pollen  from  an  anther  to  a  s?gma  

Moth  pollina?ng  flower   Bumblebee  pollina?ng  goldenrod  

Who  are  the  major  animal  pollinators?  

insects  birds  

bats  

Stigma

Pollen tube

2 3 1

2 sperm Style Ovary Ovule

Pollen grain

Polar nuclei Egg

Ovule Polar nuclei

Egg

2 sperm

Endosperm

Zygote (2n)

Double  fer?liza?on  

Hazel staminate flowers (stamens only)

Hazel carpellate flower (carpels only)

Wind-­‐pollinated  plants  usually  have  small,  inconspicuous  flowers  &  produce  abundant  pollen  

Corylus  species  

Common dandelion under normal light

Common dandelion under ultraviolet light

Animal-­‐pollinated  plants  usually  have  large,  showy  flowers  

with  rewards  

Pollinator  rewards  

pollen  Resin-­‐gathering  bee  

1.  Pollen  (protein  and  lipids)  2.  Nectar  (water,  sugar,  amino  acids)  3.  Oils  (lipids,  an?-­‐fungal  agent)  

Hummingbird  sipping    nectar  

Importance  of  pollina;on  

Necessary  for  food  produc?on!  •   Almonds  •   Apples  •   Blueberries  •   Cucumbers  •   Squash  •   Melons  •   Strawberries  •   Apricots    •   Pears  •   Plums    •   Some  citrus  (tangerines,  lemons)  •   Honey  

Lecture  Review,  Chapter  5  •  Iden?fy  and  describe  the  func?on  of  the  following  floral  structures:  

sepals,  petals,  stamens,  carpel,  filament,  anther,  s?gma,  style,  ovary,  and  ovule.  

•  Compare  and  contrast  the  life  cycles  of  animals  and  plants.  •  Diagram  the  generalized  life  cycle  of  an  angiosperm;  indicate  which  

structures  are  part  of  the  gametophyte  genera?on  and  which  are  part  of  the  sporophyte  genera?on  

•  What  cell  division  process  occurs  in  the  sporophyte?    What  does  it  produce?  

•  What  cell  division  process  occurs  in  the  gametophyte?    What  does  it  produce?    

•  What  is  pollina?on?    Is  pollina?on  the  same  as  fer?liza?on?    Provide  examples  of  pollinator  rewards  in  animal-­‐pollinated  plants.  

•  What  is  double  fer?liza?on?  Why  is  double  fer?liza?on  advantageous  to  the  plant?