Transcript Chapter 31.1

Reproductive Structures of
Flowering Plants
AP Biology
Spring 2011
 Flowers
form on a modified branch of the
sporophyte when master genes in the
apical meristem are turned on
 Flower
parts are arranged in whorls of
modified leaves on the end of the
receptacle
 Sepals:
outermost green, leaf-like parts
arranged in a ring called the calyx
 Petals: the coloured parts located
between the reproductive structures and
the sepals, arranged in a ring called the
corolla
 Stamens:
male parts, slender stalk
(filament) capped with an anther, inside
which pollen sacs enclose pollen grains
 Carpels: female parts, vessel shaped
structures with an expanded lower ovary
(with ovules), slender column (style),
and an upper surface (stigma) for pollen
landing
 Meiosis
of cells within flowers produces
haploid spores
• Microspores in the anther
• Megaspore in the ovule
 They
then undergo mitosis to produce
the haploid gametophytes that
ultimately become the egg or sperm
 The
egg and
the sperm
fuse to form
the diploid
zygote
 As the zygote
develops into
a plant, the
seed is
formed
 Complete
flowers: have all four whorls
(sepals, petals, stamens, and carpels)
 Incomplete flowers: are missing one or
more whorls
 Perfect
flowers: have both stamens and
carpel (both sexes on one flower)
 Imperfect flowers: produce either
stamens or carpels and are known as
either “male” or “female” flowers