Ch 24- Reproduction of Seed Plants
• Life Cycle of Gymnosperms
– Reproduction takes place in cones- produced by
mature sporophyte plant
• 2 types of cones- pollen cones and seed cones
– Pollen- male
– Seed- female
– Ovules- base of seed cone where female
gametophytes develop
• Pollen tube- structure that contains 2 haploid
sperm nuclei, one sperm disintegrates and other
fertilizes egg
Structure of Flowers
• Flowers are reproductive organs- composed of sepals, petals, stamens,
and carpels
• Sepals- outermost circle of flower parts, encloses bud, protects the flower
while it is developing
• Petals- brightly colored structure just inside the sepals, attracts insects
and other pollinators
• Stamen- male part of flower, made up of anther and filament
• Filament-long, thin structure that supports an anther
• Anther- flower structure where haploid male gametophytes are produced
• Carpels- innermost part of flower that produces female gametophyte
• Ovary- contains ovules from which female gametophytes are produced
• Style- narrow stalk of the carpel in flower
• Stigma- sticky portion at top of style where pollen grains land
Life Cycle of Angiosperms
• Reproduction takes place within flower- the
seeds develop inside protective structures
following pollination and fertilization
• Most gymnosperms and some gymnosperms are
wind pollinated
• Most angiosperms are pollinated by animals
• Fertilization in angiosperms
– One sperm fuses with egg to form zygote
– Second sperm fuses with two polar nuclei to form
endosperm- food rich tissue that nourishes the seed
– Double fertilization
Sec 2- Seed Development/Germination
• What is a fruit?
– Ripened ovary that contains angiosperm seeds,
any seed that is enclosed within its embryo wall
– As angiosperm seeds mature, ovary walls thicken
to form fruit
– Apples, grapes, strawberries
– Peas, corn, rice
• How are seeds dispersed?
– By animals, wind, water
• What type of seeds are dispersed by animals? By wind
and water?
• What factors influence dormancy and germination?
– Temperature and moisture
• Dormancy- period where plant is alive but not growing
– Varies between plants
• Germination- early growth stage of plant embryo
– Seed absorbs water causing it to swell and crack open