AN INTRODUCTION
TO ANGIOSPERMS:
THE FLOWERING
SEED PLANTS
Biology 11
Seed Plants
Vascular
Angiosperms- Flowering Plants
•Phylum Angiosperma
•The majority of plants alive today and
the most diverse group
Characteristics
• Vascular plants with stems, roots, leaves
• Dominant generation= sporophyte
• Flower =specialized structure for sexual
reproduction
• Pollen (dispersed by wind and insects)
• Seeds are within the fruit
•Angiosperm means “vessel seed”
Advantages for seeds being enclosed in
fruits
1. Protection
2. Seed dispersal
•Fruits (and seeds) are eaten by other
organisms or attach (barbs) to other
organisms for dispersal
3. Fruit decomposes and becomes nutrients
for growing plant
Why are angiosperms more successful
than gymnosperms in a land environment?
• Angiosperm seeds are better protected
• Angiosperms can go from seed to seed in less
than one year as opposed to the years this may
take in gymnosperms
• The xylem cells in angiosperms are more
efficient than in gymnosperms
• Pollination is more successful
• Can cross fertilize
• Use insects to fertilize (more effective and direct)
Grouping Angiosperms
There are many different ways to categorize angiosperms:
• Woody and herbaceous plants
• Annuals (lives for a year), biennials (lives
for two years), perennials (lives longer
than two years)
• Monocots and dicots
Two subclasses: Monocots and Dicots
•Named for the number of seed leaves
(cotyledons) in the plant embryo
•Angiosperm with 1 cotyledon = monocot
•Angiosperm with 2 cotyledons = dicot
Angiosperm: Monocot
• Seeds:
• Embryo with single cotyledon
• Flowers:
• Flower parts in multiples of three
• Leaves:
• Linear; Major leaf veins are parallel
• Vascular System of Stem:
• Stem vascular bundles scattered
• Vascular System of Roots:
• Xylem and phloem alternate with one another in a
circle
Examples:
Grass, palms, bamboo, lilies, orchids
Angiosperm: Dicot
• Seeds:
• Embryo with two cotyledons
• Flowers:
• Flower parts in multiples of four or five
• Leaves:
• Broad; Major leaf veins are netlike
• Vascular System of Stem:
• Stem vascular bundled in a ring
• Vascular System of Roots:
• Xylem arranged in X in middle of root, phloem in between
arms of X
Examples:
Woody plants, shrubs, trees (excluding conifers),
cacti
Angiosperms
REPRODUCTION
•Angiosperm seeds are contained within
protective wall that develops into a fruit
•Pollination brings pollen to the ovary
which develops into a seed
Structure of Flower
Pistil (♀)
Stigma
Style
Ovary
Ovule
Anther
(♂)
Stamen
Filament
Petal
Sepal
Stem (receptacle)
Sepals
•Outermost circle of flower
parts
•Enclose flower bud before it
opens and protects the flower
while it develops
•Some flowers it is green, in
others it’s the same colour as
the petals
•All sepals together called the
calyx
Petals
•Make up the second circle of flower
parts
•Often brightly coloured
•All petals together form the corolla
Pistil
•Female part of the flower (inner
most)
•Made of 3 parts:
1. Stigma
2. Style
3. ovary
Stigma
•Stigma- surface upon which pollen is
deposited by wind or animals
•Often sticky
Style
•Stalk that connects the stigma and
ovary
Ovary
•Contains the ovules which (when
fertilized) becomes the seed
Stamen
•Male part of the flower
•Made up of 2 parts:
1. Anther- makes and releases pollen
2. Filament- holds up the anther
Sexual Reproduction
• Within the ovary you will find ovules.
• The ovules contain a mother cell (2N).
Through meiosis will produce haploid
megaspores (1N).
• Three of the four megaspores die.
• 1 remaining megaspore, through mitosis
produces egg cell and two polar nuclei
(found in central cell)
Sexual Reproduction
•
•
•
Within anther are 4 pollen sacs
Mother cells undergo meiosis to produce haploid
microspores (N)
Microspore divide by mitosis to produce pollen
grains (produced in large numbers)
Sexual Reproduction- Pollination
• Pollination- The transfer of pollen grains from the
anther to the stigma
Wind-pollinated Plants
• Pollen grains fall and carried by wind
• Flowers are small and plain with little fragrance
Bee-pollinated
• Don’t see red
• See yellow, blue, green and UV light best
• Some flowers have UV markings only bees can
see
• UV colors and patterns in petals announce the
flower’s nectar and pollen
Bird Pollination
•Birds often pollinate red flowers
•Animal pollinators have coevolved with
plants
Hammer Orchid
Fertilization
• Once pollination has taken place a pollen tube will
germinate on the stigma
• The pollen tube grows down the style and enters
the tip of the ovule through the micropyle
• Male gametes move through pollen tube towards
the egg cell
Double Fertilization
• One sperm cell fuses with egg (fertilization) and
results in the formation of a diploid zygote
• A second sperm fuses with two polar nuclei which
results in a triploid (3N) endosperm
• The endosperm provides nutrients (starch) and
surrounds the developing embryo
Fruits
• After fertilization occurs the ovary walls develop
into a fruit
• The fruit protects the seeds from desiccation and
assists in their dispersal
Types of Fruit
• Fleshy fruits (peach, cucumber, apples, tomato)
• Dry fruit (hazelnut, peanuts, walnuts)
• Accessory fruit- not from ovary (strawberry,
pineapple)
Kopi Luwak
Seed Dispersal
•Reduces competition for sunlight, soil, and
water between parent and developing plant
Germination
•Occurs when an embryo in a seed develops
•Triggered by favourable conditions,
absorption of water, and oxygen.
• First part to emerge is the radicle
• Becomes root
• The hypocotyl is the first part of the plant to push
through soil
• The hypocotyl straightens out and the epicotyl will
emerge
• Plants first leaves emerge
•Complete Flower Worksheet
•Tomorrow: Flower (Dissection!) Lab
•Thursday: Angiosperm Quiz
•Thursday May 8 Plant Unit Test