plant reproduction sexual plant reproduction – seed ag-bas-8-b, sb2, sb2 (e)
TRANSCRIPT
Plant Reproduction
Sexual Plant Reproduction – SeedAG-BAS-8-b, SB2, SB2 (e)
What is a seed?
• Seeds are containers of new life.– Seeds are formed in the ovaries of flowers, which
become fruit.– Seeds ensure continuing life as well as provide
food and other products
Kinds of Seeds• Monocot– Monocots are plants that have a seed with one seed
leaf known as a cotyledon.• The embryo in the seed will have one leaf.• As the embryo grows, the leaves develop with parallel
venation.– Corn, wheat, rice, all grasses
• Dicot– Dicots are plants that have a seed with two
cotyledons. • The embryo in the seed has two leaves.• Leaves of a dicot have net venation.
– Tomatoes, beans, petunias, trees
Parts of a seed - Dicot
• Outside– Seed coat– Hilum– Micropyle
• Inside– Cotyledons– Radicle– Hypocotyl– Epicotyl– Plumule
Parts of a seed - Monocot• Outside– Seed coat– Seed scar– Silk scar
• Inside– Endosperm– Radicle– Hypocotyl– Epicotyl– Cotyledon– Plumule
Plant Reproduction
How Seeds are Formed: FlowersAG-BAS-8-(c, d), SB2, SB2 (e)
What is a flower?
• A flower is the reproductive part of a flowering plant.
• They are modified leaves.– Some have attractive colors and fragrances– This is to attract pollinators
Types of Flowers
• Flowers are categorized in two ways– Complete or incomplete– Perfect or imperfect
Complete Flower
• Has all 4 parts:– Sepals – protects the developing bud– Petals – attracts pollinators– Stamens – male reproductive structure– Pistil – female reproductive structure
Incomplete Flowers
• They do not have all of the principle parts– Some flowers do not have a sepal and petals. For
example: the flower in wheat and oats.– In some cases the female and male flower parts
are separate on plants.– Both are needed to produce a seed
Perfect vs Imperfect
• Perfect flower: It has the stamen and the pistil in the same flower
• An imperfect flower has the male sex organs or the female sex organs, but not both on the same flower
Monoecious vs Dioecious
• Plants may have both male and female imperfect flowers on them.
• They are called monoecious plants– Corn is a monoecious plant.– Others include: Squash, melons and pumpkins
• Dioecious is when some plants have male flowers and others have female flowers. – Strawberries are dioecious– Also, gourds and bradford pears
Flower combos
• Flowers can be combinations of complete and incomplete and perfect and imperfect– Wheat- incomplete and perfect– Cotton- complete and perfect
Pollination
• The transfer of pollen from an anther to a stigma of a flower of the same species– Pollen may be moved by wind, insects, birds and
other natural means.– Flowers may be cross-pollinated
• Involves two different plants.• Pollen from anther in one plant is moved to the stigma on
another plant.– or self-pollinated
• It involves flowers on the same plant.• Pollen moved from one flower on one plant to another on
the plant.
Fertilization
• It is the union of the pollen cell with the ovule (egg).
• Pollen grain develops two sperm.• One of the sperm unites with the ovule in the
ovary and forms an embryo.• The other sperm forms tissue known as
endosperm in the embryo.
Fertilization• Initiates the growth of the fruit and seed• A flower that is not fertilized will not produce
seed.• An ovary that has been fertilized forms fruit.• In some cases, the ovary grows very large and
has a seed inside.• Some examples are watermelons, cucumbers,
green peppers and tomatoes.• The seeds that are formed are products of the
parents.
Types of Fruits
• All fruit can be classified into two types.– Fleshy• Those that have large fibrous structure surrounding the
seed• Apples, pears, blackberries, oranges, grapes
– Dry• Fruit that develops as a pod or in a hull• Pods can usually be easily divided half.
– Beans, peas, peanuts and cotton have pods• Hull fruits do not have definite seams in the shell
– Pecans, acorns, corn, oats, wheat, dandelions
Seed Scattering
• Some seeds have structures that help them float long distances in the air.
• Some attach to animal coats.• Some are eaten and spread through
defecation. • Some are dropped/buried by animals.• As plants are domesticated, humans develop
systems of dispersing and planting seeds.