UNIT 7 Chapter 36: Transport in Plants Chapter 37: Plant Nutrition Chapter 38: Plant Reproduction.
Unit 23 Plant Reproduction
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Transcript of Unit 23 Plant Reproduction
22.1 Plant Life Cycles
KEY CONCEPT All plants alternate between two phases in their life cycles.
22.1 Plant Life Cycles
Plant life cycles alternate between producing spores and gametes.
• A two-phase life cycle is called alternation of generations. – haploid phase – diploid phase – alternates between
the two
fertilizationfertilization
meiosismeiosis
SPOROPHYTE PHASE
GAMETOPHYTE PHASE
22.1 Plant Life Cycles
– sporophyte phase is diploid – begins with fertilized egg – spores produced through
meiosis • The gamete-producing plant is the
mature gametophyte.
• The spore-producing plant is the mature sporophyte.
– gametophyte phase is haploid
– begins with spore – gametes
produced through
mitosis
22.1 Plant Life Cycles
Life cycle phases look different among various plant groups.
• Nonvascular plants have a dominant gametophyte phase. – moss gametophytes look like green carpet – moss sporophytes shoot up as stalklike structures
sporophyte (2n)sporophyte (2n)
gametophyte (1n)gametophyte (1n)
capsule
spores (1n)
22.1 Plant Life Cycles
sporophyte (2n)sporophyte (2n)
sori
• The sporophyte is the dominant phase for seedless vascular plants. – Fern spores form in sacs, sori, on underside of mature
sporophytes (fronds).
22.1 Plant Life Cycles
– A fern gametophyte, or prothallus, produces sperm and eggs.
gametophyte (1n))gametophyte (1n))
rhizoid
– A zygote forms on the prothallus, growing into the sporophyte.
22.1 Plant Life Cycles
– pine trees are typical seed plant sporophytes– female spores produced in female cones – male spores produced in male cones – male spores develop into pollen grains, the male
gametophytes – female spores develop into female gametophytes that
produce eggs – sperm from pollen travel down pollen tube toward egg – fertilized egg develops into embryo – ovule develops into protective pine seed
• The sporophyte is the dominant phase for seed plants.
22.1 Plant Life Cycles
• The sporophyte is the dominant phase for seed plants.
22.1 Plant Life Cycles
• KEY CONCEPT Reproduction of flowering plants takes place within flowers.
22.1 Plant Life Cycles
• sepal
Flowers contain reproductive organs protected by specialized leaves.
• Sepals and petals are modified leaves.– Sepals are outermost
layer that protectsdeveloping flower
22.1 Plant Life Cycles
– Petals can help to attract animal pollinators
• petal
22.1 Plant Life Cycles
• A stamen is the male structure of the flower.
– anther produces pollen grains – filament supports the anther
• stamen
• filament• anther
22.1 Plant Life Cycles
• carpel • style
• stigma
• ovary
• The innermost layer of a flower is the female carpel.
– stigma is sticky tip – style is tube leading from stigma to ovary – ovary produces female gametophyte
22.1 Plant Life Cycles
Flowering plants can be pollinated by wind or animals.
• Flowering plants pollinated when pollen grains land on stigma.
• Wind pollinated flowers have small flowers and large amounts of pollen.
22.1 Plant Life Cycles
• Animal pollinated flowers have larger flowers and less pollen.
• pollen grains
– many flowering plants pollinated by animal pollinators
– pollination occurs as animal feeds from flower to flower– animal pollination more efficient than wind pollination
22.1 Plant Life Cycles
Fertilization takes place within the flower.
• Male gametophytes, or pollen grains, are produced in the anthers. – male spores produced in
anthers by meiosis– each spore divides by
mitosis to form twohaploid cells
– two cells form asingle pollen grain • pollen grain
22.1 Plant Life Cycles
– four female spores produced in ovule by meiosis – one spore develops into female gametophyte – female gametophyte contains seven cells – one cell has two nuclei, or polar nuclei – one cell will develop into an egg
• One female gametophyte can form in each ovule of a flower’s ovary.
22.1 Plant Life Cycles
• Pollination occurs when a pollen grain lands on a stigma.
• pollen tube• pollen tube
• sperm• sperm
• stigma• stigma
– one cell from pollen grain forms pollen tube– other cell forms two sperm that travel down tube
22.1 Plant Life Cycles
• Flowering plants go through the process of double fertilization.
• female• gametophyte
• ovule
• egg
• sperm
• polar nuclei
22.1 Plant Life Cycles
• endosperm
• seed coat
• embryo
– one sperm fertilizes the egg
– other sperm unites with polar nuclei, forming endosperm
– endosperm provides food supply for embryo
• Flowering plants go through the process of double fertilization.
22.1 Plant Life Cycles
• Each ovule becomes a seed.• The surrounding ovary grows into a fruit.
22.1 Plant Life Cycles
• KEY CONCEPT Seeds disperse and begin to grow when conditions are favorable.
22.1 Plant Life Cycles
Animals, wind, and water can spread seeds.
• Seeds dispersed by animals can have nutritious fruits or fruits that cling.
•
22.1 Plant Life Cycles
• Seeds dispersed by wind can have wing- or parachute-like fruits.
• Cypselae
• Double samaras
22.1 Plant Life Cycles
Seeds begin to grow when environmental conditions are favorable.• Seed dormancy is a state in which the embryo has stopped
growing. – Dormancy may end
when conditions are favorable.
– While dormant, embryo can withstand extreme conditions.
22.1 Plant Life Cycles
• Germination begins the growth of an embryo into a seedling. – water causes seed to swell and crack coat– embryonic root, radicle, is first to emerge– water activates enzymes that help send sugars to
embryo
22.1 Plant Life Cycles
• Germination begins the growth of an embryo into a seedling. – water causes seed to swell and crack coat– embryonic root, radicle, is first to emerge – water activates enzymes that help send sugars to
embryo– embryonic shoot, plumule, emerges next
22.1 Plant Life Cycles
• Germination begins the growth of an embryo into a seedling. – water causes seed to swell and crack coat– embryonic root, radicle, is first to emerge – water activates enzymes that help send sugars to
embryo– embryonic shoot, plumule, emerges next
– leaves emerge last
22.1 Plant Life Cycles
• Once photosynthesis begins, the plant is called a seedling.
22.1 Plant Life Cycles
• KEY CONCEPT Plants can produce genetic clones of themselves through asexual reproduction.
22.1 Plant Life Cycles
Plants can reproduce asexually with stems, leaves, or roots. • Asexual reproduction allows a plant to make copies of itself.• Regeneration is one type of asexual reproduction.
– plants grow a new individual from fragment of parent – occurs when piece of a stem, leaf, or root falls off parent
plant
22.1 Plant Life Cycles
– stems, leaves, or roots attached to parent plant produce new individuals
– specific adaptations include stolons, rhizomes, and tubers
• Vegetative reproduction is another type of asexual reproduction.
22.1 Plant Life Cycles
Humans can produce plants with desirable traits using vegetative structures. • Vegetative propagation takes advantage of plants’ ability to
reproduce asexually. • Humans use one plant with desirable traits to produce
many individuals.
– grafting joins the parts of two plants together to form
a hybrid plant
– cutting of leaves or stems may grow new roots