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Inquiry into LifeTwelfth Edition
Chapter 10
Lecture PowerPoint to accompany
Sylvia S. Mader
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
10.1 Sexual Reproduction in Plants
10.1 Sexual Reproduction in Plants
• Plants have two stages in their life cycle.
– A diploid stage alternates with a haploid stage.
• The diploid plant is called the sporophyte.
• The haploid plant is called the gametophyte.
10.1 Sexual Reproduction in Plants
• Flowers are the reproductive structures of
angiosperms.
• Flowers produce two kinds of spores.
– Microspores develop into the male gametophyte.
• The male gametophyte produces sperm.
– Megaspores develop into the female gametophyte.
• The female gametophyte produces an egg.
10.1 Sexual Reproduction in Plants
• Upon fertilization, a zygote is formed. The zygote develops into an embryo.
• A seed forms contains the embryo and stored food.
• When a seed germinates, a new sporophyte emerges.
Alternation of Generations in Flowering Plants
10.1 Sexual Reproduction in Plants
• Parts of a Flower– Sepals - leaf-like structures that protect the
developing bud– Petals - attract pollinators– Stamens - male portion of the flower
• Anther - produces pollen grains• Filament - a slender stalk that supports the anther
– Carpel - female portion of the flower• Stigma - an enlarged stick knob• Style - a slender stalk• Ovary - encloses one or more ovules
Anatomy of a Flower
10.1 Sexual Reproduction in Plants
• Flower parts occur in three’s (or multiples) in monocots.
• Flower parts occur in four or five’s (or multiples) in eudicots
10.1 Sexual Reproduction in Plants
• Flowers may have one or multiple carpels (which may be fused).
10.1 Sexual Reproduction in Plants
• Flowers that have sepals, petals, stamens and carpels are called complete flowers. Flowers that do not are called incomplete.
10.1 Sexual Reproduction in Plants
• A monoecious plant has both staminate and carpellate flowers. If staminate and carpellate flowers are on separate plants, the plant is dioecious.
10.1 Sexual Reproduction in Plants
• Life Cycle of Flowering Plants
– Flowering plants produce:• Microspores • Megaspores
10.1 Sexual Reproduction in Plants
• Life Cycle of Flowering Plants
– Microspores become mature male gametophytes (sperm-bearing pollen grains)
– Megaspores become mature female gametophytes (egg-bearing embryo sacs)
10.1 Sexual Reproduction in Plants
• Life Cycle of Flowering Plants
– During fertilization, one sperm nucleus unites with the egg nucleus, producing a zygote.
– The other sperm unites with the polar nuclei, forming a 3n endosperm cell.
Life Cycle of Flowering Plants
10.1 Sexual Reproduction in Plants
• Pollination -
– The transfer of pollen from an anther to a
stigma.
• Self-pollination (pollen is from the same plant)
• Cross-pollination (pollen is from a different plant)
Pollinators
10.2 Growth and Development
10.2 Growth and Development
• Development of the Eudicot Embryo
– The endosperm cells divides to produce endosperm tissue.
– The zygote divides into two cells.• One cell will become the embryo.
– Embryonic cells near the suspensor become the root, and those at the opposite end form the shoot
• The other cell will give rise to the suspensor. – The suspensor anchors the embryo and transfers nutrients to it.
Development of the Eudicot Embryo
10.2 Growth and Development
• Development of the Eudicot Embryo
– The embryo changes from a ball of cells to a heart-shape
– Cotyledons (seed leaves) appear
– The embryo next becomes torpedo-shaped, and the root tip and
shoot tip become visible
– The epicotyl portion of embryo contributes to shoot development
– The hypocotyl portion contributes to stem development
– The radicle contributes to root development
10.2 Growth and Development
• Monocots Versus Eudicots
– Eudicots (two cotyledons)• Cotyledons store nutrients that the embryo uses
– Monocots (one cotyledon)• Cotyledon absorbs food molecules from the endosperm and
passes them to the embryo
10.2 Growth and Development
• Fruit Types and Seed Dispersal
10.2 Growth and Development
• Fruit Types– Fruits are derived from
an ovary– Fruits protect and help
disperse offspring– The ovary wall
thickens to become the pericarp.
10.2 Growth and Development
• Fruit Types– Simple fruits are
derived from a simple ovary or from a compound ovary.
• Legumes• Dry fruits• Fleshy fruits• Accessory fruits
10.2 Growth and Development
• Fruit Types– Compound fruits
develop from several individual ovaries.
• Aggregate fruits• Multiple fruits
10.2 Growth and Development
• Dispersal of Seeds– Seeds may have hooks or spines that attach to fur or
clothing– Seeds may pass through the digestive tract of
animals– Seeds may be gathered and buried by animals– Seeds may be carried by wind or water
10.2 Growth and Development
• Germination of Seeds– Some types of seeds remain dormant until conditions
are favorable for growth.• Temperature• Moisture• Regulatory Factors (stimulatory and inhibitory)• Mechanical Action (examples: water or fire)
10.2 Growth and Development
• Eudicot Versus Monocot Germination– Eudicots
• Cotyledons shrivel and degrade• Epicotyl produces immature leaves and is called a plumule• Young shoot is hook-shaped as it emerges through the soil
– Monocots• Cotyledon does not have a storage function• Plumule and radicle are protected by sheaths • Plumule and radicle burst through the sheaths when
germination occurs• Young shoot is straight, not hooked
Germination of Eudicots and Monocots
10.3 Asexual Reproduction
10.3 Asexual Reproduction
• Plants contain non-differentiated meristem tissue that allows them to reproduce asexually by vegetative propagation.
• Offspring may arise from the nodes of stolons or rhizomes. Stems and roots can also give rise to new plants.
10.3 Asexual Reproduction
• Tissue Culture – The growth of tissue in an artificial liquid or solid
culture medium.– Plant cells are totipotent, each cell can become an
entire plant.– Large numbers of plants with desired characteristics
and genotypes can be propagated rapidly.
Tissue Culture of Plants
10.3 Asexual Reproduction
• Genetic Engineering of Plants– Traditionally, different varieties of plants have been
crossed to produce offspring with desirable traits.– Today it is possible to directly alter the genes of
organisms, producing new varieties of plants with desirable traits.
– Plants that have a foreign gene are called transgenic or genetically modified plants.
10.3 Asexual Reproduction
• Agricultural Plants with Improved Traits – Corn, cotton, soybean and potato plants have been
engineered to be resistant to either herbicides or insect pests.
– Ongoing research is expected to yield different variety of crops that will be salt tolerant, cold tolerant, drought resistant or blight resistant.
Transgenic Crops of the Future
10.3 Asexual Reproduction
• Commercial Products– Single gene transfers have produced plants that can
manufacture various products• Hormones• Clotting Factors• Antibodies
10.4 Control of Growth and Responses
• Hormones are small organic molecules that serve as chemical signals between cells and tissues.
10.4 Control of Growth and Responses
• Hormones are small organic molecules that serve as chemical signals between cells and tissues.
• Groups of Plant Hormones– Auxins– Gibberellins– Cytokinins– Abscisic Acid– Ethylene
Plant Hormones: Mode of Action
• Plant hormones bind to a specific protein in the plasma membrane. This brings about a physiological response.
10.4 Control of Growth and Responses
• Auxins– Auxins affect many aspects of plant growth and
development. Auxins:• May promote apical dominance• Increase the development of adventitious roots• Promote the growth of fruits• Are involved with phototropism and gravitropism.
10.4 Control of Growth and Responses
• How Auxins Work– H+ is pumped out of cells– Auxins are acidic and weakens cell wall structure– Water moves into the cell and turgor pressure causes
the cell to bend toward the light (away from auxin)
10.4 Control of Growth and Responses
• Gibberellins– Gibberellins are
growth-promoting hormones that promote elongation.
10.4 Control of Growth and Responses
• Cytokinins– Promote cell division– Prevent senescence (aging)– Initiate growth
– The ratios of auxins to cytokinins play a role regarding the differentiation of plant tissues.
10.4 Control of Growth and Responses
• Abscisic Acid– Produced by green
portions of plant– Closes stomata and
maintains seed and bud dormancy
– Considered a plant “stress” hormone
– A decrease in abscisic acid and an increase in gibberellins breaks dormancy
10.4 Control of Growth and Responses
• Ethylene:– Is a gas that moves
freely through the air– Is involved with
abscission (leaf drop)– Promotes the ripening
of fruit
10.4 Control of Growth and Responses
• Plant Responses Are Influenced By:– Light– Day length– Gravity– Touch
10.4 Control of Growth and Responses
• Plant Tropisms:– Phototropism: Growth in response to light
– Gravitropism: Growth in response to gravity
– Thigmotropism: Growth in response to touch
Positive NegativePhototropism Gravitropism
10.4 Control of Growth and Responses
• Flowering
– Short-day plants
– Long-day plants
– Day-neutral plants
Photoperiodism and Flowering
10.4 Control of Growth and Responses
• Phytochrome and Plant Flowering– Phytochrome is a plant pigment that responds to light– Pr is active form; Pfr is inactive– Direct sun contains more red light than far red light;
Pfr is present in plant leaves during the day – At dusk, there is more far red light; Pfr is activated to
Pr
– Phytochrome conversion allows plant to detect photoperiod changes
Phytochrome
Phytochrome Control of A Growth Pattern
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