LECTURE PRESENTATIONS For CAMPBELL BIOLOGY NINTH EDITION Jane

LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 29 Plant Diversity I: How Plants Colonized Land Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc.

Overview: The Greening of Earth • For more than the first 3 billion years of Earth’s history, the terrestrial surface was lifeless • Cyanobacteria likely existed on land 1. 2 billion years ago • Around 500 million years ago, small plants, fungi, and animals emerged on land • Modern green algae called charophytes are the closest relatives of land plants they are thought to share a common ancestor. (1) © 2011 Pearson Education, Inc.

Evidence that Land Plants Evolved from Green Algae • Theyre both multicellular, eukaryotic, photosynthetic, autotrophs • Both have cell walls made of cellulose • Both have chlorophyll a & chlorophyll b pigments in their chloroplasts

Evidence that Land Plants Evolved from Charophytes specifically • Charophytes are the only algae that share the following characteristics with plants – Rings of cellulose-synthesizing proteins – Peroxisome enzymes – Structure of flagellated sperm – Formation of phragmoplast

Figure 29. 3 Examples of charophytes, the closest algal relatives of land plants. 5 mm Chara species, a pond organism Coleochaete orbicularis, a disk-shaped charophyte that also lives in ponds (LM) 40 m 1 m

Movement onto Land • Many species of charophytes inhabit shallow water, so it’s reasonable to assume that the common ancestor that diverged into plants & charophyts may have as well • Surviving in shallow water requires organisms to resist occasional drying • Natural selection would favor individuals can survive periods of not being submerged in water

Adaptations Enabling the Move to Land • In charophytes a layer of a durable polymer called sporopollenin prevents exposed zygotes from drying out • Sporopollenin is also found in plant spore walls Benefits & Challenges of Moving onto Land • The movement onto land by charophyte ancestors provided them unfiltered sun, more plentiful CO 2, nutrient-rich soil, and few herbivores or pathogens • Land presented challenges: a scarcity of water and lack of structural support (2)

Derived Traits of Land Plants (In other words, traits unique to land plants not found in algae) • Alternation of generations with an associated trait of multicellular, dependent embryos • Walled spores produced in sporangia • Multicellular gametangia • Apical meristems

Alternation of Generations and Multicellular, Dependent Embryos • Plants alternate between two multicellular stages, a reproductive cycle called alternation of generations • The gametophyte is haploid and produces haploid gametes by mitosis • Fusion of the gametes gives rise to the diploid sporophyte, which produces haploid spores by meiosis (Start of 3 continues for several slides)

• The diploid zygote develops into a multicellular embryo within the tissue of the female gametophyte • This provides the developing embryo with nutrients – Nutrients are transferred from parent to embryo through placental transfer cells – Placental transfer cells are similar in function to the mammalian placenta • Land plants are called embryophytes because of the dependency of the embryo on the parent © 2011 Pearson Education, Inc.

Figure 29. 5 a Gametophyte (n) Mitosis n Gamete from another plant Mitosis n FERTILIZATION 2 n Sporophyte (2 n) Haploid (n) Diploid (2 n) n Spore Gamete n MEIOSIS Key Zygote Mitosis Alternation of generations 1 m

Walled Spores Produced in Sporangia • The multicellulr diploid sporophyte produces haploid spores in organs called sporangia • Diploid cells called sporocytes undergo meiosis to generate haploid spores – Sporocytes are equivalent to the human germ cells in that they are diploid cells that give rise to a haploid cell • Spore walls contain sporopollenin, which makes them resistant to harsh environments and allows them to be dispersed in the air © 2011 Pearson Education, Inc.

Figure 29. 5 c Spores Sporangium Longitudinal section of Sphagnum sporangium (LM) Sporophyte Gametophyte 1 m Sporophytes and sporangia of Sphagnum (a moss)

Multicellular Gametangia • Gametes are produced within multicellular hapliod organs called gametangia • Female gametangia, called archegonia – produce eggs – are the site of fertilization – Location where zygote develops into embryo • Male gametangia, called antheridia – produce and release sperm – Many sperm have flagella to allow them to swim to an egg © 2011 Pearson Education, Inc.

Figure 29. 5 d Female gametophyte Archegonia, each with an egg (yellow) Antheridia (brown), containing sperm Male gametophyte Archegonia and antheridia of Marchantia (a liverwort) 1 m

Apical Meristems • Localized regions of cell division at the tips of roots and shoots where plants sustain continual growth • Cells from the apical meristems differentiate into various tissues (End 3) © 2011 Pearson Education, Inc.

Figure 29. 5 e Apical meristem of shoot Developing leaves Apical meristems of plant roots and shoots Apical meristem of root Root 100 m Shoot 1 m 100 m

• Additional derived traits include Cuticle, a waxy covering of the epidermis Mycorrhizae, Early land plants lacked roots and leaves. Without roots they relied on symbiotic associations between fungi and land plants that may have helped to obtain nutrients Mycorrhizal fungi form extensive networks of filaments throughout the soil allowing them to efficiently uptake nutrients The fungi then transfer the nutrients to their symbiotic partner © 2011 Pearson Education, Inc.

Table 29. 1 Vascular tissue refers to the cells joined to form tubes for transporting nutrients & water Seed: and embryo packaged with a supply of nutrients inside a protective coat Gymnosperms: termed naked seed plants because their seeds are NOT enclosed in 1 chambers m Angiosperms: flowering plants

Nonvascular plants have life cycles dominated by gametophytes • The gametophyte is usually larger and longer living than the sporophyte in nonvascular plants • Bryophyte sperm are flagellated and require water to migrate to an egg • Bryophyte gameotphytes typically produce ground covering mosses – Their bodies are too thin to support a tall plant – Lack vascular tissue for nutrient transport over long distances

Bryophyte Sporophytes • Can’t live independently of the gametophyte which supplies them with nutrients • Has 3 main structures – Foot: absorbs nutrients from gametophyte – Seta: conducts minerals to sporangium – Sporangium: produces up to 50 million spores by meiosis – Stomata: specialized pores that open and close to support photosynthesis by allowing exchange of CO 2 & O 2

Figure 29. 13 -3 (24 -25) Key Haploid (n) Diploid (2 n) MEIOSIS Spore dispersal Spore (n) Rhizoid Underside of mature gametophyte (n) Sporangium Antheridium Young gametophyte Mature sporophyte (2 n) Sorus New sporophyte Sperm Archegonium Egg Zygote (2 n) Gametophyte Fiddlehead (young leaf) 1 m FERTILIZATION

Derived Traits of Seedless Vascular Plants • True roots • The ability to grow taller shoots • Vascular tissue – Xylem – Phloem • Leaves • A dominant sporophyte (diploid) generation • Lignified tissue

Seedless Vascular Plants • The sperm of ferns and all other seedless vascular plants are flagellated and so these plants typically grow in moist environments • Unlike nonvascular plants, these have sporophytes that weren’t dependent on the gametophyte – Branching sporophytes with multiple complex sporangia would compete for space and light – Natural selection would favor individuals capable of growing taller

Life Cycle with Dominant Sporophytes • Fossils suggest that ancestors of vascular plants had gametophytes and sporophytes that were equal in size • Today, all extant species of vascular plants have a dominant sporophyte generation that is larger and more complex than the gametophyte

2 Types of Vascular Tissue • Phloem – Cells arranged in tubes to distribute sugars, amino acids, and other organic products • Xylem – Conducts most water and minerals – Includes tracheids: tube shaped cells that carry water & minerals up from the roots – Water conducting cells have their cell walls strengthened by a polymer called lignin

Evolution of Roots • Lignified tissue allowed plants to grow taller by providing more support, and also allowed for the evolution of roots – Roots are organs that absorb water and nutrients from the soil – Roots also anchor vascular plants allowing shoots to grow taller

Evolution of Leaves • Leaves increase surface area of the plant body and are the primary sites of photosynthesis • Can be classified as microphylls or megaphylls depending on size & complexity – Microphylls: usually small and spine shaped supported by a single strand of vascular tissue – Megaphylls: leaves with highly branched vascular system

Sporophylls & Spore Variations Sporophylls: modified leaves that bear sporangia Homosporous Heterosporous • Most seedless vascular plants are homosporous • All seed plants • Have 2 types of sporangium – Ferns that produces 2 types of • Homosporous plants have spores 1 type of sporangium that – Megasporophylls produce Megaspores which develop produces 1 type of spore into female gametophytes that typically develops which make eggs into a bisexual – Microsporangia produce gametophyte microspores which develop into male gametophytes which produce sperm

LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 30 Plant Diversity II: The Evolution of Seed Plants Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc.

Gymnosperms & Angiosperms • There are 2 groups of seed plants that are classified based on if their seeds are enclosed in ovaries as in angiosperms, or “naked” as in gymnosperms

Seeds & Pollen Grains are Key Adaptations for Life on Land • Seeds consist of an embryo and its food supply surrounded by a protective coat • Because it nourishes and protects the embryo but can move away from the parent plant its analogous to a detachable uterus

Traits Common to All Seed Plants • Reduced gametophytes – Smaller gametophytes develop from spores retained within the protective sporangium of the sporophyte nourishing and protecting them from harsh environmental conditions • Heterospory • Ovules & Pollen

Ovules & Pollen Ovules Pollen • Seed plants retain the megasporangium within the sporophyte (unlike seedless plants which release them) • Ovules consist of the entire structure containing the megasporangium, megaspore, and intugement • Each produces 1 or more eggs • Microspores develop into a pollen grain that contains the gametophyte enclosed within the pollen wall (containing sporopollenin) • This allows the male gametophyte to move via wind or animal to an egg, where it will produce sperm • Pollen is NOT dependent on water for spreading to eggs

Reproductive Adaptations of Angiosperms Include Flowers & Fruit • Angiosperms are seed plants that produce reproductive structures such as flowers & fruit • Angiosperms may be wind pollinated (grasses), or pollinated with insect/ animal helpers who carry pollen from 1 plant to another (bees and lilac)

Characteristics of Angiosperms: Flowers • The flower is an angiosperm shoot specialized for sexual reproduction • Flowers can have up to 4 rings of modified leaves (sporophylls) called floral organs – Sepals – Petals – Carpels – Stamen

Sterile Floral Organs sepals petals • Usually green and enclose the flower before it blooms • Think rosebud • Brightly colored leaves that aid in attracting pollinators

Fertile Floral Organs: Stamen • Produce microspores that develop into pollen grains containing gametophytes • Consists of a stalk called a filament and a terminal anther where pollen is produced • Each pollen grain contains a male gametophyte consisting of 2 haploid cells one divides to form 2 sperm, the other, a tube cell produces the pollen tube • These are male organs think sta. MEN & MANther

Fertile Floral Organs: Carpel • Make megaspores & their products, female gametophytes – Flowers may have a single carpel or multiple carpels, which can be separate or fused – A single carpel or group of fused carpels is called a pistil • Stigma: the sticky tip of the carpel that recieves pollen • Style: leads the stigma to the ovary • Ovary: contains 1 or more ovules which when fertilized will develop into a seed

Figure 38. 2 a (1) Stamen Anther Filament Petal Stigma Carpel Style Ovary Sepal Receptacle (a) Structure of an idealized flower

Fruits: Mature Ovaries • As seeds develop from fertilized ovules, the ovary wall thickens • Fruits protect dormant seeds & aid in their dispersal – twirly-birds and dandelions help seeds float – Burrs stick to animal fur – Apples are tasty so that animals eat and then deposit seeds along with “natural fertilizer” far away from parent plant • Fruit can be fleshy (apple) or dry (milkweed pod)

Pollintation • After its release from the anther, pollen is carried to the sticky stigma at the top of the carpel • The pollen grain then absorbs water and germinates after adherence allowing the tube cell to produce a pollen tube that grows down to the style of the carpel where the pollen tube will penetrate to the ovule and discharge 2 sperm

Double Fertilization • One sperm fertilizes the egg forming a diploid zygote • Zygote develops into sporophyte embryo with a rudimentary root and 1 or 2 leaves called cotyledons • The other sperm fuses with 2 nuclei at the center of the female gametophyte producing a triploid cell – develops into endosperm, tissue rich in starch and other foods to nourish the embryo

Function of Double Fertilization • May synchronize the development of food storage in the seed with the development of the embryo – There’s no endospore without fertilization – This prevents plants from wasting energy and nutrients on infertile ovules

Self-Pollination vs Cross-Pollination • Crosspollination increases genetic variation • Some plants have mechanisms to help ensure cross pollination instead of self pollination – In some species, stamens and carpels of a single flower mature at different times – In other species, stamen and carpels are arranged to discourage self-pollination

Monocots vs Dicots • Monocots have 1 seed leaf • When they mature they usually have leaves with parallel veins – Blade of grass • Dicots have 2 seed leaves – Usually have adult leaves with branching leaf veins – Oak leaf

Evolutionary Links Between Angiosperms & Animals • Animals and plants have influenced each others evolution since they moved onto land • For example, herbivores can reduce a plants reproductive success by eating its roots, leaves, or seeds • Some plants evolve defenses against herbivores, or adaptations to attract pollinators

Evolutionary Links Between Angiosperms & Animals • Coevolution: the process of reciprocal evolutionary change that occurs between pairs of species or among groups of species as they interact with one another. • The activity of each species that participates in the interaction applies selection pressure to the others

Evolutionary Links Between Angiosperms & Animals • Coevolution can even affect the rate of speciation • Example: Flower petal arrangement – Flower petals can be arranged with bilateral symmetry or radial symmetry

On a flower with bilateral symmetry, an insect pollinator may only be able to obtain nectar by approaching the plant from a certain direction that increases likelihood pollen will be picked up by the parts of the insect body that will come into contact with the stigma of a flower On average, a clade with bilaterally symmetrical flowers has nearly 2, 400 more species than a similar clade with radially symmetrical flowers

LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 38 Angiosperm Reproduction and Biotechnology Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc.

Concept 38. 1: Flowers, double fertilization, and fruits are unique features of the angiosperm life cycle • Plant lifecycles are characterized by the alternation between a multicellular haploid (n) generation and a multicellular diploid (2 n) generation • Diploid sporophytes (2 n) produce spores (n) by meiosis; these grow into haploid gametophytes (n) • Gametophytes produce haploid gametes (n) by mitosis; fertilization of gametes produces a sporophyte Video: Flower Blooming (time lapse) © 2011 Pearson Education, Inc.

• In angiosperms, the sporophyte is the dominant generation, the large plant that we see • The gametophytes are reduced in size and depend on the sporophyte for nutrients • The angiosperm life cycle is characterized by “three Fs”: flowers, double fertilization, and fruits Video: Flower Plant Life Cycle (time lapse) © 2011 Pearson Education, Inc.

Figure 38. 2 a (1) Stamen Anther Filament Petal Stigma Carpel Style Ovary Sepal Receptacle (a) Structure of an idealized flower

Flower Structure and Function • Flowers are the reproductive shoots of the angiosperm sporophyte; they attach to a part of the stem called the receptacle • Flowers consist of four floral organs: sepals, petals, stamens, and carpels • Stamens and carpels are reproductive organs; sepals and petals are sterile © 2011 Pearson Education, Inc.

• A stamen consists of a filament topped by an anther with pollen sacs that produce pollen • A carpel has a long style with a stigma on which pollen may land • At the base of the style is an ovary containing one or more ovules • A single carpel or group of fused carpels is called a pistil © 2011 Pearson Education, Inc.

Development of Male Gametophytes in Pollen Grains • Pollen develops from microspores within the microsporangia, or pollen sacs, of anthers • Each microspore undergoes mitosis to produce the male gametophyte, which has two cells: the generative cell and the tube cell • Generative cell eventually gives rise to two sperm cells, and the tube cell gives rise to the pollen tube. • A complete pollen grain consists of the two-celled male gametophyte and the spore wall (2 -6) © 2011 Pearson Education, Inc.

• If pollination succeeds, a pollen grain produces a pollen tube that grows down into the ovary and discharges two sperm cells near the embryo sac Video: Bee Pollinating Video: Bat Pollinating Agave Plant © 2011 Pearson Education, Inc.

Figure 38. 3 (a) Development of a male gametophyte (in pollen grain) (b) Development of a female gametophyte (embryo sac) Microsporangium (pollen sac) Megasporangium Microsporocyte Ovule MEIOSIS Megasporocyte Integuments Microspores (4) Micropyle Surviving megaspore Each of 4 microspores Ovule Male gametophyte (in pollen grain) Nucleus of tube cell 20 m (LM) Ragweed pollen grain (colorized SEM) Antipodal cells (3) Polar nuclei (2) Egg (1) Integuments Synergids (2) Key to labels Haploid (n) Diploid (2 n) 100 m Generative cell (will form 2 sperm) Embryo sac (LM) Female gametophyte (embryo sac) MITOSIS 75 m (7)

Development of Female Gametophytes (Embryo Sacs) • The embryo sac, or female gametophyte, develops within the ovule • Within an ovule, two integuments surround a megasporangium • One cell in the megasporangium undergoes meiosis, producing four megaspores, only one of which survives • The megaspore divides, producing a large cell with eight nuclei (8) © 2011 Pearson Education, Inc.

Figure 38. 3 b (b) Development of a female gametophyte (embryo sac) Megasporangium Ovule MEIOSIS Megasporocyte Integuments Micropyle Surviving megaspore Ovule Antipodal cells (3) Polar nuclei (2) Egg (1) Integuments Synergids (2) Haploid (n) Diploid (2 n) 100 m Key to labels Embryo sac (LM) Female gametophyte (embryo sac) MITOSIS

Pollination • In angiosperms, pollination is the transfer of pollen from an anther to a stigma • Pollination can be by wind, water, or animals • Wind-pollinated species (e. g. , grasses and many trees) release large amounts of pollen • (9) Video Animation © 2011 Pearson Education, Inc.

Figure 38. 4 a Abiotic Pollination by Wind Pollination by Bees Common dandelion under normal light Hazel staminate flowers (stamens only) Hazel carpellate flower (carpels only) (10 Here and on next slide) Common dandelion under ultraviolet light

Figure 38. 4 b Pollination by Moths and Butterflies Pollination by Flies Pollination by Bats Anther Moth Fly egg Stigma Moth on yucca flower Blowfly on carrion flower Pollination by Birds Hummingbird drinking nectar of columbine flower Long-nosed bat feeding on cactus flower at night

Coevolution of Flower and Pollinator • Coevolution is the evolution of interacting species in response to changes in each other • Many flowering plants have coevolved with specific pollinators • The shapes and sizes of flowers often correspond to the pollen transporting parts of their animal pollinators – For example, Darwin correctly predicted a moth with a 28 cm long tongue based on the morphology of a particular flower (11) © 2011 Pearson Education, Inc.

Figure 38. 5

Double Fertilization • After landing on a receptive stigma, a pollen grain produces a pollen tube that extends between the cells of the style toward the ovary • Double fertilization results from the discharge of two sperm from the pollen tube into the embryo sac • One sperm fertilizes the egg, and the other combines with the polar nuclei, giving rise to the triploid food-storing endosperm (3 n) Animation: Plant Fertilization © 2011 Pearson Education, Inc.

Figure 38. 6 -3 1 Stigma 2 Pollen grain Pollen tube Ovule 2 sperm Polar nuclei Style Ovary 3 Endosperm nucleus (3 n) (2 polar nuclei plus sperm) Egg Ovule Polar nuclei Synergid Zygote (2 n) 2 sperm Egg Micropyle (12 -16)

Endosperm Development • Endosperm development usually precedes embryo development • In most monocots and some eudicots, endosperm stores nutrients that can be used by the seedling • In other eudicots, the food reserves of the endosperm are exported to the cotyledons • After double fertilization, each ovule develops into a seed • The ovary develops into a fruit enclosing the seed(s) (17 -20) © 2011 Pearson Education, Inc.

Embryo Development • The first mitotic division of the zygote splits the fertilized egg into a basal cell and a terminal cell • The basal cell produces a multicellular suspensor, which anchors the embryo to the parent plant • The terminal cell gives rise to most of the embryo • The cotyledons form and the embryo elongates Animation: Seed Development © 2011 Pearson Education, Inc.

Figure 38. 7 Ovule Endosperm nucleus Integuments Proembryo Zygote Suspensor Cotyledons Basal cell Shoot apex Root apex Terminal cell Basal cell Zygote Suspensor Seed coat Endosperm

Figure 38. 7 a Ovule Endosperm nucleus Integuments Zygote Terminal cell Basal cell Zygote

Figure 38. 7 b Proembryo Suspensor Cotyledons Basal cell Shoot apex Root apex Suspensor Seed coat Endosperm

Structure of the Mature Seed • The embryo and its food supply are enclosed by a hard, protective seed coat • The seed enters a state of dormancy • A mature seed is only about 5– 15% water main mechanism for maintaining dormancy along with rigid seed coat. • Once dormancy is broken the first organ to emerge is the radicle, or embryonic root. (21 -23) © 2011 Pearson Education, Inc.

• In some eudicots, such as the common garden bean, the embryo consists of the embryonic axis attached to two thick cotyledons (seed leaves) • Below the cotyledons the embryonic axis is called the hypocotyl and terminates in the radicle (embryonic root); above the cotyledons it is called the epicotyl • The plumule comprises the epicotyl, young leaves, and shoot apical meristem © 2011 Pearson Education, Inc.

Figure 38. 8 Seed coat Epicotyl Hypocotyl Radicle Cotyledons (a) Common garden bean, a eudicot with thick cotyledons (24 Here and on next slide) Seed coat Endosperm Cotyledons Epicotyl Hypocotyl Radicle (b) Castor bean, a eudicot with thin cotyledons Scutellum (cotyledon) Coleoptile Coleorhiza (c) Maize, a monocot Pericarp fused with seed coat Endosperm Epicotyl Hypocotyl Radicle

Figure 38. 9 a Foliage leaves Cotyledon Hypocotyl Epicotyl Cotyledon Hypocotyl Radicle Seed coat (a) Common garden bean

Seed Dormancy: An Adaptation for Tough Times • Seed dormancy increases the chances that germination will occur at a time and place most advantageous to the seedling • The breaking of seed dormancy often requires environmental cues, such as temperature or lighting changes • Germination depends on imbibition, the uptake of water due to low water potential of the dry seed • The radicle (embryonic root) emerges first • Next, the shoot tip breaks through the soil surface (25) © 2011 Pearson Education, Inc.

Fruit Form and Function • A fruit develops from the ovary • It protects the enclosed seeds and aids in seed dispersal by wind or animals • A fruit may be classified as dry, if the ovary dries out at maturity, or fleshy, if the ovary becomes thick, soft, and sweet at maturity (26) Animation: Fruit Development © 2011 Pearson Education, Inc.

• Fruit dispersal mechanisms include – Water – Wind – Animals (27 Examples on following slides) © 2011 Pearson Education, Inc.

Figure 38. 11 a Dispersal by Wind Dandelion fruit Dandelion “seeds” (actually one-seeded fruits) Tumbleweed Winged seed of the tropical Asian climbing gourd Alsomitra macrocarpa Winged fruit of a maple Dispersal by Water Coconut seed embryo, endosperm, and endocarp inside buoyant husk

Figure 38. 11 b Dispersal by Animals Fruit of puncture vine (Tribulus terrestris) Squirrel hoarding seeds or fruits underground Ant carrying seed with nutritious “food body” to its nest Seeds dispersed in black bear feces

Asexual Reproduction • Fragmentation: when detached vegetative fragments develop into new offspring • Apomixis: asexual production of seeds without pollination or fertilization

Advantages Asexual Reproduction Sexual Reproduction • Generates variation in • No need for pollinator offspring and populations that • Allows plants to pass on all is advantageous in unstable genes intact to progeny, so or changing environments if a plant is already well adapted to the environment • Seeds which are more common with this type of and the environment isn’t re[production facilitate changing, that’s a benefit dispersal to more distant • Produces stronger locations seedlings • Seed dormancy allows growth to be suspended until conditions are favorable

Disadvantages Asexual Reproduction Sexual Reproduction • Genotypic uniformity puts • There is great amount of energy expenditure in sexual populations at greater risk reproduction of local extinction if there is catastrophic environmental change or disease • Often requires interactions with pollinators • Without seeds, plants can’t disperse as well • New combinations of genes may not be as fit as parental combinations

Mechanisms to Prevent Self Fertilization Dioecious Self-Incompatibility • Individuals either produce flowers with stamen, or flowers with carpels but not both • The ability of a plant to reject its own pollen • Sometimes individuals produce both stamen and carpels, but they mature ate different times • Recognition of self pollen is based on genes for self -incompatibility called sgenes

Vegetative Propagation & Agriculture • Clones from cuttings • Grafting • Test-tube cloning – GMs – Transgenic plants

Plant Biotechnology & Genetic Engineering • Transgenic: genetically modified organisms that have been engineered to express a gene from another species – Reducing world hunger – Reducing fossil fuel dependancy

Debate Over Plant Biotechnology • Issues of Human Health • Possible Effects on Non-target Organisms – Pollen from transgenic corn gets on milkweed plants and kills the Monarch butterflies that feed off of them • Transgene Escape – Transgenes may escape the intended crop and get into weeds or other plants through horizontal gene transfer or spontaneous hybridization