•The most important pollinator species is the XX, which is dying off in huge numbers (colony collapse disorder, CCD)
•Sexual Reproduction in Flowering Plants (yes, birds do it, bees do it, and plants do it too!)
oXX = unique reproductive structures found only in angiosperms (flowering plants)
Produce spores, protect gametophytes, attract pollinators
Flower anatomy
•XX = leaflike protective parts at flower base
•XX = colored parts that attract pollinators
•XX = male flower parts (anthers that contain pollen, on top of filaments)
•XX = female flower parts (sticky stigma—to catch pollen—on top of long style that connects to ovary at the base of the flower)
oRemember alternation of generations (see Fig. 16.3)
XX is dominant generation in angiosperms (flowering plants)
From spores to zygotes
•Diploid XX (“spore plant”) produces haploid spores
•Haploid spores grow into mature haploid XX (“gamete plant”)
oMicrospores undergo mitosis to produce pollen tube = male
oMegaspores undergo mitosis to produce embryo sac = female
•Haploid gametophytes produce haploid sperm (male) or eggs (female)
oPollen grain contains 2 flagellated XX
oPollen is carried from one plant to another via wind, water or pollinators
oWhen pollen lands on a stigma, it germinates (grows) into a pollen tube (male gametophyte), which delivers the two sperm to the embryo sac
When the sperm reach the embryo sac (egg + 6 cells in the ovary), double fertilization occurs
•One sperm fertilizes the egg to form the sporophyte zygote
oThis is sexual reproduction (aka pollination)
oDevelops into an embryo inside the seed, which is housed inside the ovary
•The other sperm fertilizes two nuclei to form a triploid cell (XX, which feeds the growing sporophyte embryo)
oSeed Development
Seed has three parts: seed XX (from ovule wall) + XX (from zygote) + food (from XX)
•As embryo develops, parent plant transfers food to replenish the endosperm
•For anyone with an interest in eating healthy: the embryo is referred to as the germ (like wheat germ), the seed coat is the bran (like in bran muffins) and the endosperm is the grain (when you eat “whole grains”, it means you are eating all three parts: more nutritious!)
Remember, embryonic leaves form in the seed
•One embryonic leaf = monocot
•Two embryonic leaves = eudicot
oFruits (and Seed Dispersal)
Seed develops from ovules; XX develops from mature ovary (and sometimes other flower parts)
•Embryo can only use energy stored in seed
•Fruit (tissue around the seed or seeds) is used to attract animals who eat it and XX the seeds (which pass through their gut, without harming the embryo, and come out the other end with feces, which is excellent fertilizer!)
•Other seed dispersal methods: hooks/spines on seeds to catch on animal fur, fruits that float in water or fly well in the wind
oSeed Germination (growth of new sporophyte plant out of the seed) (16.5)
Some seeds require passage through digestive tract of bird or mammal to germinate
Others require bacterial action, freezing phase (dormancy) or fire to germinate!
You do not need to know different patterns of development
•Asexual Reproduction in Flowering Plants (16.4)
oCalled “XX propagation” (no pollen or eggs… just cloning!)
oDone by strawberries, grasses, irises, etc.—new plants arise along lateral roots (rhizomes) or stems (stolons)
oCuttings of mature plants can be used to grow new plants, in some species
oGrafts can combine two or more species, to make a hardier plant
oPlant cells are “totipotent” (which means any single cell can produce a whole plant!), so single cells can be used to grow whole plants via XX XX propagation
•Plant hormones and their effects (16.6)
oPlants respond to a variety of environmental stimuli (light, gravity, seasonal changes) by producing hormones that change their growth patterns
oHormones work the same way in plants they do in animals: they are chemical signaling molecules that communicate between different cells in the plant (artificial hormones called “plant growth regulators”)
oThere are 5 major groups of known plant hormones
XX (e.g., gibberellic acid, GA3)
•Promotes growth and development: breaks dormancy, causes seed germination & flowering
XX (e.g., indoleacaetic acid, IAA)
•Affects many aspects of plant growth & development
oOne example = apical dominance (shoot tip inhibits lateral bud development)
Pruning removes the shoot tip and allows “bushier” growth
oAlso root development, fruit growth, prevention of fruit/leaves dropping, phototropism (growing toward light), gravitropism (growth in response to gravity)
XX acid (ABA)
•Produced by any green (chlorophyll-containing) plant tissue
• “Stress hormone”: causes seed dormancy (via cold stress), stomata closure (via water stress)
XX
•Promote cell division (cytokinesis), prevent leaf aging (senescence)
XX (= gas released by ripening fruit th
•Sexual Reproduction in Flowering Plants (yes, birds do it, bees do it, and plants do it too!)
oXX = unique reproductive structures found only in angiosperms (flowering plants)
Produce spores, protect gametophytes, attract pollinators
Flower anatomy
•XX = leaflike protective parts at flower base
•XX = colored parts that attract pollinators
•XX = male flower parts (anthers that contain pollen, on top of filaments)
•XX = female flower parts (sticky stigma—to catch pollen—on top of long style that connects to ovary at the base of the flower)
oRemember alternation of generations (see Fig. 16.3)
XX is dominant generation in angiosperms (flowering plants)
From spores to zygotes
•Diploid XX (“spore plant”) produces haploid spores
•Haploid spores grow into mature haploid XX (“gamete plant”)
oMicrospores undergo mitosis to produce pollen tube = male
oMegaspores undergo mitosis to produce embryo sac = female
•Haploid gametophytes produce haploid sperm (male) or eggs (female)
oPollen grain contains 2 flagellated XX
oPollen is carried from one plant to another via wind, water or pollinators
oWhen pollen lands on a stigma, it germinates (grows) into a pollen tube (male gametophyte), which delivers the two sperm to the embryo sac
When the sperm reach the embryo sac (egg + 6 cells in the ovary), double fertilization occurs
•One sperm fertilizes the egg to form the sporophyte zygote
oThis is sexual reproduction (aka pollination)
oDevelops into an embryo inside the seed, which is housed inside the ovary
•The other sperm fertilizes two nuclei to form a triploid cell (XX, which feeds the growing sporophyte embryo)
oSeed Development
Seed has three parts: seed XX (from ovule wall) + XX (from zygote) + food (from XX)
•As embryo develops, parent plant transfers food to replenish the endosperm
•For anyone with an interest in eating healthy: the embryo is referred to as the germ (like wheat germ), the seed coat is the bran (like in bran muffins) and the endosperm is the grain (when you eat “whole grains”, it means you are eating all three parts: more nutritious!)
Remember, embryonic leaves form in the seed
•One embryonic leaf = monocot
•Two embryonic leaves = eudicot
oFruits (and Seed Dispersal)
Seed develops from ovules; XX develops from mature ovary (and sometimes other flower parts)
•Embryo can only use energy stored in seed
•Fruit (tissue around the seed or seeds) is used to attract animals who eat it and XX the seeds (which pass through their gut, without harming the embryo, and come out the other end with feces, which is excellent fertilizer!)
•Other seed dispersal methods: hooks/spines on seeds to catch on animal fur, fruits that float in water or fly well in the wind
oSeed Germination (growth of new sporophyte plant out of the seed) (16.5)
Some seeds require passage through digestive tract of bird or mammal to germinate
Others require bacterial action, freezing phase (dormancy) or fire to germinate!
You do not need to know different patterns of development
•Asexual Reproduction in Flowering Plants (16.4)
oCalled “XX propagation” (no pollen or eggs… just cloning!)
oDone by strawberries, grasses, irises, etc.—new plants arise along lateral roots (rhizomes) or stems (stolons)
oCuttings of mature plants can be used to grow new plants, in some species
oGrafts can combine two or more species, to make a hardier plant
oPlant cells are “totipotent” (which means any single cell can produce a whole plant!), so single cells can be used to grow whole plants via XX XX propagation
•Plant hormones and their effects (16.6)
oPlants respond to a variety of environmental stimuli (light, gravity, seasonal changes) by producing hormones that change their growth patterns
oHormones work the same way in plants they do in animals: they are chemical signaling molecules that communicate between different cells in the plant (artificial hormones called “plant growth regulators”)
oThere are 5 major groups of known plant hormones
XX (e.g., gibberellic acid, GA3)
•Promotes growth and development: breaks dormancy, causes seed germination & flowering
XX (e.g., indoleacaetic acid, IAA)
•Affects many aspects of plant growth & development
oOne example = apical dominance (shoot tip inhibits lateral bud development)
Pruning removes the shoot tip and allows “bushier” growth
oAlso root development, fruit growth, prevention of fruit/leaves dropping, phototropism (growing toward light), gravitropism (growth in response to gravity)
XX acid (ABA)
•Produced by any green (chlorophyll-containing) plant tissue
• “Stress hormone”: causes seed dormancy (via cold stress), stomata closure (via water stress)
XX
•Promote cell division (cytokinesis), prevent leaf aging (senescence)
XX (= gas released by ripening fruit th