A pistil is made of fused carpelsOvules become fruit....
Perfect vs. Imperfect flowersPerfect Flowers: • Both male and female sex organs on the same flowerImperfect Flowers: • Only one sex per flowerFig. 20
Monoecious Vs. Dioecious• Monoecious - separate staminate and pistillate flowerson the same plant but in different locations (Corn)• Dioecious - separate staminate and pistillate flowers ondifferent plants (Marijuana)• Hermaphrodite - flowers with male and female parts(perfect flower)
Imperfect Pistillate/ Staminate Flowers• Pistillate flowers have only the pistil, no male parts• Staminate flowers have only the stamens, no femaleparts• Example: willow male and female flower clusters
Gene Regulation of Flower FOrmationMeristem identity genes initiate LEAFY and APETELAgene expression.These gene products lead to the expression of floralorgan identity genes.Expression of these genes specify whorl development inflowers.
What determines development?Homeotic genes = direct certain organs to form in theright places during development
Homeotic genes In ArabidopsisWild Type Missing A Missing B Missing C 1 2 3 4 A A A A A AA A B B B B B B C C C C C C C C “Apetala” “Pistilata” “Agamous”Se Pe St PiGene A expressed in whorl 1 and 2Gene B expressed in whorl 2 and 3Gene C expressed in whorl 3 and 4
Mutations tohomeotic geneshelped scientistsbetter understandgenetic regulation offloral development
Gamete Formationcheck it out online...Formation of female and male gametophyte
Pollination• Pollination - Transfer of pollen to the stigma• Pollen adheres to the stigma and grows a pollen tubedown the style until it reaches ovule
Pollen Grains Germinate and Form a Pollen TubeThe pollen tube contains one vegetive nucleus and twosperm nuclei.(The generative undergo mitosis which results in theformation of two germ production*)
Angiosperm Life Cycle • Fertilization - the fusion of the sperm and egg to forma zygote.• In Angiosperms double fertilization takes place.
38.2 Sexual Reproduction inAngiosperms!The embryo sac isthe female gametophyte; thepollen grain is the malegametophyte. The male andfemale nuclei meet and fuse withinthe embryo sac. Angiospermshave double fertilization, in whicha zygote and an endospermnucleus form from separate fusionevents—the zygote from onesperm and the egg, and theendosperm from the other spermand two polar nuclei.
Plant Reproduction. Key Concept:Ovules develop into seeds.Ovaries develop into fruit.
From Ovary to Fruit1. Simple Fruit• Develops from a flower with a single carpel
From Ovary to Fruit2. Aggregate Fruit - develops from many separate carpelsof one flowerex. raspberry fruit
From Ovary to Fruit3. Multiple Fruit - develop from many carpels of manyflowersex. Pineapple fruit : Each segment develops from thecarpel of one flower
Self - Incompatibility in Pollination• Plants have mechanisms toprevent selfing and enforceoutcrossing• S locus codes for proteinsinvolved in self incompatibility• Different alleles of the Slocus determine if pollen tubescan grow
Full nectary: mutualismEmpty nectary: deceit (exploiting the pollinators)
Plant Reproduction. Key Concept:What is the meaning of these “pollination syndromes”Plants specialize on certain types of pollinatorFloral traits= adaptations
Pollination SyndromesWind- pollination Syndrome:• Lots of pollen• Flowers held out• No nectar• No petals• Typical monocots
Bee pollination syndrome:• Yellow, blue, purple, white• UV patterns• Nectar guides• Flat, open, or bilateral symm• Scented• Sonication: release of pollen due to buzzing of wings
Question: What’s a nectar guidePigments that help guide pollinators to their reward(the nectar guides are those lines near the inner part ofof flower. Its there to help guide them to pollinate)
Bird pollination syndrome:• Red• Long, tubular• Nectar only, lots of it• Some with Dilute nectar, amino acids• No scents
Bat pollination syndrome:• Open at night• WHite/light flowers (color blind)• Strong scents• Large, “easy -access”
Moth Pollination• Flowers open at night• Large showy flowers• Tend to be white• Very aromatic• Nectar produced
Butterfly Pollination • Large showy flowers• Pink or lavender• Nectar rewards• Usually scented
Fly pollination syndrome:• Nasty smells• Produce heat
Photoperiodism: Flowering response of a plant to dayShort day plants (SDP): Flower only when the day isshorter than a critical maximum. ( ex. Mammoth Tobacco)Long day plants (LDP): Flower only when the day is longerthan a critical minimum. ( ex. Spinach)
Longer/ Shorter nights are what actually drive flowering time