9.4. reproduction in plants
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9.4. Reproduction in plants
Miltiadis-Spyridon Kitsos Platon IB Diploma
http://k8schoollessons.com/wp-content/uploads/2013/05/parts-of-a-flower.png
The official IB Diploma Biology guideEssential idea: Reproduction in flowering plants is influenced by the biotic and abiotic environment.
https://ibpublishing.ibo.org/server2/rest/app/tsm.xql?doc=d_4_biolo_gui_1402_1_e&part=4&chapter=3
Vegetative vs Reproductive phaseFlowering involves a change in gene expression in the shoot apex.
A young plant with stem and leaves is said to be in a vegetative phase. At some point the plants switches to the reproductive stage where the shoot meristems start to produce flowers
https://youtu.be/ryUxrFUk6MY?list=PLjGpwNulULASb4gphjcJPR5B_TecyA4Oo
But what exactly is a flower?
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The structure of a flower
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The structure of the flower
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Functions of the flower parts
Drawing of half-views of animal-pollinated flowers.
(1) First draw the outline of the flower, petals and sepals, and annotate (2) Draw the style, the stigma
and the ovary
Petals
Sepals
Ovary
Style
Stigma
Petals
Sepals
Ovary
Style
Stigma
Filament
Anther
(3) Add the filaments and the anthers
PollinationSuccess in plant reproduction depends on pollination, fertilization and seed dispersal.
http://treeonline.files.wordpress.com/2010/07/aplantstructure-pollination-51.jpg
Wind pollination
Animal pollination
https://www.pbs.org/wgbh/nova/flower/images/poll-5-celery.jpg
Water pollination
Pollination is the transfer of pollen grains from the anthers, reproductive organs of a male to a stigma (the receptive part of the female reproductive organ),
http://www.pollinator.ca/bestpractices/images/conifer%20pollen%20release.jpg
Fertilization in plants : quick access
https://figures.boundless-cdn.com/19453/large/figure-32-02-07.jpeg
https://youtu.be/0UEpq1W9C_E
Success in plant reproduction depends on pollination, fertilization and seed dispersal.
Seed dispersalSuccess in plant reproduction depends on pollination, fertilization and seed dispersal.
Seed dispersal ensures survival of plants by decreasing competition and increasing the opportunities for landing on fertile grounds.
The seeds of Alsomitra macrocarpa have ”wings”, structures that will ensure dispersal under windy conditions
https://sites.google.com/site/bolandecologicalservices2/_/rsrc/1412383164588/recent-publications/black%20willow%20seed.jpg
The seeds of Salix gooddingii are surrounded by plume increasing buoyancy and thus, dispersal.
http://www.etawau.com/PlacesInterest/Bukit_Gemok/Seed/AlsomitraMacrocarpa.jpg
Your turn now, these are the seeds of Tribulus terrestris. Can you deduce how their structure is related to their dispersal strategy?
Mutualism and pollination Most flowering plants use mutualistic relationships with pollinators in sexual reproduction.. In a mutualistic interaction both species benefit. Plant-pollinator mutualisms are particularly important, and involve nearly 170,000 plant and 200,000 animal species
Example: Yucca moths and yucca plants. The plants cannot make seeds without the yucca moth, and the moth larvae only reach maturity if they eat developing yucca seeds
https://prairieecologist.com/2010/12/08/the-yucca-and-its-moth/
Yucca moths will lay their eggs inside the ovart of the Yucca plant while at the same time delivering a ball of pollen grains right in the ovary.
This is an obligate mutualistic relationship, implying that both species may not survive without it. https://prairieecologist.com/2010/12/08/the-yucca-and-its-moth/
Inquiry: Report on two more examples of mutualistic relationships between pollinators and plant species.
http://www.nature.com/scitable/knowledge/library/mighty-mutualisms-the-nature-of-plant-pollinator-13235427
Flowering involves a change in gene expression in the shoot apex.
http://ipmb.sinica.edu.tw/IPMB_site1/sites/default/files/field/photo/ft.jpg
Floral initiation is caused by the growth and differentiation of apical cells.
The triggers for the change in gene expression vary between plants, but the most common one is day length (photoperiod)
Cells in the shoot apex change how they divide and differentiate due to changes in their gene expression.
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9.4.U2 The switch to flowering is a response to the length of light and dark periods in many plants.
9.4.U2 The switch to flowering is a response to the length of light and dark periods in many plants.
9.4.U2 The switch to flowering is a response to the length of light and dark periods in many plants.
http://glencoe.mheducation.com/sites/9834092339/student_view0/chapter41/animation_-_phytochrome_signaling.html
9.4.U2 The switch to flowering is a response to the length of light and dark periods in many plants.
https://smartsite.ucdavis.edu/access/content/user/00002950/bis10v/media/ch19/day_length.swf
9.4.U2 The switch to flowering is a response to the length of light and dark periods in many plants.
Forcing floweringMethods used to induce short-day plants to flower out of season.
Since flowering can be triggered by differential exposure to light, several techniques have been devised on forcing plants to flower.
Flowering in tulips (Tulipa sp.) is induced by shortening the dark period using different ligth sources.
http://www.charismaticplanet.com/wp-content/uploads/2015/10/124.jpg
http://www.charismaticplanet.com/wp-content/uploads/2015/10/124.jpg
On the contrary Chrysanthemum sp., a short-day plant, will flower only when exposure to light is small. Thus, the plants are either covered with a black cloth or placed in a dark room.
GerminationDesign of experiments to test hypotheses about factors affecting germination.
Germination consists of the initial phases in the growth of a seed to form a seedling.
During this stage the embryonic shoot (plumule) and embryonic root (radicle) develop and grow upwards (phototropism) and downwards (geotropism) respectively.
https://s-media-cache-ak0.pinimg.com/originals/a0/6f/91/a06f9158b2e01bda67811c6099dcade3.jpg
https://youtu.be/d26AhcKeEbE
GerminationDesign of experiments to test hypotheses about factors affecting germination.
Germination: Drawing internal structure of seeds.
Seed coat (testa)
Cotyledon
Embryo shoot (plumule)
Embryo root (radicle)
Micropyle
GerminationDesign of experiments to test hypotheses about factors affecting germination.
GerminationLets brainstorm on factors that may affect germination. Ideas for design labs?
