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9.4 plant reproduction

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IB Biology 2015

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9.4 plant reproduction

  1. 1. 9.4 Reproduction in plants Essential idea: Reproduction in flowering plants is influenced by the biotic and abiotic http://www.people.fas.harvard.edu/~ccdavis/weblinks/El_Pais_fil es/Imagen_Rafflesiaceae_alcanza_metro_diametro_kilos_peso.jp g Rafflesia keithii Meijer
  2. 2. Understandings Statement Guidance 9.4.U1 Flowering involves a change in gene expression in the shoot apex 9.4.U2 The switch to flowering is a response to the length of light and dark periods in many plants. 9.4.U3 Success in plant reproduction depends on pollination, fertilization and seed dispersal. 9.4.U4 Most flowering plants use mutualistic relationships with pollinators in sexual reproduction.
  3. 3. Applications and Skills Statement Guidance 9.4.A1 Methods used to induce short-day plants to flower out of season. 9.4 S.1 Draw internal structure of seeds. 9.4.S.2 Drawing of half-views of animal-pollinated flowers. 9.4 S.3 Design of experiments to test hypothesis about factors affecting germination.
  4. 4. 9.4 U.1 Flowering involves a change in gene expression in the shoot apex • Production of plant hormones which when exposed to the proper amount of photo- inductive daylight convert vegetative structure in reproductive structure. • The hormone is then transport from the leaf to the shoot apex cause genes to switch on causing transcription of proteins to begin. • An increase in morphological and molecular changes at the shoot apex, especially involving floral organ identity genes.
  5. 5. The mechanism of flowering • mRNA moves from leaf to flower meristem. • This mRNA provides a link between the phytochrome system (the receptor), its activation of genes in the leaf (mRNA synthesis) • Differentiation of the meristem into the flower structure comes about due to the construction of protein from protein synthesis. http://eatbetea.com/wpcontent/uploa ds/2014/04/IMG_1211.jpg 9.4 U.1 Flowering involves a change in gene expression in the shoot apex
  6. 6. 9.4 U.2 The switch to flowering is a response to the length of light and dark periods in many plants. Phytochrome and the control of flowering Flowering Cues: • Plant have to coordinate the production of flowers to coincide with the best reproductive opportunities. There are many environmental cues that affect flowering however the photoperiod is the most reliable indicator on 'time' of year. • The photoperiod the period of day light in relation to dark (night). In northerly and southern regions this photoperiod is a reliable indication of the time of year and therefore one of the most reliable indicators of the seasonal changes. Short and Long day Plants: • Short day plants (SDP) typically flower in the spring or autumn when the length of day is short. • Long day plants (LDP) typically flower during the summer months of longer photoperiod
  7. 7. 9.4 U.2 The switch to flowering is a response to the length of light and dark periods in many plants. Critical Night Length •Experiments have shown that the important factor determining flowering is the length of night rather than the length of day. •SDP have a critical long night. That the length of night has to exceed a particular length before there will be flowering. •LDP have a critical short night. That the length of night must be shorter than a critical length before there will be flowering.
  8. 8. 9.4 U.2 The switch to flowering is a response to the length of light and dark periods in many plants. Phytochrome System: •The receptor of photoperiod is located within the leaf. •The cellular location of the receptor is unclear. •The chemical nature of the receptor is a the molecule PHYTOCHROME. •Phytochrome can be converted from one form to another by different types of light. http://www.putso.com.ne.kr/lecture/img/pfr.gif
  9. 9. 9.4 U.2 The switch to flowering is a response to the length of light and dark periods in many plants. www.click4biology.com
  10. 10. 9.4 U.2 The switch to flowering is a response to the length of light and dark periods in many plants. Flowering in Short day plant (SDP) •Short day plants flower when the night period is long. *Night length is critical Steps  In day light or red light, Phytochrome Red (Pr) is converted to Phytochrome Far Red (Pfr). The conversion actually only requires a brief exposure to white or red light  In the dark, Pfr is slowly converted back to Pr. A long night means that there is a long time for the conversion.  Under short day conditions (long night) at the end of the night period the concentration of Pfr is low.  In SDP, low Pfr concentration is the trigger for flowering. http://cnx.org/resources/da0cef9ea401465d69b8142665006a50/Figure_30_06_01.jpg
  11. 11. 9.4 U.2 The switch to flowering is a response to the length of light and dark periods in many plants. Flowering in Long day Plants (LDP): *Night length is critical •Long day plants flower when the night period is short. Steps In day light (white or red) the Pr is converted to Pfr. During periods when the day light period is long but critically the dark period is short, Pfr does not have long to breakdown in the dark. Consequently there remains a higher concentration of Pfr. In LDP, high Pfr concentration is the trigger to flowering. http://jordantimes.com/uploads/repository/a98b 24c425cded558dc267e1366e05003088e2d4.jpg
  12. 12. 9.4 A.1 Methods used to induce short-day plants to flower out of season http://www.silversurfers.com/wp- content/uploads/2012/09/red-white-parrot-tulip.jpg
  13. 13. 9.4 U.3 Success in plant reproduction depends on pollination, fertilization and seed dispersal. Pollination •The process in which pollen is transferred from the anther to the stigma. •Requires a vector e.g. insects mammals, winds, birds, water. •Cross fertilization involves pollen from one plant landing on the stigma of a different plant •Self pollination involves the transfer of the plants own pollen to its own stigma http://www.pollinator.ca/bestpractices/ima ges/conifer%20pollen%20release.jpg
  14. 14. http://www.pollinis.org/wp-content/uploads/2014/05/Image- Pollination_Bee_Dandelion_Zoom2.jpg
  15. 15. 9.4 U.3 Success in plant reproduction depends on pollination, fertilization and seed dispersal. Fertilization • Fusion of the gamete nuclei (in the pollen grain) with the female gamete (in the ovule) to form a zygote. • Pollen grains often contain an additional nuclei used in the ‘fertilization’ of the food store cells. Seed dispersal • Fertilized ovules form seeds. The seeds are moved away from the parental plant before germination to reduce competition for limited resources with parental plant. There are variety of seed dispersal mechanism including fruits, winds, water and animals http://leavingbio.net/The%20Structure%20and %20Functions%20of%20Flowers_files/image018.jpg Fertilization
  16. 16. http://www.nature.nps.gov/biology/invasivespecies/Prevention.cfm Seed dispersal: Sticky seeds hitching a ride on fur
  17. 17. 9.4 U.4 Most flowering plants use mutualistic relationships with pollinators in sexual reproduction. • Sexual reproduction in flowering plants depends on the movement of pollen from stamen to a stigma • Pollen is transferred by wind, water (less common) and animals known was pollinators (more common) • Pollinators: birds, bats & insects (bees & butterflies) • Mutualism – close association between 2 organisms that both benefit from the relationship. Pollinators gain food by nectar and plants gains a means to transfer pollen to another plan http://upload.wikimedia.org/wikipedia/commons/d/db/Colibri-thalassinus-001-edit.jpg
  18. 18. 9.4 U.4 Most flowering plants use mutualistic relationships with pollinators in sexual reproduction. • Sexual reproduction in flowering plants depends on the movement of pollen from stamen to a stigma • Pollinators: birds, bats & insects (bees & butterflies)
  19. 19. 9.4 S.1 Draw internal structure of seeds Dicotyledonous seeds • Testa protects the plant embryo and the cotyledon food stores • Cotyledons contain food store for the seed • Plumule is the embryonic stem • Radicle is the embryonic root • Micropyle is a hole in the testa ( from pollen tube fertilization) through which water can enter the seed prior to germination • Scar is where the ovule was attached to the carpel wall
  20. 20. The Children Pureed Red Meat Smoothies
  21. 21. 9.4 A.2 Drawing of half-views of animal-pollinated flowers. • Sepals cover the flower structure while the flower is developing. In some species these are modified to ' petals'. • Petals surround the male and female flower parts. Function is to attract animal pollinators. • Pistil (female reproductive part)  Stigma is the surface on which pollen lands and the pollen tube grows down to the ovary.  Style connects the stigma to the ovary.  Ovary contains the ovules (contain single egg nuclei). • Stamen (male reproductive part)  Filaments support the anthers  Anther that contain the pollen. Together they are called the stamen.
  22. 22. 9.4 A.3 Design of experiments to test hypothesis about factors affecting germination. The metabolic events of seed germination: a) Water absorbed and the activation of cotyledon cells b) Synthesis of gibberellin which is a plant growth substance. (Hormone is no longer a term used to describe such compounds). c) The gibberellin brings about the synthesis of the carbohydrase enzyme amylase d) Starch is hydrolyzed to maltose before being absorbed by the embryonic plant e) The maltose can be further hydrolyzed to glucose for respiration on polymerized to cellulose for cell wall formation causing growth.
  23. 23. Weird green aliens smiled making a greeting
  24. 24. 9.4 A.3 Design of experiments to test hypothesis about factors affecting germination. Conditions for Germination Seeds require a combination of: Oxygen for aerobic respiration Water to metabolically activate the cells Temperature for optimal function of enzymes All are need for successful germination. Each seed has its own particular combination of the three factors. http://www.emperorswithoutclothes.com/images/seed_growth.jpg
  25. 25. 9.4 A.3 Design of experiments to test hypothesis about factors affecting germination.

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