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Plants

Plants. Transport in plants. Vascular vessels- Xylem – water & minerals up to leaves Ph loem – water & food – up & down to parts of plant (products of photosynthesis) http://www.youtube.com/watch?v=w6f2BiFiXiM. Roots – absorb water & minerals Mycorrhizae – fungi that live in roots

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Plants

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  1. Plants

  2. Transport in plants

  3. Vascular vessels- • Xylem – water & minerals up to leaves • Phloem – water & food – up & down to parts of plant (products of photosynthesis) • http://www.youtube.com/watch?v=w6f2BiFiXiM

  4. Roots – absorb water & minerals • Mycorrhizae – fungi that live in roots • greatly increase surface area • Increases absorption of water & minerals

  5. http://www.youtube.com/watch?v=bq1bTduTzC0

  6. Transpiration Adhesion Cohesion Tension

  7. 3. Evaporation of water continue, increased rate of transpiration, so water is pulled from surrounding cells 2. As evaporation occurs, air-water interface becomes more curved Increases rate of transpiration 1. Water is lost by transpiration, Evaporation of water film replaces it

  8. Stomata – CO2 enters, H2O exits • Guard cells balance need for CO2 with need to conserve water • Stomatal density varies among species • High light exposure & low CO2 lead to increased stomatal density

  9. What features account for the evolutionary success of angiosperms? • Why are the flowering plants so successful in terms of their ecological dominance and in terms of their great number of species (diversity)?

  10. Seeds • primary means of reproduction and dispersal; an adaptation shared with gymnosperms

  11. Flowers • the flower attracts insects, birds, and bats • has dramatically increased the diversity of flowering plants to specificity of pollinators

  12. Co-evolution (mutual adaptation) with insects • Uses only a relatively small amount of pollen compared due hoverfly • http://www.youtube.com/watch?v=MQlq5QtRI9o

  13. Closed carpels • allow seeds to develop enclosed within a fruit • protects seeds from drying out as they grow and mature • aids in the dispersal of seeds

  14. Double fertilization • results in the production of endosperm, a nutritive tissue that feeds the developing embryo.

  15. Vascular system • very efficient water conducting cells, called vessel elements, in their xylem, in addition to tracheids

  16. Leaves • Broad, expanded blades are structured for maximum efficiency in photosynthesis. • Shedding of these leaves during cold or dry spells reduces water loss • Allows some flowering plants to expand into habitats that would otherwise be too harsh for survival.

  17. Plant responses • Signal transduction pathways: • Reception  Transduction Response • hormone or stimulus interacts with receptor molecule • Relay molecules & secondary messengers • Cell responds (i.e. turning genes on or off)

  18. Plant responses

  19. Phytochrome – found in cytoplasm • - photoreceptor - • http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter41/animation_-_phytochrome_signaling.html

  20. “Greening” Etiolation – adaptation for growing in dark De-etiolation- response to light

  21. Phytochrome – plant pigment 2 subunits – each with polypeptide bound to chromophore

  22. Phytochrome – plant pigment Chromophore is reversible – from Pr to Pfr Exposure to sunlight shifts Pr to Pfr

  23. Plant hormones • Hormone – a signaling molecule produced in very small amounts that binds to specific receptors & triggers responses in target cells

  24. Phototropism • http://www.youtube.com/watch?v=zctM_TWg5Ik Growth of a plant towards or away from light Differential growth – due to auxin

  25. Auxin Plant hormone – 1st one discovered Molecule is Indolacetic acid (IAA)

  26. Circadian rhythms – an internal clock • Physiological 24 hr cycle • Rhythms continue even under set conditions • The 24 hr clock is set by environmental cues, such as light • Phytochromes – • When exposed to sunlight, Pr shift to Pfr • The sudden increase of Pfr at dawn sets the biological clock

  27. Plant survival depends on timing • Flowers bloom when pollinators are present • Seed germination needs to occur in right season • How do plants know when seasons occur? • Environmental cue – photoperiod, changing of relative lengths of day & night

  28. Photoperiodism • Response of plant to photoperiods • - i.e. flowering of plants in response to 24 hour cycle • Photoperiod is the length of day vs. the length of night • Critical night length- amount of darkness needed for plant to produce flowers (photoperiod responses controlled by night length, not day length) – must be continuous darkness

  29. Short day (long night) plants- flowers when when night is longer than critical dark period Long day (short night) plants – flower when night is shorter than critical dark period * originally the day hours were thought to determine flowering (vs. night), but it is the length of night that is critical

  30. Can disrupt with a flash of red light, can reset with a flash of far red light.

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