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Plants ch. 36.3-36.4, 38.1,39.1-39.3

Plants ch. 36.3-36.4, 38.1,39.1-39.3. Absorption of Water and Minerals. Occurs in cells near tips of the roots E pidermal cells --permeable to water D ifferentiate into root hairs--modified cells that do most of absorbing water/soil solution. Epidermal cell.

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Plants ch. 36.3-36.4, 38.1,39.1-39.3

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  1. Plantsch. 36.3-36.4, 38.1,39.1-39.3

  2. Absorption of Water and Minerals • Occurs in cells near tips of the roots • Epidermal cells--permeable to water • Differentiate into root hairs--modified cells that do most of absorbing water/soil solution Epidermal cell http://www.google.com/search?client=safari&rls=en&q=The+Cohesion-Tension+Hypothesis&oe=UTF-8&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=fFyDUfPLHqOhiAKe24GACQ&biw=1330&bih=683&sei=flyDUb-qCuaniQKUq4DoDg#um=1&client=safari&rls=en&hl=en&tbm=isch&q=epidermal+cells+of+leaves&revid=1976309581&sa=X&ei=l1yDUYLTA-OtiQKG4oH4CQ&ved=0CGcQgxY&bav=on.2,or.r_qf.&bvm=bv.45960087,d.cGE&fp=

  3. Transporting Water and Minerals • Water and minerals from soil cannot be transported to the rest of the plant until enters the xylem • Endodermis--innermost layer of cells in root cortex • Last checkpoint for selective passage of minerals • transports needed minerals from soil into the xylem and keeps unwanted substances out • Casparianstrip--barrier to minerals that reach endodermis via apoplast (free diffusional space outside the plasma membrane)

  4. Bulk Flow Transport in the Xylem • Xylem Sap- the water and dissolved minerals in the xylem • Gets transported long distance by bulk flow to the veins that branch throughout each leaf • Transpiration- the loss of water vapor from leaves and other aerial parts of the plant • If transpired water is not replaced by water from the roots, the leaves will wilt, and the plant will die http://www.google.com/search?client=safari&rls=en&q=xylem+sap&oe=UTF-8&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=yFmDUeDtG4qhiQKIvYDwBw&biw=1330&bih=683&sei=ylmDUeutJIq5iwL-ooCwCg#imgrc=vY_yafzF4jpQGM%3A%3Bcuvr97dWukOVCM%3Bhttp%253A%252F%252Fwww.bio.miami.edu%252Fdana%252Fpix%252Fxylem_sap_ascent.jpg%3Bhttp%253A%252F%252Fwww.bio.miami.edu%252Fdana%252F226%252F226F09_10.html%3B500%3B549

  5. Pushing Xylem Sap: Root Pressure • At night, root cells continue actively pumping mineral ions into the xylem and the Casparian strip prevents the ions from leaking back into the soil • The accumulation of water lowers the water potential • Root pressure is generated-- a push of xylem sap • Guttation- appearance of water drops that can be seen in the morning on the tips of plants • NOT DEW Guttation http://www.google.com/search?client=safari&rls=en&q=xylem+sap&oe=UTF-8&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=yFmDUeDtG4qhiQKIvYDwBw&biw=1330&bih=683&sei=ylmDUeutJIq5iwL-ooCwCg#um=1&client=safari&rls=en&hl=en&tbm=isch&sa=1&q=guttation+in+plants&oq=guttation+in+plants&gs_l=img.3..

  6. Pulling Xylem Sap • The Cohesion-Tension Hypothesis • States that transpiration provides the pull for the ascent of xylem sap • The cohesion of water molecules transmits this pull along the entire length of the xylem • Negative pressure potential (causes water to move upward through the xylem) develops on the surface of mesophyll cell walls

  7. Pulling Xylem Sap • This transpirational pull relies on: • Adhesion--attraction between H2O and other polar substances • Cohesion--attraction between molecules of the same substance • Surface Tension • Adhesion/cohesion facilitate the transport of water by bulk flow http://www.google.com/search?client=safari&rls=en&q=transpirational+pull&oe=UTF-8&um=1&ie=UTF-8&hl=en&tbm=

  8. Rate of Transpiration • Leaves have high surface-to-volume ratios • Positive effect: enhances light absorption • Negative effect: increase water loss by way of stomata • Stomata • 95% of water lost is through stomata • Amount of water loss depends on the number of stomata and the size of their pores • Under genetic and environmental control • Ex. Desert plants have a lower stomatal density than marsh plants

  9. Stomatal Opening and Closing • Guard cells take in water from neighboring cells and become more turgid • As a result, increases the size of the pore between the guard cells • When guard cells lose water, become flaccid and the pore closes • This change in turgor pressure relies on the absorption and loss of K+

  10. Xerophytes • Xerophytes- plants adopted to dry environments • Plants in the desert • Stomata stay open and take in more CO2 • Don’t dry out because complete life cycle during the rainy season • Crassulacean acid metabolism (CAM)- specialized form of photosynthesis • Takes in CO2 at night, stomata closed during the day http://view.ebookplus.pearsoncmg.com/ebook/launcheText.do?values=bookID::4487::platform::1004::invokeType::lms::launchState::goToEBook::platform::1004::globalBookID::CM81419602::userID::4743886::scenario::3::scenarioid::scenario3::courseid::ROISEN201213::pageid::::sessionID::30359408622357203292013::smsUserID::40436616::hsid::c62c764303314af28587427e0f7ea24a

  11. Ch. 38.1Angiosperm Reproduction http://0.static.wix.com/media/8d4b4e2fa8ea1029b0255f379602d8ce.wix_mp_1024

  12. Flower Structure and Function • Flowers : • contain four whorls of modified leaves: • sepals, petals, stamens, and carpels----which attach to a part of a stem called the receptacle.

  13. Flower Structure and Function • Sepals enclose and protect the unopened floral bud. • Petals are generally more brightly colored and may attract pollinators • Stamens consist of a filament and an anther, which contains pollen sacs (microsporangia). http://www.shaneeubanks.com/images/016_flower.jpg

  14. A carpel consists of a sticky stigma at the top of a slender style, which leads to an ovary. • The ovary encloses one or more ovules • A flower may have a single carpel or multiple fused carpels; either many be referred to as a pistil. http://www.esu.edu/~milewski/intro_biol_two/lab_3_seed_plts/images/30_07FlowerStructure-L.jpg

  15. Female Reproductive Organs • The pistil is the collective term for the carpel(s). • Each carpel includes an ovary-where the ovules are produced. • Ovules are the female reproductive cells- the eggs. • A style-a tube on top of the ovary. • A stigma-which receives the pollen during fertilization. https://d15mj6e6qmt1na.cloudfront.net/i/2515312/600.jpg

  16. Male Reproductive Organs • Stamens are the male reproductive parts of the flower. • A stamen consists of an anther- which produces pollen- and a filament. • The pollen consists of male reproductive cells- that fertilize ovules. http://mystudyexpress.com/12%20th%20science%20cbse/biology/1.%20REproduction/Img%20file/10.png

  17. Development of Male Gametophyte • Within each microsporangium (pollen sac): • diploid cells called microsporocytes undergo meiosis to form 4haploid microspores. • A microspore divides once by mitosis to produce a tube celland a generative cell, which moves into the tube cell. • The spore wall surrounding the cells thickens into the sculptured coat of the pollen grain. • After the pollen grain lands on the receptive stigma, the tube cell begins to form the pollen tube. • The generative cell divides to form two sperm cells. • The pollen tube releases the sperm cells near the female gametophyte.

  18. http://home.sandiego.edu/~gmorse/2009BIOL221/Study_guide2/ang_male_gam.jpghttp://home.sandiego.edu/~gmorse/2009BIOL221/Study_guide2/ang_male_gam.jpg

  19. Female Fertilization • There are many variations in the development of the female gametophyte: • also called an embryo sac. • Twointeguments surround each megasporangium except at the micropyle.   • Themegasporocyte in the megasporangium of an ovule undergoes meiosis to form four haploid megaspores, only one of which survives. • This megaspore grows and divides by mitosis three times, forming the female gametophyte • which typically consists of eight nuclei contained in seven cells

  20. Female Fertilization continued • At the micropylar end of the embryo sac • an egg cell is lodged between two cells called synergids, • which help attract the pollen tube, • three antipodal cells are at the other end • and two nuclei called polar nuclei are in a large central cell.

  21. Female Male

  22. Double Fertilization • In double fertilization, one sperms fertilizes the egg to from the zygote, and the other combines with the polar nuclei ton from a triploid nucleus, which will develop into a food-storing tissue called the endosperm. • http://www.youtube.com/watch?v=Gq8NWh98wQs

  23. Double Fertilization http://25.media.tumblr.com/tumblr_lllb32Jvu41qktyf1o1_r1_500.png

  24. Signal transduction, Signal reception, and Signal response:Chapter 39.1

  25. Signal Transduction • Plants receive and respond to signals differently according to their environment • Plants undergo morphological adaptations that allow them to enhance survival • The morphological adaptations for growing in the dark are referred to as etiolation • The morphological adaptations for growing in the light are referred to as de-etiolation • http://www.youtube.com/watch?v=tMMrTRnFdI4

  26. Reception • Signals are first detected by receptors • The receptor involved in de-etiolation is a type of phytochrome (a member of a class of photoreceptors that is located in the cytoplasm rather than on the membrane) https://www.google.com/search?sa=N&hl=en&tbm=isch&tbs=simg:CAQSZxplCxCo1NgEGgQICQgLDAsQsIynCBo8CjoIARIU1Ab4BekDoQf2AoQG_1wLkBfAF_1gIaIN49NnbbwBe1oEnziJ-5R52nVctxDM14jMkrdmxkiQlmDAsQjq7-CBoKCggIARIEQMQO3Aw&ei=kXB_UaX1H4mkigKs0YAg&ved=0CCkQwg4&biw=1024&bih=705#imgrc=_YxOZJBMPCUegM%3A%3BvI8UDMMWvvvUbM%3Bhttp%253A%252F%252Fclassconnection.s3.amazonaws.com%252F590%252Fflashcards%252F699456%252Fjpg%252Funtitled.jpg%3Bhttp%253A%252F%252Fwww.studyblue.com%252Fnotes%252Fnote%252Fn%252Fbio-test-3%252Fdeck%252F38238%3B411%3B259

  27. Transduction • Receptors can be sensitive to very weak environmental or chemical signals • The transduction of these extremely weak signals involves second messengers (small molecules and ions in the cell that amplify the signal and transfer it from the receptor to other proteins that carry out the response) • Changes in cytosolic Ca2+ levels plays an important role in phytochrome signal transduction • the concentration of Ca2+ is naturally very low at about 10-7M, but as a result of phytochrome activation, Ca2+ channels open causing a transient 100-fold increase in cytosolic Ca2+ levels • In response to light, phytochrome undergoes a change in shape that leads to the activation of guanylylcyclase (an enzyme that produces the second messenger cyclic GMP) • Both Ca2+ and cGMP must be produced by a complete de-etiolation response

  28. Response • Second messengers regulate one or more cellular activities • In most cases, these responses involve the increased activity of particular enzymes • Two main mechanisms by which a signaling pathway can enhance an enzymatic step in biochemical pathway: • 1. post-translational modification • Activates preexisting enzymes • 2. transcriptional regulation • Increases or decreases the synthesis of mRNA encoding a specific enzyme

  29. Post-Translational Modification of Preexisting Proteins • Many second messengers like cGMP and Ca2+ activate protein kinases directly • Often, one protein kinase will phosphorylate another protein kinase, which then phosphorylates another and so on • These kinase cascades may link initial stimuli to responses at the level of gene expression

  30. Transcriptional Regulation • In phytochrome-induced de-etiolatin, several transcription factors are activated by phosphorylation in response to the appropriate light conditions. • The activation of these transcription factors depends on their phosphorylation by protein kinases activated by cGMP or Ca2+

  31. De-Etiolation (“Greening”) Proteins • The types of proteins that are either activated by phosphorylation or newly transcribed during the de-etiolatin process are enzymes that function in photosynthesis directly—others are enzymes involved in supplying the chemical precursors necessary for chlorophyll production.

  32. PLANTS!!! Ch. 39.2 Plant hormones help: • coordinate growth development • and responses to stimuli • Plant biologist prefer the broader term plant growth regulator • Describe organic compounds (natural or synthetic) that modify or control one or more specific physiological processes within plant

  33. Tropisms The growth of plant towards/away from a stimulus • Thigmotropisms (touch) • Gravitropisms/geotropsism (gravity) • Phototropisms (light) • A growth towards a stimulus is a postive tropism • A growth away from a stimulus is a negative tropism

  34. Auxin(IAA) • Function: • Stimulates stem elongation • Promotes formation of lateral and aventitious roots • Regulates development of fruit • Enhacces apical dominance • Functions in photoropism and gravitropism • Promotes vascular differentiation • Retards leaf abscission http://www.google.com/search?q=auxins&client=safari&rls=en&tbm=isch&tbo=u&source=univ&sa=X&ei=IfZ9Ue-gBoKQiALDrYGwCQ&ved=0CEIQsAQ&biw=1231&bih=668#imgrc=kcrSXBEbiM_bQM%3A%3BXBqG6dijiwOIUM%3Bhttp%253A%252F%252Fscienceaid.co.uk%252Fbiology%252Fplants%252Fimages%252Fphototropism.png%3Bhttp%253A%252F%252Fscienceaid.co.uk%252Fbiology%252Fplants%252Fplantgrowth.html%3B442%3B293

  35. Cytokinins • Functions • Regulate cell division in shoots and roots • Modify apical dominance and promote lateral bu growth • Promote movement of nutrients into sink tissues • Stimulate seed germination • Delay leaf senescence (aging) and apoptosis http://www.google.com/search?q=cytokinins+in+plants&client=safari&rls=en&tbm=isch&tbo=u&source=univ&sa=X&ei=kfZ9UZW_Gua2igLxhICACQ&ved=0CEcQsAQ&biw=1231&bih=668#imgrc=IUSehNUt9ZmedM%3A%3B1six318kh9--7M%3Bhttp%253A%252F%252Fwww.rikenresearch.riken.jp%252Fimages%252Ffigures%252Fhi_3779.jpg%3Bhttp%253A%252F%252Fwww.rikenresearch.riken.jp%252Feng%252Ffrontline%252F5836.html%3B449%3B430

  36. Gibberellins • Functions • Stimulate stem elongation, pollen development, pollen tube growth, fruit growth and seed development and germination • Regulate sex determination and the transition from juvenile to adult phases http://www.google.com/search?client=safari&rls=en&q=gibberellins&bav=on.2,or.r_qf.&bvm=bv.45645796,d.cGE&biw=1231&bih=668&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=A_d9UYP_KsjmigKgh4HQBg#imgrc=4hmgwhxstHLrxM%3A%3BNCPyQEOkVOvQLM%3Bhttp%253A%252F%252Fwww.biyolojiegitim.yyu.edu.tr%252Fk%252FGib%252Fimages%252FGibberellin_jpg.jpg%3Bhttp%253A%252F%252Fcatherine-wwwmyblog.blogspot.com%252F2011%252F04%252Fintroduction.html%3B457%3B262

  37. Brassinosteriods • Similar to cholesterol and sex hormones of animals • Functions • Promote cell expansion and cell division in shoots • Promote root growth at low concentrations • Inhibit root growth at high concentrations • Promote xylem differentiation and inhibit pholem differentiation • Promote seed germination and pollen tube elongation http://www.google.com/search?client=safari&rls=en&q=brassinosteroids&bav=on.2,or.r_qf.&bvm=bv.45645796,d.cGE&biw=1231&bih=668&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=iPd9Ua71K-S7iwK6oYD4CQ#imgrc=kyIzrjBD9rNnfM%3A%3BiNHRellRjHGNiM%3Bhttp%253A%252F%252Fwww.ou.edu%252Fcas%252Fbotany-micro%252Ffaculty%252Fpictures%252Fli-1.jpg%3Bhttp%253A%252F%252Fwww.ou.edu%252Fcas%252Fbotany-micro%252Ffaculty%252Fli.html%3B827%3B611

  38. Abscisic Acid (ABA) • Functions • Inhibits growth • Promotes stomatal closure during drought stress • Promotes seed dormanc and inhibits early germination • Promotes leaf senescence • Promotes desiccation tolerance http://www.google.com/search?client=safari&rls=en&q=abscisic+acid&bav=on.2,or.r_qf.&bvm=bv.45645796,d.cGE&biw=1231&bih=668&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=Bvh9Uf-eN4S6iwLWiYCgDQ#imgrc=3BvTzS-n7BjNaM%3A%3BjuDpDU0mv3KUuM%3Bhttp%253A%252F%252Fusers.rcn.com%252Fjkimball.ma.ultranet%252FBiologyPages%252FA%252FABA.gif%3Bhttp%253A%252F%252Fusers.rcn.com%252Fjkimball.ma.ultranet%252FBiologyPages%252FA%252FABA.html%3B197%3B123

  39. Strigolactones • Functions • Promote seed germination • Control apical dominance • The attraction of mycorrihizal fungi to the root http://www.google.com/search?client=safari&rls=en&q=strigolactones&oe=UTF-8&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=ivh9UbnFCsSQiALHiICwBA&biw=1231&bih=668&sei=jfh9UYapFc3BiwLPloCICQ#imgrc=bDgeL_te5HRsPM%3A%3BWCEY_yT9hl_jfM%3Bhttp%253A%252F%252Fusers.rcn.com%252Fjkimball.ma.ultranet%252FBiologyPages%252FS%252Fstrigolactone.png%3Bhttp%253A%252F%252Fusers.rcn.com%252Fjkimball.ma.ultranet%252FBiologyPages%252FS%252FStrigolactones.html%3B265%3B177

  40. Ethylene • Functions • Promotes ripening of many types of fruit, leaf abscission and the triple in seedlings (inhibition of stem elongation, promotion of lateral expansion and horizontal growth) • Enhances the rate of aging • Promotes root and root hair formation • Promotes flowering in the pinapple family http://www.google.com/search?client=safari&rls=en&q=ethylene&oe=UTF-8&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=0fh9UZTXMa_siwKjq4GoAw&biw=1231&bih=668&sei=1Ph9UaLOEaSNigKFkICAAg#um=1&client=safari&rls=en&hl=en&tbm=isch&sa=1&q=ethylene+functions&oq=ethylene+functions&gs_l=img.3..0i24j0i10i24.47240.52837.0.52970.24.18.4.0.0.1.230.1797.3j9j1.13.0...0.0...1c.1.11.img.g7xboFiHXho&bav=on.2,or.r_qf.&bvm=bv.45645796,d.cGE&fp=2a5ed73fbbf81680&biw=1231&bih=668&imgrc=BcrDTDJaYI6VUM%3A%3BpO8AiNHuTIg4AM%3Bhttp%253A%252F%252Fwww.qiagen.com%252Fgeneglobe%252Fstatic%252Fimages%252FPathways%252FEthylene%252520Signaling%252520in%252520Arabidopsis.jpg%3Bhttp%253A%252F%252Fwww.qiagen.com%252Fproducts%252Fgenes%252520and%252520pathways%252FPathway%252520Details.aspx%253Fpwid%253D169%3B780%3B934

  41. Ethylene and the Triple Respone • If growing plant encounters and obstacle in the soil (like a rock) and induces stress on the tip, the plant will produce ethylene, which will then control the triple response • The triple response enables the shoot to avoid and obstacle • Ethylene production will decrease when the plant is clear of the obstacle (unrestricted growth)

  42. Ethylene and leaf abscission • Loss of leaves during autum helps prevent desiccation during seasonal peridos of climateic stress • A change in the ratio of ethylene to auxin controls abscission • Aging leaf produces less auxin, making the cells of abscission layer more sensitive to ethylene • Cause the cells to produce and enzyme that digest the cellulose and other compents of the cell wall

  43. Responses to light are critical for plant success: Chapter 39.3 http://www.google.com/search?client=safari&rls=en&q=photomorphogenesis&oe=UTF-8&um=1&hl=en&biw=1330&bih=683&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=SVaDUZGaHciUiAK8yYHoBw#um=1&client=safari&rls=en&hl=en&tbm=isch&sa=1&q=

  44. Affect of light on plants • The effects of light on plant morphology are called photomorphogenesis • Plants detect not only the presence of light but also its direction, intensity, and wavelength (color)

  45. Affect of light on plants • A graph called an action spectrum depicts the relative effectiveness of different wavelengths of radiation in driving a particular process Image source: Mastering Biology Textbook

  46. Blue-Light Photoreceptors • Blue light initiates a variety of responses in plants including: • phototropism : the light-induced opening of stomata • And the light-induced slowing of hypocotyl elongation that occurs when a seedling breaks ground

  47. Blue-Light Photoreceptors • There are three different types of pigments to detect blue light: • 1. Cryptochromes—molecular relatives of DNA repair enzymes, are involved in blue-light induced inhibition of stem elongation (ex. When a seedling first emerges from soil) • 2. Phototropin—a protein kinase involved in mediating phototropic curvatures • 3. zeaxanthin—the major blue-light photoreceptor involved in blue-light mediated stomatal opening

  48. Phytochromes as Photoreceptors and seed germination • Phytochromes regulate many plant responses to light • It has two identical subunits, each consisting of a polypeptide component covalently bonded to a nonpolypeptidechomophore, the light absorbing part of the subunit Image source: Mastering Biology Textbook

  49. Phytochromes and Shade Avoidance • Phytochrome system also provides the plant with information about the quality of light • The sensing mechanism enables plants to adapt to changes in light conditions

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