Plantsch. 36.3-36.4, 38.1,39.1-39.3

Occurs in cells near tips of the rootsEpidermal cells--permeable to water

Differentiate into root hairs--modified cells that do most of absorbing water/soil solution

Absorption of Water and Minerals

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=

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

Casparian strip--barrier to minerals that reach endodermis via apoplast (free diffusional space outside the plasma membrane)

Transporting Water and Minerals

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

Bulk Flow Transport in the Xylem

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

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

Pushing Xylem Sap: Root Pressure

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..

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 xylemNegative pressure potential (causes water to move upward

through the xylem) develops on the surface of mesophyll cell walls

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

Pulling Xylem Sap

http://www.google.com/search?client=safari&rls=en&q=transpirational+pull&oe=UTF-8&um=1&ie=UTF-8&hl=en&tbm=

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

Rate of Transpiration

Guard cells take in water from neighboring cells and become more turgid As a result, increases the size of the pore between the guard

cellsWhen guard cells lose water, become flaccid and the pore

closesThis change in turgor pressure relies on the absorption and

loss of K+

Stomatal Opening and Closing

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

Xerophytes

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

Ch. 38.1Angiosperm Reproduction

http://0.static.wix.com/media/8d4b4e2fa8ea1029b0255f379602d8ce.wix_mp_1024

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.

Flower Structure and Function

http://www.shaneeubanks.com/images/016_flower.jpg

• 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.esu.edu/~milewski/intro_biol_two/lab_3_seed_plts/images/30_07FlowerStructure-L.jpg

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.

Female Reproductive Organs   

oThe pistil is the collective term for the carpel(s). oEach carpel includes an ovary-where the ovules are produced.oOvules are the female reproductive cells- the eggs.oA style-a tube on top of the ovary.oA stigma-which receives the pollen during fertilization.

https://d15mj6e6qmt1na.cloudfront.net/i/2515312/600.jpg

Male Reproductive Organs

o Stamens are the male reproductive parts of the flower.

o A stamen consists of an anther- which produces pollen- and a filament.

o The pollen consists of male reproductive cells- that fertilize ovules.

http://mystudyexpress.com/12%20th%20science%20cbse/biology/1.%20REproduction/Img%20file/10.png

Within each microsporangium (pollen sac): diploid cells called microsporocytes undergo

meiosis to form 4 haploid microspores. A microspore divides once by mitosis to produce

a tube cell and 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.

Development of Male Gametophyte

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

Female Fertilization There are many variations in the development of

the female gametophyte: also called an embryo sac.

Two integuments surround each megasporangium except at the micropyle.  

The megasporocyte 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

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.

Female Male

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

Double Fertilization

http://25.media.tumblr.com/tumblr_lllb32Jvu41qktyf1o1_r1_500.png

Signal transduction, Signal reception, and

Signal response:Chapter 39.1

Signal Transduction

• 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)

Reception

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

• 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 10-7 M, 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 guanylyl cyclase (an enzyme that produces the second messenger cyclic GMP)

• Both Ca2+ and cGMP must be produced by a complete de-etiolation response

Transduction

Response

• 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

Post-Translational Modification of Preexisting Proteins

• 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+

Transcriptional Regulation

• 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.

De-Etiolation (“Greening”) Proteins

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

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

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

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 apoptosishttp://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

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

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

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

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

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

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)

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

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=

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)

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

Affect of light on plants

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

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

Blue-Light Photoreceptors

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 nonpolypeptide chomophore, the light absorbing part of the subunit

Image source: Mastering Biology Textbook

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

Responses to Seasons

seed germination, flowering, and the onset and breaking of bud dormancy are all stages that occur at specific times of the year

The environmental stimulus that plants use most often to detect the time of year is the photoperiod, the relative lengths of night and day

A physiological response to photoperiod, such as flowering, is called photoperiodism

Photoperiodism

Short-day plants require a light period shorter than a critical length to flower

Long-day plants generally flower in the late spring

Day-neutral plants are unaffected by photoperiod and lower when they reach a certain stage of maturity, regardless of day length

Night Length

Researchers learned that flowering and other responses to photoperiod are actually controlled by night length, not day length

Sources

Goldberg, Deborah M.S. Barron's AP Biology. 3rd ed. New York: Baron's Educational Series, 2013. Print.

Reece, Jane B., and Neil A. Campbell. Campbell Biology. 9th ed. Boston: Benjamin Cummings / Pearson Education, 2011. Print.