Week 5 Notes
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This 4 page Class Notes was uploaded by Nausheen Zaman on Sunday February 21, 2016. The Class Notes belongs to BIO1500 at Wayne State University taught by Dr. William Bradford in Winter 2016. Since its upload, it has received 55 views. For similar materials see Basic Life Diversity in Biology at Wayne State University.
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Date Created: 02/21/16
Chapter 36: Plant Forms ● Xylem principal waterconducting tissues, also conducts dissolved minerals + inorganic ions (nitrates/phosphates), supports plant body, includes fibers and parenchyma cells ○ Tracheids Dead cells that overlap one another and taper off at the end ○ Vessels Dead cylindrical cells arranged in continuous endtoend format ○ Lignified reinforced with lignin (primary structural tissue in plants) ○ Vessel members < Tracheid members ○ Primary Xylem Formed from procambium in apical meristem (primary growth = increase in height) ○ Procambium undifferentiated cells in the apical meristem that later give rise to specialized cells in plants during primary growth ○ Secondary Xylem Formed from vascular cambium (secondary growth = increase in girth) ○ Vascular cambium A ring in plants that produces new xylem (interior) and phloem (exterior). mostly common in woody eudicots ○ Transpiratio water vapor diffusion from plants ● ***SEE SLIDE 4 IN THE FEB 12 LECTURE FOR XYLEM TISSUE COMPARISONS*** ● Phloem Principal foodconducting tissues, hormone/amino acids/growth substance transporter ○ ANGIOSPERMS ○ Sievetube members responsible for the translocation of material across phloem tissue, contain sieve plants, specialized and more efficient ■ Variable pore size ■ Comes with a companion celladjacent parenchyma cell, carries out metabolic functions that allows sieve member to function, have many plasmodesmata) ● Nonflowering plants albuminous cells instead of companion cells ○ Sieve plate perforated ‘plates’ between two sieve tubes in angiosperm vascular plants ■ Larger pores than sieve areas ○ FERNS/GYMNOSPERMS ○ Sieve cell primitive sieve element with narrow pores and no sieve plate ■ Uniform pore size ○ Sieve areas parts of the sieve tube wall that are clustered pores responsible for cytoplasmic connections between different cells. Highly concentrated in areas where they are near sieve plates ■ Both are living cells ■ Contain pore clusters ■ Lack nuclei at maturity ○ ***SEE SLIDE 11 OF FEB 12 LECTURE FOR SUMMARY*** ● Roots ○ NOTE! These boundaries are not clearly defined, rather they are a group of common traits that are expressed as a stage ○ Simpler pattern of organization and development than stems ○ Root Cap ■ Stems don’t have an equivalent structure ■ Containscolumella (inner) an root capouter/lateral) cells that are continuously formed by the apical meristem ● Protects delicate tissues in the meristem (root cap) + gravitational perception (columella) ■ Golgi bodies in cells secrete slimy secretion that lubricates the root in order for it to have an easier time growing through the soil ■ Columella: ● ER in periphery (not the center!) ● Nucleus located at the top/middle of cell ● No large vacuoles for water ● Containamyloplasts(organelles that help in directing cell towards gravitational pull by gathering towards the side facing the gravity) ○ Zone of Cell Division ■ Comes from rapid divisions in root apical meristem ■ Meristem daughter cells subdivide into three main meristems ■ Genetic differentiation begins here (anatomical/morphological patterning = zone of maturation) ● Protoderm ● Procambium ● Ground meristem ■ Werewolf (WER) gene suppresses root hair development ● WER expressed = no root hair in that area ● WER not expressed = normal root hair development ■ Scarecrow (SCR) gene differentiation between endodermis and adjacent ground cell layer ● SCR expressed = asymmetrical division between endodermal cells and ground cells ● SCR not expressed = ground cells and endodermal cells grow together in one layer ● Ground meristem cells only express this gene ○ Zone of Elongation ■ Where cells grow 3x longer than wide (width only increases slightly) ■ Nothing changes above this zone ■ Mature parts of the root remain stationary for the rest of the plants life except for increase in girth ○ Zone of Maturation ■ Anatomical/morphological differentiation occurs here ■ Root surface cell = epidermal cells (very thin cuticle with root hair/nonhair cells) ■ Parenchyma cells= ground meristem → cortex (part of stem that functions in food storage and later becomes part of the endodermis) ■ Endodermal tissue= walls filled with suberin (a fatty substance that repels water) ■ Casparian strip= waterproof corky bands around endodermis that serve as a water and mineral transporter between the xylem and endodermis ● SCR mutants lack casparian strips ■ Plasma membranes control what pass through the cells ■ Stel = all interior tissues past endodermis ■ Pericycle= cylinder of parenchyma cells next to/interior of endodermis ● Gives rise to lateral roots and vascular/cork cambium (eudicots) ● Anatomy of a Woody Stem ○ ***SEE SLIDES 2627 IN FEB 12 SLIDES FOR DIAGRAMS AND COMPARISONS*** ● Differentiation of Plant Tissues ● Modified Roots ○ Derived from true roots ○ Taproot system single large root with little branching roots ○ Fibrous system many small roots of the same size ○ Adventitious root roots that grow in places other than the plant’s original root ○ Prop roots ‘props’ the plant up ○ Aerial root Obtains water from air (Aerial = air) ○ Pneumatophores Oxygen uptake (pneumo = oxygenrelated/lungs) ○ Contractile root pull plant deeper into soil (‘contracts’ plant into the soil) ○ Parasitic root penetrates host plants (parasites = leeches off host. No pun intended) ○ Food storage roots stores carbs ○ Water storage roots weight 50kg (about 110 pounds!) or more ○ Buttress roots Provide considerable stability (think of the medieval European churches with the flying buttresses) Check out this link for vocab! → http://www.uri.edu/cels/bio/plant_anatomy/glossary.html