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64 Cards in this Set
- Front
- Back
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What is development?
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The sum total of events that contribute to the progressive elaboration of the plant body, encompassing the entire life cycle.
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What are two primary features of development?
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Growth and differentiation
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What does growth represent and how does it arise?
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An irreversible increase in volume or size. Cell division and/or cell expansion. Can occur both sequentially and/or independently. Cell division is usually followed by cell expansion.
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Where does growth usually occur?
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In areas know as the meristem, which is located at the tips of roots (root apical meristem) and shoots (shoot apical meristem)
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Can cell expansion occur without cell division? Give an example if needed.
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Yes, root hairs are extension of individual epidermal cells.
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How does the cell wall prevent from being stretched too thin and rupturing during cell expansion?
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New cell wall polymers are synthesized to keep up with volume increase.
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What are two fundemental types of cell growth?
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Tip Growth= ..... -> ... . .
Diffuse Growth= ..... -> . . . . |
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Where can tip growth be found and how does it occur? What determines the rate of growth?
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Seein in pollen tubes and root hairs. Vesicles are delivered to the tip via actin microfilaments. The rate of vesicle delivery and deposition determines rate.
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What is the driving force of diffuse growth. In what directions can diffuse growth occur?
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Turgor pressure. Can occur in many directions, but it depends on the orientation of the cellulose microfibrils. If they are ordered randomly, then expansion will occur in all directions. If they are ordered in one dimension, then expansion will occur pependicular to the plane of reinforcement.
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What is a stem cell?
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An undifferentiated cell that retains the capacity for cell division indefinitely
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What is differentiation?
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Changes that occur in cells that bring about functional or morphological distinctiveness.
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Are dividing cells, such as meristimatic cells, distinctive?
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No, but their daughter cells become committed and do diffrentiate into specific cell types.
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What are the differences between plant and animal development?
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1.) Germ Line
2.) Postembryonic development: continual organogenesis 3.) Cell movement 4.) Regeneration and totipotency 5.) Intercellular communication |
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What is the difference in the germ line bewteen animals and plants?
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In animals, the germ line is set aside early in development. In plants, the decision to switch to reproductive growth comes much later in life, such as the change from vegetative to floral meristem at the shoot apex.
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What is the difference between postembryonic development between animals and plants?
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In animals, all basic tissues and organs are developed in the embryo prior to birth. In plants, continual organogenesis occurs.
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Two types of Post-embryonic plant development
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1.) Primary meristem (SAM and RAM)
-give rise to lateral organs -maintian themselves -produce axillary meristems -add length to plant 2.)Secondary Meristem (vascular cambium and corl cambium) -give rise to specific tissues, not new organs -add girth to plant |
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What is the difference between cell movement in animals and plants?
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In animals, cells are not held in place during growth and development. In plants, cell walls keep the cells in place during growth and development.
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What are the types of cell division?
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They can divide both symmetrically and asymmetrically. Also they divide on diffrent planes.
-Periclinal, in which the new cell wall is parallel to the surface of the organ -Anticlinal-radial, in which the new cell wall is perpindicular to the surface of the organ, growing outward -Anticlinal-transverse, in which it is the same as radial, except upward. |
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How is regeneration different between animals and plants?
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Plants are capable of being totipotent, in which they dedifferentiate to a more embryonic state and they can redifferentiae again. Such as with Calli, which is undifferentiated cell clumps, whihc form from plant tissues treated with hormones. Calli are then capable of generating whole plants.
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How is intercellular communication different between animals and plants?
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In plants, cells are encased in a cell wall, which have plasmodesmata span these walls interconnecting the cytoplasma of adjacent cells. This allows cell to cell communication, including movement of hormones, nutrients, and signaling molecules that influence differentiation.
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What determines developmental fate in plants?
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Cell position (not cell lineage)
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What factors control plant development?
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1.) Intrinsic factors
a.)Intracellular - gene expression, turgor pressure, mineral content, pathogens, endogenous rhythms. b.)Intercellular - Hormones regulate group of cells 2.) Extrinsic - light, temperature, gravity, nutrient status, soil moisture |
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What helps to hold cellulose microfibrils in place in the cell wall? What adds additional strength to a cell wall?
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Crosslinking noncellulosic glycans, xyloglucans, and glucuronoarabinoxylans. The interaction of pectin with Ca+ ions. The carboxyl groups contain polar negative oh groups which interact with the cations of Ca+ making bridge like structures. Also, hydroxyproline-rich glycoproteins known as extensins.
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Comparing reinforced concrete to a plant cell, what is the "concrete" and what is the "iron rebar"?
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cement=crosslinking glycans, pectins
iron rebar=cellulose microfibrils |
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Explain the primary and secondary cell wall during cell wall organization.
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Primary cell wall is formed during cell growth. It is laid down during the first division of cells and develops bewteen the two daughter cells during early telophase.
Secondary wall - Develops after cell expansion has stopped. Successive depositions of cellulose microfibrils and other compenents lead to secondary cell wall, which is responsible for distinctive thickenings of the final cell wall. Deposited inside the primary cell wall. |
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What guides deposition of cellulose microfibrils extruded through the plasma membrane?
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Microtubules with the plant cell
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What happens when microtubule function is chemically perturbed?
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1.) Microfibrils are deposited randomly
2.) Expansion occurs in all directions (radial) 3.) Cells become bulbous |
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What does cell expansion require?
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Controlled cell wall loosening
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What is the driving force for cell enlargement and why?
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Water uptake, because most of a plant cell is occupied by the vacoule
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What does the rate of growth (expansion)(dV/dT) depend on?
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1.) turgor pressure (P)
2.) cell wall yield threshhold (turgor value at which growth ceases)(Y) 3.) wall extensibility (m) dV/dT=m(P-Y) |
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How is wall stress relieved during cell expansion? What does this in turn cause? How does it work?
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Cross linking xyloglucans are readjusted. This lowers turgor pressure and allows more water to enter cell for another round of growth through expansion. Imagine two parallel rods (microfibrils) with stretchy string attatching them (crosslinkng xyloglucans). When turgor pressure increases, these strings relax, allwoing the microfibrils to readjust themselves to account for the expansion. The crosslinking xyloglucans relax from EXPANSINS ENZYMES weakening them. When they become set, the stretching string tightens back up.
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What gives rise to the embryo?
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Cell division of the zygote in the ovary of a flower
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What gives rise to the shoot and root?
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Plumule and Radicle, respectively
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What provides storage reserves for gemination in monocots and dicots?
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The endosperm in monocots and cotyledons in dicots (the endosperm is consumed by the embryo)
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What is the water content of seeds?
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Less than 5%, which makes them severly dehydrated. They must take up water to germinate.
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First sign of germination?
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Radicle emerges
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What is epigeal germination?
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Cotyledons emerge with the hypocotyl. The hypocotyl is the first part of the shoot axis to enlongate
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What is Hypogeal germination?
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Cotyledons remain underground and the epicotyl enlongates first and emerges.
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What is the epicotyl and hypocotyl?
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Epicotyl - area betweem cotyledons and shoot apex
Hypocotyl - area bewteen cotyledons and surface |
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Where does cell division and cell expansion occur?
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Cell division occurs solely in meristimatic tissue while expansion occurs anywhere
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What are apical and lateral meristems?
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Apical meristems are responsible for adding length to the shoot or root axes, which is known as primary growth.
Lateral meristem (the vascular meristem) is responsible for thickening the stems and roots, which is known as secondary growth. |
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What happens when sems undergo secondary growth?
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Epidermis derived from primary growth is usually replaced by a cork derived from another lateral meristem known as the cork cambium.
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The SAM contains 2 ddistinct zones and 3 distinct 3 layers. What are they?
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The Tunica (cell division=anticlinal)
-L1 -L2 The Corpus (cell division=random) -L3 |
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Where does the latral root meristem derive from?
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Pericycle layer
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What are Axillary Meristems?
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They form later in development. They form in the axis of leaves and are derived from the shoot apical meristem. they give rise to axillary buds or branches. thats why when you want a plant to get wider, you prune the top off, which cuts off the shoot apex, which sends signals to these causing lateral growth.
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Where does the vascular cambium come from?
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Procambium between xylem and phloem plus parenchyma between vascular bundles in stems.
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Does Vascular cambium give rise to new organs?
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No
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What is a Phytomere?
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A structural unit generated by repeated activity of the shoot apical meristem consisting of:
-leaf -node -internode -bud |
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When internodes fail to enlongate, what happens?
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Basal rosettes form
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What is Phyllotaxy? How is it determined? What does it affect?
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Arrangement of leaves around the stem. Activity of the SAM. Each species has a distinctive phyllotaxy which is genetically determined. It affects the light receiving properties of the plant.
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Can Phyllotaxy change during development?
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Yes
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Spiral phyllotaxy usually arises from succesive angle of ____degrees between the emerging leaf primordia
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137 degrees
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What are the 4 developmental zones of the root?
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1.) Root cap
2.) Meristematic zone w/ quiescent center 3.) elongation zone 4.) maturation zone |
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What is a Phytomere?
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A structural unit generated by repeated activity of the shoot apical meristem consisting of:
-leaf -node -internode -bud |
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When internodes fail to enlongate, what happens?
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Basal rosettes form
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What is Phyllotaxy? How is it determined? What does it affect?
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Arrangement of leaves around the stem. Activity of the SAM. Each species has a distinctive phyllotaxy which is genetically determined. It affects the light receiving properties of the plant.
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Can Phyllotaxy change during development?
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Yes
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Spiral phyllotaxy usually arises from succesive angle of ____degrees between the emerging leaf primordia
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137 degrees
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What are the 4 developmental zones of the root?
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1.) Root cap
2.) Meristematic zone w/ quiescent center 3.) elongation zone 4.) maturation zone |
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What are the four developmental zones of the root?
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1.) Root Cap
2.) Meristematic zone w/ quiescent center 3.) elongation zone 4.) maturation zone |
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Describe the process of floweing.
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Requires a reprogramming of the apical meristem. This occurs in 3 stages:
1.)Induction - irreversible and can occur elsewhere in the plant 2.)Evocation - Occurs at the SAM and cause it to produce floral primordia instead of leaf primordia 3.) Development |
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Floral structures can be considered modified what?
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Leaves
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What are the 4 "whorled" organs of a flower?
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1.) Stamen - male, pollen
2.) Sepals 3.) Carpels - female, contain ovules (Carpels develop into fruit while the ovules develop into seed) 4.) Petals |
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What are the 4 broad phases of pollen tube growth?
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1.) Growth on stigma
2.) Growth between cells of the transmitting tissue in the style 3.) Emergence into an ovary 4.) Grwoth along the ovule funiculus to reach the micropyle |
