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Exam 3
Plant Lectures
71
Biology
Undergraduate 2
03/29/2009

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Term
Parenchyma
Definition
undifferentiated; thin cell walls
Term
Collenchyma
Definition
undifferentiated; thick cell wals; structural support
Term
Fibers and Sclereids
Definition
thick walled, for support
Term
Plants grow from __ __
Definition
Apical Meristems
Term
All cell types are derived from just a few cells in the ____
Definition
meristems
Term
Where are Meristems found?
Definition
shoot tips, root tips, and leaf margins
Term
Dicotyledons (Dicots)
Definition
These have 2 cotyledons(proto-leaves), net like venation, vascular bundles in a cylinder around the outer portion of the stem; flower parts in 4's or 5's or multiples thereof.
Term
Monocotyledons (Monocots)
Definition
These have 1 cotyledon, parallel venation, vascular bundles scattered throughout the stem; flower parts in 3's or multiples thereof. No secondary growth
Term
Epidermis
Definition
outer layer of root
Term
Cortex
Definition
lies directly beneath the epidermis of the root
Term
Root Anatomy from Outside to Inside
Definition
Epidermis, Cortex, Endodermis, Pericycle, Stele
Term
Xylem
Definition
Very cnter of root
Term
Phloem
Definition
in the arms of xylem
Term
Tracheids
Definition
most primitive xylem cells, dead at maturity, thin, with end walls and pits
Term
Vessel Elements
Definition
found only in angiosperms, dead at maturity, wide and short, but can be stacked into VESSELS. Most vessel elements have no end walls, allowing rapid and efficient water transport
Term
What distinguishes a sun leaf from a shade leaf?
Definition
Shade leaf is thinner because it has only one layer of plaisade mesophyll, whereas sun leaves have two.
Term
The major nutrients that plants need
Definition
Nitrogen, Phosphorus, Potassium, Sulfur, Magnesium, Calcium, Manganese
Term
Why are heavy metals more available at lower pH?
Definition
because they become soluble and can be taken up by plants.
Term
What is the difference between a mobile and a immobile nutrient
Definition
Mobile nutrients can be easily moved around the plant, depending on need, while immobile nutrients generally stay where they are first distributed
Term
Water Potential
Definition
Water Potential=Osmotic Potential+Turgor(Pressure) Potential
Term
Osmotic Potential is always ___ or ___
Definition
negative or zero
Term
Turgor Potential is always ___ or ___
Definition
positive or zero
Term
Water always moves from ___ to ___ potential.
Definition
Water always moves from HIGH to LOW water potential
Term
Water always moves with respect to ___ ___ ___, not the individual components
Definition
total water potential
Term
Cohesion
Definition
attraction of water to itself
Term
Adhesion
Definition
attraction of water to other objects
Term
Capillarity(Theory of how water gets up tall trees)
Definition
water is "pulled" up by adhesion to the walls of xylem cells, while the remaining water comes along via the process of cohesion
Term
Root Pressure (Theory of how water gets up tall trees)
Definition
plants draw in water via osmosis and "push" it up into the stem
Term
Cohesion-Tension (Theory of how water gets up tall trees)
Definition
plants "pull" water up. As water evaporates from leaves, water molecules are replaced by others in the xylem. Via cohesion, this pulls up water from the roots into the shoot.
Term
Why does CAPILLARITY not work for getting water up tall trees?
Definition
risi is only about .75m, and trees can be 100m tall
Term
Why does ROOT PRESSURE not work for getting water up tall trees?
Definition
too slow, not present in day, and not powerful enough. Plus plants are not under positive pressure when transpiring, rather, they are under negative pressure which is the same as tension
Term
Why is the TENSION-COHESION THEORY the only viable theory for how water gets up trees?
Definition
Air has very low water potential. Soil water when saturated has a higher water potential, thus, there is a strong water potential gradient from soil to air through the tree.
Term
What is the water potential from soil to air through a tree?
Definition
200 bars
Term
How can xylem support a column of water 100 meters tall?
Definition
As long as it is in narrow diameter xylem such as tracheids or vessel elements. Proven through cetrifuge experiments
Term
How do stomata open?
Definition
K+ ions are moved into guard cells lowering osmotic potential and total cell water potential, causing water from nearby cells to flow into the guard cells. When water flows in, turgor pressure builds up, and the two guard cells pull away from each other allowing the pore to open up for gas exchange.
Term
How do stomata close?
Definition
K+ ions are moved out, water follows, and turgor pressure drops allowing guard cells to "flab" against each other, closing the pore.
Term
All ___ cells are alive at maturity, in contrast to xylem, which are dead.
Definition
Phloem
Term
Where does phloem transport occur?
Definition
Sieve tube cells
Term
Sieve Tube Cells
Definition
no organelles, just sap;
Term
Companion Cells
Definition
located adjacent to sieve tube cells, with full complement of organelles.
Term
Main Phloem movement cells
Definition
sieve tube cells and companion cells
Term
It appears that these control sieve tube cells.
Definition
companion cells
Term
____ are used to prevent run-away leaks, and to prevent pressure from equalizing too quickly.
Definition
Sieves
Term
Who figured out how phloem transport works? And when?
Definition
Munch in the 1930's
Term
How does phloem transport work?
Definition
When sugars load into sieve tube cells, osmotic potential goes down and water rushes in. This builds up pressure, pushing sugars and water downstream. At the end of stream, sugars are exported and metabolized, water rushes out, and pressure drops.
Term
____ involves movement of water from roots to leaves only, via dead xylem cells, using tension-cohesion theory.
Definition
Transpiration
Term
Pholoem Movement
Definition
involves live cells and metabolic energy. Uses sieve tube and companion cells, which are alive and can move materials either up or down the plant.
Term
Hormones
Definition
Signaling molecules between cells
Term
Hormones
Definition
Signaling molecules between cells
Term
The 5 known plant hormones are:
Definition
auxins; gibberllins; cytokinins; abscisic acid; ethylene
Term
These help bring about predictable patterns of development
Definition
Hormones
Term
What influences hormone production?
Definition
Environmental changes such as seasons and temperature
Term
Hormones interact with each other to:
Definition
produce specific effects on growth development
Term
This man and his son found and hypothesized about the possible existence of plant hormones.
Definition
Charles Darwin and his son Francis
Term
Growth
Definition
an irreversible increase in size
Term
Differentiation
Definition
the emergence of specialized cells and/or tissues or organs.
Term
Fritz Went
Definition
Grad student in the 1920's that decapitated coleoptiles and put the tip on agar to determine what the chemical was that was diffusing from the tip to the base that caused bending.
Term
Major functions of auxins
Definition
promotes cell elongation; assists in phototropism and gravitropism responses; helps cuttings root; responsible for apical dominance(christmas tree shape)
Term
Statoliths
Definition
(often starch grains)settle on the lower side of cells allowing the plant to know which side is up.
Term
Auxin's role in a plant's response to light
Definition
when light comes from directly above, auxin is evenly distributed down the stem and the plant grows straight up. Auxins move to shaded side when sun comes from the side.
Term
Apical Dominance
Definition
auxins are responsible for apical dominace in plants. If the apical meristem is removed, and auxin placed on the tip, the plant keeps its apical dominance, proving that it is the auxin that is responsible.
Term
The purpose of gibberellins.
Definition
cause elongation but differently than auxins; causes fruit to expand and flowering in certain parts.
Term
How is ETHYLENE important?
Definition
effects found at very low concentrations and include stimulating flowering of pineapples and related plants
Term
Abscisic Acid (ABA)
Definition
closes stomata and keeps seeds from germinating.
Term
Cytokinins
Definition
makes cells divide
Term
Phytochromes (P) come in two forms:
Definition
red absorbing and far-red absorbing
Term
How do plants determine light quality?
Definition
by using the ratio of red absorbing and far-red absorbing phytochromes.
Term
How do plants know when to flower?
Definition
Plants sense daylength. Some only flower when days are short and others when days are long.
Term
What senses the daylength?
Definition
Leaves
Term
How do leaves determine the daylength?
Definition
by determining the nightlength, they are able to determine the daylength.
Term
How can flowering induction be reversed?
Definition
by using bursts of light in the night.
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