Lab Practicum Review
What does iodine test for?
What are adventitious roots?
Why does fresh potato cause bubbling when in peroxide?
Can you identify a X.S. of a leaf, stem or root under the microscope?
What are simple or compound leaves? Can you identify leaves as such?
What are the types of germination?
Stem structure, both external and internal.
What are the differences between a monocot verses a dicot leaf?
Leaf anatomy – epidermis, mesophyll, stomata, etc.
What cells/tissue in plants make up what is termed “wood”?
Photosynthesis …..the equation
Metabolism …….. the equation
What is a cambium and what does it do in a plant stem?
The plant cell verses animal cell…differences
Plant flowers external features like sepals, petals, pistil and anthers
Functions of plant ovary or anthers
Anabolic verses catabolic metabolism (photosynthesis verses respiration)
DNA – transcription, translation
Mitosis verses meiosis
•
Seed dispersal mechanisms
•
Dehiscent vs nondehiscent fruit
•
Genetics/monohybrid and dihybrid crosses …..Mendel
•
Adaptation to the environment ….anatomical changes: sunken stomates,
reduced leaf size, hairs, thickened cuticle and external morphology such as
lost leaves, thickened water storage stems, etc
•
Nucleotide bases of DNA and RNA (G,C,T,A and G,C,U,A)
Modified Stems - Several examples of modified stems
are setup around the lab. Examine each and find the features
common to stems and how they have been modified
from “normal” stems.
Guard cells of stomates in monocot grasses (upper figure) and
broadleaf dicots (lower figure)
Leaf Modification - Plants have adapted their leaves to survive
environmental extremes, as protective structures, to aid in
support and even to catch and provide nutrition (insectivorous
plants).
Below is a cross section of an ovary.
Plants undergo double fertilization
Insect pollination is responsible for producing 80% of the
fruit and vegetables we consume. Wind, water and
animals also help to transfer pollen.
Dicot seed on the left; monocot seed on right
Seed dispersal often requires “new ground” which can could be
as simple as a field that has been plowed or a newly formed
volcanic island
In all these scenarios plants will eventually appear and grow. Seed
dispersal is what allows for this to happen and occurs through a
variety of mechanisms that have evolved over thousands of years.
Seed dispersal starts first with the fruit and whether it stays on the
mother plant and releases the seed (dehiscent fruit) or where the
seed stay within the fruit (nondehiscent fruit) which then falls or
is released from the plant. Examples of dehiscent fruit are
follicles, pods and capsules.
Wind
Do you remember as a child taking dandelions and blowing
their “fuzz” around? Of course the “fuzz” was seed that had
feathery plumes or parachutes. The seed was so light that your
breath could carry them quite some distance across a lawn.
Your actions were mimicking what would happen naturally
with a strong wind in the dispersal of these seed.
Water
Most of the earth’s surface is covered with water. Water tends to
move either through gravity or wind forces. Consequently, water
provides an excellent method for dispersal for some plants.
Plants such as Mangrove and Coconut have seed with entrapped
air that makes them buoyant. These seed can drift literally
thousands of miles before washing up on a shore where they can
take root and grow.
Additionally, there is dispersal by animals after they
eat the fruit, seeds that hitchhike by attaching to
clothing or fur
Photosynthesis
At the heart of this collection system is chlorophyll, a chemical substance
capable of capturing photons of light and generating a high energy
electron that can be used for the synthesis of food.
3-D Illustrations of the chloroplast
There are basically two major steps in
photosynthesis required to produce the
carbohydrate (sugar). The first requires
light energy (light dependant reaction).
This energy is ultimately captured in the
form of high energy compounds that we
have already studied in respiration (ATP,
NADH, etc). Note that the light reaction
DOES NOT in itself produce any
carbohydrate. The high energy
compounds are shunted to the stroma of
the chloroplast where the second
reaction (the light independent or dark
reaction) occurs to produce the
carbohydrate. Like the krebs or citric acid
cycle of respiration, the dark reaction is
also cyclic and is known as the CalvinBenson cycle.
Glycolysis
The diagrams below show the chemistry of this conversion. Note
that in alcoholic fermentation CO2 is produced, but not in lactic
acid fermentation.
Krebs Cycle, TCA Cycle or Citric Acid Cycle
Terminal Oxidation
• Desert Adaptations - With desert
conditions, conservation of water is
extremely important to survival. Rainfall
averages less than 10 inches per year.
Consequently, plants have evolved ways
to conserve or store water. Among these
adaptations are:
• Water storage tissues in stems or leaves
• Leaves absent, reduced in size or short lived only when there is rain
• Deep root systems to reach water or very wide root systems that
efficiently capture water after a rainfall
• Plants may produce a heavy thick cuticle of wax on leaves and
stems to reduce water loss
• Anatomically those plants that retain their leaves may show
anatomical changes such as reduced number of stomates, sunken
stomates or “hairy” stomates (protective trichomes that reduce water
evaporation)
• Leaves may develop numerous trichomes (“hairs”) that shade the
leaf and reduce water loss
• Photosynthesis desert and arid land plants may use C4
photosynthesis rather than C3 photosynthesis. Consequently C4
plant will show a different anatomy (Krans anatomy) in the leaves
where the mesophyll is arranged around the bundle sheath cells of
the veins. Additionally, the bundles sheaths will contain chloroplast
in the C4 leaf whereas chloroplast are absent in the C3 leaf.
Temperate Grasslands Adaptation - Grasslands, also called
prairies, have hot summers and cold winters. Rain is sparse and
droughts common. Average rainfall is 10 - 30 inches a year. The
soil of grasslands is very rich in organic matter from the annual
grasses that die off and enrich the soil. Farming has claimed the
majority of original grasslands. Only small patches or pockets of
original grassland remain. Adaptations include:
• Roots survive fire and resprout
• Prairie trees have thick bark for fire protection
• Root systems are so extensive that grazing animals
cannot pull the plants from the ground
• Shrubs resprout readily after a fire
• Narrow leaves of grasses have less water loss
compared to broad leaf plants
• Extensive and deep root system to obtain water
• Flexible stems that can bend in the winds typical of
prairies
• Most grasses use the wind for pollenation
• Some grasses also utilize C4 photosynthesis
Temperate Deciduous Forest Adaptations This climate zone is
most familiar to us here in the Ozarks. We have 4 distinct seasons;
spring, summer, fall and winter. Consequently temperatures vary from
freezing in winter to hot in summer. Rainfall is from 30-50 inches a
year.
Due to both the abundant rain and seasonal temperature changes,
the temperate deciduous forest plant ecosystem is layered with plants
of different heights. The canopy of the forest may be over 100 feet tall,
followed by an understory of smaller shade tolerant trees and young
trees. Finally beneath the understory are is a shrub layer with a herb
layer carpeting of wildflowers, mosses and ferns. Leaves and fallen
limbs and debris slowly decompose and return nutrients back to the
soil.
• Wildflower groundcover grows early in spring
before shade from canopy develops
• Tree leaves are broad and flat for very efficient
photosynthesis
• Trees are deciduous and drop their leaves in
fall/winter to prevent water loss and snow
damage
• Trees have developed thick protective bark to
insulate from winter freezing
Aquatic Adaptations of Plants - In some environments
plants may be partially or completely submerged in water.
An aquatic environment changes many physical and
anatomical requirements that terrestrial plants have in
order to survive.
• Submerged plants lack an effective vascular transport
system in the stems. Instead water, dissolved gases and
nutrients are provided by simple absorption into the
leaves.
• Stems and leaves of underwater plants are flexible to
move with currents
• Root system with root hairs are much reduced. Root
primary function may be for anchorage
• Leaves and stems may develop aerenchyma tissue. This
is parenchyma tissue that develops many air spaces or
gaps presumably for gas exchange or for floating leaves
or stems.
• Floating leaves will have chlorophyll tissue in upper
surface of the leaf. Additionally, stomates may be
primarily or totally on the upper surface of the leaf
There are three basic plant cell types that are recognizd:
parenchyma, collenchyma and sclerenchyma. For the
most part the classification is based on the extent that
secondary cell wall material has been deposited and
whether the cells are living when they reach their mature
state.
Collenchyma has secondary cell wall deposits in the corners
of the cell or along parallel walls. These thickenings provide
additional support to the young herbaceous plant stem. All
collenchyma is located near the periphery of the stem, never in
the center and usually is in “patches” of tissue. In comparison
to parenchyma the cells are usually much smaller. Like
parenchyma cells these cells are living at maturity.
4. Observe collenchyma cells from a section of a young plant
stem under the second microscope.
Sclerenchyma cells form a variety of cell types and tissues. Note
the much thicker cell walls due to secondary cell wall deposition
DNA Transcription - For a gene from the chromosome to be
“activated” the DNA that codes for it must first be transcribed
from the DNA (template) to messenger RNA (mRNA). This
copy of the DNA is then used to build proteins which direct
the expression of the gene. In RNA uracil replaces thymine
as one of the nucleotide bases. An animated illustration of the
process is found at the following link:
http://www.johnkyrk.com/DNAtranscription.html
RNA Translation - The mRNA is next used as a template
from which specific proteins will be constructed through the
action of ribosomes and transfer RNA (tRNA).
Genetics - Earlier this semester some Rapid Cycling Brassica
plants where crossed where the parents were Non-Purple
Stemmed, Standard Height (p/p, T/T) x Purple Stem, RosetteDwarf (P/P, t/t) to produce plants that had a heterozygous
genotype (Pp, Tt). If these seeds were planted what
phenotype(s) would you expect the offspring to be?
Phenotype = All Purple Stem and Standard Height
Genotype = all PpTt
If we cross two of the F1 offspring
what are the possible combinations?
So we need to set up our Punit square. First we determine the
possible gametes of the parents and put those in along the sides
of the square. Then we work out the possible combinations