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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?

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Lab Practicum Review

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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.


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).


Insect pollination is responsible for producing 80% of the fruit and vegetables we consume. Wind, water and animals also help to transfer pollen.


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.



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.



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



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.


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 Calvin-Benson cycle.


The diagrams below show the chemistry of this conversion. Note that in alcoholic fermentation CO2 is produced, but not in lactic acid fermentation.

DesertAdaptations - 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.


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 uracilreplaces thymine as one of the nucleotide bases. An animated illustration of the process is found at the following link:


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, Rosette-Dwarf (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