1. Introduction to
Plant Biotechnology
Chapter 10

2. Learning Outcomes
Describe mechanisms of plant pollination and differentiate between haploid and diploid cells and their role in sexual reproduction
Identify various natural and artificial ways to propagate plants to increase genetic variety or maintain the genetic composition
Discuss the function and composition of different plant structures, tissues, and organelles and give examples of foods that are derived from various plant organs
Describe the processes of germination and plant growth
Perform the calculations to predict expected plant phenotypes for specific genetic genotypes, using Punnett Square analysis in a plant breeding experiment
Describe the role of meristematic tissue in asexual plant propagation
Explain the role of plant growth regulators, as well as the advantages and disadvantages of plant tissue culture

3. 10.1 Introduction to Plant Propagation
There are several methods of modifying or improving plants or plant parts.
One of the first advances occurred when farmers discovered they could control pollination and the resulting seed crop.
Plant breeding involves sexual reproduction.
Plant breeding involves asexual reproduction (cloning).

4. Flower Structure. Most flowers are “complete” with both male (stamen) and female (pistil) sex organs. A seed develops when a pollen sperm nucleus reaches and fertilizes an ovule.

5. New Gene Combinations. Crossing-over and gene shuffling during meiosis (sex cell division) created new combinations of genetic information on chromosomes. The new combination of genes is carried in sex cells to the zygote of the next generation. What genetic information would a sex cell be carrying if it got one or another of the final chromosomes?

6. Vocabulary
Pollination – the transfer of pollen (male gametes) to the pistil (the female part of the flower)
Breeding – the process of propagating plants or animals through sexual reproduction of specific parents
Sexual reproduction – a process by which two parent cells give rise to offspring of the next generation by each contributing a set of chromosomes carried in gametes
Zygote – a cell that results from the fusion of a sperm nucleus and an egg nucleus
Embryo – a plant or animal in its initial stage of development
Gametes – the sex cells (ie, sperm or eggs)
Meiosis – a special kind of cell division that results in four gametes (N) from a single diploid (2N) cell
Selective breeding – the parent selection and controlled breeding for a particular characteristic
Cuttings – the pieces of stems, leaves, or roots for use in asexual plant propagation
Tissue culture – the process of growing plant or animal cells in or on a sterile medium containing all of the nutrients necessary for growth
Callus – a mass of undifferentiated plant cells developed during plant tissue culture

7. 10.1 Review Questions
How many parents are necessary for an offspring to be produced by sexual reproduction? How many parents are necessary for an offspring to be produced by asexual reproduction?
Which two cells fuse to make a zygote? From where do the chromosomes of a zygote come?
How does a cutting become a functioning, independent organism?
What is the smallest number of cells required to clone a plant through tissue culture?

8. 10.2 Basic Plant Anatomy Plant Tissue Plant Cells
Plants are multicellular organisms composed of organs and tissues.
Plants have a wide variety of organ structures.
Plant organs are grown as food or commercial crops.
Plant Tissue
Plant tissues are groups of similar cells with a specific function.
Plant Cells
Plant cells have all the organelles found in other cells, plus special organelles.

9. Vocabulary
Meristematic tissue – the tissue found in shoot buds, leaf buds, and root tips that is actively dividing and responsible for growth

10. 10.2 Review Questions
List some foods that are examples of the following plant organs: stems, roots, leaves, flowers (ovaries), and seeds (fertilized ovules).
Which plant tissue type is the source of cells for tissue culture?
Give an example of a plant that has been modified by genetic engineering.

11. 10.3 Plant Growth, Structure, and Function
Plants have specific regions where cell division can occur.
Meristems are found at each growing tip.

12. During mitosis, cells make exact copies of themselves
During mitosis, cells make exact copies of themselves. The tightly wound mitotic chromosomes are visible using a microscope.

13. Monocot Seed Germination. Four germinated corn seedlings
Monocot Seed Germination. Four germinated corn seedlings. The coleoptile protects the emerging leaves. Corn plants are monocots since they have only one section to the seed.
Dicot See Germination. The diagram shows a germinating bean seed with an enlarged radicle growing down. The epicotyl will grow up into the leaves and stem. The two cotyledons emerge from the seed as a food source, but they wither after a short while.

14. Vocabulary
Meristems – regions of a plant where cell division occurs, generally found in the growing tips of plants
Radicle – an embryonic root-tip
Differentiation – the development of a cell toward a more defined or specialized function
Plant hormones – the signaling molecules that, in certain concentrations, regulate growth and development, often by altering the expression of genes that trigger certain cell specialization and organ function
Herbaceous plants – the plants that do not add woody tissues; most herbaceous plants have a short generation time of less than one year from seed to flower
Woody plants – the plants that add woody tissue; most woody plants have a long generation time of more than one year from seed to flower; most woody plants grow to be tall, thick, and hard

15. 10.3 Review Questions
Name the parts of the plants that contain actively dividing cells.
After mitotic division, how many chromosomes do daughter cells have, compared with the parent?
When a seed germinates, what is the first plant part to emerge from the sprouting seed?
There is a vast diversity among plant cells and plant tissues. What are the chemicals called that trigger much of the cell and tissue specializations in plants?

16. 10.4 Introduction to Plant Breeding
Alternation of generations. Each sex cell gets one copy (1N) of each chromosome and, therefore, one copy of each gene. Most genes exist in one of two or more forms (alleles). When the zygote (2N) forms, it receives both sets of chromosomes (and genes) for the two sex cells. Depending on what was carried in the sex cells, the zygote could receive two matching alleles or two different alleles for a particular trait. The alleles of an organism are its genotype and, ultimately, determine the traits expressed (phenotype).

17. Genotypes and Phenotypes
The alleles an organism possesses are called its genotype.
They determine the plant’s characteristics.
Breeding Plants for Desired Phenotypes
Plant breeders try to study, predict, and manipulate crosses between flowers in an attempt to produce plants of desired phenotypes.
Using Punnett Square Analysis
Shows the possible gene combinations that could result when crossing specific genotypes.

18. Vocabulary
Diploid – having two sets (2N) of homologous (matching) chromosomes
Haploid – having only one set (1N) of chromosomes
Alleles – alternative forms of a gene
Dominant – referring to how an allele for a gene is more strongly expressed than an alternate form (allele) of the gene
Recessive – referring to how an allele for a gene is less strongly expressed than an alternate form (allele) of the gene; a gene must be homozygous recessive (ie, hh or rr) for an organism to demonstrate a recessive phenotype
Homozygous – having two identical forms or alleles of a particular gene (ie, hh or RR)
Homozygous dominant – having two of the same alleles for the dominant version of the gene (ie, HH or RR)
Heterozygous recessive – have two different forms or alleles of a particular gene (ie, Hh or Rr)
Polygenic – traits that result from the expression of several different genes
Punnett Square Analysis – a chart that shows the possible gene combinations that could result when crossing specific genotypes

19. Evaluating Validity of Data
Standard Deviation. If the SD is twice as large (right graph) as another (left graph), then we know that the data for the right graph are very dissimilar, and we would have less confidence in the data collection.
The 10% Rule Standard Deviation

20. Using Numerical Data to Ensure Accuracy
Instead of using words to describe data, scientists try to make all observations of experiments in numerical form.
Using Multiple Replications to Determine Averages
Experiments must be repeated enough to ensure that results reflect what really happens.

21. Using Goodness of Fit (Chi Square Analysis) to Test the Hypothesis
How To Calculate the Chi Square Value (c2)
C2 = S[(O-E)2/E]
The terms represent the following:
O = observed number for a phenotype group
E = expected number for a phenotype group
S = the Greek letter Sigma, which represents “sum of”

22. Vocabulary
Monohybrid cross – a breeding experiment in which the inheritance of only one trait is studied
Dihybrid cross – a breeding experiment in which the inheritance of two traits is studied at the same time
Average – a statistical measure of the central tendency, that is calculated by dividing the sum of the values collected by the number of values being considered
Mean – the average value for a set of numbers
Standard deviation – a statistical measure of how much a dataset varies
Chi Square – a statistical measure of how well a dataset supports the hypothesis or the expected results of an experiment
Degrees of freedom – a value used in Chi Square analysis that represents the number of independent observations (eg, phenotypic groups) minus one
Null hypothesis – a hypothesis that assumes there is no difference between the observed and expected results

23. 10.4 Review Questions
A plant has purple flowers and hairy stems. Is this description its genotype or its phenotype? Propose some allelic symbols for purple flowers and hairy stems.
Consider a cross between two Brassica rapa parent plants known to be heterozygous tall. Using the same allelic symbols as in the text, show the entire cross (problem), including the chances of this breeding resulting in short plants.
A set of plant DNA extractions is measured on the UV Spec. There are 13 samples, and the average concentration is 18.7 μg/mL. One sample has a value of 17.2 μg/mL. Using the 10% rule, is the sample’s value valid and acceptable?

24. 10.4 Review Questions (cont.)
An experiment is conducted to determine the number of kindergarten children with attention deficit disorder (ADD) in the United States. The result shows that 80 out of 1000 students, on average, with a standard deviation of 5, exhibit ADD. A town near a nuclear plant has an average of 84 students per 1000 with ADD. Should the citizens be concerned? Why or why not?
A family had 22 children: 14 boys and 8 girls. Calculate the Chi Square value for such a cross and determine whether the results are due to a random mating or an environmental or genetic disorder.

25. 10.5 Asexual Plant Propagation
Using breeding techniques, a plant biotechnologist can produce variety in the offspring of selected parental plants.
Asexual Plant Propagation
Identical offspring are produced by a single parent.
Methods of Asexual Plant Propagation

26. Vocabulary
Crossbreeding – the pollination between plants of different phenotypes, or varieties
Asexual plant propagation – a process by which identical offspring are produced by a single parent; methods include the cutting of leaves and stems, and plant tissue culture, etc.
Runners – the long, vine-like stems that grow along the soil’s surface
Plant tissue culture (PTC) – the process of growing small pieces of plants into small plantlets in or on sterile plant tissue culture medium; plant tissue culture has all of the required nutrients, chemicals, and hormones to promote cell division and specialization

27. Vocabulary Plant growth regulators – another name for plant hormones
Auxin – a plant hormone produced primarily in shoot tips that regulates cell elongation and leaf development
Cytokinin – a class of hormones that regulates plant cell division
Explants – the sections or pieces of a plant that are grown in or on sterile plant tissue culture media
Ethylene – a plant hormone that regulates fruit ripening and leaf development
Gibberellin – a plant hormone that regulates seed germination, leaf bud germination, stem elongation, and leaf development; also known as gibberellic acid
Abscisic acid – a plant hormone that regulates bud development and seed dormancy
Phytochrome – a pigment that acts like a hormone to control flowering

28. 10.5 Review Questions
Which of the following are examples of asexual plant propagation: PTC, crossbreeding, stem cuttings, leaf cuttings, or runners?
Leaf or stem cuttings must include at least some of what kind of tissue to form new roots?
Auxin is responsible for what kind of plant growth regulation? Cytokinin is responsible for what kind of plant growth regulation?
How can a plant tissue culturist know that an explant is beginning to respond to the hormones in the PTC media?

29. Questions and Comments?