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					Ryan Williams – 2/24/10 – Organogenesis II                                                    Page 1

T16 – Shoot Organogenesis from Cotyledon Explants of Watemelon
By Michael E. Compton and Dennis J. Gray

         Watermelon is an important crop, but it is also quite disease prone. Because of this,
genetic engineering and tissue culture are useful to create disease free and disease resistant types.
TC is also used to create somaclonal variation which aids in the creation of new and better types
of watermelon. This chapter contains protocols to conduct adventitious shoot regeneration from
watermelon cotyledons and will test the shoot generation competence of different parts of the
cotyledon and from different cultivars of watermelon.
         Pretreating plants in the dark has shown to improve shoot regeneration from cotyledons,
leaves, and petioles of several types of plant. This is not totally understood, but may be due to
darkness preserving light-sensitive PGRs. This also results in thinner cell walls and less vascular
I find it very interesting how just about any part of a plant can be cultured and produce different
types of organs. It is also very interesting how sprouting the plants in the dark causes them to
grow so differently. I would really like to see the time described in the book just after putting a
seedling from the darkness into the light. The book says it will turn green in only a few hours!

T17 – Direct and Indirect Shoot Organogenesis from Leaves of Torenia Fournieri
By: Mark P. Bridgen

         Torenia is a plant that has been used a lot in TC. It has had experiments done on it to
research somaclonal variation and a type with white flowers was made this way. It has also had
many organogenesis experiments done on it. This chapter has protocols to investigate indirect
and direct organogenesis using Torenia.
It is cool to hear of an actual example of somaclonal variation being used to create a plant with
new characteristics.

T18 – Shoot Organogenesis from Petunia Leaves
By: John E. Preece

        Petunias are very common flowering plants that originated from hybridization. Some
types of petunia cannot be propagated with seeds, so they are propagated with stem cuttings.
Petunia is a member of the tobacco family and this family has been extensively studied in TC
because they grow well in vitro. The protocols in this chapter are designed to investigate the
effects of auxin and cytokinin on the regeneration of shoots and formation of callus. The will
also demonstrate indirect and direct organogenesis.
I didn’t realize that petunias are a member of the tobacco family. They do have a huge variation
and it doesn’t surprise me that they frequently can’t be propagated with seeds.

 1. What are some of the effects germinating seeds in darkness on those plants once they are
placed in culture?
2. What is the difference between direct and indirect organogenesis?
Ryan Williams – 2/24/10 – Organogenesis II                                                Page 2

3. If I want to create plants through organogenesis with new and interesting phenotypes should I
use direct or indirect organogenesis? Esplain.
4. Briefly describe the auxin/cytokinin gradient in a normal plant.
5. If I want to produce callus, will I use auxin, cytokinin, or both in my media?