last  page

PLNT3140 Introductory Cytogenetics
Lecture 4, part 1 of 2

next page

September 19, 2017
CYTOGENETIC TECHNIQUES


REFERENCE: Chapter 2, The Handling of Plant Chromosomes .pp.7.-24 Singh.R.J. 1993. Plant Cytogenetics. CRC Press.


KEY CONCEPTS FOR TODAY

Know the main steps for observing chromosomes:

1. Collection of  material to optimize number of mitotic or meiotic cells ie. high Mitotic Index
2. Pretreatment to prevent unwanted changes
3. Fixation to stabilize cellular structures
4. Staining to create optical contrast between cellular structures
5. Slide preparation for optimal viewing
6. Data recording and micrometry


The reason that cytological techniques were developed is to obtain information on chromosome- number, structures and behaviour during cell division. The basic principles applied are generally similar for all species. However, some procedures are modified for different species and to highlight particular features of the chromosomes.

Good preparation of the cells is required for good results. Attention to detail is necessary at every step, starting with the selection and collection of material. Seeing anything at all requires good technique.

A. Collection of material for study

Chromosomes are only visible during cell division. The first step in a cytological preparation is the choice of material from which to obtain actively dividing cells.

The best material is obtained from actively growing roots of either germinating seeds or healthy plants. The key to success is to have an abundance of dividing cells from which to select the desired cell stage. Generally, root tips are collected from germinating seeds for ease of handling. The seeds are placed on moistened Filter paper in a Petri dish. The seeds of cereal species such as wheat or barley are germinated in a dark cold room or refrigerator at 0 - 4 C for 3 to 5 days. This cold treatment produces uniform and rapid seed germination. The Petri plates are then removed from the cold and maintained at room temperature until the seeds have germinated.

The best roots for collection are 1 to 2 cm long, with rounded thick ends tipped with white. The root tips are then transferred to a vial of cold water.

Germination of seeds on wet paper towels


Displayed from: http://campuscropsmcgill.blogspot.ca/2014/05/seeds-germination-and-seedlings.html

The meiotic divisions in each anther are synchronised and there are anthers at different stages in the same flower. In a wheat head or spike there are approximately 40 florets. If one floret is in anaphase, the next youngest may be in metaphase. It is possible to sample up and down the spike from a central point to obtain the desired stage.

Wheat Floret



From http://www.wheatbp.net

stigmas receive pollen dehisced from anthers



Older florets are at the bottom, and newer florets are at the top.

Correct Stage for Applying Fungicides for Scab Control in Wheat and Barley (6/23/11)

North Dakota State University
Joel Ransom - Extension Agronomist for Cereal Crops

 http://www.ag.ndsu.edu/cpr/plant-science/correct-stage-for-applying-fungicides-for-scab-control-in-wheat-and-barley-6-23-11

Unless otherwise cited or referenced, all content on this page is licensed under the Creative Commons License Attribution Share-Alike 2.5 Canada


last  page

PLNT3140 Introductory Cytogenetics
Lecture 4, part 1 of 2

next page