Chromosome number variation experiment

Summary

1. to understand the principles and methods of artificially induced polyploid plants and their significance;

2, to observe the various variations in the number of plant chromosomes and their cytological characteristics during mitosis.

Operation method

Chromosome number variation experiment

Principle

Plant chromosome numbers are generally diploid (2n), but variation in chromosome number can be induced under natural and artificial conditions. Variation in chromosome number is categorized into aneuploidy and aneuploidy. Aneuploidy variations are homopolyploid and heteropolyploid variations. Aneuploidy variations are monosomy, deletion, trisomy, tetrasomy, etc. Variations in the number of chromosomes can lead to abnormal cytological behavior during mitosis and meiosis as well as changes in morphological features. There are many methods of artificially inducing polyploidy. Polyploidy induced by colchicine is commonly used and is the most effective method. Colchicine is a phytochemical base extracted from the organs and seeds of Colchium autumnale (Colchium autumnale. L.) with the chemical formula C22H25O6N, which is highly toxic. Its role is to prevent the formation of spindle filaments dividing cells, so that the replicated chromosomes can not be divided into two poles, the cell can not be split into two cells, still in the same cell, so the number of chromosomes in each cell doubled. The cells became polyploid and further developed into polyploid plants. Identification of polyploid mutagenesis results: 1. Individual parts of polyploid plants such as stomata, floral apparatus, seeds, fruits, etc. obviously enlarged, leaf hypertrophy, plants taller than diploid, leaf epidermal tissues stomata obviously enlarged. 2. Polyploid plants in meiosis, due to homologous chromosome linkage and segregation is abnormal, resulting in a reduction of fertility. 3. The mitotic division of the polyploid plant by mutation, the number of chromosomes can be multiply.

Materials and Instruments

Fava beans, onions, barley, jute.
Colchicine Hematoxylin Hydrated Trichloroacetaldehyde Ferric ammonium alum Alcohol Glacial acetic acid Hydrochloric acid Propionic acid
Microscope Incubator Analytical balance Water bath Alcohol lamp Scissors Tweezers Dissecting pins Slides Coverslips Filter paper Pencil Labeling paper Glue

Move

1. Material preparation

Take broad bean dry seeds or onion bulbs, after soaking seeds to promote germination, when the root length of about 1 cm, absorb the water, the root with 0.1 ~ 0.2% colchicine solution submerged, the root tip down, 20 ℃ to continue to promote the growth of germination, has been immersed in the tip of the root tip is obviously enlarged, (about 36 ~ 48 hours), rinsed clean to take off the tip of the root tip of the 0.5 cm parts, by the Carnall's fixative solution fixed for 0.5 ~ 1 hour, and then 70% alcohol preservation.

2.Dissociation:

(1) Take the root tip preserved in 70% alcohol, rinse it and place it in 1N hydrochloric acid, process it for 20 minutes at room temperature, rinse the acid and spare it.

(2) Take out the fixed spare root tip, cut the part with phloem tissue about 1~2 mm, (remove the root crown and elongation zone cells) in 1NHCl dissociation for 10 minutes. The material was then washed with distilled water to remove hydrochloric acid and prepared for preparation and staining.

3、Staining preparation

Take a dissociated root tip of broad bean, put it in the middle of the slide, press the two slides in a cross shape, then uncover it, put a small drop of propionic acid - ferric alum hematoxylin staining on each part of the material, and then press the slide with a coverslip.

4, microscopic examination

Observe the cells in the middle and early stages of mitosis and perform chromosome counting.

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