Events during Mitosis Interphase: Cells may appear inactive during this stage, but they are quite the opposite. This is the longest period of the complete cell cycle during which DNA replicates, the centrioles divide, and proteins are actively produced.
The following points highlight the top twenty-one techniques of plant chromosomes analysis. Some of the techniques are: Techniques of Plant Chromosomes Analysis: In higher plants meiosis occurs in pollen microscope mother cells which are present in the anthers and also in the megaspore mother cell which lies within the ovule.
An ovule contains only one megaspore mother cell surrounded by several layers of vegetative cells; as such, it is rather difficult to work it out. Anthers, on the other hand, contain large numbers of pollen mother cells PMC which can be very easily exposed by bursting the anthers.
So, usually, meiosis is studied from pollen mother cells. Meiosis occurs only once in the life cycle of an organism and it takes only a couple of hours for meiosis to be completed. Diakinesis, metaphase I polar view and metaphase II polar view are the ideal stages for counting the chromosome number of an organism.
Hence, to work out the suitable stages of meiosis, flower buds of appropriate size are to be selected; otherwise the stage would be either too early or too late. Bud selection can be done only on trial-and-error basis.
Take a flower bud of suitable size. Dissect out 2 to 3 anthers with a needle and transfer them onto a clean grease-free slide. Gently press them with an iron scalpel to squeeze out their contents. Put a cover glass.
Tap very gently to scatter the cells so that they form an one-layered smear. Observe under a microscope. If the stain appears very faint then warm the slide gently by running it 2 to 3 times over a flame. Blot off the excess stain and seal with paraffin Fig.
If anthers are smeared with an iron scalpel then a little iron acetate is formed — it helps in staining. Tapping on the cover glass should be done very carefully. PMC walls are very fragile and excess pressure will break them and, conversely, too little pressure will cause the PMCS to remain in a lump.
After squeezing out the contents of the anthers, the anther walls may be thrown off. Meiosis usually occur during the daytime.
It is easier to find meiotic stages on bright sunny days than on cloudy and rainy days. While working out meiosis, the inflorescence stalk should be kept dipped in water, but the buds should not be kept immersed.
If buds are collected in the field, they may be fixed in acetic-alcohol 1: Mitosis occurs in all meristematic cells. So it can be worked out from root tips, shoot tips, young leaf primordia, cambium, growing floral and fruit parts etc.
Of all these organs, root tips are the most actively growing parts, so root tip is the ideal region to study mitosis.
Besides, root tip cells have very little ergastic matter and this makes staining easier. For the demonstration of the different stages of mitosis, root tips of Allium cepa are the most ideal material. Bulbs of onion are taken, the outer surface of the disc stem is scraped with a scalpel to remove the remnants of old roots and are placed in a pot containing moist sawdust and soil.
Within 2 to 3 days, roots come out. Take fresh and healthy root tips, wash thoroughly in water to remove all dirt and cut out the exact tip portion about 5 mm. Fix the root tips in acetic-alcohol 1: Keep the root tips in the mixture for 15 minutes to half an hour.
Draw and label the various mitotic stages Fig.Mitotic index of the four setups No. Statistical Tools for Analysis Mitotic index method will be used to measure the cellular division in the onion root tip.
Three hundred cells will be observed separately in the specimens from the different setups to determine the mitotic index which will be the basis of the effect of varying concentrations of paracetamol on the mitotic cell division of onion.
Kubiak J, De Brabander M, De Mey J, Tarkowska JA () Origin of the mitotic spindle in onion root cells. Protoplasma 51–56 Google Scholar Lambert A-M () The role of chromosomes in anaphase trigger and nuclear envelope activity in spindle formation.
(the common onion) assay. This model was used to determine the effects of these additives on the mean root length, mitotic index and chromosomal aberrations of onion bulbs using , and 1% (w/v) of each food additive. mitotic index The percentage of cells in a population that are actually undergoing benjaminpohle.com mitotic index is a measure of the reproductive or growth activity of a tissue.
The number of cells in various stages of mitosis and the mitotic index (% of cells examined in mitosis) in controls and BL-treated root tips are shown in Table 2. Of cells counted, control onion root tips had % of the cells in various stages of mitosis. 5 Mitotic Index Below is a formula used to calculate the mitotic index: MI = Total number of dividing cells / Total number of cells seen The mitotic index of Allium cepa root tips treated under acidic, neutral and basic pH throughout the 24, 48, and 72 hour treatment duration was calculated.