list out the apparatus (materials and chemicals)you used in the observations of root tip experiment ? explain briefly.
Answers
Explanation:
Aim Of The Experiment
To study and demonstrate mitosis by preparing the mount of an onion root tip cells.
Theory Of The Experiment
For entities to mature, grow, maintain tissues, repair and synthesize new cells, cell division is required. Cell division is of two types:
Mitosis
Meiosis
Mitosis
In mitosis, the nucleus of the Eukaryotic cells divides into two, subsequently resulting in the splitting of the parent cells into two daughter cells. Hence, every cell division involves two chief stages:
Cytokinesis – Cytoplasm division
Karyokinesis – Nucleus division
Stages Of Mitosis
The various stages of mitosis are:
1. Prophase
The process of mitosis is initiated at this stage wherein coiling and thickening of the chromosomes occurs
Shrinking and hence the disappearance of the nucleolus and nuclear membrane takes place
The stage reaches its final state when a cluster of fibres organizes to form the spindle fibres
2. Metaphase
Chromosomes turn thick in this phase. The two chromatids from each of the chromosomes appear distinct
Each of the chromosomes is fastened to the spindle fibres located on its controller
Chromosomes align at the centreline of the cell
3. Anaphase
Each of the chromatid pair detaches from the centromere and approaches the other end of the cell through the spindle fibre
At this stage, compressing of the cell membrane at the centre takes place
4. Telophase
Chromatids have reached the other end of the cell
The disappearance of the spindles
Chromatin fibres are formed as a result of uncoiling of daughter chromosomes
The appearance of two daughter nuclei at the opposing ends due to the reformation of the nucleolus and nuclear membrane
At this phase, splitting of the cell or cytokinesis may also occur
Post mitosis, the next stage is referred to as interphase, which is part of the cell cycle that is non-dividing and between two consecutive cell divisions. A cell spends most of its life in the interphase. It comprises the G1, S and G2 stages.
Why is onion root tip used to demonstrate mitosis in this experiment?
It is because of the meristematic cells that are situated in the tip of the roots that render the most desirable and suitable raw material to study the different stages of mitosis. Onion is a monocot plant. Monocotyledonous plants possess large chromosomes that are clearly visible. Hence, their root tips are used. The period of time taken for mitosis varies as it is dependent on the cell type and type of species.
Is mitosis influenced by any factor? If yes, name them.
Yes, mitosis, the cell cycle is affected by various factors such as time and temperature.
Materials Required
Compound microscope
Acetocarmine stain
Water
Burner
N/10 Hydrochloric acid
Filter paper
Coverslip
Aceto alcohol (Glacial acetic acid and Ethanol in the ratio 1:3)
Glass Slide
Onion root peel
Forceps
Blade
Watch glass
Dropper
Needle
Vial
Procedure Of The Experiment
Place an onion on a tile
With the help of a sharp blade, carefully snip the dry roots of the onion
Place the bulbs in a beaker containing water to grow the root tips
It may take around 4 to 6 days for the new roots to grow and appear
Trim around 3 cm of the newly grown roots and place them in a watch glass
With the help of forceps, shift it to a vial holding freshly prepared aceto-alcohol i.e., a mixture of glacial acetic acid and ethanol in the ratio 1:3
Allow the root tips to remain in the vial for one complete day
With the help of forceps, pick one root and set in on a new glass slide
With the help of a dropper, allow one drop of N/10 HCl to come in contact with the tip of the root. Additionally, add around 2 to 3 drops of the acetocarmine stain
Heat it lightly on the burner in such a way that the stain does not dry up
Excessive stain can be carefully treated using filter paper
The more stained part of the root tip can be trimmed with the help of a blade.
Discard the lesser stained part while retaining the more stained section
Add a droplet of water to it
With the help of a needle, a coverslip can be mounted on it
Gently tap the coverslip with an unsharpened end of a needle in order for the meristematic tissue of the root tip present under the coverslip to be squashed properly and to be straightened out as a fine cell layer
The onion root tip cells’ slide is now prepared and ready to be examined for different stages of mitosis
Observe and study mitosis by placing the slide under the compound microscope. Focus as desired to obtain a distinct and clear image
Observations and Conclusion
The slide containing the stained root tip cells is placed on the stage of the compound microscope, changes taking place are noted and sketched.
The different phases of mitosis, such as prophase, metaphase, anaphase and telophase can be observed.