Question

Discuss in brief about the formation of spindle fibers in plant cells.

Answer 1

Hint: Spindle fibers are the protein structures which segregate the genetic material in a cell. The replicated chromosomes link at their centromeres with these fibers. They later function in pulling apart the sister chromatids to the opposite poles so that the two new daughter cells that have formed will each possess one set of chromosomes.

Complete answer:
In all eukaryotic organisms, the formation of a bipolar spindle is obligatory for the proper segregation of chromosomes to the daughter cells. Chromosomes, spindle fibers and kinetochores all have significant roles during mitosis. The plant cells entirely lack centrosomes which have a major role in spindle formation. The plants have evolved new mechanisms to carry out chromosome segregation. Recent studies on plant mitosis show that plants utilize a variation of "spindle self-organization". Plant cells lack centrioles but can form a mitotic spindle from the centrosome area.
spindle formation and division in eukaryotes-
Spindle fibers have their main role in dividing the genetic material of a cell. They are absolutely imperative in equal division of the chromosomes between two daughter cells during nuclear division: mitosis or meiosis. At the time of mitosis, these fibers are called the mitotic spindles. However, at the time of meiosis, the spindle fibers are said to be the meiotic spindle. At the initial stages of karyokinesis, two centrioles (wheel-shaped) take positions at opposite sides of a cell, forming poles. The microtubules extend from centrioles to every direction possible, forming a spindle. Some of them attach the poles to the kinetochores around the centromere. At the time of division, particularly at metaphase, these tubules pull and align the chromosome at the equator of the cell, which is also known as the metaphasic plate. The chromosomes are attached to the fibres and divide. Now, during anaphase of the cell cycle, the chromosomes separate and move to opposite sides.

Note:
Spindle fibers are essential for both types of nuclear division that is- meiosis and mitosis. It helps in equal segregation; any defect in it causes chromosomal defects. The neurons do not contain the centriole, hence are not capable of division.