Question

1. Prepared slides of a hyacinth root tip specimen was also examined with a microscope. C The number of cells per zone and the total number of mitotic figures per zone (that is, cells that are in prophase, metaphase, anaphase, or telophase) were recorded. Calculate the length of each zone (in mm and to two decimal places) and the Mitotic Index (M.I.) to one decimal place. Your lab manual shows how to determine the length of each zone in the root tip. 4 marks

          M.I. = number of mitotic figures x 100

                                                           total number of cells

Zone Number	Total number of cells	Total number of mitotic figures	Distance of zone from the root tip (in mm)	Mitotic Index
1	51	3	0.43	5.88
2	62	20	0.86	32.26
3	58	39	1.29	67.24
4	41	16	1.72	39.02

2. Comment on whether there is a difference in mitotic activity as you move through the zones (from Zone 1-4). Is there more activity in one zone compared to another? Why or why not? 4 marks

Answer: Click here to enter text.

Answer 1

Roots play a key role in anchorage of plant along with absorbing inorganic nutrients and water from the soil. Cells produced from root apical meristem divide, elongate and differentiate to serve different functions.

When we observe mitotic activity in root tip, we find bell shaped curve of mitotic index with increase in distance from the root tip. The initial lowest mitotic index is found in quiescent centre. Later on the curve peaks at meristematic zone and declines at elongation zone. The lowest point in the mitotic activity again happens in maturation zone.

zone 1

0.43 mm distance from lowermost point of root tip will have the quiescent centre area . Cells of quiescent centre do not divide rapidly, because of that only we have got very low mitotic index of 5.88 in this zone. Quiescent centre is found just above the root cap. The root cap protects the delicate region of root tip from external injury.

Zone 2 We know that boundaries of different zones in root tips are not very clear.. Zone 2 is is transition zone between quiescent centre and meristematic zone of root apical meristem. Here, cells start dividing. These cells have higher mitotic index than quiescent centre but still the mitotic activity has not peaked yet

Zone 3 is meristematic zone of root apical meristem. These cells are characterized by dense cytoplasm, small or no vacuole. They divide at very fast rate. Therefore, they have highest mitotic index of 67.24

Zone 4-is elongation zone . In elongation zone cells elongate mainly. Here, mitotic activity or cell division declines after peaking at meristematic zone but cell division do not ceases completely. Mitotic index of this area (39.02) still more or less same as in transition zone of quiescent centre and meristematic zone.

Further away from this zone lies the maturation zone. This zone is characterized by completely differentiated cells with no mitotic activity.