Question

In his experiment on phloem cells of carrot, F. C. Steward used different combinations of nutrients and other factors, and obtained the following results.

Effect of light, air and nutrient medium on growth of the cultured plant cells
Conditions		Composition of nutrient medium	Increase in fresh weight (mg) of the cells from initial weight
Light	Air
✓	✗	Solid medium + nutrients	reduced
✓	✓	Liquid medium + nutrients	20% increased
✗	✓	Liquid medium + nutrients	reduced

Based upon the Table, think about these questions:

1. What do you conclude about the characteristics of phloem cells of carrot?
2. In which of the three combinations would you obtain the highest and lowest biomass? What could be the possible reason(s) for this observation?
3. Will you get the same results if you culture animal cells instead of carrot cells?
4. Think and mention any two commercial applications of the study above.

Answer 1

1. Carrot phloem cells show totipotency. They are live cells that can dedifferentiate into unspecialised cells, divide quickly, and then redifferentiate into all types of plant tissues to make a whole plant when given the right nutrition (sugars and hormones) and growing conditions.
2. Of the three combinations,
   1. The highest biomass would be obtained when:
      Liquid medium + nutrients + light + air (all factors present)
   2. The lowest biomass would be obtained when:
      Solid medium + nutrients + light (without air)
   3. Reason: Lack of air limits cellular respiration; light promotes photosynthesis; and solid media allows for less efficient nutrient intake than liquid medium, inhibiting cell division.
3. No, animal cells will not produce the same results since they are not totipotent in their mature phases. Unlike plant cells, most animal cells cannot develop and regenerate into a whole creature under standard growth conditions.
4. Two commercial applications:
   1. Micropropagation: Rapid production of vast numbers of similar and attractive plants (such as orchids, bananas, and sugarcane).
   2. Plant breeding and genetic engineering: Involves the use of tissue culture techniques to create disease-resistant, high-yield, and enhanced crop types.