The following data represents the development in dry mass of germinating seedlings within 18 weeks:

      

The following data represents the development in dry mass of germinating seedlings within 18 weeks:

dry12271072019.png



(a) Write reference to the graph, explain the changes in dry mass between:-
(i) Week 0 to 2
(ii) Week 5 to 13
(iii) Week 16 - 18

(b)
(i) What is the significance of time zero?
(ii) What difference would be expected from the above results if the experiment started with the seeds? Give a reason for your answer

(c)
(i) Describe how you carry out the experiment to obtain dry mass in the respective weeks
(ii) State one advantage of using dry mass instead of fresh weight in estimating growth of an organism

  

Answers


Martin
a(i) Lag phases; Dry mass increases slowly; became in plant has not developed
leaves; for photosynthesis hence is depending on stored food;
(ii) Expontial phase; Rapid growth /increase in dry mass, leaves developed; photosynthesis taking place leading to accumulation of food and rapid cell division / plant adapted to the environment
(iii) Death phase/ senescence; Negative growth/decrease in dry mass as some tissues die after reaching maximum maturity; Fall in photosynthesis activity; toxic wastes poison tissues;

(b)
(i) When dry mass was first recorded/at germination
(ii) Dry mass would decrease first because food is oxidized to produces energy; water and carbon dioxide/utilized in respiration;
(c)
(i) Harvest every week about five seedlings; dry in oven to a constant dry mass; Calculate the average mass for one seedling and record the results.

(ii) Advantage; Dry mass is not affected by environmental conditions while fresh weight is dependent on the amount of water in the plant which fluctuate with environmental factors affecting transpiration rate
marto answered the question on October 7, 2019 at 09:30


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