K.C.S.E Biology Q & A - MODEL 2018PP2QN06

K.C.S.E Biology Q & A - MODEL 2018PP2QN06

The effect of auxin concentration on growth response of two parts of a plant, X and Y was investigated over a period of time. The results were tabulated as shown in the table below.

(a) On the same axis, draw line graphs of the effect on growth of the two parts, X and Y (percentage inhibition or stimulation) against the concentration 
(b) With reasons, name the two parts of the plant, X and Y.
X 
Reason 
Y
Reason
(c) From the graph identify: .
(i) the point at which the percentage stimulation was the same for both X and Y. 
(ii) the optimum concentration of auxins required for part Y 
(d) State three ways in which the effects of auxins on plants is applied in flower farming.
(e) Distinguish between simple and conditioned reflex action 

answers

b) X—root; 
Reason
Low auxin concentration stimulates (rapid/faster) cell division and elongation/growth in roots;
High concentration of auxins inhibits growth in roots;
Y—shoot;
Reason
Low auxin concentration has little effect on the growth of shoots/shoots are stimulated to grow with high auxin concentration (up to a given optimum); 
c) i. 33%±2; 
ii. 1.0 parts per million; 
(d)Faster maturity of flowers/earlier flower formation/flowering;
Prunning/decapitating shoot tips to allow sprouting of lateral buds, hence more yield;
Keeping flowers fresh;
Stimulate formation/development of (adventitious) roots;