K.C.S.E Biology Q & A - MODEL 1995PP1QN14

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The diagram  below represents growing seedlings which  were subjected to unilateral light at the beginning  of an experiment:

• (a)
  • (i) State the results of P,Q and R after 5 days?   ( 5 mks)
  • (ii) Account for your answer in (a) (i) above.   ( 3 mks)
• (b)  If the tin foil were removed from the tip of the seedling R, what results would be observed after 2 days?  (1 mk)
• (c)State the expected results after 3 days if the box were removed (1 mk)

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KNEC ANSWERS

• (a) 
  • ​(i)
    P – will tend/ grow towards  light
    Q – will remain straight/ little/ no growthR – will remain/  grow  straight / Acc. Grow  upwards
  • (ii)
    P – Growth  substances or hormones/ auxins/IAA are produced by the  stem  tip. They move downwards  and get disturbed to the side away from  the side of light. Where  they  cause more rapid growth/ cell division/ elongation ( that results in bonding)
    The source of auxin has been removed and the auxins  are not  affected by light because the era has been  covered.
• ​(b) Tip will bend  towards the light
• (c) All the seedlings will grow upwards.