K.C.S.E Biology Q & A - MODEL 2019PP2QN01

K.C.S.E Biology Q & A - MODEL 2019PP2QN01

In an experiment to investigate the effect of sodium chloride on the growth rate in a spinach seedling, seeds were treated with different concentrations of sodium chloride. The results are as recorded in the table below.

​(a) From the results in the table above, explain the effect of increasing the concentration of sodium chloride. 
(b) Apart from a ruler, state two other equipment one would need to determine the rate of growth in the roots. 
(c) With a reason, state one other part of the seedling the students would focus on to determine the effect of sodium chloride on growth. 
(d) State the likely effect on the seedling of increasing the concentration of sodium chloride to 2.20mol/l

answers

​(a) Increased Nacl concentration/having more Nacl ions decreases water potential/decrease osmotic potential/ increase osmotic pressure/makes water potential more negative outside the seed/seedling in the surrounding solution to be hypertonic to the cell sap in the seedling ; seeds cells take in water by osmosis) are dehydrated/lose water molecules to the surrounding solution , reducing the growth enzyme activity; have reduced  growth  rates;
(b) Threads(wire/string)
     Books;
     Pen; Marker (pen);
    Dye/water proof ink/ bloating paper/tissue paper
(c) Rate of growth/ increase in length of shoot tip/apex
    it is a region of (active) cell division/growth
(d) The seedling will be (dehydrated) /lose water (hence) wither/die/dry