A student investigated the effect of gibberellin（GA）and abscisic acid（ABA）on the germination of wheat grains． The student found out the following information． －The molecular mass of GA is 346 g ． －The molecular mass of ABA is 264 g ． －The range of concentrations at which GA is active in plant tissues is from $$\(1 \times 10^{-6}\)$$ to $$\(1 \times 10^{-5} \mathrm{moldm}^{-3}\)$$ ． －The range of concentrations at which ABA is active in plant tissues is from $$\(1 \times 10^{-6}\)$$ to $$\(1 \times 10^{-4} \mathrm{moldm}^{-3}\)$$ ． －Newly formed wheat grains contain a high concentration of ABA which decreases over time． －When the concentration of ABA falls low enough the GA is able to promote germination． －Wheat germinates best at temperatures from $$\(10^{\circ} \mathrm{C}\)$$ to $$\(25^{\circ} \mathrm{C}\)$$ and without light． Fig． 1.1 shows the germination and early growth of wheat． To test the effects on germination of adding $$\(A B A\)$$ ，the student started by soaking wheat grains for 24 hours in a solution of $$\(1 \times 10^{-6} \mathrm{~mol}^{-3} \mathrm{GA}\)$$ ．These were then split into several groups of 50 grains and a different concentration of ABA was added to each group． The student made a stock solution of ABA with a concentration of $$\(1 \times 10^{-3} \mathrm{~mol} \mathrm{dm}^{-3}\)$$ which was then diluted to make the solutions needed for the investigation． Identify the independent and the dependent variables in this investigation. independent variable dependent variable (ii) Describe a procedure that the student could use to complete the investigation to find the effect of different concentrations of ABA on the germination of wheat grains. Your method should be detailed enough for another person to use and should not repeat any details from (a)(ii) of how to dilute the stock solution. . . . . . . . . . . . . . . .

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