A student investigates the effect of salt water (salinity) on the germination and growth of mung bean seeds.
She places 25 seeds on wet cotton wool in each of five dishes. Each dish contains a total volume of 30 cm3 of liquid, made of different mixtures of distilled water and a concentrated salt solution.
The table below shows her results after 6 days:
| Volume of distilled water in dish (cm3\text{cm}^3cm3) | Volume of salt solution in dish (cm3\text{cm}^3cm3) | Number of seeds germinated |
|---|---|---|
| 30 | 0 | 23 |
| 24 | 6 | 21 |
| 15 | 15 | 18 |
| 6 | 24 | 8 |
| 0 | 30 | 3 |
State the dependent variable in this investigation.
For the seeds grown in 30 cm3 of salt solution (with 0 cm3 of distilled water), the mean root length was 4 mm and the mean shoot length was 1.5 mm.
Calculate the Seed Viability Index (SVI\text{SVI}SVI) for these seeds.
Use the formula:
SVI=mean root length (mm)×mean shoot length (mm)×percentage of seeds germinated \text{SVI} = \text{mean root length (mm)} \times \text{mean shoot length (mm)} \times \text{percentage of seeds germinated} SVI=mean root length (mm)×mean shoot length (mm)×percentage of seeds germinatedExplain why using the Seed Viability Index (SVI\text{SVI}SVI) is a more informative way to measure the effect of salinity on seed development than simply using the number of seeds germinated.
44 exam-style questions on OCR GCSE Biology Practical skills. Each one has a worked solution and a mark scheme showing where the marks go.