The following results were obtained when a researcher investigated the effect of temperature and pH on the germination of black-eyed peas. He placed the seeds in petri dishes with some cotton wool spread out evenly at the bottom. He then added water every day and monitored the growth by counting the seeds that had germinated.
The results below on the left show the cumulative percentage of seeds that germinated over a 28 day period. Different temperatures (5, 10, 15, 20 and 25$^o$C) were investigated by placing the petri dishes in ovens at the appropriate temperature. Again, pH was investigated by adding water (with pH adjusted to 2, 3.5, 5, 7, 9, 11 and 12.5) as shown in the results.
The results on the right show the final percentage of seeds that germinated at the different temperatures and pH.
The percentage germination rate was calculated as follows, for the days the experiment was monitored.
Germination rate = (number of seeds that germinated / total number of seeds) x 100 %
A student wanted to set up an experiment to check the effect of salinity on germination and plant growth, using the data from above.
1.Based on the results shown,
1.1.State the optimum temperature for germination of black-eyed peas.
1.2.State the optimum pH for growth of black-eyed peas.
2.As an extension of the studies shown above, state what the student would
need to replace the pH solutions with if they wanted to investigate the effect of salinity on the germination of peas?
3.Other than pH and temperature, identify two controlled variables for setting up the experiment
4.Other than germination rate, state two other dependent variables that could be monitored to see the effect of salinity on the growth of black-eyed peas.
