Investigating the Effects of Salt on Seed Germination

Authors Avatar by jackbardsleystudentscotchwaedu (student)

Seed Germination Investigation


In this investigation, we are researching and investigating whether the concentration/percentage of NaCl (salt) in water affects the germination rate of seeds and if so, which concentration germinates the most seeds. We will formulate our research by conducting an experiment in which we will observe the germination of seeds in various concentrations of salt water and evaluate the results gathered. In particular, we will measure the percentage of seeds germinated in one week and formulate our conclusions from there.


I hypothesise that the highest percentage of seeds will germinate in the petri dish that contains the lowest percentage of NaCl in water- 0.5% salt salinity and the percentage will decrease as the percentage of salt in the solution increases. I predict this because I know from prior knowledge that seeds need to be able to absorb H2O to germinate and salt prevents this. So if we increase the amount of salt and therefore, decrease the amount of H2O in the solution, germination of seeds will occur less than those in lower percentages of salt, thus allowing for the 0.5% solution to germinate the most seeds as it contains the least amount of salt out of our five different samples.


The independent variable (the variable being changed): The independent variable is going to be the concentration/percentage of salt in water (%). This variable will be changed and a different percentage of NaCl will be used in every petri dish. We will measure and change the concentration of NaCl with water for each petri dish by measuring and pouring 5mL of solution from a particular solution bottle and into a petri dish, using a different solution bottle-which contain different concentration of salt-for each dish.

The dependent variable (the variable being measured): The dependent variable is going to be the percentage of seeds that germinate over one week in each petri dish/NaCl solution. We will count the total number of seeds in each petri dish and after one week; count the number of seeds that germinated so that we can calculate a percentage.

The control variables (the variables kept the same): The other variables, which we need to keep constant, are:

  • The same number of seeds used for each petri dish (10 seeds). To keep the amount of seeds the same for each sample, we will count out five groups of 10 seeds and then spread them evenly in each petri dish.
  • The same fertilizer used to place around the seeds in each sample and the same quantity of the fertilizer. We will control this variable by ensuring that we use six cotton wool balls in each petri dish and we will make sure that no soil is placed in any of the dishes.
  • The same seed species used (cress seeds) the same depth of planting. To make sure that all the cress seeds are planted the same distance into a cotton wool ball, we will carefully place them on the surface of the cotton wool ball, ensuring that we do not apply any pressure.
  • The same type of container/petri dish used for each sample and the same type of lid used. To ensure that the same type of petri dish is being used, we will measure the diameter of each of them and ensure that they are all made of plastic. So that the results are accurate and the same conditions are kept for each trial, we will place a lid tightly onto each petri dish, restricting airflow to the seeds.
  • The same length of time each seed spends in a petri dish before being observed. To keep this variable constant, we will leave each seed in the petri dish for one week before we observe them. This is the amount of time they have to be germinated in and will be length of our experiment.
  • The same volume/amount of H2O (including salt) used in each petri dish. To control the amount of water poured in each petri dish and ensure that it is the same temperature for each sample, we will carefully measure out 5mL of a NaCl solution in a measuring tube and pour drops evenly around the 10 seeds. To keep the temperature the same, we will ensure that each solution bottle is at room temperature.
  • The same spacing of seeds in the petri dish and the same gap between them (1cm). To ensure that the experiment is fair, we will equally space the seeds around the edge of each petri dish and ensure that there is 1cm gap between them.
  • The same conditions present around the experiment (room temperature, sunlight, disturbance, humidity, etc.). To keep the room temperature and sunlight consistent for each petri dish, we will place each petri dish next to each other at the same location. This way, the room temperature will be the same for all of them and the amount of sunlight will barely change. The level of disturbance around each trial will be kept to a minimum, allowing for none of the seeds to be knocked of a cotton wool ball.
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  • 5 mL NaCl 0.5% solution
  • 5 mL NaCl 1% solution
  • 5 mL NaCl 1.5% solution
  • 5 mL NaCl 2% solution
  • 5 mL NaCl 2.5% solution
  • 1x Measuring Tube
  • 5x Petri-Dishes with lids
  • 50x Cress seeds
  • 1x Desk
  • 3x Lab coats
  • 1x Laptop
  • 1x Marker
  • 30x Cotton wool balls

Setup & Plan:

Here are the details of how we will conduct our experiment and the measurements we ...

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