How Does Salinity Affect Plant Growth?
A Hands-on Activity
By Anthea Hudson
The increasing salinity of our rivers is of real concern, in many ways, one of which is the effect on naturally occuring plants which grow within the river's ecosystem, and plants that we humans use this water on as well.
Experiment and find out how varying degrees of salinity affect plants!
YOU WILL NEED
- Several small pots to grow your plants in. At least half a dozen, but more if you wish.
If you don't have real garden pots, you can make them from plastic containers, such as yoghurt or ice cream containers, even cut down milk or juice cartons will do, with holes punched in the bottom for drainage.
- Gravel or small stones to increase good drainage in bottom of pot.
- Potting mix or garden soil.
- Seeds, such as beans, sunflower, wheat or something else easy to grow.
- Container and spoon to mix water and salt solutions.
- A warm, light area to grow the plants, protected from pests.
- Put a shallow layer of gravel/stones in the bottom of each pot, then top up with soil, until about 3cm from the top of the pot.
- Press 3 or 4 seeds into each pot of soil, at depth suggested for your type of seed (a cm or so will probably do) and push soil back over hole, and firm down.
- Carefully water one pot with plain water, without disturbing the seed. This is your 'control' and will help you judge the reactions of the other plants compared with their normal growth pattern.
- Prepare salt and water solutions, ranging from barely salty to saltier than sea water. The number of different strengths will depend on the number of pots you are growing.
- Make sure you record how much salt to how much salt to water was included in each solution, and which plant they were used on, so that you can make more every couple of days or so, when they need watering again.
- Carefully water each pot, with the same amount, of a different solution.
- Keep moist, but not soggy.
- As the plants appear- or not- record what you notice, every day. Take a photo each day, if you can, to help better track their progress.
CONSIDER THESE QUESTIONS...
What do you notice in the first few days? After a while?
What do you think is happening and why?
How does your experiment relate to real world problems?
What could be done to try to lessen the problems?
Are any of these things being done?
How could you get involved with helping protect our rivers? Join Waterwatch?
WANT TO DO MORE?
To take this activity further, you could repeat the test to make a comparison between the growth of salt tolerant plants (such as pigface or saltbush) and less salt tolerant plants under the same conditions as above. What do you discover?
Once you have completed your experiments, you may also like to read the related article 'How Does Salinity Affect Plant Growth and What Can Be Done?'