To investigate the effects of salinity on the germination of wheat plants.
1.1 Defining the problem
1.1.1 Focus/Research Question
Does salinity affect the time it takes for wheat to germinate and then the rate at which it grows from that point onwards?
Germinating wheat seed in a solution of 0% salt content, 2% salt content, and 5% salt content will have the shortest, longer and then the longest germination times, respectively and then growing the shoots in a solution of 0% salt content, 2% salt content, and 5% salt content will have the most growth, less growth and the least growth respectively on a day-by-day basis from the seed’s germination as measured by height for the five days after germination within a reasonable range defined as within the first 7 days.
1.1.3 Background Information/Theory
Salinity in water used to irrigate plants and soil salinity can have a considerable effect on the intensive agriculture of wheat plant germination and growth (Effect of salts on germination of seeds and growth of young plants of Hordeum vulgare, Triticum aestivum, Cicer arietinum and Brassica juncea. Mer, R.K., P.K. Prajith, D.H. Pandya and A.N. Pandey, 2000). These marked adverse affects take place on a cellular level by affecting cellular diffusion thus affecting the mechanisms of osmosis and interfering with the ionic status of the permeable membranes that surround each of our cells (CiNii.co.jp, Latest Edition, effect of salt concentrations of various plants, website: http://ci.nii.ac.jp/naid/110000978592/). Ion concentration is central to the process of osmosis and excess of certain ions such as NaCl can affect nutrient transfer through the cell (Biology for the IB Diploma, C.J. Clegg, 2007). Indeed, the most possible cause of varietal difference most likely evolves ion transport properties and cellular compartementation (Causes of Varietal differences in
Salt tolerance. In: International congress of plant physiology, Munns, R., 1988). This, of course, affects plant life at all stages, however different plants have varying salt tolerances due to individual differences in biological mechanisms (Handbook of Plant and Crop Stress. Marcel Dekker). Thus, plant salinity is of crucial importance to germination and growth.
Germination and growth is central to farming of many plants. Wheat is a crop of immeasurable importance; in fact 607 metric tons were consumed in 2007. Wheat is the most widely grown food crop in the world, and is increasing in production. It ranks first in world crop production and is the national food staple of 43 countries. At least one-third of the world’s population depends on wheat as its main staple. The principal food use of wheat is as bread, either leavened or unleavened (Access Online Encyclopaedia, accessed Monday 23rd of February).
Salinity is of particular reference when dealing with harsh arid and semi-desertal climate of Australia (Australian Bureau of Meteorology website, accessed Monday 23rd of February) where salt crystallisation can lead to high salt concentrations in soil as air-born water born salt does not have time to be flushed through to aquifers or removed into the body of plants. Another relevant effect is that reduced rainfall in these said areas means that surface alluvial topsoil experiences salt build-up without being eroded away as would otherwise happen due to rainfall. It is therefore clear that salinity is an issue of some great importance and in this particular experiment, an experiment of singular pertinence with one of the most important global crops at stake, the effect of salt on wheat germination and growth will be tested (World Journal of Agricultural Sciences 4 Effects of NaCl Salinity on Wheat (Triticum aestivum L.) Cultivars).
1.1.4 Investigation Variables
Variable name and Explanation
Type of variable
Salinity (salt concentration in liquid used to aid germination and growth after germination)
Germination (the time it takes for the seeds to germinate)
Height (after the seeds have germinated their growth in centimetres)
Amount of water (how much water is used to aid plant growth and germination )
Type of water (the source of the water and its chemical composition)
Temperature (the ambient temperature for all of the plants)
Light intensity (the intensity of the light source )
Time of watering (when the plants are watered)
Wind (movement of air over the experiment)
Contact with water (the degree of contact that the seed has with the water it is germinating or growing in)
Insects (the insects that may consume or otherwise affect the results of the experiment)
1.2 Controlling Variables
1.2.1. Treatment of Controlled variables
Treatment of variable
Each plant will be given a specific amount of water salinity as per the requirements of the experiment.
An observation will be made as to whether the seed is in any way visually changed with the appearance of a shoot and the day on which this happens will be noted.
Each plant will be measured after germination using a 30cm ruler with a precision of ï¿½1mm.
Amount of water
All Petri dishes will receive exactly the same amount of water (10mls, precision ï¿½ 1ml) each per day.
Type of water
The same type of water will be used for all of the plants (i.e. tap water).
All seeds will be placed in the same vicinity to ensure that all seeds are kept at the same temperature. (Even temperature unnecessary or perhaps inhibitory since seeds have evolved to germinate in natural conditions: ambient temperature, hopefully similar to the optimum ambient temperature (variation)).
All seeds will be placed at exactly the same distance from the light source – the kitchen window.
Time of watering
All seeds will be watered at the same time of 3 o’clock in the afternoon.
All seeds will be placed in the same place (next to an open window to allow air flow, to simulate normal conditions, see reasoning ‘Temperature’) to control for wind factors.
Contact with water
All seeds will be placed in exactly the same place on the damp piece of paper (each with exactly the same level of dampness) that will serve as the germination medium.
The house has been sprayed with insecticides to ensure minimal possibility of insect disturbance. All possible means of entry to place of experimentation to insects have been blocked.
The control in this experiment is the 0% salt solution, or in other words the solution without salt. This should help to isolate any invalid effects concerning whether it really was the effect of the salt should the experiment indicate slower growth and germination in the seeds with the saline solutions. For example, if the control with no salt were to germinate and grow even slower than the two saline solutions we could probably assume that our hypothesis was wrong or at the very least that there were other factors involved.
1.3.2. Practical Safety and Risk Assessment
There are few practical safety requirements however, as the experiment is taking place at a residence as opposed to a laboratory instruments such as the measuring cylinder must be washed and kept separated from eating utensils and plates etc. The experiment itself poses no great danger and it can be assumed that the safety, environment and possible costs should an accident take place are ? 3 meaning that there is an unlikely risk of an insignificant incident and/or a rare risk of a minor accident taking place. These can be managed under routine safety procedures. There are some minor safety issues outlined as to the use of Sodium Chloride in the form of table salt dealing with inhaling its powdered form (not to be inhaled under any circumstances), skin contact (attempt to avoid exposure especially for prolonged periods due to skin dehydration and irritation) and eye contact (can cause eye damage/irritation). Sodium Chloride in the form to be used in the experiment is by no means hazardous and its use should pose no danger with proper routine safety procedures.
1.3.1 Diagram 1 (Experimental Setup)
1. Take the Petri dishes and separate them into halves so that there are, in fact, six dishes.
2. Place them on a table in a suitable area with little temperature fluctuation, some sunlight not that much as would cause the seeds to dry out and with minimum disturbance from insects and other factors.
3. Take the paper towels and cut them in half
4. Fold halves of paper towels into quarters
5. Place Petri dish on top of paper towel and trace outline with marker.
6. Cut out circle.
7. Transfer to Petri dish.
8. Label Petri dishes with marker.
9. Place 10 seeds per tray evenly into Petri dish on top of the paper towel (see part 2 of 1.2.1 – diagram).
10. Create 5% solution by dissolving 5mls of salt into 95mls water in the plastic container.
11. Transfer 10mls of 5% solution from plastic container to measuring cylinder.
12. Pour 20mls of 5% solution into Petri dishes (a) and (b).
13. Create 2% solution by dissolving 5mls of salt into 245mls water in the plastic container.
14. Transfer 10mls of 2% solution from plastic container to measuring cylinder.
15. Pour 20mls of this solution into Petri dishes (c) and (d).
16. Pour 20mls of pure tap water (negligible salt content) into Petri dishes (e) and (f).
17. Take a photograph of all the Petri dishes with seeds and then print and annotate the pictures with thereby labelling them giving them each a code (i.e. n1 0%) by which they can be identified.
18. Repeat steps 9 to 17 at the same time of day every day for every dish from that day onwards for the next 13 days.
19. At the point at which the seeds sprout (see definition dependant variable: germination – 1.2.1. treatment of variables), make a measurement of their growth on each day onwards until the 14th day of the experiment at which point the experiment will have ended.
Some water may have leaked in through the window, however all seeds appeared to have been affected in equal measure.
The presence of ants has been observed however this does not appear to have affected growth or health of plant. No visible changes have been made to the plants and the ants do not appear to have attempted to consume any of the germinating seeds. As soon as the ants’ presence was observed they were removed.
The seeds appear to have reached to raw limit of growth without some form of nutrition in the form of soil.
The seeds’ growth appears to be slowing perhaps due to their lack of nutrients.
One growing shoot (length 12 cms, photo taken on Day 14 of experiment 0% number 3).
Apparent Mould (difficult to see in this grainy picture but manifests itself in the form of the strange whitish brown halo around the clearly darker outline of the seed, photo taken Day 14 of the experiment 5% number 8, not having germinated)