Variables
The independent variable of this experiment is the molarity of the copper nitrate solution. this will be changed and should cause changes in the dependent variables. the dependent variables of this experiment are the chans in growth of the mustardseeds, which should occur as a result of changing the independent variable.
All variables, apart from the independent variable, must be kept constant in order to allow for a fair test. The variables include:
- The temperature. This is beacuse by increasing the temperature the kinetic energy of molecules also increases and as a result the diffusion rate will also increase.
- The time that the mustard seeds are left in the solution needs to be controle. this has to be kept constant as different times of exposure to the copper nitrate solution will result in different amounts of growth taking place.
- the same apparatus needs to be used, in order to allow for consistency.
Justification of measuring equipment and techniques
In order to conduct the experiment in as a relaible manner as possible, thereby diminshing the chance of anomalous results occuring, the procedure of measuring the changes in growth in varying molar concentration of copper nitrate will be repaeted twice for each concentration. This will also be the case with the control reading of distilled water. As a result the growth of 270 mustard seeds will be monitored.
It is also necessary to place the petri dishes in polystirene bags for storage. This prevents the loss of water by evaporation.
blotting paper, petri dishes- take covers off and let grow
The mustard seeds need to be germinated in water before being placed in to copper nitrate solution. this is because the seeds will not germinate in the copper nitrate. for this reason the effect of copper nitrate on growth will be assesed.
a range from 0.1 - 0.02
syringe- can measure small quantities of solution.
Preliminary Work
The range of concentrations of copper nitrate which will be investigated was needed to be found. initial tests were carried out on three different concentrations of copper nitrate. 1 molar solution, 0.5 molar solution, and 0.1 molar solution. it was obsereved that there was no growth of all three types of seed; mustard, mung and cress. however at 0.1 molar solution the casing of the mung and mustard split open. this led to the investigation of the effects of waeker concentartions o growth and germination. Further tests were carrdied out. it was decided that the mustard seeds was most suitable. For the investigation as the stages in growth and germination were more visible. this was found in the control group where all three seeds were grown in water. for this reason the effect of lower concentration of copper nitrate were tested on mustard seeds. the range of concentration which that when the mustard seeds are placed in small concentration of copper nitrate there is no visible germination. so then it was decided to grow some seeds in water, and once they had germinated copper nitrate would be added to asses the effects on growth. this is now what is to be investigated in the experiments to follow.
From the preliminary work it was also found that a maximum of 15 seeds could fit into each petri dish with enough room for the seeds to germinate and grow. it was also found that 5cm3 of solution was enough to provide the seeds with an efficient amount of fluid.
Method
Apparatus Reagents Seeds
21 petri dishes 30cm3 Copper nitrate (1molar) 350 mustard Seeds
Blotting paper Distilled water
Syringe (1mm and 5mm)
Measuring Cylinder (10cm3)
Tweezer
Spotting tile
Diagram
1) Germinate 315 mustard seeds. Place 15 seeds, using a tweezer, in each of the 21 petri dishes which need to be lined with blotting paper, and 5cm3 of water. The extra three dishes allow for any seeds which do not grow. Once germinated prepare 6 labelled petri dishes with lids filling them with the following solutions as shown in the diagram above using measuring cylinders and syringes to work out the concentrations; first placing a layer of blotting paper at the bottom of each dish.
a) 5cm3 of 0.02 moles of copper nitrate
b) 5cm3 of 0.04 moles of copper nitrate
c) 5cm3 of 0.06 moles of copper nitrate
d) 5cm3 of 0.08 moles of copper nitrate
e) 5cm3 of 0.1 moles of copper nitrate
f) 5 cm3 of H2O as the control test.
2) take 90 germinating mustard seeds which were previously germinated in water. Place 15 germinating mustard sseds into each petri dish as shown in the diagram. Repeat this twice.
3) Place the lids on the petri dishes and place the three petri dishes labelled (a) in a polystirene bag and seal the bag. Do the same for (b)-(f).
4) After 23 hours remove the petri dishes and measure the length of the ........ and height. Record these measurements and for each soution calculate the average lenghts of the ........
confidence limit bit....';n sjdh
However water is mainly absorbed through the roots, which are covered in specially adapted root hair cells, with large surface areas and thin cell walls to aid absorption by osmosis. Osmosis is the flow of water molecules by diffusion through a partially permeable membrane from areas of high water potential (low solute concentrations) to regions of low water potential (high solute concentrations). All plant cell membranes are partially permeable, which means they allow some some substances to penetrate them but not others. Whether water enters the cell by osmosis will depend on the balance between external and internal solute and water potentials.
It could be seen that the plants could have grown more at lower concentrations of sloute as the the water potential outside the seedling is more positive meaning that water will move into the seedling due to the water potential gradient, untill a point where the cell becomes turgid.
