Experiment examining the effect of mineral deficiencies on plant growth.
Core Practical Write Up
Investigate the effect of plant mineral deficiencies
Dependant variable: we are going to be observing the changes in root length, plant body length, number of living leaves and colours of leaves.
Independent variable: we will be varying the mineral deficiency in the agar jellies. There will be five ager jelly dishes. There will be one dish containing all nutrients; one dish lacking magnesium; one dish lacking nitrogen; one dish lacking calcium; and one without any of those nutrients.
Controlled variables: We are going to be controlling the type of plant growing in the agar jelly. We are using Mexican hat plantlets for our experiment. The time between each measurement is going to be controlled, when one plant is observed all the other plants will also be observed so plants have equal amounts of time to grow.
Hypothesis: From what I have learnt in class when a plant lacks nitrogen it should be unable to grow larger because amino acids production will be reduced. A plant lacking magnesium would be unable to produce chlorophyll therefore the leaves would become yellow coloured and not so green. The plant lacking calcium would have a stunted growth due to the role of calcium ions in the structure of the cell walls and membrane permeability. I expect the plant lacking all nutrients to have all three of these properties and possibly just die out completely. The plant containing all the nutrients should grow normally without many problems related to the nutrients.
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Key equipment: Solutions of different agar jelly plates lacking nutrients and one containing all nutrients; Standard lab equipment.
Here is a risk assessment table for the hazards associated with this experiment.
(0-5 = Safe experiment, 5-10 = Take Care, 10-15 = Teacher controlled, 15+ = Not safe)
Here are the observations I made observations:
The plant containing all the nutrients grew longer roots and body, after the 3rd observation we noticed the leaved had started to die and were dead at the last observation. We could see the leaves were dead because they have a strong purple pigmentation. These plants were supposed to grow normally throughout the experiment according to our hypothesis.
The plant lacking magnesium had a slight growth in the roots and shrinking. The body of the plant grew a little bit and the leaves stayed green and healthy throughout the observations, this was odd because we expected the leaves to turn yellow in our hypothesis due to the low production of chlorophyll.
The plant lacking calcium had a large growth in the roots and a 3mm growth of the body, the leaves all grew to be large and healthy looking. This was against our hypothesis also, as we expected a stunted growth in the plant due to the lack of calcium ions in the cell wall membranes.
The plant lacking nitrogen ions were expected to have a reduced growth due to the low production of amino acids in the plant cells. The roots appeared to have shrunk during the observations and the body grew during the observation by a few millimetres. The green leaves became slightly purple pigmented but didn’t quite die before our final observation.
The plant lacking all three types of nutrients was expected to lack growth and have yellow leaves because of the magnesium deficiency. The roots managed to exceed the root growths from all the other plants and reach a large 27mm size from 15mm. This was unexpected. The body shrunk by a few millimetres and the leaves did not grow at all and died between the 2nd and 3rd observation.
Over all the plants did follow a slight trend that matched the hypothesis but some of the observations were not expected and may need to be repeated again.
My results were not very reliable at all as there were no repeats taken for this experiment. The measurements I do have are not reliable because there are no repeats to give me confidence in my results. The errors when measuring the length of roots and plant bodies was quite high. There was ±0.5mm error when taking measurements. The measurements were also small so the percentage error was much larger giving inaccuracies. There are a lot of things that happened we did not expect to happen. The agar jelly containing all nutrients was expected to grow healthily. However the plant seemed to decay much faster than plant lacking all nutrients! This may have been due to the conditions within the Petri dishes. There must have been a source of random error. The concentration of the nutrient may have had an effect on the uptake of the mineral. There may have been a lacking source of light or moisture in the plate resulting in the lack of growth. There are many other random errors that may have occurred. The method used does test the hypothesis however when carrying out the experiment again I would have to insure another two repeats and identical conditions for the plants. The only variable must be the mineral deficiency given to the plant. The number of recording taken must be more consistent and frequent. Over all the experiment wasn’t very reliable but the results taken were very interesting as they did not agree with my hypothesis. This was due to many random errors present.
Here's what a teacher thought of this essay
A good description of an investigation which produced unexpected results. Excellent risk assessment and a clear understanding of variables and relevant theory. More detail about the method would have been useful. 4 Stars