Environmental Factors affecting plant growth

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E Rashmeen Jaggi

Science Investigation – 10B

24th September 2009

An Investigation into Plant Growth

Environmental Factors that Affect Plant Growth

This unit we looked at different ways of improving plant growth and how do different environmental factors affect the growth of plant. The experiment was mostly to find out which factors would affect the growth of the plant and how. This report mainly focuses on how deficiency of phosphorus affects the growth of a radish plant and why.

Research question

        How does the deficiency of phosphorus affect the plant growth as measured by number of leaves, surface area of leaves and root length? How much time will a plant take to grow or how healthy a plant will be if the plant does not obtain the required amount of phosphorus from the Sach solution?

The independent variables of this experiment were complete sach solution and sach solution without phosphorus, which were measured using a measuring cylinder. The amount of complete sach solution and sach solution without phosphorus were balanced in the following ways:

  • 100% complete sach solution to 0% sach solution without phosphorus
  • 75% complete sach solution to 25% sach solution without phosphorus
  • 50% complete sach solution to 50% sach solution without phosphorus
  • 25% complete sach solution to 75% sach solution without phosphorus
  • 0% complete sach solution to 100% sach solution without phosphorus

The dependant variables of this experiment were the number of leaves, the surface area of leaves and the root length of the plant. The number of leaves was measured by counting them and the surface area was measured by using a graph paper. All the data was collected in a table. The following were the control variables of the experiment:

  • The type of seed was a control variable. For every set of data, a red radish seed was used. In each tube, one seed of the plant type was planted.
  • The amount of light received by the plants was a control variable. Every time the plants were placed in the same place which was next to the window. So, daily they received the same amount of light.
  • The tubes were also a control variable. The tubes in which the plants were placed were all of the same size. They all had a volume of 22cm3.  
  • The water retaining gel powder was also a control variable as well. In each tube about 2.2g of it was used.
  • The weighing scale used to measure the plant gel was also a control variable. To measure the powder, every time the same weighing scale was used.


        My prediction for this experiment was that the deficiency of phosphorus will lead to limited growth of the plants. As the amount of phosphorus will decrease, plant growth will slow down. Due to slow plant growth, there will be fewer leaves than normal and the leaves will not fully develop; they will not have large surface areas and will die in less time. Also, the leaves will contain a purple pigment and will be dark green. The root development of the plant will slow down and lengthwise they will be very small.

        Phosphorus plays an important role in plant growth. It is a very essential nutrient for plants as it helps in energy transfer and storage during photosynthesis. Normally, with the presence of phosphorus, the roots of the plant flourish and it plays an important role in the ability of plants of better tolerance of soil born diseases. But its deficiency might lead to slow growing, weak and stunted plants that might be dark green with older leaves showing a purple pigmentation. Also roots will grow slower than usual and the plant might die before full growth.

        I expect the graph to have a positive correlation which has a gentle slop because of slow plant growth. As the plant will grow slowly, the graph will have a steady gentle slope. The points will be pretty much very close to each other.


For the experiment I required twenty five tubes for five treatments; there were about five replicates for each treatment so that our results did not contain any complications. We also required complete sach solution, sach solution without phosphorus, water retaining gel powder, measuring cylinder to measure the amount of the sach solutions, beakers that contained the sach solutions, syringes also to measure the amount of water or sach solutions, weighing scale to measure the amount of plant gel, tube holders to hold all the tubes, markers to mark the tubes, graph paper to measure surface area of leaves, pipettes to mix solutions and flasks to mix solutions in. The following diagram explains how the experiment was set up and also the method used to carry out the experiment.

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Figure 1: how the experiment was set up and the arrangement of the tubes

We started off the experiment by gathering all required equipment for the experiment and setting them up for the experiment to begin. Figure 1, is a demonstration of how the tubes were set up in five treatments and what proportions of the two types of solutions were used for the different treatments.

  • The first treatment contained tubes that contained 100% of complete sach solution. The tubes of this set were each filled up with 22ml (volume of the tube) of complete ...

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