Plant Growth vs Nitrogen and CO2 Experiments

Plant Development

The growth and development of a plant are fairly simple processes. They are based on time tables and nutrient needs.

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Objectives/Goals

The goal of this project is to figure out whether plant growth is more dependent on nitrogen or CO2 and whether plants grow stronger and faster when both of these variables are increased together. I hypothesized that plant growth is more dependent on nitrogen than CO2 because if a plant has extra CO2 in its atmosphere what good will it do the plant if it doesn#t have the nutrients (nitrogen) to break that extra CO2 down with? I also hypothesized that the plants grown with extra CO2 and nitrogen would grow the best.

Methods/Materials

I tested this by having plants grow in four groups of several separate sealed containers (all in sandy soil at room temperature and watered the same amount). In one group, plants were tested for growth with double the amount of CO2, with nitrogen in the soil in another, both doubled CO2 and with nitrogen in the soil together in another, and as my control, without nitrogen or extra CO2. I did one set of tests with pea plants (a nitrogen fixing legume) and one set of tests with lettuce plants (a legume).

Results

When the CO2 in a pea plant#s atmosphere was doubled, the plant grew about 10% taller (in three weeks) than when there was a regular amount of CO2. The pea plants grown with doubled CO2 were also thicker, healthier, and had deeper root systems than those of the control plants. The lettuce plants grown with doubled CO2 grew an average of 45% more (in weight) than the control and had slightly longer root systems. The plants, both pea plants and lettuce plants, with nitrogen in the soil and no extra CO2 all died. However, in the containers with a doubled amount of CO2 and with nitrogen, the plants survived and, although they didn#t grow as well as the control group, grew fairly well.

Conclusions/Discussion

From this project, I can conclude that plants grown with a higher amount of CO2 grow healthier, taller, and structurally differently than when without. I think the plants with nitrogen in the soil died because there was too much of the nitrogen. It was interesting to see that the plants with nitrogen in the soil and a doubled amount of CO2 survived. This just goes to show how important CO2 is in plant growth (and survival), and unlike my hypothisis, plants without nitrogen seemed to grow just fine, especially with extra CO2. 3rd party contributor