Plant Science Seed Germination Lab Hypothesis

Plant Science - Seed germination and growth

The research question: What is the effect of changing the pH of the soil on the germination and growth of mustard peas?

Hypothesis: The greatest number of peas will germinate and will grow the most when the pH is 5 or 7.

Theory: Enzymes play a vital role in the cells of plants (especially when growing) and enzymes work best when at their optimum pH value. Moreover, all chemical reactions have an optimum pH at which they work best (Howard and Loomis, no date). Generally the enzymes in plants work best at a pH of around 5-7. For examples, lipases work best at a pH of between 4-7 (Barros, Fleur and Macedo, 2010). Furthermore, celluloses, which break down specific carbohydrates, have an optimum
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Also germination is stimulated by an uptake of water and due to the shortage of H+ ions in more alkaline solutions this may delay or terminate germination. The pH of soil can affect the spread of important nutrients with in the soil, and unevenness can prevent a plant from absorbing them. Before plants can use a nutrient it must be dissolved in the soil solution. Most minerals and nutrients are most soluble and so more available for plant absorption in a pH of just below 7, rather than in soils with a pH of 7 or higher. For example, phosphorus is most available in soil with a pH of 6.5. Strongly acid soils can have high concentrations of aluminum, iron and manganese, all of which may be toxic to the growth of some plants (Bickelhaupt, no date). In very alkaline soil, plants cannot take up certain nutrients such as zinc and copper. In very acidic soil, other nutrients such as calcium, magnesium and phosphorous are not absorbed and can even be toxic. The next effect that pH of soil can have is that it can affect the beneficial microorganisms and bacterium that live in the soil. The decomposition of …show more content…
To keep the water levels the same 5cm3 of water will be added to the soil every day. Soil of the same type and water level will be used so that the water content of the soil is the same. The humidity of the room will be kept the same for all experiments so that water levels in the air are also the same. Mineral, vitamin and ion content of the soil: This needs to be kept the same as mineral, vitamin and ion levels in the soil could have an effect on growth and germination. This is hard to control with a high degree of accuracy but if the same type of soil is used and nothing is added then the mineral, vitamin and ion content of the soil should remain relatively similar. Time: The time that each seed is left to germinate and grow needs to be the same so that it is regarded as a fair test. Conducting each experiment for a week will ensure that the time, for which each experiment is left, is the

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