2019 Year 12 IB Extended Essays

Hypothesis: If the concentration of nitrates is increased, then the wheatgrass that is grown in the higher nitrate levels will be taller because plants use nitrates to grow as the nitrogen within the nitrates are key components of their proteins and chlorophyll. If the salinity levels are increased, then the wheatgrass that is grown in the higher salinity levels will be shorter because the plant will be losing water via osmosis and water plays a crucial role in transporting nutrients around the plant. If the plants are grown in 0M salinity and nitrate, then they will only complete the germination phase because they will be utilising the nutrients within the seeds themselves in the endosperm but once the seed has its first shoot, it will eventually die out as there are no nutrients in the hydroponic set up for the plant to absorb and assimilate into their cells. If the seedlings are grown in the same concentration of NaCl or NaNO 3 , then the plant grown in NaNO 3 will grow taller because the NaNO 3 supplements the growth of the plant whereas the NaCl restricts its growth as most plants don’t use NaCl for their growth and functioning and generally expel it from its cells.

Variables:

Independent variable Variable Percentage of nitrate

How it is changed

The Molarity of nitrates will be changed from 0M to 0.0068M, 0.0274M, 0.1095M and 0.4381M, enabling the researchers to determine the effect that changes in these levels of nitrates has on the growth of the wheatgrass to determine whether the water must be diluted before release into water bodies Percentage of Salinity The percentage concentrations of NaCl were maintained at 0M, 0.0068M, 0.0274M, 0.1095M and 0.4381M to mimic the levels of salt present in parts of Australia.

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