Investigate the Effect of Moisture Content on Wheat Grain Seeds Respiration Rate :: GCSE Biology A2 A-Level Coursework

Investigate the Effect of Moisture Content on Wheat Grain Seed's Respiration Rate HYPOTHESIS: There will be a positive correlation between moisture content of wheat grains and their respiration rate. Therefore as the moisture content (independent variable) increases so will the respiration rate (dependent variable). The rationale behind the hypothesis came from studying photosynthesis in plants. During the light-dependent reactions of photosynthesis, the photolysis of water (H2O) occurs inside photosystem II. The products of photolysis combine with NADP from photosystem I, to form reduced NADP. This reduced NADP passes to the light-independent reactions of photosynthesis, where it is utilised to make triose phosphate from glycerate 3 phosphate. Without water, photolysis would not occur and therefore the light-dependent and light-independent reactions would not take place at all. Therefore I would predict that the higher moisture content of wheat grain seeds the higher the respiration rate will be, this is because the seeds will be able to utilise more water than a wheat grain seed with low moisture content. VARIABLES: The independent variable used in this experiment is going to be moisture content, and the dependent variable will be the respiration rate. The other variables; temperature, air pressure and air will be kept at fairly constant levels. Carrying out the experiment inside a fume cupboard will help achieve in keeping these variables to remain constant. However another variable sunlight cannot be controlled during this experiment, and will obviously vary during the experiment. The possibility of using a standard light bulb to keep light levels constant was considered, but was rejected due to safety fears e.g. overheating when the experiment was not being monitored during the time between readings. BACKGROUNG KNOWLEDGE: Deterioration of stored grain seeds is an important economic problem in agriculture, therefore it is important to find out the most suitable conditions for stored grain seeds to be maintained in. For this experiment wheat grain has been chosen, this is because it is widely cultivated around the world e.g. the Mediterranean and West Asia, and is used to make flour and pasta. This means wheat is a staple crop throughout the world, and its storage is essential. To store grain effectively it is important to stop germination from occurring at all. Germination is the onset of growth of the embryo in a seed, this usually happens after a period of dormancy. Dormancy is the state where germination will not occur, even if environmental conditions are favourable. This is often an advantage for seeds, as it allows germination to occur in a more favourable season. In the case of wheat seeds they need several weeks or months of prechilling before the will actually germinate.