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Investigation into the effect of varying concentrations of potassium nitrate solution, on the germination and subsequent root radicle growth of cress seeds.

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Investigation into the effect of varying concentrations of potassium nitrate solution, on the germination and subsequent root radicle growth of cress seeds. The following investigation is based on seed germination and growth. In this particular study seeds will be subjected to a variety of different solution concentrations, the aim being to find out how this affects their growth and germination. Introduction The germination of seeds is dependent on the presence of three things; a sufficient water supply, a suitable temperature and an appropriate partial pressure of oxygen. Germination also relies on the maturity of the embryo as well as the presence of the three factors listed above. The picture above shows a seed in trans-section. The embryo consists of a shoot (plumule,) a root (radicle) and 1 or 2 seed leaves. The seed's food store is either contained in the endosperm (tissues surrounding embryo) or within the seed leaves. The role of the testa is to enclose and protect the seed's contents. Water, which is absorbed through the microphyle and testa, is essential for activating the enzymes that catalyse the biochemical reactions of germination. When water is absorbed it stimulates the production of gibberelin (a plant growth regulator, synthesised in most parts of the plant.) The gibberelin, in turn, stimulates the synthesis of amylase by the cells in the aleurone layer. ...read more.


Carrot - high concentration of potassium nitrate 6. Carrot - low concentration of potassium nitrate 7. Carrot - high concentration of copper nitrate 8. Carrot - high concentration of copper nitrate 9. Cress - large volume of solution 10. Cress - small volume of solution 11. Cress - control 12. Carrot - control The lids of the dishes were then replaced and the dishes were placed in a tray lined and covered with wet newspaper. The wet newspaper makes the environment damp so minimising evaporation by decreasing the water potential gradient between inside and outside the dish. Results The seeds were checked after one day and the newspaper had completely dried out. None of the seeds showed any signs of germination. The newspaper was re-dampened and the seeds left for a further 3 days. After day 4 the control groups had fully germinated with the cress seeds having an average root length of 2.75cm and the carrot seeds an average root length of 1.96cm. It was noted that some seeds had slid under the blotting paper and showed no signs of germination. None of the other seeds showed any signs of germination. It was therefore difficult to decide which solution and at what volume to use in the actual experiment. However, due to the success of the controls, it seemed that a volume of 8cm� was adequate. ...read more.


This is because the nitrogen, in fertilisers, is not needed by the plant until the embryo has developed and has begun to photosynthesise. Once the plant is developed, the nitrogen constitutes to essential biological molecules, such as proteins and nucleic acids. Variables Independent Variable - * Concentration of Potassium Nitrate solution; 0.1mols, 0.01mols, 0.001mols, 0.0001mols and 0.00001mols. Dependent Variables - * Germination of seeds * Length of root radicle grown, once germinated * Appearance of a plumule (shoot.) Control Variables - * Temperature - room temperature * Light - Dark * Total volume of solution - 8cm� * Solution used - potassium nitrate * Water used - distilled * Humidity - Quite humid due to wet newspaper * Equipment used - Consistent throughout Equipment Method 1. Lay 7 of the 14 petri dishes out on the table and remove the lids. The remaining 7 will be used in the repeats. 2. Take the blotting paper and scissors and cut 14 circles, of equal diameter, out of the blotting paper. The circles should have a diameter slightly smaller than that of a petri dish, enabling them to fit neatly inside the base of a dish. 3. Using the marker pen, label the dishes with the following: Dish 1 - '0.1 mol, Potassium Nitrate' Dish 2 - '0.01mols Potassium Nitrate' Dish 3 - '0.001 mol, Potassium Nitrate' Dish 4 - '0.0001 mol, Potassium Nitrate' Dish 5 - '0.00001 mol, Potassium Nitrate' Dish 6 - '8 cm� water' Dish 7 - '8cm� Potassium Nitrate' 4. 5. ...read more.

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