• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10
  11. 11
    11
  12. 12
    12
  13. 13
    13
  14. 14
    14
  15. 15
    15

Investigating the effects of varying pH levels on the germination of cress seeds

Extracts from this document...

Introduction

PLANNING & PREPARATORY WORK I will be investigating the effects of varying pH levels on the germination of cress seeds. A seed is a fertilised and ripened ovule, consisting of the plant embryo, varying amounts of stored food material (endosperm), and a protective outer seed coat (aleurone layer). The embryo secretes hormones such as cytokinin, and indole acetic acid, which promote cell division. The endosperm contains insoluble food stores including starch, proteins, and lipids, all of which are used in the initial germination stages. The aleurone layer contains proteins, and under the influence of gibberellic acid (manufactured and secreted by the embryo) synthesises amino acids into hydrolytic enzymes such as -amylase and a protease. These enzymes are then used to hydrolyse starch ( glucose, and proteins ( amino acids for further growth and development. The scale used to measure the acidity or alkalinity of a solution is the pH scale, which generally ranges in values from 0-14. Acidic solutions have pH values below pH 7, which is the value of a solution considered to be neither acid nor alkaline i.e. neutral. In pure water, the concentration of hydrogen ions is equal to 10� ; when an acid is added to pure water, the hydrogen ion concentration increases above this level. The pH level of the solution in which the seeds are germinating affects the availability of elements. Extreme acid/alkaline conditions may adversely affect plant growth by altering selected nutrient availability. Moreover, extreme acid/alkaline conditions can be very corrosive, and would more than likely denature vital enzymes due to their delicate nature as proteins. Slightly acidic conditions can be advantageous to germinating seeds, as the higher concentration of H� ions encourages the uptake of nutrients. I therefore predict that when grown in a variety of acidic pH values, the success of germination will decrease as the acidity increases. Null hypothesis: success of seed germination is not dependent on pH level. ...read more.

Middle

synthesises amino acids into hydrolytic enzymes such as -amylase and a protease. These enzymes are then used to hydrolyse starch ( glucose, and proteins ( amino acids for further growth and development (1). The scale used to measure the acidity or alkalinity of a solution is the pH scale, which generally ranges in values from 0-14. Acidic solutions have pH values below pH 7, which is the value of a solution considered to be neither acid nor alkaline i.e. neutral. In pure water, the concentration of hydrogen ions is equal to 10� ; when an acid is added to pure water, the hydrogen ion concentration increases above this level (3). The pH of a solution is a measure of the hydrogen ion concentration in that solution. The pH scale is logarithmic, so a small change in pH represents a large change in hydrogen ion concentration. For example, the hydrogen ion concentration of gastric juices (pH 1) is nearly 400 times greater than that of pure water (pH 7) (2). The pH level of the solution in which the seeds are germinating affects the availability of elements. Extreme acid/alkaline conditions may adversely affect plant growth by altering selected nutrient availability (3). Proteins have specifically charged groups such as carboxyl groups and amino groups. Since the charge of these groups depends on pH, a protein molecule can have different charges according to pH. In general, positive charges and negative charges on the surface of protein are well-balanced around neutral pH. Because of electrostatic attraction, the shape of the protein is compact and stable. However, for example, at extremely low pH levels, the carboxyl group is broken and negative charges are decreased. Thus, proteins will lose the stability which comes from electrostatic attraction, and gain more electrostatic repulsion between the increased positive charges. This is how proteins are denatured at extreme pH (4). Rain water is naturally slightly acidic due to the presence of carbon dioxide in the atmosphere which forms weak carbonic acid in water. ...read more.

Conclusion

Although the germination rates were different amongst the samples, there was a clear distinction between those that did germinate and those that didn't at all, and all those that did germinate reached 100% germination regardless. The highest concentrated samples (10% and 100%) did not germinate at all, most likely due to the enzymes required for germination being denatured. However, the seeds in the 10% concentrated sample always remained a lighter colour than those the 100% concentrated sample, indicating that although the concentrations were too strong for any germination, the minor difference between them still affected their outcome (although perhaps not significantly). Although limitations were fairly minor, I believe that the experiment could be improved as a whole if all the variables could be controlled absolutely. For example, if the seeds were grown in the same way, but placed on the cotton wool in a more controlled manner, one by one if necessary. This would help to prevent blocking of light or accessibility to the solutions by the cotton wool. Alternatively they could be grown in another medium similar to cotton wool in that it would not interfere with the germination process such as paper towels. Additionally, if the samples were kept in a room with a controlled temperature and the availability of natural light was controlled, this too would help to make the experiment more accurate as a whole. In terms of how acid rain affects the growth of plants in general, tests such as this one could be carried out with other acids found in acid rain such as Nitric Acid and Carbonic Acid varying the concentration of each; perhaps one particular acid in the solution of acid rain has more or less affect on plant germination than another. Furthermore, the same tests could be carried out using a variety of other seeds which may be more/less tolerant to the acidity, which could then be developed to research into what makes plants more/less tolerant to acidic conditions. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Aqueous Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Aqueous Chemistry essays

  1. Marked by a teacher

    The Effect of pH on the Strength of Keratin (hair protein).

    4 star(s)

    Unfolding of the formation due to pH is a result of ionisation of the R group inside the protein molecule. This damages and breaks the ionic and hydrogen bonds that help to hold the protein and give strength. Consequently weakening the hair strand and causing it to lose its elasticity.

  2. Marked by a teacher

    The effetct of copper nitrate on the germination of mustard seeds.

    All variables, apart from the independent variable, must be kept constant in order to allow for a fair test. The variables include: * The temperature. This is beacuse by increasing the temperature the kinetic energy of molecules also increases and as a result the diffusion rate will also increase.

  1. Effect of acid rain on germination of cress seeds

    * Don't eat, drink or run in the lab. * Don't throw objects because you could hurt someone. Scientific knowledge: Acid rain the name suggests that acid rain is just rain, which is acidic. The rain becomes acidic because of gases which dissolve in the rain water to from various acids.

  2. How much Iron (II) in 100 grams of Spinach Oleracea?

    18) Continue to add the Potassium Manganate (VII) (aq) drop by drop while swirling the conical flask until the pink colour persists for 30 seconds. 19) Repeat the experiment until 3 results within 0.1 of each other have been recorded. 20) Repeat the experiment using a second sample of Spinach Oleracea.

  1. The action of amylase and pectinase in varying amounts when clarifying cloudy apple juice.

    when I have added the amylase and pectinase I will leave them for 15 minutes. I will repeat this using a 20-minute time interval. If I do not get results then I will do a pilot experiment using a water bath at 35?C and put the 1% amylase solution, pectinase and apple juice into the water bath for 20 minutes.

  2. Investigating the effects of changing the concentration of different solutions on the refractive index ...

    When a light ray passes through a transparent material, the ray is bent or refracted. When it leaves the material, it is bent or refracted again. As a result, the ray keeps heading the same direction but is laterally displaced.

  1. Obtain pure samples of Ethanol (CH3CH2OH) and Ethanoic Acid (CH3COOH) from fermented Yeast (Saccharomyces ...

    Volumetric analysis is a common laboratory technique used to determine the number of moles of reactants involved in a reaction. In a titration, a volume of two solutions is mixed together until the numbers of moles of each reactant are at the equivalence point.

  2. What effect does Acid rain have on germination?

    The acid will denature the enzymes because enzymes work best at a certain pH and the acid will be a higher pH level than that. METHOD To see what affect acid rain has on germination, I am going to try and germinate cress seeds with different concentrations of acid.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work