• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

To investigate the affects of heavy metals such as Lead Chloride, on the length of both the stem and roots of cress seeds.

Extracts from this document...

Introduction

Affects of Heavy Metal on Stem & Root Length Aim: To investigate the affects of heavy metals such as Lead Chloride, on the length of both the stem and roots of cress seeds. Background Investigation: Lead is a soft metal having little tensile strength, and it is the densest of the common metals excepting gold and mercury. It has a metallic luster when freshly cut but quickly acquires a dull colour when exposed to moist air. Heavy metals such as lead are harmful to both humans and plants. Lead is used in the manufacture of batteries, metal products, paints, and ceramic glazes. In humans; exposure to lead can occur from breathing contaminated workplace air or house dust or eating lead-based paint chips or contaminated dirt. ...read more.

Middle

In general, inorganic lead compounds are of lower toxicity to plants than organic lead compounds such as trialkylead and tetralkylead compounds. Tetralkylead becomes toxic by decomposition into the ionic trialkylead. The toxicity of inorganic lead salts is strongly dependent on environmental conditions such as water hardness, pH, and salinity. When solid Lead Chloride is placed in water the following happens (in equilibrium): PbCl2 (s) < = > Pb+2 (aq) + 2Cl- (aq) The solubility of PbCl2 increases very rapidly as the temperature of the solution rises. However, PbCl2 precipitates very slowly, particularly when other ions that form insoluble chlorides are not present. The precipitation can be speeded up by vigorously rubbing the inside of the test tube with a stirring rod. ...read more.

Conclusion

As a result high lead concentrations in the soil are needed to cause visible toxic effects on photosynthesis and growth. Thus, lead is only likely to affect plants high concentrations of lead. There are degrees of tolerance to heavy metals in plants. Tolerance is inherited, i.e.tolerant parents transmit tolerance to their offspring. Within a plant species, there are tolerant and sensitive populations. Tolerance, therefore, develops by selection, rather than by adaptation of individuals. Two possible mechanisms for tolerance, to metals in general, are "external" mechanism prevents metal entering the plant, while an "internal" mechanisms allows entry but prevents the metal from coming into contact with sensitive processes within the organism. Prediction: We will perform the investigation seven times - each time using a different concentration of Lead Chloride solution. Hence we should be able to distinguish, clearly, the relationship between lead concentration and stem/root development. Ali Mahdi ...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 Green Plants as Organisms 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 Green Plants as Organisms essays

  1. Marked by a teacher

    An investigation into the effect of a germination inhibitor on the germination of seeds.

    3 star(s)

    the solutions are given: - Using a measuring cylinder, measure out the required amount of inhibitor and pour it into a test tube. Using another measuring cylinder measure out the required amount of water (if this is for one concentration then make sure the total amount adds up to 4.50cm3),

  2. Investigation into Cress Seeds

    On the other hand, I predict the other brands will have a high selective breeding. This would be due to the human interference I had mentioned in my scientific knowledge. These could possibly be the 'extra curl'. Farmers would get a certain selection from a crop of cress that may

  1. Effects of different concentrations of a heavy metal chloride on the growth of cress ...

    It is this deficiency that ultimately kills the plant. Toxicity of the heavy metal ion is therefore determined by its ability to bind with the chelate protein (and thus by its affinity to sulphur). Even though some heavy metals are essential micronutrients (e.g.

  2. An Investigation To Show What Different Factors Affect The Growth &amp;amp; Germination Of Cress ...

    I used a normal Sachs solution to water them. Form the experiment I found that 1.5 ml cubed for each section was to little because although the seedlings germinated the plants did not grow very quickly. I decided to use 2ml cubed for each section.

  1. An investigation into the effects of different concentrations of lead chloride on the growth ...

    It therefore, has a lower water potential than the root cells, causing water to move from a region of higher water potential (root cells) to a region of lower water potential (soil), via osmosis (Biology 1, OCR, pg 56). This disrupts the osmotic balance of the plants and prevents sufficient amounts of water entering the cells.

  2. Investigation into the effect of varying concentrations of potassium nitrate solution, on the germination ...

    This lowering of the activation energy increases the number of molecules which have enough energy to react. Therefore, more molecules react and more products can be formed. The diagram above shows the effect of temperature on an enzyme-controlled reaction. It demonstrates the importance of temperature in seed germination.

  1. Is photorespiration an effective mechanism for protecting against photoinhibition?

    Thus the conversion of glyoxylate to glycine requires the availability of amino groups resulting from the recycling of nitrogen by the GOGAT cycle. After transport back into the peroxisome serine is converted by SGAT to hydroxypyruvate which is reduced to glycerate by hydroxypyruvate reductase (HPR).

  2. The effects of organic effluent from the seweage on the biodiversty in a freshwater ...

    FACTORS TO BE CONTROLLED: ---Distance will need to controlled. The amount of distance between the three selected areas of the water stream from the sewage will need to be equal. This is to make sure that the results obtained are more accurate and not too close so that variation between can be indicated.

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