Colours Of Light Absorbed By Green Plants Biology Essay

Published:

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.

Chlorophyll is the molecule that traps this most elusive of all powers' and is called a photoreceptor. It is found in the chloroplasts of green plants, and is what makes green plants, green.

There are actually 2 main types of chlorophyll, named a and b. They differ only slightly, in the composition of a sidechain (in a it is -CH3, in b it is CHO). Both of these two chlorophylls are very effective photoreceptors because they contain a network of alternating single and double bonds, and the orbitals can delocalise stabilising the structure. Such delocalised polyenes have very strong absorption bands in the visible regions of the spectrum, allowing the plant to absorb the energy from sunlight.

RESEARCH QUESTION

What is the colour of light (wavelength) absorbed by spinach and mustard?

HYPOTHESIS

The greatest absorption in both the spinach and mustards leaves occurs in the blue; 400 - 500 abs and the red ; 650 - 700 abs parts of the spectrum. The green light is transmitted or reflected.

VARIABLES

 UNITS

RANGE

INDEPENDENT VARIABLE

Wavelength of light

nM

440-680

 DEPENDENT VARIABLE

The amount of absorption of light (wavelength)

abs

-

TABLE 1 : Independent and Dependent Variable

CONTROLLED VARIABLES

UNITS

WAYS TO CONTROL

The mass of spinach and mustard ; 8gram

g

Different amount of chlorophyll collected if different mass used.

Volume of propanone used; 20cm³

cm³

Different volume of propanone will affect the concentration of chlorophyll

Time taken for the solution placed in the dark place

Min

Chlorophyll could bleach in direct sunlight

The temperature of surrounding

°C

The result will affected with different temperature

Time taken for the centrifuged tube put in the centrifuged

Min

The result will affected with different time taken

TABLE 2 : Controlled Variables

MATERIALS AND APPARATUS

Materials / apparatus

Quantity

Volume/size

Mustard leaves

8 gram

-

Spinach leaves

8 gram

-

propanone

-

40 cm3

Beaker

2

100 ml

Mortar

1

-

Measuring cylinder

2

50 ml

Stopwatch

1

-

Aluminium foil

1 roll

-

Glass rod

2

-

Centrifudge

-

Standard size

Centrifudge tube

-

Standard size

Conical flask

2

Standard size

Set of colorimeter

1

-

Boiling water

-

50 cm3

TABLE 3 : Materials and apparatus

METHOD

Refer to the lab manual provided

DATA COLLECTING

QUANTITATIVE DATA

ABSORBANCE (%) 0.01 Abs

WAVELENGTH

440

470

490

520

550

580

590

680

MUSTARD

2.00

1.76

0.39

0.24

0.15

0.20

0.25

0.38

2.00

1.47

0.31

0.24

0.14

0.16

0.13

0.19

1.73

1.18

0.43

0.36

0.29

0.25

0.27

0.39

SPINACH

2.00

1.63

0.53

0.32

0.27

0.32

0.49

0.69

2.00

2.00

1.61

1.39

1.24

1.41

1.47

1.72

2.00

1.83

0.83

0.50

0.50

0.59

0.80

1.04

TABLE : QUANTITATIVE DATA

QUALITATIVE DATA

Mustard and spinach leaves are green plants.

The acetone have strong smell and colourless.

After the concentrated chlorophyll is put into the centrifuged, a concentrated dark green solution is produced with green precipitate. The green precipitate is at the bottom of the centrifuged tube while the solution is above.

DATA PROCESSING

Average of Light Absorbance

The average of the light absorbance by the green plant is calculated by using the formula :

∑ light absorbance by each trials number of trials

PLANT

WAVELENGTH (ÊŽ) (nM)

AVERAGE LIGHT ABSORBANCE (%) (±0.01 Abs)

PLANT

WAVELENGTH (ÊŽ) (nM)

AVERAGE LIGHT ABSORBANCE (%) (±0.01 Abs)

MUSTARD

440

1.91

SPINACH

440

2.00

470

1.47

470

1.82

490

0.38

490

0.99

520

0.84

520

0.74

550

0.19

550

0.67

580

0.20

580

0.77

590

0.22

590

0.92

680

0.32

680

1.15For example, the average light absorbance by mustard at the wavelength 0f 440 nM is calculated by using the formula :

∑ light absorbance by each trials number of trials

= 2.00 + 2.00 + 1.73 3

= 1.91 % Abs

The average of light absorbance of mustard and spinach for other wavelength are calculated by using the same formula.

TABLE : The average of light absorbance of mustard and spinach

Standard Deviation

The standard deviation of the average of the light absorbance by the green plant is calculated by using the formula :

∑ (light absorbance by each trials)² - (mean)² number of trials

For example, the standard deviation of the average light absorbance by mustard at the wavelength 0f 440 nM is calculated by using the formula :

∑ (light absorbance by each trials)² - (mean)² number of trials

= 2.00² + 2.00² + 1.73² - 1.91² 3

= ± 0.13

The standard deviation of the average of light absorbance of mustard and spinach for other wavelength are calculated by using the same formula.

PLANT

WAVELENGTH (ÊŽ) (nM)

STANDARD DEVIATION (±0.0001)

PLANT

WAVELENGTH (ÊŽ) (nM)

STANDARD DEVIATION (±0.0001)

MUSTARD

440

0.1273

SPINACH

440

0.0000

470

0.2368

470

0.1512

490

0.0499

490

0.4552

520

0.0566

520

0.4678

550

0.0685

550

0.4299

580

0.0368

580

0.4635

590

0.0432

590

0.4090

680

0.0920

680

0.4276

CONCLUSION AND EVALUATION

Discussion

Visible light have a range of colour from red to violet. Different colours of light have different wavelengths.

400 - 525 = violet to blue

525 - 625 = green to yellow

625 - 700 = orange to red

Not all the colours of the spectrum is absorbed by the green plant; chlorophyll.

From the graph, spinach has higher level of absorbance of light compared to mustard. Start from 440 to 470 nm, the level of absorbance for both spinach and mustard is at the highest level. From 470 to 550 nm, the level of absorbance for both spinach and mustard fall. From 550 to 680 nm, the level of absorbance increase again.

As a conclusion, violet to blue colour of spectrum is being absorbed most efficiently by green plant. Red is absorbed efficiently than green colour of spectrum. Green colour is less absorbed. Green colour is usually transmitted or reflected.

Evaluation

Limitations

Suggestions

Mustard and spinach are not fresh enough when the experiment is done and make the amount of chlorophyll to be lesser.

Use the fresh leaves for the experiment to obtain an accurate result.

The green leaves are not being ground well the extract of chlorophyll is not fully obtained.

Grind the green leaves well so that the chlorophyll is full extracted from the leaves.

There might be light strike to the chlorophyll extract after taken out from 30 minutes being kept in dark.

Make sure no strong light or direct sunlight from outside

The green chlorophyll extract used was too dilute

Use the green extracts that not too dilute to get a consistent than before.

CONCLUSION

The greatest absorption in both the spinach and mustards leaves occurs in the blue (400 - 525 abs) and the red (625 - 700 abs) parts of the spectrum. The green part is reflected or transmitted because its absorption is the least. Hypothesis is accepted.

Writing Services

Essay Writing
Service

Find out how the very best essay writing service can help you accomplish more and achieve higher marks today.

Assignment Writing Service

From complicated assignments to tricky tasks, our experts can tackle virtually any question thrown at them.

Dissertation Writing Service

A dissertation (also known as a thesis or research project) is probably the most important piece of work for any student! From full dissertations to individual chapters, we’re on hand to support you.

Coursework Writing Service

Our expert qualified writers can help you get your coursework right first time, every time.

Dissertation Proposal Service

The first step to completing a dissertation is to create a proposal that talks about what you wish to do. Our experts can design suitable methodologies - perfect to help you get started with a dissertation.

Report Writing
Service

Reports for any audience. Perfectly structured, professionally written, and tailored to suit your exact requirements.

Essay Skeleton Answer Service

If you’re just looking for some help to get started on an essay, our outline service provides you with a perfect essay plan.

Marking & Proofreading Service

Not sure if your work is hitting the mark? Struggling to get feedback from your lecturer? Our premium marking service was created just for you - get the feedback you deserve now.

Exam Revision
Service

Exams can be one of the most stressful experiences you’ll ever have! Revision is key, and we’re here to help. With custom created revision notes and exam answers, you’ll never feel underprepared again.