Lab Report Exp 7 - Plant Physiology

Lab Report Exp 7 - Plant Physiology

l Objective

i. Learn some common research techniques used in plant physiology

ii. Increase student’s appreciation for plants and their complex, integrated nature

iii. Increase student’s understanding of how plants grow, develop and sense their environment

l Introduction

Plants consists of two categories of pigment that used for photosynthesis which are primary and accessory pigment. Chlorophyll is a primary pigment in organelle chloroplast with two types of chlorophylls which are chlorophyll a and chlorophyll b. The chlorophyll are green pigment that absorb blue, red, orange and yellow but reflect green light as light containsdifferent colours of different spectrum. Besides, accessory pigment are red, yellow or orange that absorb all the other colours. Paper chromatography is a porous paper that used to separate the plant pigments from plant using hydrophobic solvent. Different molecules from a mixture have different solubility. With the aid of the solvent, the rate of solubility of the molecule can be known from “molecular race track” that are created. Some compounds are hydrophobic that do not like to dissolve in water (water fearing) and some compounds are hydrophilic that like to dissolve in water (water loving). Chromatography is a method of separating and isolating molecules based on their level of hydrophobic or hydrophilic properties. Different plants pigments will move at different rates through the piece of paper as the liquid solvent is absorbed upward. From the band or distance of different movement of pigment in the paper chromatography, the solubility of pigment can be know.

l Material

ü Microbiurette/pin

ü Prepared chromatography paper

ü Hair dryer

ü Cork stopper

ü Test tube

ü Pencil

l Method

1. The microburette/pin head was used as the dropper, the chloroplast extract was dropped on the prepared chromatography paper .
2. The extract about 1.0cm from the pointing end of the paper was dropped. The drop  with a hair dryer were dried and the process was repeated for 3-4 times until one small of dot of thick pigment available
3. The paper strip was attached at the cork stopper using a pin . The strip vertically and was placed straight into the test tube which contained solvent.
4. The solvent moved and the paper were removed when the solvent front reached the top of the chromatography paper.
5. The last range of the solvent was marked with pencil.

l Results

1. Identify each pigment obtain from the experiment, and record your result in table.

2. Calculate the R_f  value of each pigment observed.

 

Leaf A : Green Spinach

Pigment/Colour	Colour	Rf
Pigment 1	Light green (chlorophyll b )	2.4 / 10.8 = 0.22
Pigment 2	Light yellow (carotenoids)	4.8 / 10.8 = 0.44

Leaf B : Red Spinach

Pigment/Colour	Colour	Rf
Pigment 1	Blue green (chlorophyll a )	3.2 / 10.4 = 0.31
Pigment 2	Light yellow (carotenoids)	4.9 / 10.4 = 0.47

Leaf C : Yellow flower

Pigment/Colour	Colour	Rf
Pigment 1	Blue green (chlorophyll a )	2.6 / 8.0 = 0.33
Pigment 2	Light green (chlorophyll)	1.8 / 8.0 = 0.23
Pigment 3	Light yellow (carotenoids)	3.9 / 8.0 = 0.49

l Discussion

When a sample is placed on a filter paper, the colors separate from the sample by placing one of the paper in a low-level solvent. The solvent diffuse up to the filter paper, dissolving the various molecules in the sample according to polarities of the molecules and the solvent. The sample contain more than one color shows that it have more than one kind of molecule. The unequal solubility cause the various color molecules to leave at different places as the solvent continues to move up the paper.   

l Conclusion

From the experiment, there are two pigments that exist from the separation of photosynthetic pigment from two leaves, which were leaf A and leaf B at the paperchromatography. The separation of pigment from leaf A can be seen based on their colourwhich pigment 1 was green and pigment 2 was light yellow. The separation of pigment fromleaf B was observed and pigment 1 was purple while pigment 2 was green in colour. Theseparation of pigment on the paper chromatography was with the aid movement of developingsolvent mixture that was prepared fresh before use. This is because the developing liquid phasecomprises of a pure solvent but more often it is a mixture of two or more solvents in specified proportions. In case solvents are mixed and stored for long periods there could be loss ofvolatile component which will alter the mixing proportions. The paper chromatography with aline that contain a dot of leaf extract was placed in the test tube and it is important to keep thedye spots above the solvent level because the dye spots will dissolve in the developing solventthat preventing the spots contain pigment from separating out and no observation andmeasurements could be taken.During the paper development, it is necessary to cover the test tube to prevent theevaporation of the eluting solution from the paper. The paper development was let for few minutes without disturbing or shaking the system and it is important to stop the chromatogram before the solvent front reaches the top of the chromatography paper because to measure theRf value, the starting and front of solvent must be known. The stop line should be done belowthe top of the paper so that Rp value can be measured from the starting line to the stop line andthus, Rf value can be calculated. As the solvent reach the stop line, the paper was removedfrom the test tube and the separation spots observed was immediately marked to able usmeasure how far it travelled.

l Reference

· Anna Sala. (September, 2014). BIOO 434.01: Plant Physiology Laboratory. University of Montana. Retrieved from https://scholarworks.umt.edu/cgi/viewcontent.cgi?
article=2565&context=syllabi

· B. E. Clark And S. H. Wittwer. (February 4, 1949). Plant physiology. Retrieved from http://www.plantphysiol.org/content/plantphysiol/24/4/555.full.pdf

· Lawrence Rappaport. (December 3, 2018). Effect of Gibberellin on Growth, Flowering and Fruiting of the Earlypak Tomato, Lycopersicum esculentum 1,2. California. Retrieved from http://www.plantphysiol.org/content/plantphysiol/32/5/440.full.pdf