Scientific Research in School Volume 3 Issue 1 2021
Effect of time after harvest on chlorophyll concentration in spinach leaves Kyle Scholtz Barker College Chlorophyll-a and chlorophyll-b are chemical compounds found in photosynthetic plants and its application in medicine is becoming widely accepted. This report aimed to reveal how time after harvest affects chlorophyll-a and chlorophyll-b concentration. Spinach leaves where stored over different time periods and dimethylsulfoxide was used to extract chlorophyll from leaf tissue. A colourimeter was used to determine chlorophyll-a and chlorophyll-b concentration. The results demonstrated that chlorophyll-a concentration had no significant difference after each harvest time, but concentration of chlorophyll-b did have a statistical difference after each harvest time. Concentration of chlorophyll-b was found to be higher 48 hours after harvest compared to instantly after harvest which resulted in the rejection of the null hypothesis. Abbreviations Chlorophyll-a (Chl-a), Chlorophyll-b dimethylsulfoxide (DMSO).
(Chl-b),
Literature review Chlorophyll is a chemical compound or green pigment which is found within the cells of the thylakoid membrane of the chloroplast. Chl-a and Chl-b are present in higher plants whereas chlorophyll c, d and e are found in photosynthetic algae. Chlorophyll reflects and absorbs certain wavelengths of light; its primary role is to absorb light to use for photosynthesis. Plants use the energy collected from the chlorophyll to convert carbon dioxide and water into glucose and oxygen. The glucose produced through photosynthesis is used for energy and the oxygen produced is released into the atmosphere. Without chlorophyll, plants would be unable to undergo photosynthesis and hence would be unable to synthesise carbohydrates.
heads. The structure of a chlorophyll molecule includes a porphyrin ring in the centre of the molecule, as seen in Figure 1. Chl-a and Chl-b differ by one atom in a side chain on the third carbon, Chl-b contains an aldehyde group (-CHO) whereas Chl-a contains a methyl group (CH3), as seen in Figure 1. Chl-a is the primary pigment of photosynthesis whereas Chl-b is an accessory. Chl-a absorbs light from the orange-red and violet-blue regions of the visible spectrum whereas Chl-b absorbs light from blue areas of the visible light spectrum.
The process of photosynthesis is written in the equation: 6CO2 + 6H2O → C6H12O6 + 6O2.
Figure 1: Structure of chlorophyll (Source: May, 1999).
The two main types of chlorophyll are Chl-a and Chl-b, Chl-a is generally found in higher concentration then Chl-b by a 3:1 ratio but it varies between species and can be influenced by a number of factors including pre- and post-harvest treatment and agroclimatic conditions (Ferruzzi & Blakeslee 2007). Chl-a and Chl-b have different roles in the process of photosynthesis, and they have different structures. Both Chl-a and Chl-b are similarly shaped with hydrophobic tails and hydrophilic
It is known that as plants lose the green colour, otherwise known as degreening, it is a result of the degradation of chlorophyll. None of the genes which encode for the catabolic enzymes responsible for the breakdown of chlorophyll have been isolated but chlorophyll degradation has been proven to have multiple degradative pathways (Matile, Hörtensteiner & Thomas, 1999). A study conducted by Yamauchi and Watada (1991) concluded that the degradation of
Science Extension Journal • 121
