The goal of this paper is to research the change in pigments that exist in different species of leaves that were collected before, during and after senescence. The species of leaves that were tested were Cornus Mas, Juglans Regia, Tilia Cordata, Prunus Serrulata and Fraxinus Excelsior with four different samples of each leaf from greenest to brownest. The pigments were extracted by baking the leaves in the oven to prevent bacterial growth and to dry the samples. Next, the leaves were grinded with a mortar and pestle which is then weighed to 60 mg. A solution is made by mixing the leaves with 5 mL of 80% alcohol to extract the pigments more effectively. A spectrophotometer was used to record the wavelength absorbance, then the data was graphed to visualise the absorbance changes throughout the wavelengths. The amount of chlorophyll A and chlorophyll B was calculated using absorbance at 663 and 640 nm, and the data showed that the amount of chlorophyll A in each sample decreases as the ‘brownness’ of the leaves increases, from 796 to 41,33 microgram/gram. However, this was not the case for chlorophyll B. While most results had shown a decrease of chlorophyll B from 416 to 62.5 microgram/gram dm, some had varied results which did not indicate an increase or decrease. The results have concluded that the content of chlorophyll is inversely proportional to the content of anthocyanins in the leaves as senescence occurs. There were research limitations, for instance each sample of the leaves were not weighed exactly to 60 mg and were off by a few milligrams. This investigation took a few weeks to complete which may also continue the leaves’ senescence causing a decrease in chlorophyll. The identification of pigments in autumn leaves is a well established area of study that has yet to be applied in the local conditions of Timisoara because environmental factors also affect leaf colour by influencing anthocyanin and chlorophyll metabolism. It is important to have more local data about plant physiology to assist those in other fields of science for research in this topic.

Chlorophyll, Spectrophotometer, Pigments, Anthocyanins

agronomy

Presentation: poster