The Effect of Green Tea and Deionized Water on the Growth Rate and Chlorophyll

 

Green tea has many claims to its health benefits on humans. In this experiment, we tested whether green tea had health benefits to plants. The relationship between green tea, deionized water, and tap water was determined by measuring the growth rates and chlorophyll concentration of three groups of Catharanthus roseus that were watered with the respective mediums. Stem diameters were measured twice a week and chlorophyll concentration was measured by spectrophotometry. The resulting data showed no significant difference in growth rates and chlorophyll concentration data was inconsistent. Therefore, null hypothesis was supported. There were external factors including aphid infestation which might have contributed to our inconsistent results.

Introduction

Extensive research has gone into studying the effects of green tea on humans and animals. However, if out there, official research on the effects of green tea on plants is scarce. Also, there is much media on the health benefits of green tea, mostly concerning the antioxidant properties. Some advocates of green tea make strong claims that it can cure rheumatoid arthritis, reduce body fat, cure gastric ulcers etc. (Johnson 2009). Other research has shown that green tea consumption may reduce the risk of leukemia (Kuo 2008). The consumption of green tea has also been repeatedly shown to play a protective role against liver disease and may lead to a reduced risk of liver disease (Jin 2008). However, research of green tea consumption and cancer is less conclusive.  Most studies showed no relationship between green tea consumption and cancer, and few showed that green tea consumption was associated with a decreased cancer risk (Sturgeon 2009). The one thing in common with most studies is that they attribute the beneficial qualities to certain chemicals that are contained in green tea.  These chemicals are found in the tannins released from the tea leaves when it is steeped in hot water. Tannins contain polyphenols and flavonoids which are subgroups that contain the antioxidative chemicals that are the source of beneficial health effects. Catechins are one of the classes of flavonoids also called flavin-3-ols. The specific catechin that is known for its potent antioxidant properties is epigallocatechin gallate (EGCG).

Plants along with many other organisms produce free radicals as byproducts or intermediates of metabolic pathways.  In plants, photosynthesis is a major producer of free radicals (Uri 1955). In order to counter the free radical intermediates, plants must also produce antioxidants; this is the source of catechins that is acquired from tea when consumed. Therefore, if human consumption of tea possesses many health benefits, then it seems reasonable to presume that it will have similar effects on plants. Our objective was to determine if there was a relationship between plant health and different watering mediums including: green tea, deionized water, and the control group with tap water. We hypothesized that Catharanthus roseus watered with green tea would have improved health and therefore increased growth rates and chlorophyll concentrations compared to Catharanthus roseus watered with tap water and that Catharanthus roseus watered with deionized water would have worse health and therefore decreased growth rates and chlorophyll concentrations compared to Catharanthus roseus watered with tap water.

Methods

We began with young Catharanthus roseus in three groups of ten each: a green tea group, deionized water group, and the control group with tap water. We used soil from same bag and pots, both provided by Saddleback College. The Catharanthus roseus was purchased from Green Thumb International Nursery in crates of 16 plants per.  The plants were kept in the greenhouse at Saddleback College in a controlled environment. The experiment lasted for five weeks. Measurements of stem diameter were taken using a digital caliper at location level with the top of the pot. These measurements were taken about twice a week for the duration of the experiment. Also, we noted any plants whose health appeared compromised or if the plant appeared deceased. Each group was watered with the three different mediums: green tea, deionized water, and tap water five days a week for the first week. However, due to soil conditions from this watering frequency being detrimental to the health of the plants and in attempt to use optimal conditions for the experiment, we watered them four days a week for the remainder of the experiment. Each plant received 50 ml of watering medium when watered.  An attempt to determine chlorophyll concentration was done with leaf samples taken in the third and fifth week of the experiment. We used methods derived from other research experiments that determined chlorophyll concentration by photospectroscopy (MacKinney 1941, Cate et al. 2003). These leaf samples were then measured out to 0.2 g of leaf material per group and added to 15 ml of 80% acetone solution and left overnight in 4ºC in the dark. Absorbance of the acetone solution containing the chlorophyll was then taken. The absorbance was taken for each group first at 940 nm wavelengths as a reference and then at 660 nm. We used ANOVA tests on the stem diameter data and for the chlorophyll concentration absorbance data a ratio was taken to determine chlorophyll content index (CCI).

Results

Results should generally just report numbers, figures and taken by the researchers. It is a little wordy.

An analysis of variance (ANOVA) single variable test was performed on the average values of stem diameters for each day of measurement. This first test included the measurements of healthy and unhealthy or dead plants. Green tea did not significantly increase health and deionized water did not significantly decrease health of Catharanthus roseus (p=0.44) compared to the control group. The average stem diameters for each day measured was plotted over time and is shown in figure 1. Then we performed another ANOVA singlevariable test on the data with the unhealthy and dead plants omitted. Again, green tea did not significantly increase health and deionized water did not significantly decrease health of Catharanthus roseus (p=0.69)