Effects of coffee & caffeine on the growth of plants

Use of tea grounds for the growth of plants is a common practice in horticulture. Tea contains tannic acid and many other nutrients. When added to soil, they decompose to liberate many useful organic compounds which are essential for the growth of plants. Coffee is used as a fertilizer in kitchen gardens and I wanted to check the extent to which growth of plants is affected by the presence of coffee in the soil. I will be comparing the growth in the presence of coffee and the growth in presence of pure caffeine to check whether only caffeine stimulates the plant growth or other factors of the coffee also help stimulate growth within plants. Caffeine has been reported to be a potential stimulant for both central nervous system and cardiac system. It has an ability to prevent cancer caused by the carcinogens present in environment and foods. Mutagenic potential of caffeine has also been proved against bacterium E. coli. It has also been found to show a major synergistic effect in mutation of chromosomes. Effect of caffeine on the quantitative and qualitative parameters of plant has been a significant area of research. The current investigation deals with the study of effect of caffeine on the growth of plants. Thus, I have decided to narrow down my Internal Assessment in Biology based on the research question stated below-

How do different concentrations of 1,3,7-Trimethylpurine-2,6-dione (caffeine) and Coffea (coffee) (0.3%,0.6%,0.9%,1.2%,1.5% and 1.8%) effect the root growth in the plant Vigna radiata?

Vigna radiata is a widely grown plant. This plant is germinated overnight and then eaten. People generally refer Vigna radiata to green gram and sprouts. Green gram is very good for human health if consumed directly after germination when it has sprouted a radicle. Green gram is very rich in protein and other nutrients and also is a powerful antioxidant and is also rich in nutrients and protein. This particular plant belongs to the category of legume because of which they contain bacteria in their roots. This bacteria fixes the free nitrogen from the atmosphere into nitrogenous compounds in the plant body through the process of nitrogen fixation. Apart from a rich source of protein for vegetarian diets, it is also the source of trace amounts of Riboflavin, Vitamin-C and thyamine. It can also be used as a manure crop and a cattle feed.

Coffee is a widely used stimulant for human beings. It is used especially by people who have stress and long working hours. The component in coffee that helps people keep awake and calm their nerves is caffeine. Caffeine is naturally found in coffee in small amounts. Coffee is acidic in nature and contains nutrients like phosphorous, nitrogen and potassium. Coffee has its benefits to humans and has shown to have positive impacts on the growth of plants too. Coffee stimulates shoot and root growth in plants. Coffee grounds are a very rich source of Potassium, Phosphorous and Nitrogen for the plant. Phosphorous is very useful in the maturation process of the plant. Due to the presence of excess phosphorous the cells in the root of the plant there is a higher rate of cell division and the size of cells is larger. These effects of coffee are the reason for longer shoot and root growth. The coffee tree belongs to tropical evergreen shrub in the genus Coffea. It is mainly found in the regions of Tropics of Cancer and Capricorn. The main varieties are - Coffea arabica (Arabicas) and Coffea canephora (Robustas). One cup of coffee is reported to contain around 180 mg of caffeine. For an adult, it is safe to consume around 200-300 mg of caffeine per day. Decaf coffee is another variety of coffee which contains much less amount of caffeine in comparison to normal coffee. A cup of decaf coffee contains 7mg of caffeine in comparison to 70-80 mg of caffeine in a normal cup of coffee.

1,3,7-Trimethylpurine-2,6-dione also known as caffeine in its pure form is a white powder. Pure caffeine has antibacterial properties. When coffee leaves fall to the ground they release caffeine as they decompose and the caffeine which is released acts like a natural pesticide to some of the insects. Caffeine is also very slightly basic in nature. Pure caffeine can also be used by humans as a stimulant by mixing with water to boost body processes to make people feel more alert and awake.

The independent variable of the investigation is the concentration of coffee and caffeine used during the growth of the plants. The concentration chosen were - 0.3%,0.6%,0.9%,1.2%,1.5% and 1.8%. The solutions were prepared by adding the requisite amount of solid in distilled water within a glass beaker. A 30% stock solution was prepared by adding 30 g of solid coffee powder and caffeine in 100 cc of distilled water. The other solutions were made by dilution of this stock solution. A research article- Caffeine: The Allelochemical Responsible for the Plant Growth Inhibitory Activity of Vietnamese Tea (Camellia sinensis L. Kuntze) reported that growth of plant (red clover) was inhibited by 1.00% by caffeine solution while 0.50% solution has been proved to be effective. Thus, the concentration range of this investigation has been kept within the range of 0.30% to 1.80% so that it also gives us an idea about the effect of the concentration both below and above the permissible range. A very high concentration could lead to possible stunting of the growth of the plant.

The dependent variable is the shoot growth because the coffee provides the nutrients like phosphorous which help with the maturation of the plant and increased growth in root. The caffeine prevents the plants from getting infected and boosts the growth due to its ability to stimulate the body processes. We take shoot (radicle) length because in seeds that is the first part to come out. The shoot is most affected by different factors and root helps absorption of nutrients and grows extremely fast in the initial stages and so it is easy to measure using a ruler.

30.00 ± 0.01 g of caffeine powder was weighed on a watch glass placed over a digital mass balance using a spatula to transfer the solid to the watch glass. The exact mass of the solid was transferred to a 250 cc glass beaker and dissolved in 100 cc tap water. A graduated measuring cylinder was used to transfer tap water to the beaker. 1.00 ± 0.05 cc of this stock solution was transferred to a 100 cc reagent bottle using a graduated pipette and diluted to 0.30% by adding tap water. The other solutions of caffeine were prepared in the same method. 2.00 ± 0.05 cc, 3.00 ± 0.05 cc, 4.00 ± 0.05 cc, 5.00 ± 0.05 cc and 6.00 ± 0.05 cc of the stock solutions were diluted to 100 cc in a reagent bottle to prepare 0.60%, 0.90%, 1.20 %, 1.50% and 1.80% solutions respectively.

The same process was followed to prepare coffee solutions of the same concentration.

• Seeds of Vigna radiata were soaked overnight in water to start the germination process.

• After preparing different concentrations of coffee and caffeine 2 petri plates per concentration were taken for each concentration including three for water (0.0%) which represents our control solution.
• In each petri plate 15 cc of their respective solutions were added to each petri dish using a measuring cylinder. The solution was soaked in cotton plugs and kept within the petri dish.
• Five germinated seeds were then added to each petri dish. A total of 140 seeds and 28 petri plates were used in total.

• The plants were let to grow for 5 days and measurements of the length of the roots were measured at the end of five days using a ruler.
• The results were taken down and average for every concentration of coffee and caffeine were taken.

• The use of safety gloves to avoid direct contact with caffeine as it is a possibly addicting substance and can impact body if ingested.
• Use of mittens to move the hot beakers containing boiled coffee grounds. Mittens help avoid burning of skin as beaker can be hot after preparing coffee.
• Use of mittens to move the hot beakers containing boiled coffee grounds. Mittens help avoid burning of skin as beaker can be hot after preparing coffee.
• The use of lab coats as the stain of coffee is very tough to get rid of and can be permanent.
• Use of a well ventilated area or an area with an exhaust to remove fumes produced during boiling coffee and caffeine.

For control (0.0%)

Average length of root = \(\frac{4.10\ +\ 3.30\ +\ 4.30\ +\ 3.00\ +\ 3.30\ +\ 3.70\ +\ 3.60\ +\ 3.00}{8}\) = 2.83 ± 0.05cm

Standard deviation (SD) = \(\frac{(4.10-4.63)^2+(3.30-4.63)^2+(4.30-4.63)^2+(3.00-4.63)^2+(3.30-4.63)^2+(3.70-4.63)^2+(3.60-4.63)^2(3.00-4.63)^2}{8}\) = 1.47

The readings highlighted in red are anomalous and thus discarded.