Enzymes are crucial to the function of any living being however, exposure to temperatures that are too high or too low beyond the enzyme's optimal temperature will cause it to denature or become inactive. As such when a plant is grown in temperature that is too high or too low the enzymes that perform vital functions for the plant's growth and survival will no longer be able to do their job leading to a slowing of growth and eventual plant death.

Temperature is hard to control in the lab because, would require a lot on energy to keep consistent high temperatures, high enough to see an effect on the dependent variable and exceed the tolerance limit. High temperatures for hydroponic plants also means the risk of bacteria and the error of evaporating water is exceeded hard to keep consistent for both the plants in cooler temperatures and hotter temperatures increasing possibility for systematic error.

Too much light not only dries out the plant as the heat will evaporate moisture but can also cause bleaching and pale leaves that can no longer photosynthesize. This leads to a lack of glucose and if too far beyond the plant's tolerance limit for too long, eventual death.

Too little light means photosynthesis cannot take place and the plant will not be able to produce glucose and as a result energy (ATP) necessary for biological processes and chemical reactions crucial to the function of the plant. Because plants are autotrophs photosynthesis is the only way they can access this energy and without sufficient light the plant will die.

Measure Daily for more accuracy, at the same time each day

Pros: nutrients are completely controlled, plants grow quickly, roots can be measured easily, water availability is not a factor.

Cons: Harder to set up (equipment must be water proof), water can evaporate creating possible inconsistencies for different trials, still water may attract bacteria and insects changing variables, any necessary nutrients must be sourced externally which requires more time

Root length may decrease or increase based on the availability of necessities as the plant searches for water or nutrients as opposed to the health of the plant. Not only this but the length and width of roots is very hard to measure and has a high risk of error.

If salinity is too high due to the difference in solute concentration in the environment and in the plant roots water will exit the plant and into the soil. As plants rely on osmosis for the uptake of water without the solute concentration being lower in the environment little water can be taken in by the plant despite a possible abundance of water surrounding it. Without water the plant cannot function and so will eventually die out. If salinity is too low na+ ions are not present and the plant cannot

If oxygen concentrations are too low the mitochondria in the plant cells cannot perform aerobic respiration and cannot convert its glucose into usable energy. This means that functions in the cell that require energy cannot take place and the plant will eventually die out.

Light intensity is hard to quantify with the limited equipment available in the lab and so it would be difficult to produce accurate and specific data points relevant for future research.

Controlling oxygen concentrations requires a well sealed system to prevent any gas from escaping, and makes checking up on and maintaining the plants' need much more complicated as well. Because this process would not be possible in the available laboratory it would not be a feasible independent variable to investigate.

Pros: Easy to buy soils already containing all necessary nutrients, bacterial, microbes, etc., increasing the likelihood of successful growth. A wider range of plants can grow in soil even after germination and until maturity.

Cons: Nutrients are hard to isolate if using soil as a growing medium. Roots are visually obscured and soil type and quality can vary greatly depending on brand introducing potential for random error. This is because depending on the attributes of the soil it may absorb water, nutrients, toxins, etc., differently.

Pros: Many seeds can be tested at once/many trials can be completed in the experiment very easily, improving the reliability of results. By testing so many seeds the impact of random error is reduced as results are not as relent on the behavior of one or two plants. Seeds also only require minimal maintenance and
tend to germinate quickly increasing the chance of a successful experiment unaffected by human error.

Cons: To test how tolerance limits impact plant growth is difficult if only the germination period is considered. While it is an important part of plant growth, seed germination often has slightly different parameters to actual plant growth such as --. This means that determining the tolerance limits of certain plant species would not be as accurate.

While discoloration is a clear sign of nutrient deficiencies similarly to difficulties when measuring the surface area of leaves, measuring the amount of plant impacted by discoloration can be hard due to the unusual shape of leaves and the fragility of dead leaves. Some amount of personal say may also go into what would be considered discoloration, leading to potential differences each time the experiment is repeated.

To test how tolerance limits impact plant growth is difficult if only the germination period is considered. While it is an important part of plant growth, seed germination often has slightly different parameters to actual plant growth such as --. This means that determining the tolerance limits of certain plant species would not be as accurate.

While other species of mint such as peppermint generally require cooler temperatures to thrive, spearmint can more comfortably grow in warmer temperatures and as the lab is likely to lean towards warmer temperatures spearmint is chosen to minimize the risk of any plants dying due to external factors.

Macronutrients like potassium, phosphorus, sulfur, calcium or magnesium and micronutrients like iron or zinc, etc., all are crucial for the growth of plants. For example, potassium and phosphorus are used in plants in their vascular systems and in vegetables and fruits, as well as for root and seed growth and nucleotide production.

While important, micronutrients are used by plants in such small quantities that performing different trials with varying levels of these nutrients would be difficult to complete accurately. And, while macro nutrients like potassium and phosphorus are used in larger quantities and necessary for plant survival are not quite as impactful on a plant's biomass as nitrogen is.

While mint does grow primarily vertically depending on variables such as light location (plant leaves and stems will generally grow towards the closest light and unless this light is directly above the plant this will cause a perceived decrease in the vertical height of the stem.,

Measuring the mass of the plant includes growth of the roots, stem and leaves and takes into consideration growth through height but also width as well. This ensures to a better ability that any growth, even if not visible to the eye, is measured. And therefore, a more accurate image of the impact the ID has on the plant can be formed.

While understanding the salt concentration tolerance limits of plants can be relevant and useful information, often times this information would only be used by larger commercial farms, soil testers, etc., and may not be as applicable as the tolerance limits of ammonia sulfate. This is because nitrogen fertilizers are often added by hand and understanding the limits could directly influence the actions of many gardeners.

Simply counting the number of leaves, etc., does not take into account the size and health of these parts of the plant. It also may not be very specific as all the plants may only grow one or two flowers each, providing little data to analyze. Fruits, flowers and vegetables can also be very dependent on the season or the fertilization of the plant's gametes restricting the experiment quite significantly.

While a healthy plant will have a higher number of larger leaves when compared to an unhealthy plant of the same species, surface area of a biological organism can be very hard to accurately calculate because of its unique shape, and other simpler measurements can be just as insightful.

Measuring the rate at which each plant is growing ensures that initial differences in mass do not influence results and all plants have a level playing field. It also provides some flexibility

While looking at the rate of growth does eliminate discrepancies in the initial masses of the plants, it fails to take into consideration the fact that smaller plants with smaller leaves and roots would

Mint generally takes only two weeks to grow to full height and has a fast growth rate ensuring that a clear impact should be clearly visible in the data. Mint also thrives when grown hydroponically, is cheap and easily accessible.