What are the potential factors (stimulus) that could be altered to affect the plant and what does it affect?
Temperature
pH
salinity
water avaliability
water is essential for reactions in the plant such as photosynthesis, respiration, and cellular growth
Water carries nutrients and is transported through the roots. The roots can rot if the soil has excessive water and the roots and rot, thus the plant cannot uptake sufficent amounts of oxygen and nutrients. Insufficient amount of water corresponds to nutrient deficiency, affecting function and growth of the plant.
IV: volume of water (mL)
Temperature influences certain chemical reactions such as photosynthesis, respirtation, and germination. Increase in temperature would increase the rates of these reaction, therefore supporting plant growth. However, if the plant experiences extreme temperatures, it could potentially denature proteins (enzymes) and thus distrupting the plant's health. This could possibly lead to the death, or sickness of the plant.
IV: temperature (°C) = 15,20,25,30,35,40,45
The soil pH directly affects nutrient uptake of plants as it influences the chemical forms and avaliability of essential nutrients in the soil. It also affects the solubility and mobility of nutrients. Imbalanced pH may prevent nutrients to be transported through the roots, thus plant growth.
DV: the mass of the plant (grams) as water uptake would significantly affect overall plant growth. Other DV's are more difficult to measure when IV is water volume.
DV: as temperature would affect the plant's growth rate more significantly, measuring the length change in the root system or leaves would conduct a more precise experiment.
IV: pH of soil: 3,4.5,6,7.5,9
DV: as the pH would also directly influence plant growth, measuring the change in mass of the plabnt (grams) or the increase in length (leaves and root) would be reasonable.
light
Salt concentraiton affects the osmotic balance, which affects the plant's ability to absorb water from the soil. High salinity increases the concentraiton of sodium, chloride, and sulfate ions, which limits water and nutrient uptake. Extreme levels can be toxic and therefore limiting growth.
IV: salt concentraion: 0%, 0.5%, 1%, 1.5%, 2%, 2.5%
DV: plant length growth
Closely related to plant growth as it is a major factor in photosynthesis. Plants convert light energy into chemical energy and thus energy needed for other reactions.
intensity of light
DV: as the factor would significantly impact photosynthesis, the measurement of chlorophyll content would produce more effective quantitative data (µmol m-2)
IV: light intensity (cd m^-2) - 1000, 2000, 3000, 4000