Final answer:
If seeds are respiring anaerobically, the level of coloured liquid in a manometer would rise due to CO₂ gas production from fermentation. Facultative anaerobes will ferment in the absence of oxygen affecting the reading on a TSI slant. Fluid levels in a manometer equalize when both sides are exposed to the same atmospheric pressure.
Step-by-step explanation:
If a student repeated Experiment 1 using seeds that were respiring anaerobically, the level of colored liquid in the right-hand side of the manometer tube would rise. This is because, during anaerobic respiration or fermentation, gases such as carbon dioxide (CO₂) are produced. In the presence of a substrate, such as glucose, yeast cells will ferment the sugar anaerobically, producing CO₂ as a byproduct. The increased production of CO₂ gas in the closed side of the manometer would cause an increase in pressure, leading to a rise in the level of the colored liquid on the opposite side of the manometer that is open to the atmosphere.
Depending on the experimental setup, if the bacteria in the manometer are facultative anaerobes, they may continue to respire aerobically if oxygen is present but will switch to fermentative metabolism when oxygen is scarce. The result of the TSI slant, showing aerobic respiration (dark red on the slant) and fermentation of glucose (acid only in the butt), indicates that the bacteria can perform both types of respiration depending on the conditions.
When both sides of a manometer are open to the atmosphere, the fluid reaches equal levels on either side regardless of the tubes' diameters because the atmospheric pressure is the same on both sides, exerting an equal force on the liquid in the manometer.