Correct option is C
Water potential is the measure of the free energy of water in a system, typically expressed in megapascals (MPa). Water moves from areas of high water potential (less negative) to areas of low water potential (more negative).
Pre-dawn leaf water potential declines over the 7 days:
Pre-dawn leaf water potential, the lowest point in a daily cycle, decreases over seven days without watering. This happens because the plant loses water through transpiration but can't replenish it, resulting in less water in the leaves each morning.
Leaf water potential shows a diurnal cycle of highs and lows:
Even without watering, a plant's leaf water potential still follows a daily (diurnal) rhythm. It rises slightly during the day due to transpiration and falls at night when transpiration slows. While the difference between the daily high and low points may lessen over seven days, this daily fluctuation is likely to continue.
Root water potential falls below leaf water potential at night:
If a plant's root water potential becomes lower than its leaf water potential at night, water cannot move from roots to leaves. This is because water flows from high to low potential, and the roots need a higher potential than the leaves to supply them, even at night. Without this movement, the plant dehydrates.
Root water potential fluctuates between day and night:
Root water potential changes throughout the day, influenced by both soil and leaf water potentials. It may become slightly less negative during the day due to transpiration and adjust at night. Despite the overall decline in root water potential over seven days, smaller daily fluctuations will still occur.
