Average Transpiration Rate from Mass Loss

Steps:

• Find total mass loss: 1276 g (09:00) - 1252 g (15:00) = 24 g.
• Determine total time: 15:00 - 09:00 = 6 hours.
• Calculate rate: 24 g ÷ 6 h = 4 g/h.
• The plastic bag prevents soil evaporation, so mass loss is due to transpiration from leaves.

Why D is correct:

• Transpiration rate is the average water loss per unit time, measured as mass decrease per hour over the full period.

Why the others are wrong:

• A: 43 g/h overestimates by using incorrect total loss or time (e.g., 24 g ÷ 0.56 h).
• B: 12 g/h misapplies time, perhaps dividing by 2 hours instead of 6.
• C: 8 g/h errors on time, like using 3 hours for the full interval.

Final answer: D