▶️ Answer/Explanation
To find the transpiration rate, we calculate the water loss: Tube $X$ lost $40.3 – 34.6 = 5.7$ g, while Tube $Y$ lost only $41.0 – 39.4 = 1.6$ g. This confirms transpiration was lower in tube $Y$. The plastic bag around tube $Y$ traps water vapor released by the leaves, significantly increasing the humidity levels inside the bag. A higher humidity reduces the concentration gradient of water vapor between the leaf interior and the surrounding air. Consequently, the rate of diffusion out of the stomata slows down, leading to lower overall water loss compared to the exposed plant in tube $X$.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
To find the water loss from the upper surface, we compare the “no grease” scenario (loss from both surfaces) to the “upper surface greased” scenario (loss from lower surface only). The difference is the amount lost through the upper surface over $7$ days: $12.0\text{ g} – 8.7\text{ g} = 3.3\text{ g}$. To calculate the mean daily rate, divide this total by the duration of the experiment: $3.3\text{ g} \div 7 \text{ days} \approx 0.4714\text{ g / day}$. Rounding to two decimal places gives $0.47\text{ g / day}$. This calculation isolates the transpiration occurring specifically through the stomata or cuticle on the top side of the leaf.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
Transpiration is the evaporation of water from leaf surfaces, which is driven by a concentration gradient. High temperatures increase the kinetic energy of water molecules, speeding up evaporation. High wind speeds prevent water vapor from accumulating near the leaf, maintaining a steep diffusion gradient between the inside and outside of the leaf. Conversely, low humidity ensures the surrounding air is dry, further maximizing the rate at which water diffuses out of the stomata. Therefore, the combination of hot, windy, and dry conditions results in the maximum water loss.
✅ Answer: (B)