What approximate percentage of water absorbed by plant roots is lost to the atmosphere via transpiration?

Correct answer: About 99%

Answer: B, about 99%. Roots absorb water from the soil, and that water travels through the plant’s conducting tissues toward leaves. Most of it eventually escapes as water vapour through tiny pores called stomata; this loss is transpiration. The water lost in this way is not usually used to build plant tissues. A small fraction is retained in cells, used in metabolism, or involved in growth and other plant processes. Therefore, the school-level approximate value is about 99% lost through transpiration and about 1% retained or used. A, C, and D are too small or do not represent the accepted approximate proportion. The exact percentage can vary with plant species, weather, soil water, and growth conditions, so 99% should be understood as a general textbook estimate, not an identical value for every plant. Memory cue: plants take up much water, but most of it passes back to the atmosphere through leaves.