SAT Subject Test in Biology › Water and Nutrient Transport
Which of the following contribute to the upward movement of water through the xylem and throughout the plant's tissues?
I. Transpiration
II. Adhesion
III. Cohesion
I, II, and III
I only
I and II
I and III
III only
All three given properties contribute to water's motion up the xylem of a plant, as transpiration brings up the water through evaporation due to heat and sunlight. However, as water is a polar molecule and has properties of cohesion and adhesion, molecules of water stick together and resist forces that would push the water out of the plant. This dynamic is referred to as the cohesion-tension theory.
In plant vascular tissue, ____________ is primarily used to transport water from the roots to the other organs of the plant, and ___________ is primarily used to transport nutrients such as sucrose to the organs of the plant.
xylem . . . phloem
dermal tissue . . . phloem
ground tissue . . . dermal tissue
phloem . . . xylem
xylem . . . ground tissue
The correct answer is "xylem . . . phloem." Water and nutrients move from the roots through plant stem to the rest of the plant. Stems are made from three tissues: ground, dermal, and vascular. Vascular tissue is primarily divided into xylem, which primarily transports water, and phloem, which primarily transports sugars.