Color change is the answer because that is a physical change
The water enters the xylem first by osmosis. Water moves from the soil to the root hair cell down a water potential gradient, and to the root cortex cell from a higher water potential to a lower water potential, this process will be repeated until water enters xylem. Because transpiration is occurring in the leaf, water is lost so there is a lower water potential inside the leaf. Osmosis moves water from the xylem to the leaf because the xylem has a higher water potential. Water moves from the xylem to the cells of the leaf. This pulls water up the xylem via cohesion which is the process of water molecules attracting each other and sticking together. Water does not fall down the xylem as here is adhesion which is the process of water molecules sticking to the inside of the xylem.
The association of a DNA or RNA strand to its complement is one of the basic research tools of the molecular biologist. Binding of a compliment can identify target regions of DNA or RNA, and can be used to disrupt the process of DNA manufacture. If the complementary DNA is labeled with a compound that fluoresces, then the binding of the fluorescent probe can actually be visualized using a microscope<span>. This permits the "real time" examination of </span>DNA synthesis.<span>
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Silt would be your answer here
