A gardener stands a cut sunflower stem in dyed water. Within an hour the dye shows up in the veins of the topmost leaves. Which tissue carried the dye, and in which direction?

A strip of bark is cut away in a complete ring around a young tree, removing the outer transport tissue but leaving the wood intact. The leaves stay green for weeks while the roots slowly starve. What does this show?

In early spring a maple moves sugar from storage in its roots up to its opening buds. In summer the same tree moves sugar from its leaves down to those roots. Which tissue carries the sugar on both journeys?

Which description matches the cells that actually conduct water up the trunk of a tree?

A tomato plant absorbs dissolved nitrate from the soil, and the nitrate later turns up in the newest leaves. Which tissue carried it there, and what did it travel with?

As water evaporates from a leaf, the entire column of water in the xylem below it is pulled upward without coming apart in the middle. Which property of water holds the molecules of that column to one another?

Water climbs higher in a very narrow tube than in a wide one, creeping up along the tube's inner surface. Which property of water, at work in narrow xylem vessels too, explains the climb along the wall itself?

The pull of one water molecule on the next and the grip of water on a xylem wall both come from the same feature of the water molecule itself. What is that feature?

An air bubble forms inside one xylem vessel of a maple, and water stops moving through that vessel. Why does a single bubble stop the flow?

In a tall tree, water reaches the top leaves because living root cells spend ATP to push it up the stem, rather than because evaporation from the leaves pulls it up.

A shoot was set up in a potometer and its water uptake measured at four levels of relative humidity, with light and temperature held constant. Look at the graph. About how much water was the shoot taking up at 60% relative humidity?

One shoot's water uptake was measured under four air conditions at the same temperature. Which statement is best supported by the table?

The same shoot was measured at four air temperatures, with humidity and light unchanged. Use the graph. How much more water did it take up each hour at 30 degrees Celsius than at 20 degrees Celsius?

A shoot's water uptake was recorded at four light levels, with temperature and humidity held constant. Which explanation best fits the pattern in the graph?

Four leaves from one plant were coated with petroleum jelly in different ways and weighed again after 3 hours. What do the results in the table indicate about these leaves?

A bean plant was measured through one hot dry day. Use the table. What is the plant giving up when its stomatal opening drops at noon?

A potted plant was left unwatered for a week in a growth chamber at constant temperature, humidity and light. Which explanation best fits the change shown in the graph?

Two shrubs were grown side by side and measured under identical conditions. Use the table. What does the desert shrub give up in return for losing so much less water?

A tomato plant was measured across one full day and night. Use the table. Why is closing the stomata after dark a good trade for this plant?

Guard cells on one leaf were sampled through a morning. Use the table. What opens the stomatal pore?