A mutant plant lacking the ability to pump protons out of leaf companion cells will be unable to do which of the following?a. initiate transpirationb. load sucrose into sieve-tube elementsc. carry out photosynthesisd. transport water through the xylem

Explain how guard cells limit water loss from a plant on a hot, dry day. How can this be harmful to the plant?

Draw a plant cell in pure water. Add dots to indicate solutes inside the cell. Now add more dots to indicate an increase in solute potential inside the cell. Add an arrow showing the net direction of water movement in response. Add arrows showing the direction of wall pressure and turgor pressure in response to water movement. Repeat the same exercise, but this time, add solutes to the solution outside the cell at a concentration that is greater than inside the cell.

Compared with a cell with few aquaporin proteins in its membrane, a cell containing many aquaporin proteins willa. have a faster rate of osmosis.b. have a lower water potential.c. have a higher water potential.d. accumulate water by active transport.

Transpiration is fastest when humidity is low and temperature is high, but in some plants it seems to increase in response to light as well. During one 12-hour period when cloud cover and light intensity varied frequently, a scientist studying a certain crop plant recorded the data in the table (top right). (The transpiration rates are grams of water per square meter of leaf area per hour.) Do these data support the hypothesis that the plants transpire more when the light is more intense? If so, is the effect independent of temperature and humidity? Explain your answer. (Hint: Look for overall trends in each column, and then compare pairs of data within each column and between columns.)

Which of the following would tend to increase transpiration?a. spiny leavesb. sunken stomatac. a thicker cuticled. higher stomatal density

Your friend claims that phloem always carries sugars down a plant. What, if anything, is wrong with that statement?

Consider a tree that is 50 m tall and is transpiring roughly 90 liters of water each day. Approximately how many calories will the tree use to transpire this quantity of water?

Salt is used to melt snow and keep roads clear during the winter in many cities. Land adjacent to de-iced roads often ends up with a high concentration of salt in the soil. Explain why plants growing near salted roads may appear wilted in the spring.