17. Plants that grow in low-moisture climates have A. few stomata B. a large number of leaves C. a large number of stomata D. long stems 18. Cells responsible for the majority of photosynthesis in the leaf are called B. spongy layer cells C. palisade tissue cells D. guard cells 19. Decide whether each statement is true (T) or false (F) a. Gas exchange in all plants occurs only through the leaves. __ b. Spongy layer cells are loosely packed so air can move between the cells. __ C. Leaves do not contain vascular tissue. __ d. Palisade tissue cells contain chlorophyll. __ e. The opening and closing of stomata is sometimes regulated by the amount of carbon dioxide available. __ 20. The attraction of water molecules to other water molecules is known as A. adhesion B. cohesion C. osmosis D. capillary action 21. Water seen early in the morning only on the tip of a blade of grass is due to A. active transport B. turgor pressure C. capillary action D. root pressure

17. **A. few stomata**<br /><br />Plants in low-moisture climates need to conserve water. Having fewer stomata reduces water loss through transpiration.<br /><br />18. **C. palisade tissue cells**<br /><br />Palisade tissue cells are located just beneath the upper epidermis of the leaf and are packed with chloroplasts, making them the primary site of photosynthesis.<br /><br />19. <br />a. **F** (Gas exchange can also occur through stems and other plant parts, especially in plants adapted to arid environments.)<br />b. **T** (The loose packing of spongy layer cells facilitates gas exchange within the leaf.)<br />c. **F** (Leaves contain xylem and phloem, which are vascular tissues responsible for transport.)<br />d. **T** (Chlorophyll, the pigment necessary for photosynthesis, is contained within the chloroplasts of palisade tissue cells.)<br />e. **T** (High levels of carbon dioxide can cause stomata to close, while low levels can stimulate them to open.)<br /><br />20. **B. cohesion**<br /><br />Cohesion refers to the attraction between molecules of the same substance, in this case, water molecules attracting other water molecules.<br /><br />21. **D. root pressure**<br /><br />Root pressure is the force that pushes water up from the roots and can result in guttation, the formation of water droplets on the tips of leaves, especially in the morning. While capillary action plays a role in water movement within the plant, root pressure is the primary driver for this specific phenomenon.<br />