20

Plant Structure and Transport

1. Dermal tissue is the skin of the plant. It can protect the plant against water loss by secreting a waxy coating. Ground tissue composes most of the “filling” of the plant and is specialized for photosynthesis and storage. The vascular tissue is the circulatory system of the plant, responsible for moving glucose and water around the plant’s body.

2. Parenchyma cells are the “typical” plant cell, whose main roles are photosynthesis and storage. Collenchyma cells provide structure without restraining growth. Sclerenchyma cells are specialized for structure and are no longer able to elongate.

3. The upper, sunny side of the leaf is composed of a palisade layer that is tightly packed with cells filled with chloroplasts. A leaf has openings in the bottom to allow carbon dioxide gas to enter (required for photosynthesis). The gas is able to move through the leaf tissue into the palisade layer because it can freely travel through the airspaces in the spongy layer. The vascular tissue (both xylem and phloem) forms the veins of the leaf, providing easy access to water and a place to deposit the glucose.

4. The root cells actively move ions from the soil into the root’s xylem. This lowers the water potential in the root xylem (compared to the water potential in the surrounding soil). Water will move from [higher water potential] → [lower water potential], so water will passively flow from the soil into the root. This provides a bit of “push” up the body of the plant.

5. Both phloem and xylem are components of the plant’s vascular tissue. Phloem moves downward, transporting photosynthetically derived glucose from the leaves down toward the roots. Xylem, on the other hand, moves upward, transporting water taken in to the roots up toward the rest of the plant.

6.

a. Has two cell walls (S)

b. Found in strings of celery because they provide structure without restraining growth (C)

c. Has lignin in its cell walls (S)

d. Primary function is photosynthesis (P)

e. The reason a pear has a gritty feel (S)

7. The process of transpiration is the major force that pulls water from the roots up a plant’s body. As water evaporates from the top of the plant, it pulls a chain of water molecules up the xylem. Each water molecule creates a chain through the process of cohesion, and the entire chain sticks to the sides of the hollow tracheids and vessel elements through the process of adhesion.

8. b. Stomata are the openings in the leaves for the uptake of carbon dioxide gas.