Question
7. The xylem and phloem: a. Compare their stuclure. b. What do they transport? c. Where does the material they transport flow to? 8. Another name for the Dermal tissue is __ 9. What is the difference between adhesion and cohesion? 10. After waking up one morning you go outside and see water on the tip of plants. This is due to __
Solution
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Roger
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Answer
7. **The xylem and phloem:** **a. Comparing their structure:** * **Xylem:** Composed of dead cells at maturity (tracheids and vessel elements). These cells form long, hollow tubes strengthened by lignin, providing structural support. Tracheids are elongated with tapered ends and pits for water movement between cells. Vessel elements are wider, shorter, and arranged end-to-end forming continuous vessels. * **Phloem:** Composed of living cells (sieve tube elements and companion cells). Sieve tube elements are elongated cells lacking a nucleus and with perforated end walls called sieve plates. Companion cells are adjacent to sieve tube elements and provide metabolic support. **b. What they transport:** * **Xylem:** Transports water and dissolved minerals (unidirectional flow - upwards from roots to shoots). * **Phloem:** Transports sugars (primarily sucrose) produced during photosynthesis, as well as other organic molecules like amino acids and hormones (bidirectional flow - from source to sink). **c. Where the transported material flows:** * **Xylem:** Water and minerals are transported from the roots, through the stem, and to the leaves, where they are used for photosynthesis and other metabolic processes. Some water is also lost through transpiration. * **Phloem:** Sugars are transported from source tissues (primarily leaves where photosynthesis occurs) to sink tissues (such as growing roots, fruits, and developing seeds) where they are used for growth, energy storage, or other metabolic processes.8. Another name for the Dermal tissue is **epidermis**.9. **Difference between adhesion and cohesion:** * **Adhesion:** The attraction between water molecules and other substances (e.g., the walls of xylem vessels). * **Cohesion:** The attraction between water molecules themselves (due to hydrogen bonding).10. After waking up one morning you go outside and see water on the tip of plants. This is due to **guttation**.