Overview
This lecture explains how plants transport water, minerals, and nutrients using specialized tissues, focusing on the roles and structure of xylem and phloem.
Plant Transport Systems
- Plants move water, minerals, glucose, and amino acids using specialized tissues instead of blood and a heart.
- Transport occurs through two main systems: xylem and phloem.
Xylem
- The xylem transports water and dissolved minerals from the roots to the leaves.
- Xylem is made of elongated dead cells, impermeable to water, with walls strengthened by lignin (woody material).
- Xylem vessels form continuous tubes along the length of the plant.
- In roots, vascular bundles with xylem are located in the center for protection and to prevent being pulled out.
- In stems, vascular bundles are near the edge to resist squashing and provide support.
Phloem
- The phloem transports sucrose (form of glucose from photosynthesis) and amino acids throughout the plant.
- Phloem is made of living cells arranged in continuous tubes.
- Movement in phloem can be both upward and downward, depending on where nutrients are needed.
- Phloem and xylem are grouped in vascular bundles, and their positions vary in roots and stems.
Transport Direction Summary
- Xylem: moves water and minerals only upward (roots to leaves).
- Phloem: moves sucrose and amino acids in both directions as needed.
Key Terms & Definitions
- Xylem — plant tissue transporting water and minerals from roots to leaves.
- Phloem — plant tissue transporting sucrose and amino acids throughout the plant.
- Vascular bundles — groups of xylem and phloem arranged together in stems and roots.
- Lignin — woody material reinforcing xylem cell walls.
Action Items / Next Steps
- Prepare for the next lesson covering xylem and the process of transpiration.